哪吒大桥地震响应分析

Analysis to seismic response of Nazha suspension bridge

建立了哪吒大桥———钢桁加劲梁悬索桥的三维有限元计算模型,对该桥进行了振动特性和地震响应研究,对比分析了一致激励下和考虑局部场地效应、行波效应非一致激励下的桥梁地震时程响应的差异。计算结果表明,由于悬索桥的钢桁加劲梁采用半飘浮体系,纵向约束较弱,桥梁第1阶振型为钢桁加劲梁的纵飘;各阶振型的频率呈现出密集分布的形态;考虑地震波传播速度产生的行波效应的影响,桥梁的地震响应与一致激励下的地震响应有一定差异;局部场地效应对哪吒大桥的地震响应影响较大,特别是对大缆应力及结构变形影响很大;哪吒大桥在7度设防(地震波峰值加速度不超过0.15g)时,大桥的抗震安全性是可以得到保证的。

Introducing 3D model and free vibration of Nazha suspension bridge in detail, the paper analyzes seismic time-history response under uniform excitation and considering traveling wave effect and local site effect non-uniform excitation. According to analytical result, longitudinal stiffness is weaker than vertical stiffness because of half- floating system, and the first vibration mode is longitudinal floating. Traveling wave effect is non-significant to seis- mic response of the bridge, and local site effect is distinct to cable＇ s stress and structural stress of seismic response of the bridge. When seismic wave acceleration is no more than 0. 15g according design document＇s 7 degree seismic zone, the bridge is secure.