Development of seismic fragility curves for the existing RC building with plain bars

Abstract

Concrete buildings reinforced by plain bars are one of the special types of old structures generally built before the 1970s. According to the experiences of earthquakes and experimental tests, the dominant damage mode in these structures includes a deep crack at the intersection of the beam with the joint panel zone. In this study, seismic fragility curves of existing concrete buildings reinforced by plain bars were investigated by means of incremental dynamic analysis and by consideration of soil-type effects and construction quality effects. A relatively simple and efficient non-linear model based on the experimental behaviour of exterior and interior joints of the represented building is used to simulate pre- and post-elastic behaviour of the joints which fail under bar slippage mode. Two record sets were considered corresponding to the soil types C and D of the NEHRP provision. The results indicated that the seismic vulnerability of the represented building increases at all damage states as the type of soil changes from C to D. On average, the median capacity of the building is decreased by about 30% for the moderate limit state as the type of soil changes from C to D. Also, the normal distribution function with median data is the best distribution function for seismic fragility assessment of the represented building.

Keywords:

• Fragility curve
• incremental dynamic analysis
• existing RC buildings
• plain bars
• beam-column joint

Disclosure statement

No potential conflict of interest was reported by the authors.