近断层地震作用下大跨度拱桥响应研究

目的对比研究近场地震作用下大跨度拱桥采用7组时程波的计算结果平均值与采用3组时程波的计算结果最大值的差异,为近断层地区大跨度拱桥的抗震设计提供参考.方法针对某大跨度拱桥建立有限元分析模型,在PEER数据库选取近场地震作用并施加于拱桥,得到时程响应的峰值.针对现行规范7组波作用时响应峰值的平均值与采用3组波组合时计算结果的最大值以及7组近场和远场地震作用的响应峰值的平均值进行对比研究.结果采用3组近场地震波组合计算所得的拱顶竖向位移、拱顶轴力、拱脚弯矩和跨中吊杆内力响应最小值分别是7组近场地震波计算结果平均值的0.42倍、0.48倍、0.79倍、0.75倍;采用3组近场地震波组合计算所得的四项响应最大值分别是7组近场地震波计算结果平均值的2.7倍、2.8倍、1.9倍、1.5倍.7组近场地震波作用所得的四项响应峰值的平均值分别是远场地震作用相应值的0.82倍、0.85倍、0.61倍和0.61倍.结论对于Ⅲ类场地的大跨度拱桥,按照规范规定采用3组近场地震波进行响应计算时,3组地震响应结果的最大值与按7组地震波计算结果的平均值之间存在很大差异、离散性很大;采用7组地震波进行时程响应计算时,近场地震响应峰值的平均值小于远场的平均值.

Response of Long-Span Arch Bridge under Near-Fault Earthquake

To study seismic responses of bridge,a finite element model for long-span arch bridge on site classification of III is established in this paper. Seven records of near-fault seismic w aves w ere selected from the PEER database and the corresponding peak responses w ere calculated. According to the Guidelines for Seismic Design of Highw ay Bridges（ JTG / T B02- 01- 2008）,peak averages for four responses（ vertical crow n displacement,arch axial force,arch foot bending moment and internal force of hanger rods） under the seven seismic w aves and the maximum values of responses under each combination of three w aves w ere obtained. The global minimum values of responses are respectively 0. 42,0. 48,0. 79 and 0. 75 times of the corresponding average values. Correspondingly,the global maximum values of these responses are 2. 7,2. 8,1. 9 and 1. 5 times of the average values,respectively. But the response average values under seven near-fault seismic w aves are respectively 0. 82,0. 85,0. 61 and 0. 61 times of the corresponding ones calculated by seven far-field seismic w aves. Results show that for a long-span arch bridge on site classification of III,thedifference is very large betw een the maximum values of responses under a combination of three w aves and the average values under seven near-fault seismic w aves. The average values of responses under seven nearfault seismic w aves are smaller than that ones by seven far-field seismic w aves.