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Re: One way slab design with point load.

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I sometimes use ACI recommendations for effective width of slab to act as a 
tee beam flange for guidance (ACI 318-95, 8.10.2).  This would allow 16 x slab 
thickness (8xt each side of web) but no greater than 0.25 x span.  Although 
not directly applicable, this gives some idea as to ability of a slab to 
distribute load and seems reasonably conservative.  Thus 0.25x22 ft = 5.5 ft 
would govern for your case.   
 
On the other hand, PCI (4th Edition), Fig. 4.8.1 gives "assumed load 
distribution" for concentrated loads on hollow core slabs (with grouted 
keyways) - in general, for loads within the middle half of the span, they 
assume an effective slab width of 0.50 x span.  This seems quite similar to a 
one-way slab design.  This would increase your effective width to 11 ft (still 
less than 16xt).   This is still less than a 30-degree spread from the point 
of load to the support.   
 
When I have a concentrated load very close to a supported edge, I usually 
assume a 45-degree distribution between the load and the support for shear 
design.   


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What is an appropriate  effective width for a one-way slab with point load
occuring at the center span?  I have a 22 foot long span, 12" deep, 4000 psi
concrete.  




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