Performance-based Probabilistic Seismic Demand Analysis Of Bridge Structures

In recent earthquakes, many structures and their component have experienced severe damage. Most of this damage was the consequence of excessive seismic displacements and deflections that have been substantially underestimated in design. Such intensity- based design deficiencies challenged the general philosophy of earthquake-resistant structual design codes, which has been to preserve human lives in structures by preventing structural collapse. This paper proposed the performance-based probabilistic seismic demand analysis which is able to overcome shortcomings of traditional seismic disign codes. This method considers the uncertain of groud motions and the randomness of structures.Basing on the probabilistic seismic demand analysis, seismic performance of ordinary conrete bridges has been studyed in this paper. The fragility curves of the limit state of NO, IO, CP, and LF of the structure were presented and compared. The probability assessment of the seismic performance has been presented during the seismic design period of 50 years. The results show that , when the different engineering demand parameters were regarded as the quantitative indicators, the fragility results were affected, and the bridge met the multi-level seismic fortification.With this method, the damping bridge also has been researched in this paper. The fragility curves of the structures with and without dampers were presented and compared. Combining the fragility curve with seismic hazard curve, the 50 years demand hazard curves of the structure were obtained. The results show that, during fifty years, the exceeding probability of collision for without dashpots of the bridge was close to the limit probability, nevertheless, it could well meet the performance level when with dashpots for the bridge.During weak earthquake, the dampers for structural seismic performance improvement was not very clear but very significant during strong earthquake.