Seismic Reliability Assessment of Existing R/C Flat-Slab Buildings

Abstract

The reliability of existing reinforced-concrete flat-slab buildings, designed and detailed to resist gravity loads only, was studied for punching failure at connections under earthquake-type loading. Two flat-slab buildings, three and 10 stories in height, designed according to the ACI 318-56 building code, were used in the nonlinear dynamic analysis and reliability calculations. Results from previous experimental results on the seismic resistance of slab-column connections were employed to establish the effective slab widths, unbalanced moment-transfer capacity of connections, and their punching strength. The member dimensions, material strengths, and live load were treated as random variables and the effect of model uncertainty was included in the calculations of reliability indices. Random earthquake time histories were generated with the Kanai-Tajimi power spectrum. The limit-state function was based on the punching failure capacity of the interior slab-column connections. Based on the reliability analysis, the probability of failure of existing flat-slab buildings are presented for different soil conditions and peak ground accelerations varying from 0.05