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Looking for opinions on the best wa

Looking for opinions on the best wa

Looking for opinions on the best wa

(OP)
Looking for opinions on the best way to analyze the following situation:

One-way concrete slab reinforced top & bottom both ways, 6 1/2" thick with 1" Kalman topping (7 1/2" thick total).

Slab supported by WF steel beams @ 6'-8" O.C. with top flange embedded in slab (no shear studs).  Beams frame into WF steel girders spaced @ 20'-0" O.C. with top flange embedded in slab (no shear studs).  Beams & girders frame into steel columns on a 20' by 20' grid.  Slab designed (and confirmed) for 500 psf LL and 100 psf DL.

The problem:  the floor is used as a warehouse area, using heavy-duty storage racks typically used on slabs-on-grade.  Obviously, the storage rack legs create high point loads on the slab.  How can I get accurate results for shear, moment, deflection based on this point loading.  I need to know if the floor is being overloaded.

It seems to me that applying the loads over a 1' strip of slab and analyzing as a 1' wide conc. beam would be way to conservative.  Am I right or wrong?  Any suggestions?

RE: Looking for opinions on the best wa

AASHTO Specsfor Highway bridges cover point loads on concrete slabs.  Also see many concrete texts,e.g.,"Design of Concrete Structures, Nilson & Winter,11th Ed.

Be sure to check slab for punching shear.

Frank hartzell
frank.hartzell@jacobs.com

RE: Looking for opinions on the best wa

To space the point loads by hand, I would agree with Frank and simply use the AASHTO equation:

The concentrated load is spread over a distance E

E = (4 + 0.06 x S)  but not more than 7 feet (or, I would add, the center to center spacing of the posts).

S = span, ft.\

Alternatively, you could use a finite element analysis on the slab, modeling the beams and girders, and get moment contours.

In either case, you should check punching shear through the slab per ACI 11.12.

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