Variance of Reinforced Concrete Slab Depths

摘要

Slab depths were measured on 3 floors of a reinforced concrete office building. Measured depths were, on average, about 8mm greater than nominal (design) depths. The mean variation from the nominal depths varied significantly from floor to floor, but not between regions of the individual floors. For each floor, the standard deviation of the depth variations was roughly 8mm. The depth variations were compared with construction tolerances specified in several standards. The specified tolerances appeared to be unrealistic, inappropriate and unenforceable. Apparently, the accuracy of construction has not changed much over the last 35 years. On the basis of the results, a detailed mathematical model of slab depths is proposed, and statistics of the model parameters are estimated. Applications of the model are discussed with regard to design estimates of the strength, weight, stiffness and deflections of reinforced concrete floor slabs.