Time-dependent Seismic Fragility for Aging RC Frame Structures in the Inland Atmosphere Environment

Abstract

ABSTRACT For inland cities with high concentration of carbon dioxide in the air, the seismic performance of RC structures deteriorates over time. In this study, a previously developed concrete carbonation and corrosion model was introduced to the framework of seismic fragility analysis to investigate the effects of environmental factors on the seismic performance of RC structures, considering carbon dioxide, humidity, and temperature. An approach to quantify the effects of these environmental effects on the time-dependent fragility of deteriorated RC buildings in the inland atmosphere environment was proposed. A four-story three-bay RC structure was analysed as a case study. Pushover analysis was performed to identify the damage limits of the structure as a function of the exposure time (0, 25, 50, 75 and 100 years). Fragility curves of the structure at different exposure times were developed based on the time-dependent seismic demands and predefined limit states. The results show that the structure deteriorates when exceeding the design life of durability. In general, the damage to the deteriorated structure increases with time and intensity of ground motions. In particular, the margin between severe damage and collapse decreases significantly over time. This means that aging structures are likely to collapse suddenly after severe damage occurs. Therefore, the time-dependent seismic performance of the aging structures in the inland cities should be carefully considered.