大跨门式钢管桁架结构多点输入地震响应分析

Seismic Response Analysis of Large-Span Gate-Type Tube Truss Structures Under Multi-Support Excitation

地震动空间效应导致结构不同支座处的地震激励不一致,大跨结构应进行多点输入地震响应分析.本文对一大跨门式钢管桁架结构进行多点输入时程分析计算,考察该类型结构分别受水平和竖向地震多点输入行波效应作用下的弹性响应特征.计算结果表明,多点输入地震动激发门式结构的水平对称振型和竖向反对称振型,是导致结构多点输入地震响应与一致输入产生差别的重要原因;地震波波速对结果影响较大,为保证结果的可靠性,应取有效范围内的多个视波速进行计算;上部结构和下部结构相比,刚度小的部位结构响应受多点输入影响大;水平多点输入桁架梁中部构件、竖向多点输入桁架梁端部构件内力变化极大.

Viewing the inconsistency of earthquake ground motions of structural bases for large span structures, it is necessary to take the multi-support excitation into account. A typical large span Gatetype Tube Truss is taken as an example to investigate the seismic response properties of the structure form under horizontal and vertical multi-support excitation considering the wave-passage effect via time-history method. The results show that （1） the difference between multi-support and uniform excitation is primarily attributed to the different excited modes, which are horizontal symmetric modes under horizontal earthquake while vertical antisymmetric modes under vertical earthquake; （2） more wave velocities are proposed to be employed to obtain reliable results since they have a strong influence on the seismic response; （3） for the upper and lower parts of the structure, the parts with smaller stiffness are more sensitive to the multi-support excitation; （4） under horizontal multi-support excitations, the internal forces of elements near the centre of truss beam differed greatly from the counterpart under uniform excitation, and so did the elements near the end of truss beam under vertical multisupport excitations.