Raised Concrete Median at Tapered Unit

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Raised Concrete Median at Tapered Unit

I am trying to model a concrete median at a tapered unit. As the unit tapers, the median remains at a certain offset from one side of the bridge, while its distance from the other side increases. I figured it would be best to model the dead loads in place of the median, but wouldn't PGSuper place live loads in the area where the median is supposed to be?

Is there any way around this? Can you tell PGSuper where you would like the live loads to be placed?

Rick Brice
Raised Concrete Median at Tapered Unit

PGSuper performs analysis based on AASHTO LRFD (Approximate Method for Beam-Slab Bridges). Transverse live load placement in a 2D plane frame model isn't really applicable. The live load distribution factors are based on number of beams and number of design lanes based on the out-to-out width of the bridge (there are other factors like stiffness too). In future configurations median barriers and other appurtenances of the deck may be removed and those areas used for traffic lanes. AASHTO recommends consideration for future changes to the physical or functional clear roadway width.

The default action in PGSuper is to consider live load on all girders. You have a variety of other options with PGSuper. The median dead load can be modeled with user defined loads on the portions of girders where the load acts. The loads are per girder so you will need to consider dead load distribution to girders not directly beneath the median. You can create separate models, one without the median and one with the median but using live load distribution factors of your choosing (a LLDF of zero would eliminate the live load from certain girders). Care should be taken to distribute the appropriate amount of live load to median areas that are not within the bounds of striped lanes. You could build a 3D bridge model with a finite element package and analyze the bridge with the median and actual striped lanes, then convert the results into user defined dead loads and live load distribution factors and input them into PGSuper.

Also see this post - https://pgsuper.com/content/node/512

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