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A review on design and analysis of H-frame hydraulic press

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The Hydraulic press system is a type of a system which works is to provide compressive force with the arrangement of hydraulic actuator through hydraulic fluid. It works on the basis of Pascal’s law. This law told that in a hydraulic fluid at static condition in an enclosed container, a pressure distribute in all direction to the wall of the container. Hydraulic press machine are mostly used for various purposes in industries as well as in our life such that forging, pressing, punching, deep drawings, metal forming operations, etc. 200-ton capacity hydraulic press machine body and actuator are designed with the help of Solid works and analysed by solid works simulation by FEA method. The objective of this paper is to analyse the entire mass and price of hydraulic press system while assuring suitable rigidity with the honeycomb formation on ram. Honey comb formation permits the minimisation of material used to reach the minimal weight and low material price by maintaining high toughness without compromising the output quality.

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Design of hydraulic control system for press machine and analysis on its fluid transmission features.

© 2021 IIETA. This article is published by IIETA and is licensed under the CC BY 4.0 license ( http://creativecommons.org/licenses/by/4.0/ ).

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The stability and reliability of hydraulic control system have a direct bearing on the overall dynamic performance of the press machine. Hydromechanical analysis on the hydraulic control system is of theoretical and practical significance to improving the transmission performance and structural design of the entire press machine. From a quantitative perspective, this paper firstly analyzes the fluid transmission features of the hydraulic control system for the press machine, and presents the fluid transmission route and design drawings of the hydraulic control system. The next step is the design of the hydraulic control system. The authors specified the steps of design and calculation for the hydraulic control cylinder, and the principles for determining the power of the diesel engine. After that, experiments were carried out to verify the dynamic and static features of the designed system, and prove that our system is scientific and rational.

press machine, hydraulic control system, analysis on fluid transmission features

The hydraulic control system is the core working component of the pressure machine. The stability and reliability of the system have a direct bearing on the overall dynamic performance of the press machine [1-3]. Hydromechanics mainly discusses the mechanical movement and equilibrium law of the liquid in the hydraulic control system, as well as the interaction pattern between hydraulic components. Hydromechanical analysis on the hydraulic control system is of theoretical and practical significance to improving the transmission performance and structural design of the entire press machine.

Raz and Vaclav [4] studied the structure, movement, and force of the hydraulic pump with fluid-heat-structure coupling features under specific working conditions, discretized the oil film feature model by finite-volume method, drawing on theories of dynamics and fluid dynamics, and simulated the liquid thickness, pressure, and temperature fields in the hydraulic pump on MATLAB, revealing the change law of these fields in a cycle.

Currently, there are few studies on the operating mechanism of modern hydraulic systems under extremely high or low temperatures [5-9]. From the perspective of fluid mechanics, Coetzer [10] simulated the fluid flow in the orifices and gaps of the hydraulic system, and constructed the corresponding experimental device; then, Coetzer conducted structural design of the mechanical platform and drive equipment for the system, and designed the electrical, measurement and control systems in terms of component selection, circuit design, and drive control; finally, Coetzer completed test bench construction, process integration, system debugging and sensor calibration.

If the fluid has a low lubricity, the parts of the hydraulic transmission system will easily fail due to friction damage [11-15]. To avoid the failure, Malygin et al. [16] replaced the traditional hydraulic medium to improve the lubrication conditions of the system components, selected the magnetic fluid that meets the viscosity requirements based on sedimentation stability and viscosity features, and demonstrated the superior lubricity of magnetic fluid through comparative experiments against anti-wear hydraulic oil.

The traditional press machine cannot meet the strict requirements on the deep drawing of thin sheets. There is a high market demand for press machines supporting user-defined kinematic indices like stroke and speed [17-21]. Huang et al. [22] provided an overall design plan for the hydraulic control system of computer numerically controlled (CNC) servo press machine, checked the pressure and heat losses of the system after determining the components and parts, and constructed an Adams simulation model on the stability, observability, and controllability of the system.

In metal sheet compression molding, the preparation of new-generation high-performance materials put forward stricter requirements on the performance design of the hydraulic control system for the mechanical press machine. According to the process requirements on advanced press machine, Malygin et al. [23] designed and analyzed the hydraulic and electrical control programs for each action of the mechanical press machine, and developed detailed wiring diagram, control principle diagram, and design diagram of automatic protection and control system. Monn et al. [24] completed the detailed design of the hydraulic control system for the press machine of compressed garbage; after selecting the components and parts, Monn simulated and modeled the drive system, and analyzed the reliability of the main propulsion circuit; the design of the main propulsion control, electronic control, hydraulic circuit, and internal pipes was proved reasonable and correct. From both static and dynamic aspects, Kramer and Rexroth [25] conducted feature analysis and simulation modeling of the main circuits of the hydraulic system for the brick press machine, namely, moving beam descending circuit, pressing circuit, and ejection circuit, examined the physical features like displacement, pressure, and flow, and presented an effective scheme to reduce the water hammer in the system.

To sum up, the existing studies at home and abroad mainly focus on the theoretical analysis, numerical simulation, and experimental research on the hydraulic control system of press machines. The hydraulic fluid transmission technology has reached an advanced level in foreign countries. Chinese scholars have also achieved quite a few results in this respect. However, the fluid transmission features are mostly obtained based on lots of assumptions and simplifications, the empirical system design faces many limitations, and no one has yet applied the analysis results of fluid transmission features to the design of hydraulic control system for press machines.

To overcome the above defects, this paper firstly analyzes the fluid transmission features of the hydraulic control system for the press machine, and presents the fluid transmission route and design drawings of the hydraulic control system. Next, the authors specified the steps of design and calculation for the hydraulic control cylinder, and the principles for determining the power of the diesel engine. Finally, experiments were carried out to verify the dynamic and static features of the designed system, and prove that our system is scientific and rational.

According to the different functions of the confluence or shunt power for the planetary gearset, the transmission mode of the hydraulic control system for the press machine can be divided into the output shunt type (where the planetary gearset lies at the output end of the system) and the input shunt type (where the planetary gearset lies at the input end of the system). This paper chooses to discuss the fluid transmission features of the output shunt type system.

Figure 1 shows the structure of the output shunt type hydraulic control system. Using the variable pump-constant drive motor circuit, the hydraulic closed circuit of the press machine outputs a constant torque; the relative change rate of the displacement of the variable pump is proportional to the speed of the drive motor in the circuit. The speed of the drive motor can be regulated by adjusting the displacement of the variable pump. Thus, this hydraulic control system is an ideal choice for industrial and agricultural mechanical press machines.

Figure 1. Structure of the output shunt type hydraulic control system

The fluid displacement of each link in the system is multiplied with the speed of the drive motor. Then, the output flow of the hydraulic pump w HPO equals the input flow of the drive motor w HMI :

$w_{H P O}=w_{H M I}$    (1)

Let P HPD and m HPS be the displacement and speed of the hydraulic pump, respectively. Then, w HPO can be calculated by:

$w_{H M I}=p_{H P D} \cdot m_{H P D}$    (2)

Let P HMD and m HMO be the displacement and speed of the drive motor, respectively. Then, w HMI can be calculated by:

$w_{H M I}=P_{H M D} m_{H M O}$    (3)

Figure 2. Output speed curve

Figure 2 shows the output speed curve of the output shunt type system. Let P HPD-max and τ be the maximum displacement and relative displacement change rate of the hydraulic pump, respectively. Then, P HPD can be calculated by:

$P_{H P D}=P_{H P D-m a x} \tau$    (4)

Since P HPD-max× m HPS× τ = P HMD× m HMO and P HPD-max = P HMD :

$m_{H M O}=m_{H P S} \tau$    (5)

Formula (5) shows that m HMO is proportional to τ . Under operating conditions, general industrial and agricultural mechanical presses have a limited range of force. The single planetary gearset is sufficient to meet the working requirements. Let m SW , m RT , and m i be the speeds of the sun gear, ring gear, and planetary carrier, respectively; l be the characteristic parameter of the planetary gearset. Then, the kinematics equation of the planetary gearset can be expressed as:

$m_{S W}+l m_{R T}-(1+l) m_{i}=0$    (6)

Let W SW , W RT , and W i be the input or output powers of the sun gear, ring gear, and planetary carrier, respectively. Then, the input and output powers of the planetary gearset satisfy:

$W_{S W}+W_{R T}+W_{i}=0$    (7)

Let T SW , T RT , and T i be the torques of the sun gear, ring gear, and planetary carrier, respectively. Then, the torque feature of the planetary gearset can be expressed by:

$T_{S W}: T_{R T}: T_{i}=1: l:-(1+l)$    (8)

Figures 3 and 4 are the schematic diagrams of the fluid transmission route of the hydraulic control system for the press machine, and the detailed design drawings of 6 different transmission routes, respectively. The following is an analysis on the features of the route(s). Let m ET be the speed of the input shaft. Then, we have:

$m_{H P S}=m_{E T}$    (9)

Figure 3. Fluid transmission route of the hydraulic control system for the press machine

Figure 4. Design drawings of the hydraulic control system

Combining formulas (8) and (9):

$T_{S W}=\frac{T_{R T}}{l}=\frac{T_{i}}{-(1+l)}$    (10)

Let λ HR be the shunt ratio of hydraulic power; W HR be the power of hydraulic circuit; W CS be the output power of the transmission system. Then, the shunt ratio of hydraulic power can be expressed as:

$\lambda_{H R}=-\frac{W_{H R}}{W_{C S}}$    (11)

Formula (11) shows the power transmitted from the hydraulic circuit to the planetary gearset depends on the negative ratio of W HR to W CS . If the input of the hydraulic part is the sun gear, the input of the mechanical part is the planetary carrier, and the total output of the system is the ring gear, the fluid transmission feature of the hydraulic control system for the press machine can be deduced as follows.

The relationship between m HMO and m SW can be described by:

$m_{S W}=\frac{m_{H M O}}{j}$    (12)

where, j is the transmission ratio of reduction gear. The relationship between m HPS and m i can be expressed by:

$m_{i}=m_{H P S}$    (13)

Let m CS be the output speed. Then, the relationship between m i and m CS can be expressed as:

$m_{R T}=m_{C S}$    (14)

Combining formulas (13) and (14):

$m_{i}=m_{E T}$    (15)

From formula (15), m SW can be described by:

$m_{S W}=\frac{m_{H M O}}{j}=\frac{m_{H P S} \tau}{j}=\frac{m_{E T} \tau}{j}$    (16)

Then, m RT and m CS can be respectively obtained by:

$m_{R T}=\frac{(l+1) m_{i}-m_{j}}{l}=\frac{(l+1) m_{i}-\frac{1}{j} m_{E T} \tau}{l}$

$=\left(\frac{(l+1)-\frac{\tau}{j}}{l}\right) m_{E T}$    (17)

$m_{C S}=m_{R T}=\left(\frac{(l+1)-\frac{\tau}{j}}{l}\right) m_{E T}$    (18)

Next is an analysis on the torque features of the hydraulic control system for the press machine. According to plan 1, the relationship between input torque T HMO and T SW can be described by:

$T_{S W}=j T_{H M O}$    (19)

The relationship between T RT and output torque T CS can be described by:

$T_{C S}=T_{R T}$    (20)

Combining formula (19) with formula (8):

$T_{S W}=\frac{T_{R T}}{l}$    (21)

Combining formula (20) with formula (8):

$T_{C S}=l j T_{H M O}$    (22)

Under the same condition, the power shunt ratio of the hydraulic control system can be expressed as:

$\lambda_{H R}=-\frac{W_{H R}}{W_{C S}}=-\frac{T_{S W} m_{S W}}{T_{R T} m_{R T}}$    (23)

where, the ratio of T SW to T RT can be calculated by:

$\frac{T_{S W}}{T_{R T}}=\frac{1}{l}$    (24)

where, the ratio of m SW to m RT can be calculated by:

$\frac{m_{S W}}{m_{R T}}=\frac{l \tau}{(l+1) j-\tau}$    (25)

Formula (23) can be updated into:

$\lambda_{H R}=-\frac{W_{S W}}{W_{C S}}=\frac{\tau}{\tau-(l+1) j}$    (26)

3.1 Design and calculation of hydraulic control cylinder

The hydraulic control cylinder is the core component of the hydraulic control system in industrial and agricultural mechanical press machines. The former undertakes the task of direct compression molding, and provides the main space for fluid transmission. Table 1 presents the outer diameters of piston rods in oil cylinder and air cylinder. Based on the measured results on sample equipment, the following parameters of the hydraulic control cylinder can be determined: the piston rod diameter f , working pressure V of hydraulic control cylinder, and maximum stroke K of hydraulic control cylinder. Table 2 presents the working pressure of the oil cylinder under different piston rod diameters. According to the general correspondence between the working pressure of the oil cylinder and the diameter of the piston rod, the piston rod diameter F of the designed oil cylinder can be selected according to the working pressure:

$F=\frac{f}{0.7}$    (27)

Table 1. Outer diameters of piston rods in oil cylinder and air cylinder

Table 2. Working pressure of the oil cylinder under different piston rod diameters

Then, the piston width E can be calculated by:

$E=(0.5 \sim 1.1) \times F$    (28)

The length C of the sliding surface of the guide sleeve (Figure 5) can be calculated by:

$C=(0.6 \sim 1.0) \times f$    (29)

Figure 5. Length of the sliding surface of the guide sleeve

When the piston rod is fully extended, if the distance from the midpoint of the piston bearing surface to the midpoint of the sliding surface of the guide sleeve is too small, the initial deflection of the hydraulic control cylinder will increase, undermining the stability of the cylinder. Therefore, the guide length G must be minimized in the design. Let K be the maximum stroke of hydraulic control cylinder, and F be the inner diameter of the oil cylinder. Then, G must satisfy the following inequality:

$G \geq \frac{K}{20}+\frac{F}{2}$    (30)

A spacer can be installed between the guide sleeve and the piston to minimize G . The length of the spacer can be calculated by:

$S=G-(C+E) / 2$    (31)

Let ξ be the wall thickness of hydraulic control cylinder. The diameter of piston rod f and ξ must pass strength check before being applied in high-pressure press machines. If the F/ξ is greater than 10mm, the wall is thick; if it is smaller than 10mm, the wall is thin:

$F / \xi<10$ or $F / \xi>10$    (32)

Let V b and μ be the test pressure of the cylinder and allowable stress of cylinder material, respectively. If the hydraulic control cylinder has a thick wall, then ξ can be checked by:

$\xi \geq \frac{F}{2} \sqrt{\frac{[\mu]+0.4 V_{b}}{[\mu]-1.3 V_{b}}-1}$    (33)

Let U be the force on piston rod. Then, f can be checked by:

$f \geq \sqrt{\frac{4 U}{\pi[\mu]}}$    (34)

Let f c be bolt diameter. During the system operation, the set bolt on the cover of hydraulic control cylinder is subject to both torsion stress and tensile stress. Let W be the load of the cylinder; r be the number of set bolts; υ be the thread tightening coefficient. Then, f c can be checked by:

$f_{c} \geq \sqrt{\frac{5.2 l U}{\pi r[\mu]}}$    (35)

Let L be the system leakage coefficient, and ∑ FL PO-max be the larger flow between oil cylinder and drive motor. Tables 3 and 4 present the parameters of the drive motor and hydraulic pump, respectively. Throughout the pressing process, hydraulic control cylinder and hydraulic drive motor do not work at the same time. The output flow of the hydraulic pump can be described as:

$F L_{P O} \geq L \sum F L_{P O-m a x}$    (36)

Table 3. Parameters of hydraulic drive motor

Table 4. Parameters of hydraulic pump

Let PR 1 be the maximum working pressure of hydraulic control cylinder or hydraulic drive motor, and ∑Δ v be the total loss on the pipes between hydraulic pump and hydraulic control cylinder or hydraulic drive motor. Then, the maximum working pressure of hydraulic pump can be expressed as:

$P R_{O H} \geq P R_{1}+\sum \Delta v$    (37)

3.2 Determining the power of diesel engine

For a hydraulic pump driven by a diesel engine, the inputs are torque and speed, and the outputs are fluid flow and pressure. Energy loss is inevitable in the conversion process of fluid transmission energy. Thus, the output power of the system is smaller than the input power. The output-input power ratio is the total efficiency of the system ω . Let PR MOH and PR HPO be the maximum working pressure and maximum flow of hydraulic pump, respectively. Then, the driving power of the diesel engine can be calculated by:

$P R=\frac{P R_{O H} w_{P O}}{\omega}$    (38)

Based on the driving power calculated by formula (38), the diesel engine can be selected according to the power loss of the conversion process and the power requirements of the auxiliary equipment of the hydraulic control.

During the operation of the hydraulic control system for the press machine, the design parameters and input speed were fixed to analyze the static features of the system. Figure 6 shows the variation in the transmission ratio with the relative change rate of pump displacement. It can be seen that, the system output speed changed linearly with τ . Thus, the output speed of the fluid transmission system can be regulated by changing the τ value, giving a suitable force range of the press machine. Because the linear increase or decrease directly affects the operating direction of the variable pump, it can be judged that plans 4 and 6 have relatively high sensitivity and wide range of speed adjustment; plans 1, 2, 3, and 5 have relatively low sensitivity and narrow width.

Figure 6. Variation in the transmission ratio with the relative change rate of pump displacement

Figure 7(a) shows the dynamic features of the system under different pump displacement adjustment rates, and Figure 7(b) displays the dynamic features of the system under different load torques. It can be seen that, from 0 to 25s, the relative change rate of hydraulic pump displacement exhibited a linear growth from -0.8 to 0.8; from 25 to 38s, the relative change rate linearly declined from 0.8 to -0.8; from 38 to 46s, the rate changed from -0.8 to -0.2; from 46 to 50s, the rate changed from -0.2 to -0.8. During the period of 25-50s, the system load torque changed to 50N·m.

The on-off valve and logic valve, the oil cylinder and the oil pump, and the accumulator were treated as three subsystems. Then, MATLAB simulation was conducted to analyze the fluid transmission features of the piston in the upward and downward strokes. Figure 8 records the simulated curves of downward displacement, downward speed, upper and lower compartment pressures, accumulator flow, and accumulator pressure during the upward stroke of the piston. It can be seen that, the piston descended rapidly at the beginning. With the elapse of time and increase of displacement, the accumulator saw a gradual decline in pressure and flow. The pressure in the upper and lower compartments of the oil cylinder continued to decrease, and resulted in an inflection point at about 4m. The inflection point appears as the hydraulic pump changes from oil filling state to oil discharging state.

Figure 7. Variation of input parameters

Figure 9 records the simulated curves of upward displacement, upward speed, upper and lower compartment pressures, accumulator flow, and accumulator pressure, during the downward stroke of the piston. The upward speed of the piston was slow at the beginning, and quickly tended to stable. The upper and lower chambers of the oil cylinder had a small pressure. During the upward stroke, the accumulator was first filled by the hydraulic pump until it was fully filled with oil. Only in this case, was the liquid oil supplied to the lower chamber of the oil cylinder, serving to drive the upward motion of the piston. The test results agree with the actual situation, reflecting the rationality of our design for the hydraulic control system of the press machine.

Figure 8. Simulation curves in the downward stroke

Figure 9. Simulation curves in the upward stroke

This paper mainly pursues the reasonable design of the hydraulic control system for press machines, and analyzes the fluid transmission features. From the quantitative angle, the fluid transmission features of the hydraulic control system were examined for press machines, and the fluid transmission route and design drawings were prepared for the hydraulic control system. Then, design flow of the hydraulic control system was described, including how to design the hydraulic control cylinder and the selection of diesel engine power. After that, several experiments were carried out to observe the variation of transmission ratio with the relative change rate of pump displacement, as well as the dynamic features of the system under different pump displacement adjustment rates and load torques. The dynamic and static features of the designed system were also analyzed. Through the simulation of the upward/downward stroke of the piston, the operating results of the designed model were proved consistent with the actual situation, reflecting the scientific nature and rationality of the proposed system.

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International Journal of Engineering Research and

Ankit Parmar

The goal of structure optimization is to decrease total mass of hydraulic press while assuring adequate stiffness. Structural optimization tools and computer simulations have gained the paramount importance in industrial applications as a result of innovative designs, reduced weight and cost effective products. A method of structure optimization for hydraulic press is proposed in order to reduce mass while assuring adequate stiffness. Key geometric parameters of plates which have relatively larger impacts on mass and stiffness are extracted as design variables. In order to research relationship between stiffness, mass and design variables, common batch file is built by CREO and analysis is done in ANSYS. Top plate , movable plate and column design and analysis done.

International Journal of Engineering Research and Technology (IJERT)

IJERT Journal

https://www.ijert.org/design-characterization-and-testing-of-hand-operated-hydraulic-press https://www.ijert.org/research/design-characterization-and-testing-of-hand-operated-hydraulic-press-IJERTV5IS050457.pdf Hydraulic Press is one of the oldest basic machine tools. In its modern form, is well adapted to press work ranging from coining jewelry to forging aircraft parts. A hydraulic press is a machine using a hydraulic cylinder to generate a compressive force. In this paper the components like frame, cylinder, pillar and plates are designed by the design procedure. They are analyzed to improve their performance and quality for press working operation. Using the optimum resources possible in designing the hydraulic press components can effect reduction in the cost by optimizing the weight of material utilized for building the structure. An attempt has been made in this direction to reduce the volume of material. So in this paper consideration for an industrial application consisting of mass minimization of H frame type hydraulic press.

Saurin Sheth , Tejas Patel

The aim of this paper is to integrate the mechanical system of hydraulic press with hydraulic system to facilitate the ease of operation to manufacture the smaller parts in a bulk. In the present scenario, time constrain is a crucial part for completion of any production process. Thus with the aid of automization, the production time can be reduced as well as higher degree of accuracy can be achieved as the human efforts will be alleviated. Thus an attempt has been made to provide the smooth and rapid functioning of press work with the help of hydraulic system.

IJRAME Journal

Oluwole Ojo

Gireesha Chalageri

The hydraulic pressing machine used for converting shape of the material to the required form by compressive force of action. In this work hydraulic pressing machine of twelve Ton capacity is Designed and Analysed. The design has to resist the generated force during operation and to calculate design parameters like stress induced and total deformation developed during operation. This pressing machine is made for manufacturing of automotive body buildings and sheet metal applications. The machine is designed for special purpose only, to the load capacity of 12 Ton. Structural analysis becomes a part to identify the product design. The frame and cylinder is modeled using CATIA V5 and analysis by ANSYS software.

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Highway Hydraulic Engineering State of Practice (2020)

Chapter: chapter 2 - literature review.

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

5 Introduction The literature review summarizes the results from searching state DOT manuals, additional policies, procedures, and technical memoranda for topics as defined in the scope. The informa- tion collected from the states was informed by the results from the survey—the responses from the states provided a guide to policy and practice that was researched. The states highlighted overall in the literature review are shown in Figure 1, and for each topic, the states highlighted within the literature review are shown in Table 1. This literature review contains information based on available documents and assumes that an updated manual corresponds with an update in the practice. There may be a lag between the state of practice and when the state of practice is documented in a policy document or manual; for example, DOTs may be implementing a state of practice that is not yet documented in a policy/manual. Additionally, practice may have advanced but the DOT may not have updated its manual. Roadway Drainage Proper roadway drainage is imperative for safety and traffic flow during storm events. Road- way drainage is typically achieved through the installation of inlets and culverts, but to operate effectively, they must be clear of debris. Spread criteria (i.e., allowable depth and width of flow on the road surface) are essential to conveying peak discharges with minimal disruption to traffic in locations where inlets catch excess runoff (Urban Drainage Flood Control District 2016). Posi- tioning and malfunctioning of inlets through clogging can lead to reduced inlet efficiency (Leitao et al. 2015). This literature review is limited to the subject topics that include spread criteria—both temporary and permanent—for roadway drainage. NCHRP Project 15-55, “Guidance to Predict and Mitigate Dynamic Hydroplaning on Roadways” provides information on water depth on pavement in regard to hydroplaning. The state policy and practices with respect to spread criteria are included in the following paragraphs, along with inlet design and reduced inlet efficiency. Some highlights are that Minnesota considers shoulder-to-shoulder width in some cross-section designs, Colorado con- siders hydroplaning potential in designs, and Ohio designs for temporary and permanent drain- age conditions. Also, to account for reduced inlet capacity, North Carolina assumes 50% debris blockage for inlet capacity and 50% blockage for inlet spacing design depending on the condi- tion, Virginia designs for off-site drainage interception before it reaches the roadway, and Utah requires a 6-inch upsizing of pipe culverts with fill heights of 8 ft and greater. This review is not comprehensive, but it is intended to be representative of practices and policies at the state level. C H A P T E R 2 Literature Review

6 Highway Hydraulic Engineering State of Practice Colorado Colorado DOT considers design storm frequency and roadway type in determining spread criteria. In Colorado, highway classification (along with highway speed) are major consider- ations as public expectations are that a certain amount of water will be on a given road surface. Design speed is selected after evaluating hydroplaning potential, but some leeway is provided as a likelihood exists that this speed will be exceeded (Colorado DOT 2013). Colorado uses design storms to determine spread criteria, using 2-year through 10-year design storm frequency and 50-year storms for a sag point on arterials (Colorado DOT 2013). Indiana Indiana DOT specifies a clogging factor of 50% is to be used for inlet spacing design, but this is not always required. Exceptions are made for special cases, a full list of which can be found in Chapter 203 of their drainage manual. Slotted drain inlets are no longer considered for use in sags as there is a tendency to collect debris (Indiana DOT 2013). Minnesota Minnesota DOT bases spread criteria on average daily traffic (ADT), lane width, and speci- fied design storms. Lane width may either be the parking lane width, shoulder width, or driving lane width (Minnesota DOT 2000). A memorandum introduced in 2016 expands spread criteria to consider shoulder width with an additional factor of safety for varying roadway types. The document further details design frequency and allowable spread for specific roadway types such as Trunk Highway Turn Lanes and Roundabouts. Design storm events currently include the 5-year event and above (Minnesota DOT 2016), representing an increase from the previously specified 3-year event (Minnesota DOT 2000). Created with mapchart.net © Figure 1. States highlighted in the literature review for NCHRP Project 20-05/ Topic 50-02, “Highway Hydraulic Engineering State of Practice.”

Literature Review 7 State Roadway Drainage Culverts Aquatic Organism Passage Bridges Scour Computations and Countermeasures Advanced Hydraulic Modeling Regulatory Requirements Floodplain Impacts and Mitigation Coastal Hydraulics Alternative Project Delivery Methods Alaska x x California x x Colorado x x x x Delaware x x Florida x Georgia x x x Hawaii x Illinois x Indiana x Louisiana x Maine x x Maryland x x x x Michigan x x Minnesota x x x x x Nebraska x New Hampshire x New Mexico x New York x x x North Carolina x x x Ohio x x x Oregon x x x Pennsylvania x x x Rhode Island x South Dakota x Tennessee x x Texas x x x x Utah x x x x Vermont x x Virginia x x x x Washington x x x West Virginia x Wyoming x Table 1. States highlighted within the literature review.

8 Highway Hydraulic Engineering State of Practice North Carolina In North Carolina, permanent spread criteria for major arterials depends on the speed limit: speeds less than 45 mph and sag points use the shoulder width plus 3 ft, while speeds greater than 45 mph use shoulder width only, with both using a 10-year design storm. For minor arterials and speeds less than 45 mph with sag points, spread is calculated using half of a travel lane width; spread for those arterials greater than 45 mph are calculated using shoulder width only (North Carolina DOT 2016). An assumption of 50% debris and potential blockage is required when computing inlet capacity for sags. During construction, the allowable spread is based on traffic volume, road classification, speed limit, and lane width. The drainage manual does not provide specific values for temporary spread conditions (North Carolina DOT 2016). Ohio Ohio DOT incorporates different spread criteria for permanent drainage and temporary drainage for construction. For temporary conditions, a dry lane width of 10 ft is necessary for each traveled lane, determined using a 2-year design storm. Any drainage system designed incorporates both permanent and temporary solutions, with permanent drainage preferred for the project. Temporary systems may include inlets, storm sewers, culverts, ditches, catch basins, conduits, French drains, and pavement saw cut openings, among others. These tem- porary systems may be removed if not included in the final design. Ohio DOT specifies that final designed sizes should be used where feasible and temporary storm sewers must have a minimum diameter of 12 inches, while temporary culverts must have a minimum diameter of 18 inches (Ohio DOT 2018). South Dakota South Dakota DOT limits the use of standard grate inlets to minor sag points as they are susceptible to clogging, with oversized grate inlets recommended for major sag points and in areas prone to clogging. Alternatively, combination curb-opening and grate inlets may be placed in sags to accommodate reduced inlet efficiency in the event of excessive debris. The most com- monly used inlet by South Dakota DOT is a combination inlet with a grate featuring curved vanes sloped in the direction of flow to increase hydraulic capacity. Drop inlets are typically designed with sumps to collect debris (South Dakota DOT 2011). Utah Utah DOT references HEC-9 (FHWA 2005) for sediment and debris control for pipe culverts to account for reduced inlet efficiency. Pipe culverts with fill heights 8 ft or greater are to be upsized by 6 inches. Additionally, minimum pipe diameters that can be specified are 24 inches for off-site flows and 18 inches for on-site flows (Utah DOT 2018b). Virginia Virginia DOT prefers curb-opening inlets to grate inlets as more debris can be handled. Any runoff from land off site is intercepted from cut slopes and other areas draining toward the road- way before it reaches the curb and gutter section. This minimizes sediment and debris build-up on the roadway, as well as reduces the amount of water flowing into an inlet. To account for clogging, an efficiency of 50% is adopted when grates are used in a sag (Virginia DOT 2019a). Culvert Aquatic Organism Passage Information reported here pertains to culvert replacements, as little guidance for culvert rehabilitation for aquatic organism passage (AOP) was available; rehabilitation may simply consist of retrofitting the existing culvert. Advances in culvert AOP consist of estimating local

Literature Review 9 and average velocities using flume and computational fluid dynamics models for low flows in large culverts. Culvert assessment and asset management systems have been developed to account for AOP. Stream simulation methods for low-impact designs, such as embedded or open bottom culverts and countersinking, have also been used for AOP. Alaska, Georgia, Maryland, Michigan, Minnesota, Vermont, and Wisconsin DOTs in Alaska, Georgia, Maryland, Michigan, Minnesota, Vermont, and Wisconsin partici- pated in a FHWA pooled fund study to fill the need for national attention placed on designs for successful AOP. To accurately predict fish movements (and impediments), the study developed a method to reliably estimate local and average velocities for low flows in large culverts, as well as velocity variations in embedded and non-embedded culverts, to replace unreliable velocity esti- mates that have typically been determined from bankfull conditions or even higher flows. Culvert materials, shapes, lengths, slopes, bed material, and entrance and outlet conditions were examined. Full-scale flume experiments and computational fluid dynamics (CFD) simulations were per- formed, with CFD modeling calibrated to physical results. The proposed procedure will allow the design engineer to reliably estimate average and local velocities to produce a velocity distribution over the cross section modeled. The method was developed for circular culverts and could be expanded to other shapes (FHWA 2014). The study concluded in 2014 with the goal of incorpo- rating the results in future versions of HEC-26 and other guidance documents (FHWA 2016b). Maryland Maryland DOT State Highway Administration (SHA) has indicated that currently AOP design is case by case as agreed upon with environmental agencies, and future designs will be based on policy guidelines being developed by the Maryland DOT SHA/MDE (Maryland Department of the Environment) Hydraulics Panel. The Maryland DOT SHA/MDE Hydraulics Panel has delegated AOP to a subcommittee to identify regulations, policies, and procedures that should be updated and developed for integration of effective AOP practices (Maryland Hydraulics Panel 2018). Minnesota Minnesota DOT has a new AOP guide, Minnesota Guide for Stream Connectivity and Aquatic Organism Passage Through Culverts (2019), that includes some changes that Minnesota DOT has made over the last 10 years to address fish passage. This guide was created from existing literature, design documents, expert input, and a survey to identify best practices that will allow Minnesota DOT to: 1. Design the culvert to be similar to the stream channel (reference reach) by matching its slope, alignment, bankfull width, and flow depth to maximize AOP; 2. Provide a continuous sediment bed with roughness similar to the channel, while maintaining continuity of sediment transport and debris passage; 3. Design for public safety, longevity, and resilience; 4. Improve AOP; 5. Account for sediment transport; 6. Reduce long-term maintenance costs; and 7. Increase culvert life span. Design procedures incorporated in this document include both geomorphic simulation (US Forest Service Stream Simulation) and hydraulic simulation (FHWA HEC-26) (Minnesota DOT 2019). The report considers not only design but also site assessment parameters, and hydraulics including sediment transport, floodplains, energy dissipation structures, water level controls, and cost considerations (Minnesota DOT 2019).

10 Highway Hydraulic Engineering State of Practice New Hampshire New Hampshire DOT follows New Hampshire Department of Environmental Services (NHDES) rules for structure permitting and the New Hampshire Stream Crossing Initiative Field Manual that was created from a partnership of state agencies. Through the expertise of the partnership, stream crossing survey protocols and data management measures were refined for a multi-agency effort to score stream crossings characterized by size, safety, and flooding. The data is stored in the Statewide Asset Data Exchange System (SADES) online ArcGIS geodatabase. The culvert assessment initiative is aimed at collecting coarse level data during a stream survey to rank culverts in terms of: 1. Geomorphic Compatibility (GC; structure fit with river form and processes); 2. AOP (ranking of whether the structure is a barrier to animal passage); 3. Condition (New Hampshire DOT asset condition score); and 4. Hydraulic Capacity of the structure to transport predicted flows under storm events (NHDES et al. 2019). New Hampshire DOT creates sensitive designs for aquatic organism passage on a case-by-case basis, as evidenced by several projects and coordination efforts between the New Hampshire Bureau of the Environment and the Natural Resource Agency (New Hampshire DOT Bureau of the Environment 2015). Oregon Oregon DOT uses hydraulic methods and/or stream simulation. The method defined in Stream Simulation: An Ecological Approach to Providing Passage for Aquatic Organisms at Road-Stream Crossings by the U.S. Department of Agriculture (2008) intends for unrestricted movements of aquatic organisms by designing crossings that mimic the stream. Additionally, FishXing software and Hydrologic Engineering Center’s River Analysis System (HEC-RAS) aid in low-impact design as they can simulate flow in embedded or open bottom culverts. A stream assessment is conducted for stream simulation, and the goal is to provide a crossing that minimally inhibits the natural channel flow. There is no set rule for stream simulation, and the designer should be aware that this is a dynamic approach as stream simulation guidelines are always changing. Considerations for design include natural alignments, careful design of transi- tions, size and mobility of bed material, and pool depth and location. The Stream Simulation: An Ecological Approach to Providing Passage for Aquatic Organisms at Road-Stream Crossings guide provides many examples and scenarios for consideration (U.S. Department of Agriculture 2008), including the following alignment examples: “(a) Matching culvert alignment to stream alignment. (b) Realigning the stream to minimize culvert length. (c) Widening and/or shortening the culvert.” Pennsylvania The Pennsylvania highway design manual includes policy for risk assessment and coordina- tion with the PA Fish and Boat Commission regarding “potential for changes to the ecology or the aquatic habitat of the stream channel and floodplains.” Specifications for “channel con- struction involving fishable streams” include considerations for erosion protection, natural channel relocation, bench widening, turbidity, and open bottom structures. It is stated that the specifications listed in the highway manual are not all-inclusive and that the Engineering Dis- trict Office will make recommendations for the hydrologic and hydraulic report (Pennsylvania DOT 2015).

Literature Review 11 Virginia The Virginia DOT Drainage Manual requires countersinking of culverts, whereby the bottom of the culvert is placed below the bed of the stream, as prescribed necessary in a streambed under jurisdiction of the U.S. Army Corps of Engineers (USACE). The USACE countersinking method must be followed and is outlined in Virginia DOT Drainage Manual Chapter 8 (Virginia DOT 2019a). Design for fish habit requires passage accommodations, and VDOT design criteria are speci- fied in the following: • An Analysis of the Impediments to Spawning Migrations of Anadromous Fish in Virginia Culverts (Pages 61 through 66) August 1985, by Mudre, Ney and Neves; and • Nonanadromous Fish Passage in Highway Culverts Report No. VTRC 96-R6 October 1995 by Fitch (Virginia DOT 2019a). Virginia DOT will evaluate any project where circumstances do not allow for countersinking on a case-by-case basis (Virginia DOT 2019a). Washington The Washington State DOT Hydraulics Manual specifies guidance for fish passage in addi- tion to the Washington Department of Fish and Wildlife Water Crossing Design Guide- lines Manual (WDFW 2013) and the Fish Passage Inventory, Assessment, and Prioritization Manual (WDFW 2019). The design engineer should inspect for aquatic habitats with particu- lar attention to large woody material (LWM; also known as large woody debris). LWM has a significant effect on aquatic habitat in Washington, and the Washington State DOT hydraulics manual outlines detailed design and placement criteria for its use (Washington State DOT 2017b). Figure 2 shows the U.S. Department of Agriculture (USDA) Natural Resource Con- servation Service (NRCS) Thunder Road fish barrier project in La Push, Washington. This project restored floodplain connectivity and allowed fish to pass four barriers. Wyoming Wyoming DOT uses “FishXing” software for assessment and design of culverts for AOP. The models constructed by this software provide several aids in the design of parameters that allow for unobstructed fish passage, such as comparing culvert hydraulics with organism capa- bilities, performing water surface profile calculations for different culvert shapes, and calculating leap condition velocities (FishXing 2006). Bridge Scour Computations and Countermeasures Information from several states is summarized pertaining to bridge scour. Design scour depths could be reduced through new methods based upon the unconfined compressive strengths of the natural soils (Illinois DOT), advanced calculations on bridges in tidal waterways (Maryland SHA), rigorous hydrologic and hydraulic modeling (New Mexico DOT), detailed guidance for various bridge/culvert types (Texas DOT), and use of rock quality designation (Virginia DOT). New countermeasures used are standalone riprap installations, matrix riprap, geobags or geotextile containers (Minnesota DOT), elimination of the filter fabric wrap within the toe for easy maintenance and repair (Illinois DOT), inspection and asset management for critical structure determination (Maine DOT), and 3D sonar infrastructure mapping for rapid assessment (Minnesota DOT).

12 Highway Hydraulic Engineering State of Practice Illinois Illinois DOT conducted a research study on contraction and pier scour prediction in cohesive soils: Pier and Contraction Prediction in Cohesive Soils at Selected Bridge in Illinois (Illinois Center for Transportation, et al. 2010). One of the results was that calculated scour depths could sometimes be reduced based upon the unconfined compressive strengths of the natural soils. This information was used to produce adjustments to scour calculations now included in the Illinois DOT Bridge Manual (Illinois DOT 2012a). The reductions are only considered after a geotechnical analysis has been conducted and subsequently recommended on a case-by-case basis (Illinois DOT 2012a). Obvious benefits are the cost savings realized by the reduction in substructure costs (VanBebber 2019). Illinois DOT recently modified a revision to a scour countermeasure, standalone riprap instal- lation. These installations are used to protect slope walls that secure abutments, bridge piers, channel, or streambed revetment, etc. Recent research has eliminated the filter fabric wrap within the toe and now terminates at the lowest toe point. When failure of the riprap pro- tection occurs, the riprap can be easily repaired without the filter wrap (Illinois DOT 2012b). The revision is based upon the filter fabric guidance provided by the FHWA (Illinois DOT 2012b, VanBebber 2019). Maine Changes in precipitation and streamflow instituted the need for adaption policies that included scour-related goals of bridge inspections every 2 years and underwater scour Figure 2. Thunder Road fish barrier project (reprinted from U.S. Department of Agriculture [USDA] Natural Resource Conservation Service [NRCS] West Area Biologist Rachel Maggi, Thunder Road fish barrier project La Push, Washington, 2018).

Literature Review 13 inspections. Maine DOT evaluated over 350 bridges during 2007-08, and the scour-critical bridges were flagged as requiring flood monitoring or countermeasures (Maine DOT 2014). During the program, information such as water surface elevations, scour depths, and debris were collected. Maine DOT then completed several scour countermeasure projects in the 2013–2014 time frame. The projects in general were very challenging from an environmental and construct- ability perspective. During that time frame, Maine DOT was trying to rapidly reduce the number of scour-critical bridges in the inventory by funding many projects. The projects were on many single span bridges with concrete abutments which had exposed footings. Less scour-critical bridges now exist so there are currently fewer such projects (Myers 2019). Originally, some projects used precast concrete block mat applications, but they did not perform well so changes include designing a specific layout and final grade of the precast con- crete block mats. Additionally, larger blocks have been used for recent applications than had previously been used (Myers 2019). Pier scour countermeasures are usually riprap installation, and this approach continues to perform well. No changes to scour design practice have been made for new bridges (Myers 2019). Maryland Maryland SHA has a scour program for existing bridges, as outlined in Chapter 7 of the Manual for Hydrologic and Hydraulic Design, and also detailed instructions on scour calcula- tions, as outlined in Chapter 11 of the manual (Maryland SHA 2011, 2016). A key change in scour analysis was incorporation of the use of the two in-house programs: ABSCOUR 10 for scour evaluation and TIDEROUT (Kosicki 2019). The ABSCOUR 10 Pier Module incorporates HEC-18, but does not account for bed load material composition. Additionally, HEC-18 coarse bed pier scour is incorporated, but without spread footings and pile caps. Pier scour and debris, the pressure method, MDSHA abutment and contraction scour, bottomless culverts, erodible rock, design flood selection, and bridge foundation design criteria are also included (Maryland SHA 2016). Manual for Hydrologic and Hydraulic Design, Chapter 11, Appendix B: TIDEROUT2 specifies use of this software to perform scour calculations on bridges in tidal waterways. TIDEROUT2 can model scour in tidal basins up through upland watersheds and is particularly useful in scour estimation for older bridges that constrict waterways. TIDEROUT2 is user-friendly software that can model unsteady flow, potential storage benefits, and worst-case scour scenarios involving combinations of tidal flow and riverine hydrographs. Some limitations are that littoral drive or sediment transport and complex currents cannot be modeled. Also, local abutment and contrac- tion scour must be separately computed (Maryland SHA 2015). There is a learning curve for new users, but the method allows for quick and easy sensitivity studies. The inputs to the software should be based on full-scale hydraulic models, and coeffi- cients used should be input mindfully. Maryland DOT follows the FHWA guidance and does not account for any riprap protection while computing scour depths (Kosicki 2019). Minnesota Minnesota DOT is incorporating a new scour countermeasure called matrix riprap instal- lations for use at spill-through bridge abutments. Matrix riprap uses Class 5 riprap with grout placed in the riprap to glue the individual stones together, but not entirely filling the void space (Minnesota DOT 2015a). This option allows for smaller size riprap stones to be used as the grout provides increased shear resistance (Minnesota DOT 2015b). Minnesota DOT con- ducted laboratory experiments in a steep slope flume and also field experiments, with results

14 Highway Hydraulic Engineering State of Practice showing that matrix riprap can provide up to three times the shear strength of non-grouted riprap (Minnesota DOT 2015b). The grout penetrates the void spaces, connecting the stone contact points. Optimal fill for matrix riprap in the total void layer is 50%, where one-third of the bottom layer is filled and two-thirds remains in the top layer. Grout consistency is important and should be approximately 7 inches in a slump test so that it has the proper viscosity (i.e., it does not all remain in the top layer, nor does it all flow to the bottom). In lieu of the slump test and for more accurate results, Minnesota DOT uses the European Tapping Table spread before and after agitation. Grout place- ment is accomplished with a concrete pump truck with hose diameter of 2 to 3 inches; the hose operator will fill the riprap voids as specified above (Minnesota DOT 2015a). Use of geobags or geotextile containers are another countermeasure recently used by Minnesota DOT. Geobags consist of a geotextile filter bag that contains coarse aggregate (Minnesota DOT 2016). Geobags are placed next to bridge abutments with a clamshell. Geobags are approximately 4 ft wide x 4 ft long x 2 ft thick, weighing approximately 1900 lbs., and with 400 lbs. of fabric tensile strength as specified by Minnesota DOT 2511. Minnesota DOT 2511 specifies that a bag is filled with a coarse filter aggregate using a standing funnel and a loader, and then the open end is stapled (Minnesota DOT 2012). Additionally, Minnesota DOT is active in bridge monitoring technology, where 3D sonar is used to image underwater conditions to document defects for condition assessment. This technology is used in scour evaluation, construction pre-planning, flood damage assessment, and in diver safety applications (Minnesota DOT 2017c). New Mexico Previously, New Mexico DOT analyzed a limited number of bridges using the U.S. Geological Survey (USGS) 96-4310 Method for Rapid Estimate of Scour at Highway Bridges Based on Limited Site Data (USGS et al. 1997). New Mexico DOT recently addressed bridges where scour calculation and evaluations have not been made (FHWA 2001) and began evaluating them using the Rapid Scour Method (Level 1) (USGS et al. 1997). Based on the results of the Rapid Scour Method analysis, bridges were either reclassified as NBIS Item 113 ratings of 5, 7, or 8, where the bridge foundation was determined to be stable (USGS et al. 1997), or further analysis was performed. For those bridges requiring further analysis, more rigorous hydrology was devel- oped, and all bridges were analyzed using HEC-RAS and HEC-18 (Level 2). Some bridges were reclassified as scour-critical after the Level 2 analysis, and these bridges are being replaced or countermeasures designed and installed based on severity of risk, budget available, and schedule (Morgenstern 2019). This change was not a radical change in methodology used in engineering analysis but instead a change in management approach. New Mexico DOT is in compliance with the FHWA Metric 18 Inspection Procedures Scour Critical Bridges, has a much better understanding of the scour susceptibility or stability of an increased number of bridges, and has an understanding of where projects and funds are needed for scour mitigation (Morgenstern 2019). Texas The Texas DOT geotechnical manual update included updating the scour section with more detailed guidance for various bridge/culvert types. This helps improve consistency and qual- ity. This edition includes definitions of the following bridge/culvert types: new bridges with known foundations, existing bridges with known foundations, existing bridges with unknown foundations, bridge class culverts, and scour-critical bridges. Recommended methods for

Literature Review 15 performing scour analysis for the different bridge/culvert types are provided (Nuccitelli 2019, Texas DOT 2018a). HEC-18 is widely used, and scour calculations are performed using this guidance; however, calculations using this provide maximum depths and not allowable limits or critical depth thresholds for single scour components. The critical depth threshold is typically not the same as the maximum as provided by HEC-18 (FHWA 2012b). Texas Secondary Evaluation and Analysis for Scour (TSEAS) manual (Texas DOT 1993) provides maximum allowable depth for pier scour. A new study, Allowable Limit Contraction Scour and Abutment Scour at Bridges, is directed at determining maximum allowable scour depths for abutments related to potential abutment failure and contraction scour related to bridge pier failure (Texas DOT 2017, 2018b). Factors considered in these new criteria are soil slope, the support structure for the abutment deck, the supporting embankment for the access roadway, and embankment material geotechni- cal stability (Texas DOT 2017, 2018b). Virginia Virginia DOT has made three substantial changes to scour policy and practices, allowing inclusion of practical judgment and thus resulting in more shallow foundations for more cost- effective design practices. The changes include: 1. During the evaluation of the rock core barrel, material with a rock quality designation (RQD) of less than 50% can now be considered as granular material based on the contents to a max D50 of the core barrel. This allows Virginia DOT to account for the material resistance that is less than actual interlocked material but is greater than the overburden (Virginia DOT 2019c, USGS 2018, Matthews 2019). 2. When evaluating live bed scour conditions, Virginia DOT also uses clear water equations when available to assess the effects of the D50 of the material on the scour potential. This is especially helpful when the material is increasing in size with depth. If the clear water equa- tions indicate that a particle is too large to scour at a given depth, then this should be the limiting factor regardless of the results of the live bed equations. This approach works well when applying the change in material evaluations as stated above (Matthews 2019). 3. Based on guidance from FHWA HEC-18, Virginia DOT focuses on the NCHRP Project 24-20 “Abutment Scour Results Over HIRE and Froelich” (Matthews 2019). For scour counter- measures, Virginia DOT uses the riprap abutment guidance in HEC-23 but will adapt the apron as necessary to increase the thickness if the defined extents cannot be met (Matthews 2019). Virginia DOT is also participating in the FHWA field pilot study of the in-situ device for the determination of the clay shear resistance and hopes to adopt the shear force method soon (FHWA 2018c, Matthews 2019). West Virginia The West Virginia DOT drainage manual specifies that scour computations should be per- formed in accordance with HEC-18 (West Virginia DOT 2015). A change was made to adopt scour calculation methods presented in NCHRP Project 20-24. Using NCHRP 20-24 is more time consuming but provides more realistic scour predictions. The previous methods used by West Virginia DOT are those in HEC-RAS, so scour calculation time was short (Kirk 2019). Since West Virginia is primarily located on the backbone of the Appalachian Mountains, rock is relatively shallow, and scour is not a major problem unless the rock is erodible (Kirk 2019, West Virginia DOT 2019). In the case of erodible rock, a scour prediction technique has been developed based on foundation inspection, coring, measuring scour depths, rock-water interac- tion, and gage flow measurements to rate the rock on a scale developed for scour versus stream power (Keaton et al. 2012, FHWA/WVDOT 2010–2012).

16 Highway Hydraulic Engineering State of Practice Advanced Hydraulic Modeling State information available focused on 2D hydraulic modeling, as most states responding indi- cated little use of 1D unsteady, 3D steady/unsteady, or sediment transport modeling in policy or practice. New Mexico and Rhode Island indicated sediment transport capacity calculations were previously required, and California and Ohio indicated policy pending, but information regarding use of 2D or 3D modeling was not located. Well-known limitations of 1D models are that velocities are averaged over cross sections and flow is assumed normal to the cross section, which may lead to inaccurate representation of flow and velocity distributions (Pierce 2018). For example, Figure 3 shows velocity distributions depicted in a 2D model that are not normal to the cross section. 2D models are accepted by FEMA if the specified criteria are met (FEMA 2019). Decisions to change practice to 2D hydraulic modeling have involved evaluation of technical aspects, time requirements, available data, and experience (Gosselin et al. 2006). In 2D hydraulic models, the depth-averaged velocity and direction of flow are calculated at every point in the domain, thus avoiding many assumptions required by 1D models (Pierce 2018), specifically that variables (velocity, depth, etc.) change predominantly in one specified direction along the channel. Since channels are rarely straight, 2D hydraulic models allow for more accurate rep- resentation of water surface profiles (Wagner 2007), flow conditions (Gosselin et al. 2006), and contraction scour (Rossell and Ting 2013). Two-dimensional models may also provide more accurate hydraulic representation of bridge crossings, especially for natural channels, compound channels (well-defined channel with floodplains), bridges on a skew, and crossings with multiple openings in a wide floodplain. To overcome 2D modeling challenges, FHWA Everyday Counts initiatives include use of next-generation hydraulic applications to improve understanding of interactions between trans- portation assets and river environments (FHWA 2019). Many state DOTs have joined FHWA in this effort as FHWA has partnered in pilot projects and provided National Highway Institute Courses with free licenses for DOTs (Nguyen 2019). Many states are also acquiring statewide Light Detection and Ranging (LIDAR) data, which may help overcome challenges associated with limited or unreliable data (Delaware DOT 2017a, Carleson 2019). Colorado Colorado DOT uses 1D steady-state models, generally HEC-RAS, for most hydraulic studies due to lower complexity and less data requirements. The Colorado drainage manual states that 5.0 4.0 3.0 2.0 1.0 0.0 Vel_Mag_ft_p_s Figure 3. Velocity distributions depicted in a 2D model that are not normal to the cross section. Courtesy of Georgia DOT (2019).

Literature Review 17 steady and unsteady models may be applied to complicated hydraulic conditions such as large overbank bridge crossings, large variations in roughness, multiple channels, and islands, where 1D models may lead to costly or improper overdesigns (Colorado DOT 2009). Georgia Georgia DOT incorporated 2D modeling as policy because traditional 1D modeling would not have accurately represented hydraulic conditions in a number of important cases (Georgia DOT 2018b). These include locations with wide floodplains, skewed embankments, significant roughness, complex geometry and ineffective flow areas, and where more accurate flow patterns are necessary to design countermeasures. Accepted modeling software programs as outlined in the Georgia DOT Drainage Design for Highways Revision 3.4 are Surface Water Modeling System version 11.1.4 (SMS), Finite Element Surface Water Modeling System version 3.22 (FESWMS/FST2DH), and Surface Water Modeling System version 4.56 (RMA2), each with specific strengths. In general, these software programs provide a comprehensive hydrodynamic environment for 1D and 2D surface water models and finite-element hydrodynamic computa- tions of horizontal velocity and water surface elevations in open channels under subcritical flow regimes (Georgia DOT 2018a). Michigan To overcome difficulties and FEMA permit acceptance, Michigan DOT practices routinely include comparing water surface elevation results; for example, Michigan DOT is currently applying 1D HEC-RAS and SRH-2D via SMS in parallel for a culvert replacement project (Carleson 2019). This practice has gained enough traction in Michigan such that FEMA now accepts 2D hydraulic models in the state (Carleson 2019). New York New York State DOT generally uses HEC-RAS for most hydraulic studies, but the New York State Bridge Manual states that 2D hydraulic analysis can be performed using SMS at com- plicated locations, such as multiple-inlet tidal bays or condolences to more accurately model geometry (New York State DOT 2019). Texas Texas DOT completes a few models using 2D analysis. The current Texas drainage manual states that 2D modeling techniques are highly specialized and recommends contacting the Design Division’s Hydraulics Branch for consultation (Texas DOT 2016). However, Texas DOT has seen a significant increase in 2D modeling in the past few years and is developing new policy guidance for 2D modeling that is planned to be released in early 2020. Utah Utah DOT specifies that 1D or 2D models may be used for culverts conveying irrigation water or culverts located in a FEMA Special Flood Hazard Area (SFHA). Additionally, a 2D model must be used for bridge hydraulic analysis, or else a Deviation from Drainage Design Criteria form must be submitted when a 1D model is used instead of a 2D model. The request for devia- tion must specifically address how the channel will be accurately represented using 1D (Utah DOT 2018a). Vermont Vermont uses 1D steady-state models, generally HEC-RAS, for most hydraulic studies because of the lower data requirements and time constraints. Vermont recently conducted a

18 Highway Hydraulic Engineering State of Practice pooled fund study with the FHWA in which they identified more applicable models for unsteady tidal hydraulics and associated scour analysis: UNET, FESWMS-2D, and RMA2 (Vermont DOT 2017). Regulatory Requirements Regulatory requirements establish a process for consultation and compliance with one or more federal laws. These agreements allow for predictability for projects in addition to intro- ducing standards (Center for Environmental Excellence 2018). Federal laws include the NPDES and the NEPA. State highlights include memoranda of understanding for permits for projects disturbing more than 1 acre, along with required LID solutions for treatment of municipal separate storm sewer system discharge (MS4). LID minimizes negative environmental impacts when properties are developed and impervious surface area increases. LID is aimed at mimick- ing pre-development conditions through techniques such as bioretention, permeable pavement, and grass swales (Dietz 2007). LID typically focuses on controlling quantity not quality of water (Davis 2005); however, some Best Management Practices (BMPs) used in conjunction with LID treat both water quality and quantity while others target one specifically (Ohio DOT 2018). State Oversight for FHWA National Environmental Policy Act (NEPA) and Clean Water Act (CWA) Section 404 New York New York State DOT maintains erosion and sediment control under NEPA and CWA. All federally aided projects involving clearing, grubbing, grading, or excavation must have erosion control and require sediment control plans included in plans, specifications, and estimates. In New York State a memorandum of understanding for the State Pollutant Discharge Elimina- tion System (SPDES) General Permit covers development in which the excavation is more than 1 acre of non-Tribal Indian land. An EPA NPDES Construction General Permit is necessary if Tribal Indian lands of 1 acre or more are disturbed and involve a stormwater discharge to surface water. A project is not eligible for a SPDES general permit if 2 or more acres of land with no existing impervious cover are disturbed, the land is characterized as Soil Slope Phase E or F, or if the project is within watersheds of AA or AAs waterbodies; in these cases, the permitting is deferred to NPDES (New York State DOT 2018). Compliance with Local Floodplain Requirements Ohio Ohio DOT requires use of HEC-RAS to model conveyance showing artificial effects on flood- plain encroachments, with an allowable water surface surcharge (up to 1 ft) established as a means of floodplain management, in accordance with the National Flood Insurance Program (NFIP) rise allowance. Highways that encroach on floodplains require design to the 100-year flood event to minimize property damage. If construction occurs within a FEMA A Zone, an Ohio DOT self-permit process is required along with coordination with a Local Floodplain Coordinator who determines the allowable surcharge. The Local Floodplain Coordinator is the liaison between the NFIP and the Ohio Department of Natural Resources Floodplain Manage- ment Program (FMP) for work in a FEMA Special Flood Hazard Area (Ohio DOT 2018). Tennessee and Colorado Tennessee DOT includes an Executive Order for floodplain management to avoid long and short-term impacts of floodplain modification, as well as to restore and preserve values presented

Literature Review 19 by floodplains. This applies to federal buildings, structures, roads, or facilities impacting a flood- plain (Tennessee DOT 2012). A similar Floodplain Management Executive Order is in place in Colorado (Colorado DOT 2004). Utah FEMA requires a Floodplain Development Permit from local jurisdictions in Utah, along with obtaining a Conditional Letter of Map Revision causing any change to the base flood elevation (BFE) when a floodplain is encroached. This allows for documentation of a changing floodplain as well as any necessary revisions to a previous FEMA map. For channels, culverts, and bridges, coordination with a Floodplain Administrator is required for proper floodplain management (Utah DOT 2018b). Requirements for NPDES and Requirements for LID (e.g., bioretention, permeable pavement, etc.) Delaware Delaware DOT aims to maintain water quality and reduce non-point source pollution under NPDES using biofiltration swales, bioretention areas, infiltration ditches, and retention ponds. Examples of a biofiltration swale under construction and a completed biofiltration swale are shown in Figure 4. Delaware DOT uses multiple or redundant LID measures for increased reli- ability, and these measures include maximizing retention of native forest cover, use of natural topo- graphic features, creating a hydrologically rough landscape to slow stream flows, and increasing time of concentration (Delaware DOT 2008). Hawaii Effective as of 2013, Hawaii DOT incorporates LID solutions for treatment of MS4 per the EPA NPDES; updates in the DOT manual include and prioritize these practices. Swales, bio- retention, infiltration trenches, and engineered wetlands are required LID options to treat the water quality design volume (WQDV). Figure 5 shows an example of a bioretention pond under construction. Any new development or redevelopment is required to have LID stormwater man- agement if an acre or more of impervious surface is generated. However, circumstances arise when LID is impossible or unsafe to implement. These variances are based on hydrogeological, Figure 4. Biofiltration swale under construction is shown on the left and a completed biofiltration swale on the right. Reprinted from Wikimedia Commons. 2010.

20 Highway Hydraulic Engineering State of Practice physical, and operational constraints, and all solutions must be considered before a waiver is granted (Hawaii DOT 2015). Maryland Maryland DOT incorporates LID practices (Maryland DOT 2009). The 2009 Maryland Transportation Plan addresses environmental challenges through coordinating land use and transportation planning to promote “Smart Growth,” preserving natural resources, and sup- porting environmental initiatives to commit to environmental quality. These ideas are based on the Smart, Green and Growing initiative enacted by Maryland state legislation (Maryland DOT 2009). Virginia Virginia DOT also incorporates LID practices (Virginia DOT 2019c). In Virginia, LID solu- tions include preserving riparian buffers, wetlands, steep slopes, mature trees, floodplains, woodlands, and highly permeable soils (Virginia DOT 2019c). Requirements for National Pollutant Discharge Elimination System (NPDES) and Clean Water Act (CWA) Section 404 Alaska In October 2008, the Alaska Pollutant Discharge Elimination System program was imple- mented in a phased transition to assume primacy for NPDES permitting. The Alaska Depart- ment of Environmental Conservation became the stormwater permitting authority in Alaska; however, the EPA is still involved with permitting, compliance, and enforcement. Alaska DOT also requires use of BMPs such as detention ponds, treatment swales, temporary vegetative buffer strips, and vehicle tracking entrance/exit designs (Figure 6) to protect water quality. Alaska DOT regulates stormwater from MS4s, discharges from industrial activity, and stormwater from construction sites, with each permit type having different requirements under NPDES (Alaska DOT 2011). Figure 5. Leucaena leucocephala habitat and water retention basin, Waikapu-Maui. Reprinted from Wikimedia Commons. 2009.

Literature Review 21 California The Caltrans NPDES Statewide Stormwater Permit regulates stormwater and non-stormwater discharges from Caltrans properties. Construction must comply with a construction general permit, implement a year-round program to control discharges, and meet water quality stan- dards through BMPs such as biofiltration swales and strips, earthen berms, sand filters, and solids removal devices. Since 2013, projects in Caltrans’ right-of-way must also incorporate new post-construction stormwater treatment requirements. A separate NPDES permit is needed if discharge is anything other than stormwater (Caltrans 2017). Georgia The EPA administers CWA permitting in Georgia; however, individual and general NPDES permits are issued at the state level. A Notice of Intent (NOI) must be submitted to the Georgia Environmental Protection Division. There are three general permit types: Stand-alone Construc- tion Activity, Infrastructure Construction Sites, and Common Development Construction. These permits are reissued every 5 years, along with an NOI and an Erosion, Sedimentation, and Pol- lution Control plan. MS4 permitting requires consideration of LID and green infrastructure. Georgia considers water quality early in the design process and implements green infrastructure options that include grass channels in place of curb and gutter in rural sections, bioretention basins, open-graded friction course (substituted for conventional asphalt), and stormwater wetlands (Georgia DOT 2018a). Nebraska Nebraska Department of Roads (NDOR) is required by the FHWA to identify erosion and sediment-sensitive areas in addition to NPDES and erosion and sediment control plans for sites 1 acre or larger. MS4 permitting develops strategies to include a combination of structural and/or nonstructural treatment BMPs. A local public agency (LPA) is permitted as an MS4 and operates under its own NPDES, reviewed by the Nebraska Department of Environmental Quality and EPA. Any LPA stormwater program overrules a NDOR stormwater program except when an LPA project is being constructed on a state or federal highway in an MS4 area (NDOR 2013). Figure 6. Vehicle Tracking Schematic. Source: Created by Tetra Tech for the U.S. EPA and the Kentucky Division of Water.

22 Highway Hydraulic Engineering State of Practice As a part of the Clean Water Act, a Total Maximum Daily Load (TMDL) is created for pol- lutants impairing a given body of water. This includes a treatment standard to lower pollutant levels in all bodies of water entering the water of interest. Highways may have additional require- ments if stormwater discharges into waters of interest with a TMDL established. For LID solu- tions for excess stormwater, NDOR implements vegetated filter strips, grass swales, infiltration trenches, infiltration basins, bioretention, media filters, extended dry detention, wet detention ponds, stormwater wetlands, pervious pavements, proprietary structural treatment control, and other BMPs (NDOR 2013). Ohio Ohio DOT requires a one-page NOI application for NPDES projects. The application is a certification provided by the applicant that ensures compliance of NPDES. These projects are earth disturbances of >1.0 ft and are projects susceptible to stormwater erosion. A NOI or post- construction BMPs are not required for routine maintenance projects less than 5 acres. However, the Ohio EPA has designated certain watersheds that require NPDES permits post-construction BMPs and also groundwater recharge mitigation, riparian setback mitigation, and temporary sediment basin locations. Based on earth disturbing activities, post-construction BMPs for construction include extended detention, retention basin, bioretention cell, infiltration meth- ods, and constructed wetlands as necessary to provide stream protection. Additionally, post- construction BMPs for any non-routine maintenance activities are required to treat runoff when disturbed earth for a project is equal to or greater than 1 acre (Ohio DOT 2018). Pennsylvania NPDES Permitting, Monitoring, and Compliance discharges associated with industrial activity and discharge from storm sewers are included in the drainage manual under Commonwealth of Pennsylvania, Title 25, Chapter 92 (Pennsylvania DOT 2015). Tennessee and Colorado Both Tennessee DOT and Colorado DOT abide by a Nationwide General Permit granted by the USACE. This permit involves Section 404 of CWA, which states a federal permit must be obtained for any activity impacting water quality of U.S. waterways, along with a water quality certification from their respective environmental state departments (Colorado DOT 2004, Tennessee DOT 2012). Floodplain Impacts and Mitigation Floodplain impacts and mitigation pertain to the requirements an agency must meet in regard to improvements in the floodplain. Agencies compare existing conditions to FEMA recorded and modeled water surface elevations in FEMA regulatory floodways. Agencies must comply with published water surface elevations and/or zero rise. Several states have made changes to policy and practice regarding mitigation and no adverse impact/zero rise, as indicated by survey responses. Colorado In 2017 the Colorado DOT Region 4 Hydraulics Unit issued Standard Operating Procedures specifically for pavement treatment construction and maintenance activities in FEMA regulatory floodways. For crossing or contact with any regulatory floodway, Colorado DOT must apply for a floodplain permit from the local agency of governance. Conditions to be achieved with any development are “no rise” or no change in 100-year water surface elevation or BFE; otherwise,

Literature Review 23 a Letter of Map Change from Colorado DOT must be sent to the FEMA Flood Insurance Rate Map (FIRM) requesting a revision and certification (Colorado DOT 2017). Even though final certification for floodway mitigation of highway projects is ultimately at the discretion of FEMA, Colorado DOT Region 4 general procedures for impacts from pavement treatment construction and maintenance activities are aimed to simplify the required Colorado DOT certification for these less complex projects. Colorado DOT has Standards of Practice (SOPs) intended for the least complex activities for “no-rise” in Colorado DOT applications for FEMA certification. These activities include patching, pavement maintenance, and the majority of mill and overlay projects, and SOPs indicate the level of detail and time frame required for engineering and planning, thus leading to better understanding of the time frame for compli- ance. Additionally, Colorado DOT mentions that the SOPs are not an exhaustive list, and each project should be considered on a case-by-case basis (Colorado DOT 2017). Maryland The Maryland SHA recently revised procedures to combine separate MDE and FEMA hydrau- lics models so that only one application is necessary for acceptance. Previously, MDE would review and approve models separately from the FEMA model updates according to Letter of Map Revision (LOMR)/Conditional Letter of Map Revision (CLOMR) procedures. Addition- ally, the regulations were different—MDE allows water surface level increases of 0.10 ft on prop- erties that were insurable per FEMA, but FEMA regulations call for “no rise” or 0.00 ft increase in 100-year water surface level (Maryland SHA et al. 2017). To accomplish the joint effort, FEMA and the MDE first began creating a Digital FIRM (DFIRM) database using Geographic Informa- tion Systems (GIS) through a DFIRM Outreach Program, and now 75% of the FIRM maps are no more than 3 years old (Maryland SHA 2016; FEMA 2019). The new joint modeling process between the Maryland SHA and FEMA involved the Maryland SHA Office of Structures creating milestones and revising the Hydraulics and Hydrology Design Manual Chapter 5 in 2016 and again in 2017. Maryland SHA tested the updated procedure with a pilot project: Maryland Route 144 over Evitts Creek. For this project, Maryland SHA used a 2017 FEMA model and best available 2015 FEMA map, extended the model limits, and incorporated Maryland SHA cross sections. The Maryland SHA floodway was wider than the FEMA floodway, and the resulting proposed condi- tions model included the revisions from the MDE FEMA coordinator’s review (Maryland SHA et al. 2017). In summary, the Maryland SHA and FEMA integrated modeling follows the new FEMA/MDE CLOMR Process Flow Chart from the Office of Structures Hydraulics and Hydrology Design Manual Chapter 5, Figure 2, (Figure 7) and also revisions to the Maryland SHA Hydraulics Report Checklist (Maryland SHA 2017). Minnesota Minnesota DOT has a statewide flood mitigation program that requires completion of hydraulic flood analysis, floodplain assessment, and a risk assessment for encroachment design. The risk assessment for encroachment design collects and reports detailed information regard- ing flood damage to existing structures such as shopping centers, hospitals, chemical plants, power plants, and housing developments during 100-year (1% AE) and 500-year (0.2% AE) flood frequency events. Reporting seeks to find the value of structures and contents and aims to justify whether further analysis and possibly redesign is needed to minimize damage. Traffic- related losses in the form of annual capital costs are evaluated for the 100-year and 500-year flood frequency events. Embankment, roadway, and scour protection costs are weighed against additional culvert and bridge capacity costs (Minnesota DOT 2011a).

24 Highway Hydraulic Engineering State of Practice Figure 7. Integrated MDE/FEMA Submittal Process Flow Charts. Reprinted from Maryland SHA. 2017., Maryland Hydraulics Panel. 2017. http://gishydro.eng.umd.edu/hydraulics_panel/report_2018/Hydraulics_ Panel_Report_2018.pdf.

Literature Review 25 Additionally, Minnesota DOT has many ongoing flood mitigation projects across the state. One example is the Minnesota River Flood Mitigation Study initiated by Minnesota DOT to investigate feasible designs at river crossings in the Minnesota River Valley that minimize flood risk during seasonal flooding. This study involved stakeholder input, traffic analysis, historical floods and modeling, cost estimation, and alternatives analysis. Alternatives analysis was con- ducted and funding pursued by Minnesota DOT (2011b). Pennsylvania Pennsylvania DOT is conducting a multi-phase effort in order to prepare for the conse- quences of extreme weather for a resilient transportation system. Phase I Pennsylvania DOT Extreme Weather Vulnerability Study is the first step to prioritize funding needs. The study included historical risk assessment, vulnerability mapping and forecasting, development of a damage cost system, best practices, etc. The study also included analyzing impacts to the state road system during 1% annual chance or 100-year flooding impacts. In the last decade, $140 million emergency funds were allocated to repair damaged Pennsylvania DOT federal- aid infrastructure, roadways, and bridges, due to flooding from weather related events such as Hurricane Sandy. These events have severely affected the planned life cycle of the infrastructure (Pennsylvania DOT 2017). In the second part of the Phase I Pennsylvania DOT Extreme Weather Vulnerability Study, Pennsylvania DOT in conjunction with FHWA has selected projects to conduct adaption studies to evaluate impacts due to climate change. The projects will include hydrologic and hydraulic analysis with precipitation forecasts, design options for adaption, and economic analysis. Out- comes will include a detailed hydrologic and hydraulic analysis template for climate change impact inclusion in studies, case example review for strategies and cost effectiveness of adaption designs, and evaluation of precipitation data and flooding forecasts (Pennsylvania DOT 2017). Phase II Resilient Designs starts with two workgroups. One internal workgroup will manage design, maintenance, and construction, and the second will focus on traffic operations. Resilient designs will be multi-year, and implementation of some items will start 6 months or more after the initiation of Phase II and span for several years. Items will range from embankment loss pre- vention and pipe encapsulation using geotextiles to updating the Pennsylvania DOT hydraulics and hydrology manual. The manual updates will include USGS equations revised with current precipitation data and also any stream flow statistics updates. Modifications to bridge opening design will include provisions for no allowable backwater or 0.00 ft rise. Scour design modifica- tions will include evaluation of the 100-year and 500-year storm events. Foundations will be designed for the 100-year event, and 500-year stability will be checked. Culvert design is similar to bridge design, checked for the 100-year storm event and impacts downstream, with possible bridge opening increases of 20% suggested. Stabilization measures such as rock embankment slopes or interlocking block designs will be added (Pennsylvania DOT 2017). Coastal Hydraulics Shore protection along coastal zones that are subject to storm surge and wave attack can be a critical element in highway design, construction, and maintenance. State response to the survey was limited; however, several state hydraulic design and drainage manuals have sections dedicated to coastal shore protection. State coastal engineering practices include vulnerability assessments based on sea level rise projections, advanced coastal flood risk modeling, and assess- ment and design practices to elevate, harden, abandon, or apply nature-based solutions. Para- metric models have also been developed to determine design storm surge and wave parameters for computing surge/wave loads on bridge superstructures (e.g., OEI, Inc.). Solutions include practices to elevate, harden, or abandon, as well as nature-based solutions.

26 Highway Hydraulic Engineering State of Practice With the increased use of coastal hydrodynamic modeling by transportation engineering professionals, the FHWA issued a manual (Webb 2017) to provide guidance on the use of coastal models in the planning and design of coastal highways and bridges, as well as when to solicit the expertise of a coastal engineer. Specifically, the manual provides information needed to determine scopes of work, prepare requests for professional services, communicate with consultants, and evaluate modeling approaches and results. The manual also provides guidance on the use of hydraulic and hydrodynamic models, including how they are used to determine the dependence of bridge hydraulics on the riverine or coastal design flood events. Finally, the manual gives recommendations for the use of models in coastal vulnerability assessments (Webb 2017). Other emerging technologies promise to advance approaches for coastal flood protection. For example, Unmanned Aerial Vehicle-based remote sensing is being used to conduct high spatial and temporal resolution assessment of infrastructure conditions and mapping shoreline condi- tions. Shilling (2019) combined this approach with real-time kinematic geo-positioning systems (RTK-GPS) field measurements for multi-scale visualization of shoreline change due to sea level rise. Shilling (2019) also demonstrated high-resolution terrain-mapping methods for estimating coastal flood impacts on coastal infrastructure and adjacent ecosystems, and described how this information could be used to validate sea level rise models and inform adaptation planning for shoreline infrastructure. In addition to the recent FHWA manual on coastal hydrodynamic modeling, a revised ver- sion of FHWA’s HEC-25 Highways in the Coastal Environment is planned for publication later in 2019. California The Caltrans (2016) Hydraulic Design Manual has a chapter focusing on the procedures, methods, and materials commonly used to mitigate shoreline erosion and attendant damage to transportation facilities. The guidance focuses on quantifying exposure to sea level rise, storm surge, and wave action (i.e., design high water, wave height, and wave break). The manual pro- vides design guidance for various types of armor protection, including revetments (rock slope protection), bulkheads (concrete or masonry walls, crib walls, and sheet piling), sea walls, and groins. The manual also states, “The practice of coastal engineering is still much of an art . . . for a variety of reasons including that the physical processes are so complex, often too complex for adequate theoretical description, and the design level of risk is often high” (pp. 880–1), which indicates that additional research is needed (Caltrans 2016). Delaware Nature-based solutions include a range of natural vegetation and other landscape features that serve as alternatives to, or ecological enhancements of, traditional techniques for shoreline stabilization and infrastructure protection. Nature-based solutions have been used extensively in diverse coastal settings such as in SR1 rehabilitation in Delaware (FHWA 2018b). Under- standing green engineering tools and methods for designing nature-based solutions can achieve alternative solutions (FHWA 2018b, Webb et al. 2018) addresses these issues through examples of nature-based solutions, highlighting the best available science that describes their perfor- mance as solutions for coastal highway resilience. Further, an implementation guide is planned based on monitoring and peer exchanges and will address the issues outlined here for the use of nature-based solutions (Webb et al. 2018). Traditional construction includes existing gray coastal stabilization infrastructure and drainage systems subject to erosion, sedimentation, and clogging, such as those experienced along SR1. Adaptation projects or green infrastructure along SR1 included raising and reshaping the dunes,

Literature Review 27 preserving existing and creating additional marshes, and protecting the eroding shoreline using oyster reefs and oyster shell bags (Figure 8). Engineered features that mimic natural features include naturally occurring materials instead of concrete or rock revetments and riprap. These naturally occurring materials include coastal vegetation, dunes, wetlands, maritime forests, beaches, and reefs. Larger culverts, or additional culverts with tide gate systems at the outlets, may be installed to improve the drainage system capacity (FHWA 2018b). Implementing green stormwater infrastructure in coastal areas poses challenges. Property owner access during construction and planning for long-term access is a typical challenge. Lighter construction equipment and construction dewatering are often necessary due to work- ing with sensitive habitats (FHWA 2018b). In Glenville, Delaware, FEMA and the Delaware DOT came together with stakeholders to relocate 172 families whose homes were located in the 100-year floodplain and had been subject to repeated flooding events. This approach has multi-use benefits of restoring wetlands and habitat, providing recreational area, and expanding flood storage (FEMA 2011). Support pro- grams, such as shared development of the University of Delaware Institute for Public Adminis- tration (IPA)toolkit for community development and land use planning, can help stakeholders avoid building in flood prone areas. Additionally, Delaware DOT has completed projects with partners such as the Department of Natural Resources (DNR) to combat chronic flooding (Delaware DOT 2017b). Florida The US 98 project on Okaloosa Island in Florida focused on the vulnerability of the barrier island roadway to overwashing from sea level rise and storm surge. Specifically, the assessment evaluated a Florida DOT critical coastal roadway with a buried sheet pile wall and gabions installed along the shoulder as a countermeasure to reduce erosion from overwashing during storm events. Overwash and wave velocities that scour out the road shoulders and damage the pavement (referred to as the “weir-flow-damage mechanism”) is a common cause of storm damage to roadways that run parallel to the coast. The study concluded that the buried sheet pile and gabion mattress measure is an economic adaptation option (FHWA 2016b). Figure 8. Building oyster reef breakwater structures or castles. Reprinted from Wikimedia Commons. 2018.

28 Highway Hydraulic Engineering State of Practice Louisiana Sheppard et al. (2016) conducted a hindcasting analysis of 50 of the most severe storms that have impacted the Louisiana coast over the past 160 years, including hindcasting of alternative paths for a selection of storms. Extreme value analyses were then performed on water eleva- tions, wave heights and peak periods, and wind speeds to produce a GIS-based Wave and Surge Atlas for the design and protection of coastal bridges in South Louisiana. Other products of the study included developing an AASHTO Wave Load Calculation Program based on the AASHTO Guide Specifications (AASHTO 2008), providing a training session for Louisiana DOT and Development (DOTD) employees so that DOTD will be able to update or modify the program as needed. The study also allowed Louisiana DOTD to compute the forces and moments on the spans of bridges determined to be vulnerable. New York Tang et al. (2018) conducted a vulnerability study of coastal bridges in the New York City (NYC) metropolitan region to storm surges and waves. Predictions were made for potential surges, waves, and consequent hydrodynamic loading and scour at bridge piers under condi- tions of sea level rise and a change in hurricane patterns. Computer modeling of storm surges and waves in the greater NYC area during Hurricane Sandy compared reasonably with field observations. Study results indicated that both sea level rise and changing hurricane patterns could result in a significant increase in hydrodynamic load and scour at bridge piers, and such potential increases should be considered in the development of resilient coastlines. North Carolina The North Carolina DOT commissioned a study by Ocean Engineering International, PLLC (2013) to determine the design storm surge and wave parameters needed to compute the loads on bridge superstructures deemed vulnerable to coastal storms. To perform this analysis, 62 of the most severe tropical storms and hurricanes that have impacted North Carolina coastal waters over the past 160 years were hindcasted, and extreme value analyses were performed on water elevation, wave heights, and depth-averaged current velocities to obtain 1% annual exceed- ance design conditions. To increase the data set for the extreme value analyses, the hindcasted storm paths were shifted to the right and left of the actual path and the modified-path storms hindcasted, resulting in a total of 186 storm paths. The results from the extreme value analyses were presented in a GIS database for ease of access and use (Ocean Engineering International PLLC, 2013). Computation of the surge/wave loads on bridge superstructures requires knowledge of the superstructure type, dimensions, and span low chord elevation, as well as the design water eleva- tion and wave parameters. A proprietary computer model developed by OEA, Inc. produced the data for development of the parametric equations in the AASHTO code “Guide Specifications for Bridges Vulnerable to Coastal Storms,” which were used to compute the surge/wave loads on the bridge superstructures. Following a Level I screening analysis, 191 bridges were selected for evaluation, and 105 were classified as potentially vulnerable to these types of loads (Ocean Engineering International, PLLC 2013). Oregon The FHWA supported a study by Oregon DOT to analyze how green, or nature-based, infra- structure, could mitigate storm impacts and coastal bluff erosion along the Oregon Coast High- way. Building on prior Oregon DOT research on dynamic revetments (i.e., cobble beaches or berms), and incorporating lessons learned from similar projects, the study developed conceptual design plans for three high-risk sites. Further analysis of the preferred designs was conducted

Literature Review 29 and included protection against anticipated future coastal impacts, estimated construction and maintenance costs, and implementation benefits and challenges (Oregon DOT 2014, Oregon DOT 2016). Rhode Island Given uncertainties in long-term projections of sea level rise, a scenario-based approach is typically used. For example, the Rhode Island Statewide Planning Program (2015) used a GIS- based approach to analyze the exposure and vulnerability of transportation assets, including roads and bridges, under 1, 3, and 5 ft of sea level rise. The study, however, did not consider projections of erosion, storm surge, or precipitation. Also, it was noted that there may be inland areas affected by sea level rise that are not included in the projections, and high tide and sub- sequent sea level rise scenarios may be higher in inlets. At longer timescales, Knott et al. (2017) assessed the impacts of rising groundwater levels from sea level rise on the service life of coastal road pavements. Texas The current manual (Texas DOT 2016) does not provide specific design guidance for coastal flood protection. However, it directs the designer to determine the FEMA SFHA zone designa- tion with the current, correct FIRM. In Texas, zones V, VE (V1-30), A, and AE are coastal zones flooded by the Gulf of Mexico stormwaters rather than riverine flows. It is recognized that FEMA modeling for coastal zones is not the same as for riverine modeling. The designer is not required to acquire the model but is directed to consider tidal flows, wave action, and storm precipitation, as well as to ensure the project will not trap flood waters or block drainage (Texas DOT 2016). More extensive guidance for coastal hydraulics, including risk assessment, modeling, and design, is to be included in the next version of the manual. Washington Washington DOT conducts vulnerability assessments for infrastructure planning and miti- gation, accounting for sea level rise as a long-term trend that threatens coastal transportation infrastructure (Washington State DOT 2017a). Guidance addresses potential impacts of sea level rise, higher storm surge, and more frequent and extensive inundation of low-lying areas (both temporary and permanent), including the following: coastal erosion and landslides that weaken roadbed and bridge footings; damage to stormwater drainage and tide gates; saltwater corrosion of facilities; and detours around frequently flooded coastlines (Washington State DOT 2017a). Alternative Project Delivery Methods The aim of this section is to discover and document alternative delivery policy for the hydraulic engineering aspects of projects. Thirteen out of the 38 responding states have hydraulic policy in RFP documents to accommodate alternative project delivery methods, while three have policy pending. RFPs are the mechanism that states are using to specify hydraulics guidance via scope outline documents for alternative delivery method projects. Additionally, other alternative project delivery methods exist. For example, Maine DOT, Ohio DOT, Minnesota DOT, North Carolina DOT, and Tennessee DOT use design-build. Tennessee DOT, Utah DOT, and Washington State DOT also use Construction Manager/ General Contractor Projects. Ohio DOT uses Value-Based Design-Build and Least-Cost Design- Build, and Washington State DOT uses Design-Bid-Build. However, hydraulics policy for the Construction Manager/General Contractor was not located, and thus this section focuses on design-build hydraulics policy.

30 Highway Hydraulic Engineering State of Practice Maine Maine DOT uses the alternative project delivery methods of “Design-Build Projects” and “Construction Manager/General Contractor Projects.” The Design-Build Project flowchart that Maine DOT uses is shown in Figure 9. For the Design-Build Projects, the process starts with issuance of a Request for Statement of Interest (RFSOI) for selection of design-builders. Then the design-builders selected are invited to submit proposals via RFP for the project. The RFPs are expected to include specified design and construction parameters, which may change. For example, Maine DOT is currently in the RFP stage for the Hampden Bridge Bundle project, which includes design and construction of eight bridges. The Hampden Bridge Bundle project is illustrated here to gain an understand- ing of how hydraulic policy is imbedded into the design-build policy. Maine DOT issues the project documents, information available, and design criteria via the Internet site. The design criteria includes survey, plan and profile design, geotechnical, utilities, right-of-way, NEPA/ environmental permits, historical investigation, U.S. Coast Guard permits, Disadvantaged Business Enterprise goals, and on-the-job training requirements. The Hampden Bridge bundle criteria is as follows: • Eight durable bridges with minimal maintenance needs; • Cross sections consisting of two 12-ft travel lanes with a 6-ft inside shoulder and a 10-ft outside shoulder within the project limits, transitioning to the existing shoulders on the approaches; • Providing a minimum 0.5% longitudinal profile grade across the structures; Figure 9. Contract procurement process flow chart. Reprinted from George Macdougall, PE, Contracts and Specifications Engineer, Maine DOT. Feb. 26, 2019.

Literature Review 31 • Locating the new bridge in the same location as the existing bridge; • Demolition and removal of the existing steel girder bridges; • In-water pier construction; • Design speed of 70 mph; • On-site maintenance of two lanes of interstate traffic in each direction at all times; • Approaches to tie as quickly as possible into the existing interstate alignment; • Net zero impact to the FEMA 500-year and 100-year floodplains; • Design speed of 55 mph for temporary works during construction; and • Cross sections consisting of two 12-ft travel lanes and two 2-ft shoulders for each direction during construction (Maine DOT 2019a, 2019b, 2019c). In the Hampden Bridge Bundle project, three of the structures span waterways. A Draft Hydrology, Hydraulics, and Scour Report is issued in the RFP Project Documents containing information for proposed structures as modeled and hydraulic requirements. Among other criteria, key personnel must contain a hydraulics/scour engineer with demonstrated experience in Maine DOT hydrologic and hydraulic analysis policies and practices (Maine DOT 2019a, 2019b, 2019c). Additional RFPs are issued for sub-proposals for other separate contract items; a specific sub- contract in this project is for automatic traffic control. A meeting is held and the question period is extended with the invited design-builders and Maine DOT. The Technical and Price Proposal Packages are submitted, Maine DOT issues a Notification of Technical Proposal Responsive- ness, and then the guaranty package is submitted by the design-builders. Maine DOT awards the contract based on price (Maine DOT 2019a, 2019b). Additionally, Maine DOT issues an $80,000 stipend to each design-builder who submits a proposal, and if the particular design-build contractor is not selected and agrees, ownership of the proposal would be transferred to the department upon agreement with the design-builder for use in the project. The design-build contractor may refuse (Maine DOT 2019b). Minnesota Minnesota DOT uses low-bid design-build and design-build best value. Like Maine DOT and Ohio DOT, Minnesota DOT provides the scope using a scope book methodology, in which different parts of the scope are contained in each book. These scope books follow the Minnesota DOT Design-Build Manual Section 4 templated outline. The scope as defined in Section 4: RFP outlines that standards, manuals, technical memorandums, standard specifications, and special provisions must be used on the project (Minnesota DOT 2017a). The drainage scope will be completed specifically by Minnesota DOT following the Minnesota DOT RFP template Book 2 Section 12: Drainage, along with hydraulic and drainage policies and procedures, and then the Minnesota DOT Design Build Program Manager will issue the RFP. The drainage scope is outlined in the Minnesota DOT RFP template Book 2 Section 12 summarized as follows: This section identifies the design and construction requirements associated with temporary and per- manent drainage, including culverts, storm sewer systems, bridge hydraulics, roadway ditches, perma- nent and temporary erosion and sediment control, structural pollution control devices, stormwater ponds, and infiltration/filtration features (Minnesota DOT 2017b). Section 12 lists in detail the complete drainage scope outline, and Section 12.1 lists the specific Minnesota DOT policies, including hydraulic and drainage policies and procedures, that must be followed. The design-build contractors are responsible for addressing all project specific items in proposals and in the design and construction (Minnesota DOT 2017a).

32 Highway Hydraulic Engineering State of Practice North Carolina The North Carolina DOT design-build program and submittal process was developed for expedited review with emphasis on project safety; ensuring environmental compliance, national, and state manuals and code requirements are met; and that RFP requirements are fulfilled. North Carolina DOT hydraulics policy is clearly defined in North Carolina DOT Design-Build Submittal Guidelines (North Carolina DOT 2009). North Carolina DOT scopes the project and may provide a culvert or bridge report as neces- sary per the project, depending on the contract with the Design-Build Team. Unless transferred to the Design-Build Team in the scope documents, FEMA compliance documents are trans- ferred upon receipt and review by North Carolina DOT. The North Carolina DOT Hydraulics Unit reviews permit application packages and the Design Build Team is responsible for designs in compliance with permits (North Carolina DOT 2009). North Carolina DOT conducts several plan reviews, including review by the North Carolina DOT Hydraulics Unit. The Design-Build Team is required to provide Release for Construction Plans (RFC), which North Carolina DOT agrees is the final plan set, with the only exception being the erosion control plans. The RFC contains the final roadway drainage design that has been accepted as final by North Carolina DOT. The RFC Erosion Control plans are submitted after the drainage design is accepted in the RFC and modifications are acceptable in the Design- Build process (North Carolina DOT 2009). Ohio Similarly, Ohio DOT has been using a design-build process in which hydraulic design is spe- cific for the project and the delivery type (Ohio DOT 2009a). Ohio DOT outlines specific project selection considerations in which a project is eligible for the design-build process. Among other considerations, the project must have a defined scope by Ohio DOT according to the Ohio DOT Design-Build Manual and Instructions for Completing the Scope of Services Form (Ohio DOT 2009a). For example, hydraulic considerations that are necessary for waterway permits must be determined prior to scope approval. For example, if a USACE Nationwide Permit is required, the permit must be obtained prior to and included in the Scope of Services provided by Ohio DOT (Ohio DOT 2009a). The drainage requirements for any project are scoped by Ohio DOT Design-Build Manual and Instructions for Completing the Scope of Services Form (Ohio DOT 2009a) by providing information per the applicable items using the following outline: 14.5 Drainage a. Address mainline, side roads and ramps. b. Retain existing system? c. Specify clean out or repairs needed. d. New open or closed drainage system? e. Raise catch basins, inlets and manholes to accommodate resurfacing or feather pavement? f. Catch basins or sodded flumes for bridge drainage? g. County Engineer flow line approvals? h. FEMA approvals? i. COE/EPA approvals? j. Additional right of way required at culverts? k. Can existing drainage conduits be reused if there is not a conflict with new construction? l. Will new headwalls be required for existing drainage conduits? m. Is there any intent to address possible drainage problems outside the toe of the embankment? n. If new underdrain runs are required, are there any ROW restraints for ditches? Would a closed system be required for outlets? Note: indicate that additional ROW acquisition is not allowed.

Literature Review 33 o. Post-construction stormwater Best Management Practices (BMP) according to Ohio DOT Location and Design Manual (Ohio DOT 2009a). In addition, hydraulic requirements are scoped by providing information as follows: a. ODOT shall determine if a flood hazard evaluation is necessary. b. Be aware that a decrease in the waterway opening must be carefully considered. In a designated Flood Insurance Area, generally a decrease in the waterway opening is not acceptable (Ohio DOT 2019a). The project is scoped by Ohio DOT for value-based design-build reconstruction projects and within the scope permits, environmental commitments, and hydraulic design of storm sewers is scoped. The Ohio DOT Construction and Material Specification Book specifies that the design- build team (DBT) provide engineering, design, and detailed construction plans for the project (Ohio DOT 2009b). The final design is the responsibility of the DBT, but Ohio DOT will identify project limits and also transfer any hydraulic or FEMA study to the DBT in the scope documents (Kahlig 2019). Typically, Ohio DOT will acquire floodplain and other associated hydraulic permits, but the FEMA floodplain risk and permit risks are assigned to the DBT on some proj- ects, e.g., if “no rise” is allowed (Kahlig 2019). An example of such scoping is the Ohio DOT I-71/I-670 Interchange project, for which the DBT is required to obtain Ohio EPA NPDES permits and is responsible for compliance (Ohio DOT 2011). Additionally, Environmental Commitments are included in the scope and are the responsi- bility of the DBT, for example: FEMA Flood Insurance Program: DBT shall submit a letter identifying any temporary or permanent impacts to the floodplain to the Department. Existing hydrology reports and information pertaining to existing sewers are included in the scope and transferred to the design-build team (Ohio DOT 2011). Tennessee Tennessee DOT uses Design-Build and CM/GC alternative contracting methods. Tennessee DOT provides a Request for Qualifications (RFQ), scopes the project, then follows the same bridge and hydraulic design policy and practice regardless of whether traditional or alterna- tive project delivery methods are used. For example in the project US 64 over the Ocoee River, Tennessee DOT provided all existing bridge plans, HEC-RAS files, and preliminary bridge layout. Engineering design and construction for Design-Build drainage are paid for in one lump sum. For Design-Build, Tennessee DOT provides scope books similar to Minnesota DOT (Tennessee DOT 2019b). In 2013, Tennessee DOT used the Construction Manager/General Contractor (CM/GC) Services Pilot Program on three projects that included at least 12 bridges on interstates. The first project allowed Tennessee DOT to obtain feedback on all project aspects, reduce risk, and improve constructability (Tennessee DOT 2019a). The proposal contract for Interstate I-240 Overhead Bridges at Norfolk Southern R/R, SR 57 (Poplar Ave. EB and WB) and Park Ave. in Shelby County, Tennessee, states that proposed structures will follow drainage requirements as specified in detail in the proposal contract (Tennessee DOT 2019c). Additionally, the proposal contract includes a required list of solutions for the CM/GC to explain certain project aspects such as management of drainage from the bridge, roadway, and during temporary construction. The CM/GC is responsible for obtaining all permits unless provided in the proposal contract (Tennessee DOT 2019c). Drainage calculations and plans must be submitted during Preliminary Engineering for approval as specified in the proposal contract at various completion milestones: concept, 30%, 60%, right of way, and 100% (Tennessee DOT 2019c).

34 Highway Hydraulic Engineering State of Practice Utah Utah DOT uses Design-Build and CM/GC alternative contracting methods. The schedules for documents are set using a Microsoft Project template. The Utah DOT Best Value Design- Build Selection Manual of Instruction (Utah DOT 2017) is similar to the Maine DOT process. Utah DOT stores all design-build templates including LOI, RFQ, and scope documents on Google Drive; the scope document for drainage is in Chapter 4 of the manual and includes a 17-page outline of detailed drainage design (Utah DOT 2019). Utah DOT construction manager-general contractor templates appear to be located in the same website but the link is under construction (Utah DOT 2019). Washington State Washington State DOT uses Design-Build, Design-Bid-Build, and CM/GC alternative contracting methods. The Design-Build Manual specifies that supplemental hydraulics and stormwater requirements be defined in RFP Technical Requirements and that hydraulic analysis must be completed for a design-build project. The manual also specifies that the templated RFP Section 2.14: Hydraulics clearly defines design and construction requirements using the Washington State DOT Highway Runoff Manual, M 31-16 and Washington State DOT Hydraulics Manual, M 23-03. The RFP is project-specific (Washington State DOT 2018).

The TRB National Cooperative Highway Research Program's NCHRP Synthesis 551: Highway Hydraulic Engineering State of Practice documents significant changes in highway hydraulic engineering practices implemented by state departments of transportation (DOTs) over the past decade.

The synthesis focuses on eight subtopics of highway hydraulic engineering: roadway drainage; culvert aquatic organism passage; bridge scour computations and countermeasures; advanced hydraulic modeling; regulatory requirements; floodplain impacts and mitigation; coastal hydraulics; and alternative project delivery methods.

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Modelling and Simulation of Automated Hydraulic Press Brake

• Conference paper
• Open Access
• First Online: 13 October 2022
• Cite this conference paper

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• Ilesanmi Daniyan   ORCID: orcid.org/0000-0002-7238-9823 12 ,
• Khumbulani Mpofu   ORCID: orcid.org/0000-0003-3429-7677 12 ,
• Bankole Oladapo   ORCID: orcid.org/0000-0003-1731-9117 13 &
• Rufus Ajetomobi 14  

Part of the book series: Lecture Notes in Mechanical Engineering ((LNME))

Included in the following conference series:

• International Conference on Flexible Automation and Intelligent Manufacturing

8520 Accesses

In this study, a reconfigurable hydraulic press brake was designed using Solidworks and simulated on a hydraulic Automation Studio Fluidsim. The designed press brake comprises of the frame balance, conveyor rollers and support, belt, chuck, six hydraulic cylinders assembled with bolts and nuts. The buckling force was determined analytically and compared with the Finite Element Analysis (FEA) simulation to prevent distortion of length and section. The Von mises stress theory was used to determine the stress, resultant load and displacement. The results obtained from the FEA simulation were compared with the mechanical properties of the hydraulic press brake. The maximum stress induced is significantly lower than the tensile strength of the hydraulic press brake. Hence, the stress induced due to bending cannot cause the cast alloy to yield. Also, the buckling force significantly exceeds the resultant force giving no chances for buckling. The designed hydraulic press brake is flexible enough to control using hydraulic cylinders and enhances sufficient strength and rigidity during clamping and loading conditions.

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Design, simulation and experimental investigation of a novel reconfigurable assembly fixture for press brakes

The Influence of Loading Conditions on the Static Coefficient of Friction: A Study on Brake Creep Groan

A finite element analysis (fea) approach to simulate the coefficient of friction of a brake system starting from material friction characterization.

• Buckling force
• Hydraulic cylinder
• Press brake

1 Introduction

According to Thomas et al. [ 1 ], a hydraulic press is a machine press which uses hydraulic cylinder to generate a compressive force to perform various pressing operations such as metal forging, punching, stamping, etc. The press provides an efficient means of pushing and pulling, rotating, thrusting and controlling load [ 2 , 3 ]. Some hydraulic press applications include compression moulding, injection moulding, drawing, forging, blanking, coining, clamping, compacting, Forming, pad forming, potting, punching, and stacking, bending, stamping and trimming [ 4 , 5 ]. The use of hydraulic cylinders for controls boasts of cost-effectiveness, high rate of production, positive response to changes, ease of control of parameters and primarily suitable when a heavy workpiece is to be machined [ 3 , 6 , 7 ]. Other advantages include tonnage adjustment and cycle time maximisation [ 8 , 9 ]. According to Maneetham and Afzulpurkar [ 10 ], Hydraulic Servo Systems (HSS) have been used in many modern industrial applications by their small size to power ratios and their ability to apply considerable force and torque.

On the other hand, by using a simulation model for hydraulic systems, the dynamic performance of these systems may be validated in the absence of actual hardware, which is accomplished via the use of specialised modelling and simulation tools [ 11 , 12 , 13 , 14 ]. In addition, the bending forces and moment can easily be predicted using simulation tools to determine the magnitude of stain, buckling and distortion [ 15 , 16 , 17 ]. This will enhance the use of hydraulic cylinders with sufficient clamping force that ensures adequate strength without distortion. This study aims to design a reconfigurable press brake assembly with hydraulic cylinders for holding a workpiece and adjusting the ram height during machining operations on a press brake. This is to enhance adequate clamping and precision during manufacturing operations. Despite productivity gains achieved through automation of design routines and manufacturing tasks, the authors Kumar et al. [ 18 ] and Ulah et al. [ 19 ] report that nearly 85% of all fixture processes and design plans are still performed manually, and detailed optimisation plans are rarely created. The interchangeability of parts is critical to the successful operation of any mass production facility because it allows for quick assembly and lower unit costs. Mass production methods demand fast and easy positioning for accurate operations [ 20 , 21 ]. When designing jigs and fixtures, the strength of the clamp should be sufficient to hold the workpiece firmly in place and to withstand the strain of the cutting tool without springing [ 22 , 23 ]. When producing large quantities of different materials on a large scale, a significant amount of time is spent setting up the device and clamping it [ 24 , 25 ]. According to Pachbhai and Raut [ 26 ] as well as Daniyan et al. [ 27 ], hydraulic cylinders instead of manual adjustment are characterised by quick and automatic adjustment, greater accuracy, high productivity, consistent performance clamping force, and repeatable clamp location. Computer-aided design, modelling, and simulation tools have been used to improve the development of fixtures. For instance, Ruksar et al. [ 28 ] carried out the FEA and optimisation of machine fixtures, while Wang [ 29 ] applied a polynomial fit-based simulation method in a hydraulic actuator control system. Shrikant and Raut [ 30 ] employed computer-aided design for fixture development. It is necessary to reconfigure existing machines to have efficient work holding capacity to increase overall productivity, location accuracy, and surface finish quality of the finished product. The study aims to design the locating, supporting and clamping methods for a reconfigurable press brake using hydraulic controls.

2 Methodology

This paper proposes a six-cylinder automated hydraulic brake press. The press brake is constructed with a balanced frame, conveyor rollers and support, belt, chuck, and six hydraulic cylinders that are bolted and nutted together. Solidworks was used to design and model the fixture. According to Khurmi and Gupta [ 31 ], the maximum distortion energy theory for yielding is expressed as Eq.  1 .

where: σt 1 is the maximum principal stress (N/m 2 ); σt 2 is the minimum principal stress (N/m 2 ), and σy t is the stress at yield point (N/m 2 ); F.S is the factor of safety. The maximum and minimum principal stress calculated from Von mises stress analysis is given as 2.39365 × 10 5  N/m 2 and 5.44655 × 10 7 N/m 2 respectively. The volumetric parameters for the entire model are given as mass: 442.634 kg, volume: 0.056748 m 3 , density: 7800 kg/m 3 , and weight: 4337.82 N. Buckling is a possibility in the lower beam, which is the area where the fixture is loaded. The analytical results are compared to those obtained from the FEA simulation to determine the likelihood of buckling. With a length of 150 mm, the support for the tested section flexural rigidity equals 6.6 × 10 –6 . Nm −2 . This is calculated as the modulus of elasticity and moment of inertia for the section under consideration. As a result, the buckling force is represented by Eq.  2 .

F b is the buckling force (N), EI is the flexural rigidity 6.6 × 10 6 Nm −2 , and L c is the effective length (m). Since both ends are pinned, the effective length equals the actual length. Hence,

The model of the designed fixture assembly and the assembly drawing are shown in Fig.  1 .

The model assembly drawing of the fixture.

From Eq.  2 , the buckling force is calculated as 2.8958 × 10 9  N. Due to the fact that the section only has to support a resultant load of 499.716 N, the buckling force exceeds the resultant force, thus, giving no chances for buckling. The design was based on the maximum tonnage of the press brake, which is determined by the material type, thickness, length, and method of bending and clamping. When performing Von Mises stress analysis, failure or yielding occurs at a point in a member where the distortion strain energy is most significant [ 31 , 32 ]. Furthermore, according to the results of a simple tension test, the shear strain energy per unit volume in a bi-axial stress system reaches the limiting distortion energy at the yield point per unit volume at the yield point.

The area of the piston is expressed by Eq.  4 .

where ‘D’ is the internal diameter of the piston-cylinder (m). The stress-induced is expressed by Eq.  5 .

‘F’ is the force applied (N), and ‘A’ is the piston cross-sectional area (m 2 ). Introducing the maximum stress given as 2.47903 × 10 5  N/m 2 , reaction force 69.4426 N calculated from Von mises stress analysis and cross-sectional area calculated from Eq.  2 as 0.7854 d 2 m 2 into Eq.  3 ; we have

Using a safety factor of 2 and correcting to the nearest standard size, the piston diameter is calculated as 40 mm; therefore, the area is calculated as

The piston will be subjected to shear stress; hence its thickness should be sufficient to resist failure by shearing. The minimum thickness of the piston required to resist shearing is given by Eq.  6 .

where: d is the internal diameter of the piston-cylinder is 0.04 m, σ is the maximum allowable stress (7.23826 × 10 8  N/m 2 ) and ρ is the pressure in the cylinder (2.47903 × 10 5  N/m 2 ), and thickness is calculated as 0.006849 m. Using a safety factor of 2, the thickness is calculated as 0.015 m to the nearest standard thickness. The volumetric properties of the hydraulic cylinder are as follow; mass: 0.618573kg; volume: 8.03342e-005 m 3 ; density: 7700 kg/m 3 and weight: 6.06202 N.

2.1 Computer Aided Modelling and Simulation

The modelling and simulation for the two components under investigation (hydraulic cylinder and assembly fixture) were carried out in the Solidworks 2018 environment. The study type is to investigate the stress, displacement and strain of the hydraulic cylinder and fixture analysis. The the linear elastic isotropic model type and the Von mises failure criterion was used to determine the stresses induced in the component member, resultant loads and the corresponding displacements. The general standard static analysis of the finite element modelling was set up for the model analysis. From the material database, the mechanical properties of the materials selected for the hydraulic cylinder and assembly fixture (stainless steel 304 and cast alloy steel, ASTM A216) were selected. This was followed by the free body model of the components and the assignment of the loading conditions vis-à-vis the service requirements. Next is the dicretisation of the model. This is to mesh the developed models into finite elements and the application of the mesh control. The properties of stainless steel 304 employed for the design of the hydraulic cylinder are presented in Table  1  while Table 2  presents the mechanical properties of the cast alloy steel employed for the design of the fixture model.

The linear elastic isotropic model type was selected and the Von mises failure criterion was employed for the failure analysis. A mesh size of 2 mm was employed in the Solidworks environment to mesh model into finite elements.

Using a mesh interval of 0.2 mm, it was observed that the computational time decreases with an increase in the mesh size up to 2.0 mm for the hydraulic cylinder. Further increase in the mesh size up to 2.6 mm resulted in a slight increase in the computational time. Hence, the mesh size of 2.0 mm which produced the least computational time (152 s) was selected for the hydraulic cylinder. For the fixture, it was observed that the computational time decreases with an increase in the mesh size up to 2.2 mm. Further increase in the mesh size up to 2.6 mm resulted in a slight increase in the computational time. Hence, the mesh size of 2.0 mm which produced the least computational time (367 s) was selected for the fixture (Fig. 2 ).

The mesh time and the corresponding computational time.

2.2 Model Control of Triplet Cylinder

The category of the technical properties used to control the component variables can be assigned to other variables in the “read” or “write” mode for sending or receiving control signals. The driving force is an assignable variable to apply a driving force to the component. If there is not enough pressure, this force will drive the rod-piston assembly. The curve defining the external driving force is expressed in terms of the percentage of the cylinder position. From 0% to100%, the force is applied during the extension of the cylinder until the cylinder reaches the end of its stroke. Once the end of stroke is reached, the curve used will be in the −100% to 0% quadrant. Between 0% and 100%, if the read value is positive and there is not enough pressure to oppose, the rod-piston assembly will retract; inversely, but if the force is opposing, it will extend. Between −100% and 0%, if the value of the force is positive and there is not enough negative pressure, the piston-rod assembly will retract and extend if negative. This curve is of null value by default—external mass assignment variable of mass to allow the dynamic change of the mass during simulation. The default unit of the variable is the kilogram. The resistive force assignable variable is to apply a resistive force to the component. This force is resistive and will oppose the displacement of the piston-rod assembly. The curve that defines this force is expressed in terms of the percentage of the cylinder position. When the cylinder is extending, the curve is read in the 0–100% quadrant; inversely, the force will be read between −100 to 0% quadrant when the cylinder retracts. The value of this force can only be positive by convention. Figure  3 presents the mechanical working principles of the double-acting triplet cylinder.

Mechanical working principles of the double-acting triplet cylinder.

2.3 The Operational Model of the Triplet Cylinder

The hydraulic press brake utilises mechanically connected cylinders that operate in parallel. Linear actuators are devices that convert fluid energy to mechanical energy. As the name implies, the linear actuators will deliver the powers straight. In fluid power systems, linear actuators are often available with various components attached to the end of the rod. Mechanical linkage, levers or cables can be attached to the cylinder to transform the force in the type of movement wanted—technical modelling category of the properties that affect the components simulation model. The drop-down list options allow to edit other parameters or enable/disable the performance curve modelling. For the operating condition, the category of the properties relates to the components operating conditions, especially those that describe its operation limits. Most of these properties assess a faulty component and automatically trigger a failure, thus, activating the respective simulation option as “Automatic Failures”. The maximum force that can be applied to the component, or the maximum force range that the directional valve command can apply in proportional operation mode can be selected. The maximum pressure supported by the component supposes the option Monitor Faulty Components is activated in the simulation options. In that case, a visual warning will be displayed next to the component to inform the user that the value is exceeded during the simulation. If the option “Automatic Failure Trigger” is activated in the troubleshooting branch, the user will trigger a failure when this maximum value is reached during simulation. The failure must first be declared and selected, which will only be triggered with this property. The maximum distance travelled by piston per unit time is the distance moved by the piston from one end of the cylinder to the other end. Suppose the option “Monitor Faulty Components” is activated in the simulation options, a visual warning will be displayed next to a component to inform user that the value is exceeded during simulation. If the option “Automatic Failure Trigger” is activated in the troubleshooting branch, the user will trigger a failure when this maximum value is reached during simulation. The failure must first be declared and selected. It will then only be triggered with this property.

Figure  4 shows the model design of the automatic and manually operated triple cylinders.

Model design of the automatic and manually operated triple cylinders.

3 Results and Discussion

The result of the simulation of the hydraulic cylinder using Solidworks and the linear elastic isotropic model type and the Von mises failure criterion is presented in Tables 3  and 4  as well as Fig.  5 . While Table 3  summarises the reaction forces and moments, Table 4  and Fig.  5 present the strain, stress and displacement analysis. The resultant force from Table is 69.4426 N with the highest reaction experienced along the vertical axis (Y-axis).

It can be seen in Table 4  that the deformation per unit length is negligible, if not completely non-existent. It indicates that the clamping force is sufficient to prevent distortion in this particular instance. Furthermore, the stress-induced is minimal, and the cylinder will not yield to the applied force due to this stress.

(a) Strain analysis of the hydraulic cylinder (b) Von mises stress analysis of the hydraulic cylinder (c) Displacement analysis.

Figure  5 (b) shows the modelling result of the stress-induced in the hydraulic cylinder due to machining. The maximum stress induced is 2.47903 × 10 5  N/m 2 while the minimum is 4.48733 × 10 –7  N/m 2 . From Fig.  5 (c), the maximum relative displacement of the cylinder from its mean position is 0.000114313 mm. Comparing the magnitude of the maximum stress induced in the cylinder to the yield strength of the material (2.40 × 10 8  N/m 2 ), then it can be concluded that the material is not likely to fail under the required service condition.

Table 5  presents the summary of the reaction forces and moments for the fixture. The resultant reaction force obtained from Solidworks simulation is 499.716 N. This force is insufficient to produce any bending as the resultant bending moment is zero.

The summary of results of the simulations for the strain, stress and displacement analyses are presented in Table 6  and Fig.  6 for the fixture. The maximum and minimum strains were found to be 5.58621 × 10 –7 and 2.26322 × 10 –16 respectively. Both are negligibly insignificant. In this case, the fixture orientation does not change significantly while the bending operation is being performed.

From Fig.  6 a the maximum strain is 5.5862 × 10 –7 while the minimum is 2.2633 × 10 –16 . For the entire fixture model, the maximum stress induced is 2.26322 × 10 5  N/m 2 while the minimum is 5.44655 × 10 –7  N/m 2 (Fig.  6 b). From Fig.  6 c, the maximum relative displacement of the cylinder from its mean position is 8.77685 mm. As shown in Fig.  6 c, the front beam has a larger displacement while the beam along the neutral plane has a smaller displacement. This is due to the fact that at the neutral plane, the beam is not under the influence of any stress either compressional or tensional stress. The Von Mises analysis also revealed that the maximum and minimum stress-induced are 2.394 × 10 3  N/m 2 and 5.447 × 10 –7  N/m 2 respectively. The maximum stress induced is lower than the yield strength (5.56 × 10 8  N/m 2 ) of the cast alloy from which the fixture was designed (ASTM A216). As a result, the stress induced by bending may not cause the cast alloy to yield. The tensile strength is also sufficient to withstand bending forces without displacement or distortion as the maximum value of displacement is 8.77695 mm.

(a) Strain analysis of the entire fixture (b) Stress analysis of the entire fixture (c) Displacement analysis of the entire fixture

Figure  7 shows the hydraulic circuit comprising a configurable 3/n way valve with three connections and negligible hydraulic resistance and the 4/n way valve with four connections. It also comprises a double-acting cylinder with a shock absorber at the stroke end. The connected pressure loads control the cylinder piston while the shock absorber can be adjusted using two adjustable screws. The piston of the cylinders contains a permanent solenoid that can be used to operate a proximity switch. The diameter of the piston is 20 mm with a maximum stroke length of 200 mm. The tank is a part of the pump unit and is integrated into it. To reduce the risk of damaging the component, the filter with negligible hydraulic resistance limits the amount of contamination in the fluid. The pump unit delivers a volumetric flow, with the operating pressure being limited by an internal pressure relief valve within the pump units housing. There are two tank connections on the pump. In addition, the relief valve is included in the circuit, which is closed in the normal position. Assume that the operating pressure has been reached at one of the end openings, the other opening opens when the pressure falls below the current level. The valve closes with the pilot pressure generated by the input pressure, resulting in the valve being closed again. It also has a pilot stage and the main stage; when the pilot stage is open. Thus, there is less volumetric flow through it than when the main stage is closed.

The hydraulic circuit

Figure  8 shows the variation in force as the piston position varies. The maximum force at a piston position of 46 mm is 0.58 kN. The magnitude of the force applied decreases with an increase in the piston position. At a maximum stroke length of 200 mm, the magnitude of the force becomes negligibly small. The simulation result from the AUTOMATION STUDIO Fluid sim is in agreement with the FEA simulation, which calculates the resultant reaction force as 0.499716 kN. This force is insufficient to produce any bending, strain or displacement, which confirms conclusively that the designed hydraulic brake press has sufficient strength to withstand bending stresses and forces without distortion.

Change in force with piston position.

4 Conclusion

A reconfigurable hydraulic press brake was designed using Solidworks and simulated on a hydraulic AUTOMATION STUDIO Fluidsim. The maximum strain, stress, and displacement values obtained from manual Solidworks simulation and Von mises stress analysis were found to be 8.29 × 10 –7  N/m 2 , 2.48 × 10 3 N/m 2 and 0.000114 mm respectively. The hydraulic cylinder boasts greater efficiency than manual means or the use of a jack. It facilitates quick adjustment and greater accuracy in equipment and workpiece setting as the ram retreats automatically, and the machine is quickly returned without any waste of time. The results indicate that the hydraulic cylinder actuator can sufficiently withstand the machining forces while providing sufficient strength and rigidity during machining operations. Hence, the reconfigured actuator system possesses efficient work holding capacity without sacrificing rigidity and stiffness. Results obtained from FEA simulation when compared with the mechanical properties of the hydraulic press brake indicate that the reconfigurable hydraulic press brake possesses adequate strength to prevent buckling, strain, distortion, and displacement. Future work can consider the development of the designed hydraulic press brake.

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Acknowledgement

Funding: The authors disclosed receipt of the following financial support for the research: Technology Innovation Agency (TIA) South Africa, Gibela Rail Transport Consortium (GRTC), National Research Foundation (NRF grant 123575) and the Tshwane University of Technology (TUT).”

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Daniyan, I., Mpofu, K., Oladapo, B., Ajetomobi, R. (2023). Modelling and Simulation of Automated Hydraulic Press Brake. In: Kim, KY., Monplaisir, L., Rickli, J. (eds) Flexible Automation and Intelligent Manufacturing: The Human-Data-Technology Nexus . FAIM 2022. Lecture Notes in Mechanical Engineering. Springer, Cham. https://doi.org/10.1007/978-3-031-18326-3_7

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