Maximum live load shear

[aun]

I read a book that shows how to place a wheel load over the concrete slab to create the max reaction at beam end and it comes up with the following equation, R = P(3-10/S) Where P is 16 kip, S = beam spacing and R = reaction at support. (this equation is achieved by AASHTO 3.23.1.2 and also can be found in Design of Modern highway Bridges book) That is for the rear axle load placed at the end beam. And then using distribution factor of S/5.5 (for I steel stringer) for the other 2 axle loads. (HS-20 loading)
While I see other book ( bridge design For PE exam) ,applying the distribution factor for all three axle loads. I believe that the first book showing the correct calculation. Am I right??

 

[Qshake]

Well you do have to calculate the reaction due to the wheel (axle) loads out in the span. Whether or not you apply the distribution factor (S/D) to all of the wheel loads might depend on what type of abutment is involved. It seems appropriate to apply this to open seat abutments where the girders are still very much independent but at integral abutments the load would seem to be spread out more.

 

[bridgebuster]

Normally, the distribution is applied to all axles for shear and moment. I agree with QShake about the integral abutments.