Regarding selection of connecting bolts for Footover Bridge 1

[Arbu]

Dear All,

I am designing a foot over bridge crossing the road (State Highway) and all connections are bolted connections. I am having a doubt about the selection of bolt. Shall I go with 8.8 Grade bolt or HSFG bolt. Is there will be too much Vibration due to pedestrian movement in bridge? I think this vibrations will be less as compare to road bridge and doesn't need HSFG bolt. Please suggest.

Regards,
Arbu

 

[BridgeSmith]

Vibrations for a pedestrian bridge are similar, or in some cases worse, than bridges carrying vehicle traffic. I'm not familiar with the specifics of the bolt grades you referred to, but I believe slip-critical connections would be required per the AASHTO bridge design specification in the USA. The bolts would have to meet the requirements of high strength bolts according to ASTM F3125, Grade A325 or Grade A490.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[12345abc6ttyui67]

Not my area of expertise but I'd be inclined to agree that slip critical (e.g. HSFG in the UK) are required. Purely from a practical point of view I'd want to make sure the bolts didn't come loose and fall on traffic / require lane closures to replace.

I also expect that pedestrian induced vibration leads to the requirement for HSFG. Take a look at the ped. bridge in London which had to shut for stiffening due to 'in step' forces making it oscillate too much for example.

 

[hokie66]

8.8 is the grade of bolt. What you are wondering about is how to specify the tightening. I agree that they should be fully tightened.