Pedestrian Bridges Reduced Live Load 1

[Inzynier]

AASHTO Guide Spec for Design of Pedestrian Bridges
allows for live load reduction if deck influence area exceeding 400 psf. This reduction is allowed for design main structural members. The reduction formula is reasonably based on reduced probability of large influence areas being loaded to maximum.

I would like to know other members interpretation of using reduced LL for substructure design vs. 85 psf used by more conservative designers.

 

[wiktor]

The probability of the full 85psf live load is low, so that's the reason for the reduction.
However, for the substructure design I will never reduce the LL. The savings realized from this approach, doesn't justify reduced safety factor. In any case, for the typical pedestrian structure Live Load will be not more than 30-40% of the total load, so the savings will not significant.
Another reason - while it's relatively easy to strenghten the superstucture, same could not be said regarding the foundations.