Live Load Distribution Factors 1

[willijamie]

I have a small bridge project in which the bridge varys in width (37' to 51') over a short distance (42'). Based on this varying width, the framing plan will have splayed girders (7'-3" to 10-9"). A question was raised about the live load distribution factors in regards to what the LRFD 3rd Edition says about how these factors are calculated. I have read through the code but have not seen where it addresses varying girder spacing. Does the 3rd edition address this issue and where? Thanks.

 

[TTK]

For this splay angle, your best bet would be to ignore the simplified LL distribution factors from AASHTO and perform a refined analysis as allowed by the specifications.

If your client is not willing to compensate for this increased design effort, then you could revert back to the simplified factors with conservative girder spacings used for moment and shear.

 

[jbasto]

You can use the Lever Rule in those cases.