Lateral and Torsion Bracing
Lateral and Torsion Bracing
(OP)
Hello All,
I am getting a little confused by the bracing required during steel girder erection and was hoping for some clarification.
I know that during steel erection LTB can become a problem because the concrete deck has yet to be installed. I know that this restraint can be provided either by Lateral(plan) bracing at the top flange or K/X(torsional) bracing. Typically girders are erected in pairs with X-bracing preinstalled to mitigate this issue.
My question arises when there is additional diagonal lateral bracing installed in between one or more girder lines. I have included a picture below:
This bracing is usually connected to the top flange and I usually see this when large lateral forces are expected. Am I correct that this bracing is used to increase strength against lateral loads? How exactly is it adding more lateral strength?
I am getting a little confused by the bracing required during steel girder erection and was hoping for some clarification.
I know that during steel erection LTB can become a problem because the concrete deck has yet to be installed. I know that this restraint can be provided either by Lateral(plan) bracing at the top flange or K/X(torsional) bracing. Typically girders are erected in pairs with X-bracing preinstalled to mitigate this issue.
My question arises when there is additional diagonal lateral bracing installed in between one or more girder lines. I have included a picture below:
This bracing is usually connected to the top flange and I usually see this when large lateral forces are expected. Am I correct that this bracing is used to increase strength against lateral loads? How exactly is it adding more lateral strength?
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RE: Lateral and Torsion Bracing
In the layout shown, it appears the lateral bracing does not add any additional braced points for LTB beyond what's provided by the X or K frames.
The lateral bracing creates what amounts to an open web truss, with the girders as the flanges, the lateral bracing members as the diagonals, and the X or K frames as 'vertical' struts.
Rod Smith, P.E., The artist formerly known as HotRod10