User Manual - Culvert Design
Contents
1. Rational Method US Units SI Units Information Panel Runoff Coefficient C 0 75 C Table Rainfall Intensity i 125 in hr Drainage Area A 17 m le Maj Hybrid Runoff Coefficient Calculator Til of ion or Results i USGS Topographic Maps Peak Discharge 10200 ft s 5 iew Report 4 m x PageRank Alexa Figure 3 The Rational Method Calculator 4 1 Background The rational method calculator presents a simple intuitive and quick method of determining design flows at a site The formula is as follows Q kCiA Where Q Runoff ft s or m s is the constant 0 00278 for metric and 1 0 for U S units runoff coefficient rainfall intensity in hr or mm hr A drainage area hectares k C i The Rational Method makes the following assumptions e The rainfall intensity is uniform over the entire watershed during the entire storm duration e The rainfall lasts at least as long as the time of concentration of the watershed Because of these assumptions care should be taken in the selection of the runoff coefficient C This coefficient takes into account all the hydrological abstractions soil types and antecedent conditions and its selection has a direct impact on the result 4 2 Inputs Input Description Runoff The runoff coefficient C Coefficient Rainfall Intensity The intensity of the rainfall assumed to occur over the entire drainage basin for at least the time of concentration in inches hour or mil2. 1 Rational Method Design Flow 2 SCS Method Design Flow 3 Tailwater Tailwater Elevation Design Flow 4 Culvert Hydraulics Headwater Elevation Design Flow Inlet and Outlet Tailwater Elevation Velocities 5 Culvert Length Culvert Length The Time of Concentration of the watershed is an input into the Rational Method and SCS Method but there is no stand alone calculator for it Rather it is found as a background information calculator in the Information Panel for both the Rational and SCS Methods 2 2 External Information Required The only external information generally required is basic rainfall data for the site which is used by the Rational Method and SCS Method Calculators This should be obtained in the form of Intensity Duration Frequency IDF curves which are available in most jurisdictions throughout the world If IDF curves have not been produced for your area a similar topographic region can be used to estimate the rainfall In order to use the IDF data the designer must choose a return period In the United States 1 100 year return periods are common for important infrastructure such as ports and major highways On the other extreme local roads and rural low use infrastructure is often designed for 1 25 year return periods Once the return period is chosen the IDF curves show the designer what the rainfall statistics are under that return period A single line will indicate the relationship of rainfall intensity
3. and the invert elevation matches the slope of the embankment therefore the culvert projects from the fill 3 3 Results CulvertPro s Hydraulic calculator will produce the following results Headwater The elevation of the water above the culvert inlet This is a common design variable Typical values are the culvert crown or road elevation Some jurisdictions specify a certain height above the culvert crown Local infrastructure which requires protection from flooding should be surveyed to ensure it is not below this headwater Upstream Velocity The localized extreme velocity at the upstream end of the culvert Downstream The localized extreme velocity at the downstream end of the culvert Velocity Flow Profile FF Full Flow M1 Mild slope Slope is greater than normal depth M2t Mild slope Slope is greater than critical depth but less than normal depth M2c Mild slope Slope is less than critical depth Sif Steep slope Tailwater is above the culvert crown Sit Steep slope Tailwater is above normal depth S2n Steep slope Tailwater is below normal depth and flow is assumed at critical depth on the upstream end Normal Depth The depth of flow when outside the influence of inlet and outlet tailwater Normal depth occurs when gravitational force of the water is equal to the friction drag along the culvert and there is no acceleration of flow Critical Depth The depth of flow in which the sp
4. is the road station of the centerline of the culvert Vertical Alignment Either flat grade or vertical curve e Flat Enter the road elevation e Grade Enter a point anywhere on the gradeline defined by the point s station elevation and grade e Vertical Curve Enter the stations and elevations of the three points defining the curve the Point of Vertical Curvature PVC Point of Vertical Inflection PVI and Point of Vertical Tangency PVT These are also known by the terms Beginning of Vertical Curvature BVC Point of Inflection PI and End of Vertical Curvature EVC Horizontal Alignment 6 3 Results Either straight or curved e Straight There are no more inputs e Curved Enter the direction of the curve corresponding to the viewing direction defined above the curve radius and the superelevation This superelevation will be used across the entire roadway currently CulvertPro cannot compute transition zones CulvertPro s length calculator produces the following results Culvert Length The required length of culvert given all of the inputs Square Length The length of the culvert on square to the roadway i e non skewed length This number is often put on design drawings Upstream skewed The skewed length on the upstream side of the road centerline Upstream square The square length on the upstream side of the road centerline Downstream The sk
5. most commonly used methods to help you determine the time of concentration of the watershed which is defined as the time it takes for the furthest drop of water in the drainage area to reach the site USGS Topographic Maps Since you will want to see some topographic maps if you don t already have them we have included the link to the American ones right in the software 6 The Culvert Length Calculator 8 CulvertPro Mozilla Main Hydraulics Rational Method SCS Method Culvert Length Tailwater Culvert Length Calculator US Units SI Units Culvert Rise 96 inches Invert Elevation at Road CL 994 7 f Gradient 0 012 f R Downstream Let Skew 15 degrees RHF LHF End Section StraightEnd vw Road Cross section Width Crown Sideslope Sideslope Criteria Culvert Road Station Vertical Alignment Elevation 1008 37 ft Horizontal Alignment Straight Results Culvert Length 72 138 ft Square Length 69 68 ft Upstream Skewed 34 33 ft Upstream Square 33 16 ft Downstream Skewed 37 808 ft Downstream Square 36 52 ft View Report J gt PageRank Alexa Figure 5 The Culvert Length Calculator 6 1 Background This calculator assists with culvert length calculation in a highway setting It can handle sideslope issues like minimum clear zones horizontal and vertical curves skews and various culvert end types In order to properly communicate culvert length
6. three most commonly used methods USGS Topographic Since you will want to see some topographic maps if you don t already have Maps them we have included the link to the American ones right in the software 5 The SCS Method Calculator www culvertpro com CulvertPro 30000 SCS CP_SCS php DA 17 amp CN 83 amp Tc_SCS 23 amp i_SCS 1 25 amp RainfallDuration 18 amp Calculate Calculate amp Units_SCS US amp UnitsC SCS Method US Units SI Units Information Panel Drainage Area 17 mi Curve Numbers Curve Number 83 Hybrid Curve Number Time of Concentration 23 hrs Calculator Design Rainfall Event View Drainage Area in oajva e a Google Maps A Time of Concentration Calculator Results Peak Discharge 7296 ft s View Report PageRank Alexa Figure 4 The SCS Method Calculator 5 1 Background To account for the potential storage of rainfall in the soil the Natural Resources Conservation Service NRCS developed the SCS Method for determining the runoff of a watershed It is named after the agencies former name the Soil Conservation Service In this method the runoff rate is calculated as follows 484 AQ Te 05D 0 6 t Where qp Runoff ft s or m s A Drainage area square miles or square kilometres Q Depth of runoff inches or millimetres See below D Duration of rainfall hours te Time of concentration hours See be
7. with rainfall duration The designer should experiment with different storm durations but generally the storm duration corresponding to the time of concentration of the watershed defines the correct design rainfall event 3 The Culvert Hydraulics Calculator Man ttromuics BabooalMeinod SCS Metnog Cuverilengin Tubeamer Cutvert Hydrautics US Units S Units Cuien Longa Flow Tadwater Depa Upstream inver Elevator 10012 Downstream imen Elevator 1000 Cutvert Buna 12 Manreng s n of Cuban 002 Entrance Loss Cosficiont 07 End Section Contermagto Slope Resuts Headwater 1010 059 A Upstream Velocity 5 97 fs Oownstream Velocity 5 07 fs Flow Profie FF inlet Control Heacwater 1007 762 ft Outlet Control Heaceater 1010 050 n Normal Depin 5 02 n Cracail Depth 4 38 8 View Report Figure 2 The Culvert Hydraulics Calculator 3 1 Background Culvert hydraulics calculations are based on the Federal Highway Administration s FHWA Hydraulics Design Series 5 HDS 5 algorithms In full flow conditions headwater elevations and inlet outlet velocities are determined by the greater of inlet control conditions and outlet control conditions Under inlet control conditions the culvert is assumed to be first an orifice when flowing full and then a weir when not flowing full The calculations are performed for each and a sufficient interpolation is derived for the area between Based on the tailw
8. 7 63 Resulta aliada 18 TheTallwater Calculator sorrise russie paasi tansan vie o dd Chev vina ANE a da viald ides ASRA dida ii as 19 Tel BACK A A SO 19 Tel RAN 20 Ta Result a A ia 20 TA Information Panel onnncccncccnnnnnnnnccnncnnncnnnnnannn nana nan iaaiaee ono no nna nan cnn nan nn rand ale 20 1 Introduction 1 1 General CulvertPro is an internet based app that is intended for use by engineering professionals in the design of engineered culvert structures It runs in your browser and the calculations are done ona server It is accessible from www culvertdesign com or www culvertpro com CulvertPro contains the following calculators e Culvert Hydraulics e Rational Method e SCS Method e Culvert Length e Tailwater 1 2 Signing Up To sign up for CulvertPro simply point your browser to www culvertdesign com and click on Sign Up on the right sidebar Follow the prompts to enter your login credentials and billing information 1 3 Running CulvertPro Once signed up the application is executed by pointing your browser to www culvertdesign com From any page on the site the login box will appear on the right sidebar Enter your login credentials to access the application 1 4 Pop Up Windows Please note that you must enable pop up windows on the site to allow CulvertPro to load Due to ease of use to keep the vast array of diverse background information out of the way of the simplified interface w
9. Bevel Used in many jurisdictions the step bevelled culvert has a sloped end with two vertical steps at the top and bottom of the sloped end The required inputs are o Step Height Both steps require the same height o Step Length The length of the sloped section o Road slope tie in point The road slope can tie in to the top edge of the top step the bottom of the top step the top of the bottom step or the bottom of the bottom step Road Width The design width of the roadway in feet or metres Crown The crown of the roadway Sideslope The sideslope of the roadway Sideslope Criteria e None The sideslope is calculated down the specified road slope tie in point e Minimum Clear Zone Use this is you would like to leave the top of the culvert a certain clear distance from the road shoulder You will need to enter the clear distance and the maximum slope within that clear zone if you would like to keep a different maximum If the culvert length is greater than the clear zone due to other factors the calculator will create a broken back slope using the maximum slope within the clear zone and road sideslope entered above below the clear zone e Benched If you need to have a bench within the sideslope use this option You will need to enter the bench width and the vertical distance below the road shoulder Culvert Road Station Used for vertical and horizontal alignments this
10. ater specified the appropriate headwater is obtained Under outlet control conditions the headwater is calculated directly using an energy balance equation Losses are calculated at the inlet barrel and outlet and the results are summed to obtain the total head loss 3 2 Inputs Flow gt Tailwater Depth Theoretical avg Streambed Upstream Invert A Elevation eee Cul iS _Uiert Length E S Downstream Invert Qt Elevation Note Tailwater Depth is the average flow depth of the channel if the culvert were not there measured from the deepest point of Manning s n Roughness factor see table in Information Panel Entrance Loss See Information Panel the channel Coefficent End Section Square Edge w Headwall Conforming to Slope Projecting from Slope Red Inputs to the Culvert Hydraulics Calculator Input Description Culvert Shape Either round box horizontal ellipse or pipe arch We have included horizontal ellipse and pipe arch shapes for convenience however the designer should be aware that there are problems with structure definition for these shapes Manufacturers normally design the plate sizes and radii manually for each project and there is no calculator that can universally define every possible shape CulvertPro attempts to put the shape together with the given variables but designers should use the Shape Selector Tool in the Information Panel whenever poss
11. e have designed CulvertPro with pop ups for the background information e For Microsoft Internet Explorer go to Tools gt Internet Options gt Privacy gt Pop up Blocker gt Settings e For Mozilla Firefox go to Firefox gt Options gt Content gt Block Pop up Windows gt Exceptions e For Google Chrome choose Tools gt Settings gt Privacy gt Content Settings gt Pop ups gt Manage Exceptions www culvertpro com CulvertPro 30000 CulvertProHome php Calculators Culvert Hydraulics Asimple quick and intuitive culvert hydraulics calculator Rational Method A simple and intuitive method to determine design flows SCS Method A more comprehensive method to determine design flows Culvert Length A calculator for culvert length calculation in a highway scenario Tailwater A manning s formula calculator for average channel properties including tailwater depth You are on a monthly subscription plan cancel i gt PageRank Alexa Figure 1 The CulvertPro main screen 2 Getting Started 2 1 The Design Process If starting from scratch with no other sources of information the order of calculators to proceed through a culvert design project is as follows Design Flow gt Headwater gt Inlet and Outlet Velocities Time of Concentration Method O Concentration Method Culvert Length Order Calculator Result Required Inputs
12. e site The handy calculator in the Information Panel utilizes the three most commonly used methods Rainfall Intensity The intensity of the design storm in inches hour or millimetres hour Rainfall Duration The duration of the design storm in hours Together with the rainfall intensity this will define a theoretical storm The SCS method assumes a storm of this intensity and magnitude and calculates a theoretical triangular runoff hydrograph 5 3 Results CulvertPro s SCS Method calculator produces the following result Peak Discharge The runoff Q at the site in ft s or m s Viewing the report will show the intermediate variables Q runoff depth and S potential retention 5 4 Information Panel The following items are contained in the SCS Method Information Panel CN Table A table of curve numbers and soil type descriptions to assist with the input Curve Number Hybrid Curve Number Calculator When different areas of the drainage basin have different characteristics you can assign multiple curve numbers and scale the final value to the respective areas View Drainage Area in Google Maps To assist in choosing a curve number CulvertPro contains this handy feature Google Maps satellite view shows you how wooded or treed a basin is among other things and the topographic map shows you the relief Time of Concentration Calculator This handy calculator utilizes the three
13. ecific energy is a minimum Also it is the boundary between supercritical and subcritical flow 3 4 Information Panel The following items are contained in the Culvert Hydraulics Information Panel Shape Selector Tool This handy tool assists with choosing shapes and sizes Any shape and size on this list will be specifiable without any problems as they have been taken from industry published shape tables It is not however a comprehensive list as manufacturers can create customized shapes and sizes to suit any project Manning s n Table A table of manning s roughness values for culvert types to assist with the Manning s n of Culvert input Entrance Loss A table of entrance loss coefficients related to culvert inlet types to assist with Coefficients the Entrance Loss Coefficient input Normally jurisdictions have design criteria which include one of more of the following 1 Headwater Elevation eg Lower than culvert crown or any surrounding buildings 2 Velocities eg No more than twice the normal channel velocity on each end 3 Head losses eg Maximum head loss 4 The Rational Method Calculator 8 CulvertPro Mozilla Firefo w w culvertpro com CulvertPro 30000 Rational CP_Rational php C 0 75 amp i 1 25 amp DA 17 amp Calculate Calculate amp Units_Rational US amp UnitsChange Main Hydraulics Rational Method SCSMethod Culvert Length Tailwater
14. ewed length on the downstream side of the road centerline skewed Downstream The square length of the downstream side of the road centerline square 7 The Tailwater Calculator 8 CuivertPro Mozilla www culvertpro com CulvertPro 30000 FlowDepth Main Hydraulics Rational Method SCS Method Culvert Length Tailwater Tailwater US Units SI Units Information Panel nning s n Table Flow 530 R s Channel Slope 0 012 ff Manning s n 0 04 Channel Shape Trapezoidal Channel Bottom 12 ft Channel Sideslope _ 1 1 Channel Depth 6 ft Calculate Results Channel Flow Depth 4 09 ft Channel Velocity 8 06 ft s View Report mS PageRank Alexa SY a Figure 6 The Tailwater Calculator 7 1 Background The tailwater calculator assists in the calculation of the Channel Flow Depth value in the Culvert Hydraulics calculator The user must assume certain channel cross section parameters and the calculator uses manning s equation to determine a flow depth Manning s equation is as follows ARS E n Where qQ Flow ft s or m s A Cross sectional area of flow in ft or m R Hydraulic radius Area Wetted Perimeter in feet or metres S Slope of channel in feet foot or metres metre n Manning s roughness coefficient 7 2 Inputs Input Description Flow The flow in the channel in ft s or m s Channel Slope The slope of the channel i
15. ible as this uses predefined sizes Culvert Length The length of the culvert in feet or metres This value has very little effect on the result and can be estimated if the culvert length has not been calculated yet Flow The flow to analyze through the culvert in ft s or m s Channel Flow The natural depth of the channel averaged through the localized area of the Depth culvert and measured from the lowest point Upstream Invert The elevation of the upstream invert feet or metres Elevation Downstream The elevation of the downstream invert feet or metres Invert Elevation Manning s n of Manning s roughness value for the culvert This varies based on corrugation Culvert profile for corrugated steel type of material and any other factor that introduces roughness to the edge of the culvert which contacts water flow A table of manning s n values for commonly used culverts is included in the Information Panel Entrance Loss Entrance losses are determined by the type of inlet Entrance loss coefficients for Coefficient common inlet conditions are included in the Information Panel End Section The type of end section is used to calculate the exit loss coefficient Ke e Square Edge w Headwall The culvert contains a vertical wall headwall around its ends Conforming to slope The culvert end is sloped or bevelled to conform to a road or other embankment Projecting from Slope The culvert ends are vertical uncut
16. limetres hour Drainage Area The drainage area in square miles or square kilometres Most representations of the rational method formula use hectares however CulvertPro uses square miles or square kilometres for ease of use 4 3 Results CulvertPro s Rational Method calculator produces the following result Peak Discharge The runoff Q at the site in question in ft s or m s 4 4 Information Panel The following items are contained in the Rational Method Information Panel C Table A table of runoff coefficients for common drainage basin characteristics to assist with the input Runoff Coefficient View Drainage Area To assist in choosing a runoff coefficient CulvertPro contains this handy in Google Maps feature Google Maps satellite view shows you how wooded or treed a basin is among other things and the topographic map shows you the relief Hybrid Runoff When different areas of the drainage basin have different characteristics you Coefficient can assign multiple runoff coefficients and scale the final value to the Calculator respective areas Time of The rainfall intensity i should be such that it will occur over the entire Concentration drainage area for at least the amount of time it takes for the furthest drop of Calculator water in the drainage area to reach the site This time frame is defined as the time of concentration of the watershed and this handy calculator uses the
17. low The depth of runoff is determined based on the retention of the initial rainfall within the soil B P 0 25 P 0 8S Where Q the depth of runoff inches or millimetres P Cumulative rainfall depth intensity x duration inches or millimetres S Potential retention inches or millimetres See below A theoretical triangular hydrograph is assumed with the following time to peak 5 1000 T CN Where S Potential retention inches or millimetres CN Curve Number Looked up from published tables 5 2 Inputs Input Description Drainage Area The drainage area in square miles or square kilometres Curve Number This value is looked up on tables included in the Information Panel The curve number defines the soil cover and hydrologic conditions of the land surface They are based on four soil types Group A High infiltration low runoff Sand loamy sand or sandy loam Infiltration rate gt 0 3 in hr when wet Group B Moderate infiltration moderate runoff Silt loam or loam Infiltration rate 0 15 to 0 3 in hr when wet Group C Low infiltration moderate to high runoff Sandy clay loam Infiltration rate 0 05 to 0 15 in hr when wet Group D Very low infiltration high runoff Clay loam silty clay loam sandy clay silty clay or clay Infiltration rate 0 to 0 05 in hr when wet Time of The amount of time it takes for the furthest drop of water in the drainage area to Concentration reach th
18. n ft ft or m m Manning s n The manning roughness coefficient of the channel Channel Shape The calculator can compute rectangular triangular and trapezoidal channels e Rectangular Enter the channel bottom width and channel depth e Triangular Enter the channel sideslope and depth e Trapezoidal Enter the channel bottom width channel sideslope and channel depth 7 3 Results CulvertPro s tailwater calculator produces the following result Channel Flow The depth of flow in the channel in feet or metres Depth Channel Velocity The velocity of the flow in the channel as defined in ft s or m s 7 4 Information Panel The following items are contained in the Culvert Hydraulics Information Panel Manning s n Table A table of manning s roughness coefficients for typical channel conditions to assist with the input Manning s n
19. s when the culvert is skewed and the road is curved the user must choose a direction of viewing which is along the road and indicate to the calculator which direction is left and right upstream or downstream 6 2 Inputs Input Description Culvert Rise The vertical dimension of the culvert in inches or metres Invert Elevation at The invert elevation of the culvert at the road centerline If the culvert is Road CL cambered using the straight line elevation between the inverts will still produce an accurate result Gradient The slope of the culvert in ft ft or m m Downstream The direction which is downstream The user must choose a direction of viewing which is along the road in either direction and indicate which direction is downstream Skew The degree of skew of the culvert Skew Direction The direction of skew Based on the direction of viewing see Downstream above this value is either Left Hand Forward LHF or Right Hand Forward RHF End Section The type of end section of the culvert and how the sideslope ties in to it Possible values e Straight End The culvert has a vertical uncut end and the sideslope ties in to the bottom edge e Full Bevel The culvert has a sloped end conforming to the road slope The user must input o Bevel Length The horizontal length of the sloped end o Road slope tie in point Either at the top or the bottom of the bevelled end e Step
20. ulvertPro User Manual Contents 1 Introduction A eT A ee SE SSG at 3 I A O O OT AN 3 1 2 Signing UP ici id td ad 3 13 Running Culver PrO cima DEDE EAA 3 L4 Pop Up WINDOWS serraria le ia adi E REE S 3 Getting Startede rresten ere a ia ia 5 22 The Design PrOCESS veces vsazesctstecauesvnancetcaieeassqacd anne amp itavscaeeaces seaiga sa meametteiteane Jena aaa ee 5 2 2 External Information Required cccccccccsssssssscececessesesseseeeeeceseeaeeeceessessesaeaeeessessesaeaeeeeseseeeeaaeas 5 The Culvert Hydraulics Calculator c ccccccccssssssseccecsceesesssaececececeseeaeceeecscessesaeaeeeeceseeaaeaeeeesesseessaeeeeess 7 3 1 Back BOU iii iia 7 A A eaa EE E E E EAE EE AAE AE 8 Jo Resulta E E ida 9 eE Information Panel E E NT 10 The Rational Method Calculator cccccccccssccccestececeesnecececsaeeeceeeeeeseaeeeeeesaeeeeeeaeeeseesaeeeeeeaaeeeseeaeeeeesaas 11 AW Background ivi A debated A A a 11 4 S REN oo UtS O E E E E E tadhwsebieieeleledewiulasucectevwedvavideweushd E sateen 12 BE RSU E E A tE 12 AA Information E 12 THESES Method Calculator iii id 13 BAe BACK RrOUNG ERE E E E AEE EE 13 eZ O E aaa 14 So Reess AAE N EAA ANE 14 54 Information Panel eesriie ana A A AAA a E AAEE ENS 15 The Culvert Length Calculator ccccccccccccscssssscecececsssessaeseeceseesesaeeeeeescsssesaaeeeeeeeseesaaaaaeeeesessesesaeeesess 16 Gell Backgrounds ad 16 62 MIOS cai A A ua vi dee A A A 1
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