Effect of Age at Loading and Load Arrangement on Immediate Deflections of One-Way Slabs

摘要

This paper demonstrates the influence of the effects of time-dependent properties, shrinkage restraint, age at loading, and load configuration on the immediate deflection of one way slabs based on the results of laboratory tests in which one-way slabs were initially loaded at varying ages (3, 7, and 28 days) with a concentrated load at midspan producing the service load midspan moment. The one way slabs were subjected to curing for either three days or seven days. The slabs were initially uncracked under self-weight only. The slabs were subsequently loaded at 156, and 333 days with the same concentrated load level at midspan. After 596 days, the slabs were re-loaded using third point loading to produce a midspan moment corresponding to the service load level. The test results clearly demonstrate the effect of shrinkage restraint stresses on the initial cracking moment and the effect of load arrangement and age at loading. Measured deflections are compared with calculated deflections based on Branson's effective moment of inertia and the more recent formulation by Bischoff.