Pedestrian Bridge Horizontal Wind Load Application 1

[minorchord2000]

For a pedestrian bridge does the wind force calculated get applied to BOTH trusses or only the windward truss?

 

[BAretired]

Both, but the leeward truss may be considered partially sheltered by the windward truss.

BA

 

[STrctPono]

BAretired is correct. AASHTO Pedestrian bridge design guide actually refers to the Signs and Luminaires Guide for wind design. The Signs and Luminaires design guide for parallel trusses is a bit vague. It's all based on shielding and solidity ratios. If the trusses are close together, then the windward side truss shields the leeward side truss completely. As they get farther apart the leeward side truss offers less and less shielding and the solidity ratio dies out. This is addressed by the Wind Drag Coefficient (Cd). Since the signs and luminaires manual is a bit ambiguous in regards to the actual Cd value to use for leeward side trusses, I default to AASHTO LRFD Bridge Design Specs and use 2.0 and 1.0 for windward and leeward truss loads, respectively, for angles and 1.0 and 0.5 for windward and leeward truss loads, respectively, for tubular members.

 

[minorchord2000]

Thanks for your great post STrctPono. These trusses are only 3'-4" apart and they are HSS 4x4s. Since they are relatively close, I will use your recommendation for wind on the leeward truss.