土-输电塔-线体系在地震动差动作用下的地震反应分析

首先,建立土-输电塔-线体系的三维空间有限元模型,土、输电塔以及导(地)线分别采用实体单元、梁单元和索单元;然后,根据场地条件并依据GB 50260—96《电力设施抗震设计规范》生成支座位置的非平稳空间地震差动;最后,对该结构体系进行空间差动激励下的地震反应的时程计算。由分析结果可以看出:1)考虑土的共同作用后,与塔-线结构体系相比,土-塔-线结构体系的自振特性变化很小,说明对于这种高柔结构而言土层对结构的自振特性影响可以忽略不计。2)无论是对于塔-线结构体系,还是土-塔-线结构体系,差动因素增大输电塔的底部杆件的弯矩和剪力,这说明差动作用在工程中是需要考虑的;3)与结构自振特性分析结果不同,对于结构的动力响应而言,土-塔-线体系中塔的内力(弯矩和剪力)均比塔-线体系中塔内力大,这说明土层对地震动输入有放大作用。

SEISMIC RESPONSE ANALYSIS OF STRUCTURAL SYSTEM OF SOIL-TRANSMISSION TOWER-LINES SUBJECT TO SPATIALLY VARIABLE EARTHQUAKE GROUND MOTIONS

In this paper,a three dimensional finite element model of structural system of soil-transmission tower-lines is firstly established using FE software.Then,according to soil condition and "Code for Design of Seism of Electrical Installations"(GB 50260—96),the spatially variable ground motion time histories at the location of support are generated.At last,the seismic responses of the soil-transmission tower-lines under uniform excitation and multiple support excitations are studied by adopting the time history analysis method.From the numerical analysis results,it can shown that: 1) considering the soil-structure interaction effect,modal analysis results of tower-lines system and soil-tower-lines system are almost the same,which indicate that the influence of soil on self-vibration character such as this kind of tall flexible structure can be neglected.2)multi-support input can increase the seismic response of the shear force and moment of bottom frames of tower-lines system and soil-tower-lines system.3) different from modal analysis results,dynamic response(moment and shear force) of frame in soil-tower-lines system is larger than those of frame in soil-tower-lines system,which further shows soil has magnify effect on earthquake motion input.