## Distribution factor Bridges with multiple girder types

## Distribution factor Bridges with multiple girder types

(OP)

Hello everyone,

I was wondering if any of you have come across the situation of having two different prestressed girder types, such as Bulb Tee(BT) and Tub girders in the same bridge cross section. If yes, are the distribution factors from AASHTO still applicable? if not what other types of analysis could one use to determine the loading?

Thanks in advance

I was wondering if any of you have come across the situation of having two different prestressed girder types, such as Bulb Tee(BT) and Tub girders in the same bridge cross section. If yes, are the distribution factors from AASHTO still applicable? if not what other types of analysis could one use to determine the loading?

Thanks in advance

## RE: Distribution factor Bridges with multiple girder types

Otherwise, the grillage analogy model will suffice.

## RE: Distribution factor Bridges with multiple girder types

Thanks for your reply.

AASHTO distribution factors aside; do you think lever rule is still applicable if the girders were of considerably different (20%) stiffnesses.

## RE: Distribution factor Bridges with multiple girder types

Rod Smith, P.E.

## RE: Distribution factor Bridges with multiple girder types

I think you could add together .25DF for each of the adjacent girders and .5DF for the girder under consideration to calculate the DF for each girder. However, my understanding of the mechanics involved is not advanced enough to say with any certainty that this approach would be accurate.

A detailed finite element model is likely the only way to get close to the real distribution.

Rod Smith, P.E.

## RE: Distribution factor Bridges with multiple girder types

## RE: Distribution factor Bridges with multiple girder types