Fragility Analysis Method Based on Seismic Performance of Bridge Structure considering Earthquake Frequencies

Dept. of Civil Engineering, ChungAng University, Ansung 456-756, KoreaABSTRACT This paper presents a systematic approach for estimating fragility curves and damage probability matrices for dif-ferent frequencies. Fragility curves and damage probability indicate the probabilities that a structure will sustain different degreesof damage at different ground motion levels. The seismic damages are to achieved by probabilistic evaluation because of uncer-tainty of earthquakes. In contrast to previous approaches, this paper presents a method that is based on nonlinear dynamic analysisof the structure using empirical data. This paper presents the probability of damage as a function of peak ground acceleration andestimates the probability of five damage levels for prestressed concrete (PSC) bridge pier subjected to given ground acceleration.At each level, 100 artificial earthquake motions were generated in terms of soil conditions, and nonlinear time domain analyseswas performed for the damage states of PSC bridge pier structures. These damage states are described by displacement ductilityresulting from seismic performance based on existing research results. Using the damage states and ground motion parameters, fivefragility curves for PSC bridge pier with five types of dominant frequencies were constructed assuming a log-normal distribution.The effect of dominant frequences was found to be significant on fragility curves.Keywords : fragility curve, displacement ductility, curvature ductility, frequency