Bridge geometry

[cuba28]

Hello,

I would like to verifiy something concerning the geometry of a bridge according to the following diagram :

Concerning the width of the deck, is it A or B ?

Regards

[Anonymous]

It is neither. The width of the bridge is the length from the upstream side to the downstream side. See page 6-36 of the User Manual for more information.

[cuba28]

Thank you Sir. Actually, I’ve already seen the diagram in the user manual but I think that I didn’t understand. So, according to what I’ve understood, the deck width is W as shown in the following figure :

The BU and DU are the cross sections just upstream and downstream of the bridge that are definied automatically by the HEC RAS, is it right ? So the width is the distance between these two typical cross sections. Am I right please ? If not, could you help me please ?

Thanks

[jadams]

Bridge “Width” is the width of the bridge deck; i.e. (40ft) while the “Distance” is the length along the stream from the up stream cross section (BU in your diagram) to the upstream edge of the bridge deck.

So as you said RAS knows the distance between Bu and DU. By giving the “Distance” value you tell RAS where the upstream edge of the bridge is. By giving the “Width” value RAS then calculates the downstream edge of the bridge and can thus accurately place it between Bu and DU.

[Author]

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