Fragility Assessment in RC Bridges Considering the Cumulative Damage over Time Due To Earthquakes

This study presents a criterion to estimate the structural fragility of reinforced concrete bridges considering the cumulative damage over time caused by seismic sequences. Fragility curves are obtained for different instants of interest associated with different levels of performance. The occurrence of seismic loads are characterized by a stochastic Poisson process. Uncertainties related with the construction processes of the structural elements and the manufacturing of the materials are considered. Fragility curves at the instants of 0, 50, 75, 100 y 125 years are obtained from nonlinear dynamic analysis which the maximum drift of the bridge deck is considered as the parameter of seismic demand measurement. The criterion is illustrated in a continuous RC bridge designed to satisfy a performance level equal to 0.002, the bridge is structured by AASHTO – type beams and circular columns. The structure is located in Acapulco, Guerrero, Mexico. The probability of exceedance of the drift design threshold of 0.002 associated with intensities of 0.05 sa/g increases up to 58% between 0 years (without damage) and 125 years after the bridge construction when the cumulative damage given by seismic sequences over time is considered.