Lateral Load distribution on bridge deck: Traditional methods vs FEM 2

[BridgeDOR]

I posted this matter in another forum Computers and Structures: SAP2000. Until now cant get any response so i am posting here again.

Traditionally the lateral load distribution on bridge deck girders are done by different semi imperical methods mainly based on lever theory. By such methods most of the times we get that the outermost longitudinal girder is loaded more than internal girders.

But when i analyse a bridge deck with slab & girders by FEM software(SAP2000), many times the moment on intermediate girders is more than external girders. This happens when the CG of the moving load is nearer to the intermediate girder.

Is this natural? Or is my FE model wrong?

Please see my thread on forum "Computers and Structures:SAP2000" for more clarification.
Thank you!

 

[cooperDBM]

The traditional methods give you an envelope of distributed long. moments which accounts for the extents of the lateral variation in the position of the live load. Your model shows the results for a single load position which is almost centered on the bridge. Making the load more eccentric, if actually possible, will increase the loading on the exterior girders.

Modeling the deck will also have a significant impact on the distribution. I would also recommend modeling wheel lines instead of the CG of a truck/lane.

 

[dtoli]

This, of course, depend on deck arrangement and mostly on the cantilever length.

Normally for short cantilevers (supporting sidewalks) the envelope of moments is most severe on the first internal beam (the one after the external) under the condition that heavy traffic loads can reach the external.

So probably your analysis is not wrong.


URL:

http://www.diolkos-eng.gr

 

[BridgeDOR]

Thank you guys. In my post i presented a simple arbitrary model to make my case clear. In reality there are multiple lanes and moving loads with different eccentricity. And of course the deck slab is also there. I am still checking my models and i feel more confident in my analysis after your opinions.