Effect of Construction and Service Loads on Reliability of Existing RC Buildings

Abstract

For existing structures, information about “safe” past performance (such as prior load history) may be used to update the probability distribution of resistance and hence reliability. This technical note investigates the effect of realistic construction loading with sustained dead and live loads and extraordinary live loads on time-dependent probabilities of failure. Structural configurations considered include RC floor beams and slabs designed to ACI 318, for various live-to-dead load ratios and construction periods for typical RC multistory buildings. The results show, for example, that the probability of failure for an existing structure after 5–10 years of occupancy is one or more orders of magnitude lower than that prior to the application of construction loads. This suggests that, if a structure survives construction and early service (occupancy) loads, then its reliability is increased significantly. Finally, for cases where prior service live loads are unknown, the inclusion of construction dead loads alone will still lead to significant increases in structural reliability.