Tuesday Tip of the Week–HTAB Headwater Maximum for Bridges

Have you ever looked at your profile plot from an unsteady flow model and found “walls of water” on top of your bridge?  Or just unexplained unrealistically large amounts of energy loss over a bridge?  Take this for example: Notice the three large “steps” in energy grade line (and water surface elevation).  It’s hard to […]

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Skew Angle for Bridges

  FIGURE 1 If a bridge is not oriented perpendicular to the flow lines going through the bridge, HEC-RAS has an option for skewing the bridge deck and/or piers.  (A user can also skew cross sections in a similar manner)  When skewing a bridge, the user reduces the bridge’s deck/roadway stationing by multiplying the values […]

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Hotstarts and HTab Parameters at Bridges

An advantage of running a step-down scheme hotstart run is the ability to spatially evaluate stability issues with difficult reaches. One of the elemental features of the step-down scheme is the artificially raising of the downstream boundary during the hotstart simulation to “drown-out” the reach and effectively create a very stable environment. During the hotstart […]

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Bridge on a Spillway

Written by Chris Goodell, P.E., D. WRE | WEST ConsultantsCopyright © RASModel.com. 2010. All rights reserved.I just got an interesting question. How do I model a bridge that has a spillway just downstream of it? Here’s an example of what I’m talking about: As I see it, there are a three ways to approach this. […]

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