Is Torsion analysis needed? Concrete Bent Cap Design

Question

Is Torsion analysis needed? Concrete Bent Cap Design

KMA (Structural)

(OP)

26 Sep 03 18:53

I am currently reveiwing a conrete bent cap design that supports Prestressed Concrete Ty IV Girders on an 8" slab (4" topping + 4" Prestressed Panel). One side of the bent cap supports 130'+ span with 13 beams, the other side supports 70'+ span with 8 beams. The bent is rectangular cast in place concrete with 4 square columns as supports. The bent is normally designed for maximum moments and shears for fixed and movable (AASHTO Truck) loads. With these unequal spans, should I be considering torsion as well? Does AASHTO Address this?
Thanks in Advance

rowe (Structural) · Answer 1 · 2003-09-28 16:42:59

According to several pier designs using "RCPIER", torsion can be a significant design force for pier caps. However, the pier design, using this software, does not consider any contribution of the slab or end diaphragm(s) in distributing the torsion due to unequal live loads.

In my judgement, for normal span arrangements, torsion of the cap is not a major concern. For your span arrangement, you may have to consider torsion, but I would also include the torsional resistance of the slab and diaphragm.

good luck.

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Is Torsion analysis needed? Concrete Bent Cap Design