HEC-RAS Bridge Modeling Tutorial - Create a bridge in HEC-RAS

[Music] greetings my name is andy carter and i'm a professional engineer out of the state of texas in this video we're going to model a hec-ras bridge from scratch specifically we're going to look at a bridge over the navidad river on interstate 10 midway between houston and san antonio to follow along with this tutorial three files are necessary the first is a three foot resolution bar earth terrain model it's a ghif that was projected to the local south central texas u.s survey foot projection i provided a link to a tutorial to show you how this terrain was acquired second is projection file that was created with qgis that referenced this project's projection third i'm providing as built reference plans provided by the state department of transportation if desired download this project's data from this provided link let's start a new hec-ras project and import the project's terrain with the start menu i'm just typing in hec-ras i'm going to open hec-ras 5.0.7 once this opens i'm going to say file new project this new project i'm just going to put in the root of the c drive under raz dash bridge call that project navidad and we'll say ok we're going to set it up in us unit so we should be okay we'll immediately go gis tools to razmapper we'll mapper first thing we're going to do is set the projection for the project so under the esri projection file we're going to find that file that i previously created that is in south central texas us survey feet that's that prj file and we'll say apply and ok so now the project is set up in the right coordinate zone under terrain right click and say create a new raz terrain hit the plus button i'm going to navigate and go find that geotiff that was previously created for the site and under that folder i picked that folder icon i like to name my surface something other than just what it defaults to so i'm doing eg lidar underscore three foot to say what resolution it was created in once we have all that we'll hit create and everything will go off and process this takes a few seconds to minutes depending on the size of the terrain file i'm going to pause here for a second and there we go there's the site the next step is to create a geometry file we're going to do this inside of hec-ras mapper so back in hec-ras mapper i'm right-clicking on geometries and saying add new geometry data just going to call this existing and say ok on the geometry i'm going to right click on rivers and say edit geometry make sure that the pencil tool is selected i'm going to zoom in and figure out where we're going to start the stream i'm going to digitize that stream from upstream to downstream down the foul wig make sure it is upstream to downstream it's very important you can kind of notice i'm being a little rough here but i'm roughly getting in the location of the creek in its appropriate location you don't have to be super detailed just depends on what kind of model you're building once that's done i'm going to call that river navidad and the reach name i'm going to change to main and say ok so now with the edit session still active we're going to right click on the cross sections still having that pencil tool selected i'm going to draw cross sections from left to right looking downstream that standard hec-ras nomenclature i am trying to draw those cross-sections to be perpendicular to the conveyance or the flow notice i'm skipping right over the bridge we're going to come back and do the bridge a different way mainly i'm just trying to get a geometry file on which i can host the desired bridge once that's done that edit session is done just right click and say stop editing and say yes to save your edits for this bridge modeling we're going to export shape files and google earth aerials to assist with the modeling let's go back into raz mapper and first let's export the river center line so i just right click on rivers and i say export shapefile i'm going to name this as stream underscore ln just to denote it's a line shape file and that is the stream shapefile under cross sections i right click on that say export layer and say save features as shapefile and we're going to save this one to xs ln for cross section lines and we'll say save so now we want to get some google earth aerials as well so under map layers we'll check that right click and say add web imagery layer i'm going to go find google satellite and say ok since we've already specified a projection file aerial comes in in the right place i want a relatively low res aerial of the road location so i kind of zoom in to a point where i'm happy i right click on google satellite and say export to tiff that's going to export a geotiff where it's going to have the correct projection embedded into it this one's going to be ge dash road for google earth road now i'm zooming in to get a little bit of detail around the bridge itself that i'm trying to model specifically i'm going to model the northern bridge so i'm going to right click and say export to geotiff we're going to put it in the same place we're going to call this one ge dash bridge and we'll say save and ok i'm going to use civil 3d to help manage the bridge modeling so in civil 3d i need to make sure that that drawing is set up on the same projection so right clicking on the settings tab i'm going to set that drawing up under usa texas and we're going to go find nad 83 south central zone u.s survey feet and say apply and ok now that i have that in i can bring in those two geotiffs we created with a map i insert map image insert i'm gonna go find those two geotiffs and we'll open them up the low res one the bigger one came on top of the hi-res one so i'm going to do a draw order and push the the big one to the back so we can see the detail bridge on top once that's done now we can bring in the two shape files and i'm going to do that as a map import and i'm going to import the cross section and the stream center line and say ok and ok again to bring those line work in using the aerial images reference we can now create the bridge and bounding cross sections inside of civil 3d i'm going to draw a polyline down the center line of the road this is going to represent the bridge deck this line is left to right looking downstream once that center line polyline is completed offset it upstream and downstream 40 feet these three lines all now are relatively the same length which is important with bridge modeling inside of civil 3d i'm going to use the map export command and we're going to export a shape file that's all of the sections plus the three new ones or browse to location where we had those files already exported call this new cross section shapefile xs-ln underscore rev1 for revision one use the line option select manually and pick all those cross-sections and export it out back inside of hec-ras we're in razmapper and we're going to right-click and say add new geometry data this new geometry data is going to be called existing underscore rev1 for revision 1. we're going to right click on it and say edit go to the rivers right click on it to layer properties select the features tab bottom right import features and then select the stream underscore ln for the streamline this will come in and retain the name as previously done we'll right click on the cross sections go to layer properties go to the features tab the import features button on the bottom right and select the cross sections revision one that we just created this will re-cut and resample all the cross sections including the three new ones once that's completed just right click and save your edits to existing underscore revision one back in hec-ras in general we're just going to open the geometry editor it's the third button from the left and we're going to say file open geometry data and select existing revision 1. this has those three new cross sections which have been cut off of the terrain under tools go to cross section point filter find the cross section that's down the middle of the road in this case it's cross section 1400 on the bottom we're changing the horizontal filter tolerance and the vertical filter tolerance etc to 0.15 the last one which is co-linear minimum change in slope will change to 0.060 and we'll filter the points the goal is to create a bridge deck down the center line of the road right-click and say graphical cross-section edit if you see if you right-click you can select delete objects i'm going to delete all the points that represent points that are not indicative of the bridge deck so we're effectively just trying to model the center line of the road itself now that i'm complete i can say exit editor and we can save the geometry file we now have enough information to start modeling a bridge deck inside of hecara's going back to the reference construction drawings we'll note that the bridge is 41 foot one and a half inch wide now we'll go into cad and get the distance between the upstream bounding cross section in the road deck just drawing a simple polyline and querying it and that tells me that the length is 22.6 feet both these numbers are important to model going back into hec-ras we'll select the geometric editor on the cross-section edit tool i'm going to find cross section 1400 which represents the road deck i'm going to highlight all of the station elevation data and copy it to the clipboard now that i have it i can say options delete cross section can remove cross section 1400 close the cross-section editor go to the bridge editor and say options add bridge culvert i'm going to add one at 1400 we'll go to the bridge roadway deck tool the distance between the upstream boundary cross section and the road deck was 22.6 feet as we figured it out the width of the road deck is 41.125 for the plans for station and high cord i'm just control v the data on the clipboard i'm hitting copy upstream to downstream and we'll say okay and we've got our bridge deck back on the construction drawings we'll look at the bridge deck information to get the geometry that we need to model i've highlighted the bridge deck in red everything that's pertinent for modeling i've highlighted in yellow it's a 315 foot long span it's composed of six 40 foot girder spans and one i-beam span which is 75 feet long the elevation that starts the bridge is noted as a 296.13 and it's a zero percent slope so it's flat across all the piers are 24 inch diameter piers at the 40 foot spans we go to the next sheet we'll notice that there's a 75 foot span which is flanked by 30 inch diameter piers and also has a little thicker bridge deck and then we return back to the normal section which is the girder section and the piers change back to a 24 inch diameter looking at the sections we'll note that the girder section is 36 inches from the top of pavement to the bottom of the bridge itself this excludes the vents and you'll notice here that the road deck and the i-beams on the longer span this is the 75-foot span is 51 inches thick from top of road to bottom of beam back in civil 3d i'm going to create an alignment from the road center line this is going to be used as station control to assist with modeling the other pertinent items of the bridge i'm going to call that alignment bridge note that the station is left to right looking downstream i'm going to draw a polyline the first one is going to be at the abutment the left abutment of the bridge then i'm going to offset that 40 feet that's going to be to the termination of the first bridge span we'll offset that one 40 feet and this is the big span that goes over the main center line of the creek we'll offset that 75 feet and then we'll continue to offset 40 feet each until we get to the right abutment i'm going to add a station offset label at the termination of each one of these polylines this is going to assist with the high and low cord bridge modeling as well as the placement of the piers once i have labeled one station and offset i can copy that style and just snap it to the endpoint of the other lines i've created a brand new excel file and entered in the stations for all points that were queried as we noted from the construction plans the high court is 296.13 and it is flattened across the entire bridge so we can just copy that all the way down the low cord is going to be 36 inches below the high cord where we have a 40 foot span so we can just assume for now that it's 293.13 and that low cord is all the way down now going back to where that 75 foot span is we noted that it's actually 51 inches thick and the difference between the high court and the low cord minus 51 inches is 291.88 and that is at the first point and the second point there's a couple things that we need to do to adjust these stations i'm going to insert a row right before and one right after so let's do this one at 440.12 and we'll do the last one at 755.14 what i'm trying to do here is i know that i have a high cord and then the low cord is going to be zero it's going to go as far down as it can go and we'll do the same thing on this high court the other things that we're going to want to do is we want to insert a point right before we have the variance between the beam thickness i'm going to insert and shift those cells down we're going to insert and shift those cells down so we're going to do one that is practically right next to that point 0.12 and we'll do 595.14 we'll put the high court as the same and this high chord is the same and the low cord will actually do with the 40-foot span back in hec-ras we're now going to append the roadway deck data we've found that bridge we'll click on roadway deck we'll just highlight and pick all those ordinance control cm and then we'll control v them back into excel we'll note that we now have everything between 440 and 755 so we will go ahead and delete the point that we have on the road deck already and we'll just right click and say insert and we'll insert those cells down and we'll just copy these and we'll stick them in so now we can come back and delete this to clean it up and now we've got appended road deck data we'll just copy and we will paste it into the road deck to overwrite it and we'll make sure we'll click this button that says copy upstream to downstream and we'll say ok and there is our road geometry our opening area with the bridge deck in now we can start modeling both the piers and the abutments the next step is to add the peers i've highlighted in excel the location of the six peers that need to be modeled on the bridge editor i'm going to select the peer button and we're going to add a pier at 480.13 that is for both the upstream and the downstream station the pier width is going to be two feet or 24 inches per the reference construction plans the first elevation will be at zero the second elevation will be just above the low cord so i'm going to set that at 293.5 and i'm going to select this button copy upstream to down once one pier has been created it can be copied to another location i'm just going to copy pier 1 i'm going to change its station to 520.12 both upstream and downstream will be at the same station its pure width is 30 inches so we'll change the pier width to 2.5 and once we've done it for the upstream i can just copy the upstream to the downstream and say okay and there is our second pier i've just completed modeling all the piers i've jumped ahead now i'm going to model the abutments note on the geometric editor you can pick a point and it will tell you the station and elevation of that given point this helps with modeling the sloping abutments the construction plans say that we have a two to one concrete abutment so i'm going to go ahead and model that now i'm starting at a 440.12 and an elevation of 293.13 and then i'm progressing 50 station feet to 490.12 and sloping down at 2 1 ends us at a 468.13 i will copy upstream to downstream and say ok and there is our first abutment now we need to model the abutment on the other side so back to the sloping abutment tool i will say add and we've got another one so we'll start at a station of 700.14 at an elevation of 268.13 and we will end 50 feet at a 755.14 and will be 25 vertical feet higher at 293.13 we'll copy up to down as again and say okay and there's our other sloping abutment now we're going to edit the ineffective flow areas on the upstream and downstream bounding cross sections for the bridge hectares makes this easy as they give you a button on the bridge editor so we'll go to 1440. when you select that it automatically defaults to the ineffective mode the left station is going to be where the abutment started which is 440.13 and we're going to do an elevation right below the high court of the deck which is going to be 296.13 and on the right we're going to put that at a station at where the abutment ends which is 755.1 and its elevation is going to be the same when i model ineffective flare areas i always check the permanent mode specifically around the bridges and say okay back on the bridge editor now we're going to add ineffective flow areas to the downstream bounding cross section we'll pick this 1360 that will go to the ineffective mode by default we'll put it at the same stations which is 440.13 and that's going to be an elevation of 296.13 and on the right side it is going to be a 555.14 at the same elevation 296.13 again we'll set both modes to permanent and say ok in addition to the upstream and downstream bounding cross sections hecariz has guidance that recommends that the cross section upstream and downstream of those two bounding cross sections also take into account ineffective flow areas coming from that abutment on the approach it is recommended a 45 degree angle for where that ineffective conveyance is flowing so i'm drawing a line perpendicular and then i'm just rotating it negative 45 degrees on one side and 45 degrees on the other side this is mimicking a one-to-one expansion of effective conveyance we don't know the station as to where those two points hit on that cross section so as before i'll say alignment create alignment from objects i'll pick that and we'll say that alignment we'll just call upstream and we'll say okay and picking that alignment contextually the ribbon comes up and i'll just say station offset and i'll pick a point here with zero offset and i'll do the same thing as the other side we'll snap to that point make sure we've got it and enter so those are the two stations where ineffective area begins for that upstream cross-section for this tutorial we're going to ignore and pretend like we don't have a downstream bridge to model the downstream ineffective expansion will come off of that same point and we will go perpendicular to that cross-section downstream for the expansion it's recommended as a 30 degree which would be a two to one so we're going to rotate that 30 degrees it takes a little longer for the water to expand back to its conveyance limits and we'll do that again there and i'll rotate this guy in this case negative 30 degrees and expand it out again we'll just create an alignment from the object which is that cross section we'll hit enter and we'll call that eds for downstream having that we can now pick the alignment add a label and we want to station an offset where that hits we'll hit zero for the station and offset that's at 317.03 roughly and the other one is going to be at 283.02 so we now have the limits of the contraction and expansion of the ineffective flow areas on the approach to the bridge going back over into hec-ras specifically to the geometry editor i've made a note as to where those limits are for those two cross-sections so we'll go to the cross-section editor and we will go find that cross section so the first one is 1657. so i'm going to go find 1657 i'm going to say options ineffective flow areas and we're going to add it to the same station which is seven move this down which is going to be 275.16 and the second one is going to be at 9.97 i'm going to set those elevations to 296.13 which mimics the bridge deck downstream we'll copy that over set both of those as permanent and we'll go to the next cross section which is 1017 and we'll say options add ineffective flow areas we will set that at 317.27 and 983.02 and we will set those at the same elevation of 296.13 copy that make them both permanent and say okay now we need to adjust the expansion and contraction coefficients for the two cross sections upstream and downstream of the bridge this is to accommodate the loss of energy caused by the contraction of water as it approaches the bridge we'll go to cross section editor and we'll go find cross section one six five seven that's the most upstream it's two upstream of the bridge so let's go find that you'll notice the expansion contraction coefficients typically default to 0.1 and 0.3 around a bridge we change that to 0.3 and to 0.5 for the expansion we do this for the four cross-sections so this one the upstream bounding cross-section changes to three and point five the downstream bounding cross section changes to point three and point five and then finally that expanded cross section on the downstream side is zero point three and zero point five and we'll say apply and we'll save the geometry now i'm going to quickly run a little bit of magic to get this hec-ras model to run under the geometry editor i'm just going to go tables manning's ends i'm going to select everything set values to 0.060 that sets a mannings in on every cross section we'll say ok and file save geometry data now i need a flow file just to make it run so i'm going to create a new flow file we'll just put a default 20 000 cubic feet per second reach boundary conditions i'm going to set it at normal depth of 0.005 percent or 0.5 percent we'll save the flow data and we'll just call it temp for kind of an existing one we'll say okay and we'll exit the flow data and now we'll do a steady state plan and i'll say file save plan as we'll just call this temp and we'll call it temp on the shorthand name and say okay and just hit compute and everything should execute so now we can kind of go back to razmapper and see what we did with the bridge that we modeled this should give us some results and there's our depth grid back in the main hec-ras window we're going to click the profile tool and you'll notice that we've got the bridge and you can see the back water that's being caused and the acceleration as it goes through the bridge itself let's take a look at the cross sections specifically the ones around the bridge if we can find them there's the bridge upstream and the bridge downstream and the two cross sections that are bounding relative to it if you see this cross hatch that means it's ineffective flow area and while it's getting wet it is not counted as computational conveyance and this is one of those downstream cross sections as it expands back out you can see that again we also have ineffective flow area where it's not flowing to completion of this exercise there was a lot of things that i had to change regarding manning's ends and effective and expansion contraction areas if you notice i actually modeled two bridges for each bridge crossing and there was an upstream and a downstream bridge let's look at that in profile and see what we've got i've modeled a lot of profiles so we're just going to pick one and let's go back and just pick that 20 000 cfs like we did in the other model so there are the two bridges that you can see if we look at the cross sections specifically around the bridge itself there's the upstream and downstream bounding cross sections i've actually got two bridge openings in this instance and that's the first bridge there's your expansion contraction your ineffective flow areas that are set same thing there and it's just a an expansion of what we just showed you this concludes my introduction into bridge modeling with hecariz i appreciate the opportunity to show you what i do every day and if you got any questions please feel free to reach out to me i appreciate your time [Music] you

Channel: Civil Envoy

Views: 34,837

Keywords: HEC-RAS, bridge, ineffective, pier, abutment, RAS, tutorial, Civil3D, model, modeling

Id: Ec1ulkYOUv0

Length: 27min 15sec (1635 seconds)

Published: Mon Oct 12 2020