FLAT SLAB THICKNESS REQUIRED TO SATISFY SERVICEABILITY INCLUDING EARLY AGE CONSTRUCTION LOADS

The use of higher strength concretes and steel yield strengths allows designers to design thinner slab systems which satisfy all the require ments of strength. However, the use of thinner slabs lends to increase d deflections and the possibility of violating deflection serviceabili ty criteria. The shore-reshore method of construction applies signific ant construction loads to the immature supporting slabs. The span/thic kness provisions of ACI 318-89 do not consider the sensitivity of slab deflections to early-age construction loads or rate of construction A parametric study showed the current code requirements for minimum sla b thickness to be over conservative in some cases and insufficiently c onservative in others. A span-thickness criterion, which includes the effect of early-age construction loads, concrete strength, and panel a spect ratio, was developed from the results of the parametric study.