Seismic Vulnerability Assessment of Existing Multi-Story Reinforced Concrete Buildings in Egypt

Although seismic design codes are often subjected to improvements after each earthquake disaster, old constructions are left unprotected by new technology. The purpose of this paper is to promote public welfare and safety by reducing the risk of death or injury that may result from the effects of earthquakes on existing reinforced concrete (R/C) building stock in Egypt. It aims to evaluate seismic vulnerability of the most commonly used type of multi-story RC buildings. Special attention is placed upon examining R/C buildings with vertical irregularity. The seismic vulnerability assessment for existing R/C buildings is assessed through examining two types of damage indicators: damage index and inter-story drift limit state. A sample building set is selected to reflect existing construction practice including regular buildings and those with vertical irregularities. The effects of vertical irregularity at different floor levels are examined by developing fragility curves of medium-rise gravity load designed R/C buildings. Fragility curves of the investigated building set are determined by nonlinear time history analysis to evaluate the damage state. These curves are used to represent the probabilities that the structural damages, under various levels of seismic excitation, exceed specified damage states by means of earthquake intensity damage relations. The analytical damage evaluation in this study shows that the seismic effects of earthquakes experienced in Egypt may be significant. Moreover, it shows that some of the earthquakes may impose excessive displacement demands on the investigated buildings. The results also show that the irregular buildings are more vulnerable than the regular ones.