BridgeDude1487
Structural
- Mar 10, 2016
- 7
I am load rating what is basically an elevated slab structure, which consists of 1) a grid of columns, 2) in one direction, a "pile cap" beam spans the columns, 3) precast panels connected by shear keys and concrete overlay sit on top of that. I am assuming that the panels act together, similar to if the entire thing was one giant cast-in-place slab. What this ends up being is essentially an extremely wide bridge with a wide slab as the sole "beam". The structure supports a train at various locations.
I am unsure how to distribute the train axle loads, which are essentially point loads, laterally over the slab. My initial attempt was to use one panel width, approximately 9-10 ft, as the width resisting the loads i.e. I am basing my ΦMn and ΦVn values on this width. I am first rating the structure for the as-built condition, for its design load, the Cooper E-80 design train. Even with 0% impact, the rating is about 0.5. This tells me that I'm obviously treating something differently than the original designers. Because the structural analysis is so simple (a moving load over a simply supported beam), I'm assuming that the problem lies with my capacities.
This seems like such a simple thing, but I can't find any information on how to approach this (especially in AREMA).
I am unsure how to distribute the train axle loads, which are essentially point loads, laterally over the slab. My initial attempt was to use one panel width, approximately 9-10 ft, as the width resisting the loads i.e. I am basing my ΦMn and ΦVn values on this width. I am first rating the structure for the as-built condition, for its design load, the Cooper E-80 design train. Even with 0% impact, the rating is about 0.5. This tells me that I'm obviously treating something differently than the original designers. Because the structural analysis is so simple (a moving load over a simply supported beam), I'm assuming that the problem lies with my capacities.
This seems like such a simple thing, but I can't find any information on how to approach this (especially in AREMA).
