Seismic Response Of Simply-supported Girder Bridge Subjected To Near-fault Ground Motion

Compared with the far-field ground motion， near-fault ground motion hadsignificant different special effect and great destractive power to structures. Velocitypulse caused by the directivity effect and fling-step effect was an important factor todamage the strctures near the fault zone. The great Wenchuan earthquake, occurred insouthwest China where had complicated topographical and geological conditions, mademany bridges near the fault zone seriously destroyed. Some special demagecharacteristics, such as rotation of the upper structure was very prominent in the faultzone within2km. The proportion of the bridges destroyed almost100%near the faultzone and the destruction factors were complex and diverse. As a component oftransportation lifeline system, it was an important task to ensure the earthquakeresistance capacity of bridge structures. Therefore, it was very important for studyingthe seismic damage mechanism of bridges near the fault zone. Yingxiu Minjiang Bridgewere selected as an example to study the earthquake damage mechanism of bridges innear-fault zone, herein considering the effect of pole-soil-bridge dynamic interaction,this paper studied the seismic response of the simply supported girder bridges undernear-fault ground motion. The main works were as follows:(1) The mainly bridges damage region and damage characteristics in Wenchuanearthquake were summarized. The typical characteristics of near-fault ground motionwere elaborated, near-fault ground motion research status was also introduced.(2) Near-fault ground motion frequency spectrum characteristic were analyzed intime domain and frequency domain by use of earthquake ground motion responsespectrum (including acceleration, velocity and displacement response spectrum), thefourier spectrum and power spectrum.(3) As an example, Yingxiu Mingjiao bridge, a typical simply-supported girderbridge, its seismic response under near-fault and far-fault ground motion were analyzedand compared in details, and herein, pile-soil interaction was considered. The resultsindicated that seismic response of the bridge under near-fault ground motion was muchgreater than that of far-fault ground motion. It had a great influence on the seismicresponse of bridge with or without considering the pile-soil interaction, particularly forthe displacement response of bridge system. (4) Simply-supported girder bridges with lead rubber bearing(LRB) in near-faultzone were studied in the last. The result showed that the isolated effect for bridge innear-fault field was poorer than that in far field. Whether considering the pile-soilinteraction affected the seismic response in certain extent.