带高位大跨钢桁架转换层建筑结构动力分析

Dynamic Analysis on Building with Transfer Steel Trusses Located at a Higher Level

根据一栋带高位大跨钢桁架转换层建筑结构实际工程,建立了考虑楼板面内弹性变形高精度有限元空间质点系计算模型,进行了采用Ritz法求解技术的模态分析、单点加速度响应地震反应谱分析和时程分析。结果表明,转换钢桁架产生局部振型,形成结构薄弱环节,结构主振周期对应着地震力贡献最大的振型;转换钢桁架位置较高及其相邻层质量悬殊,使得高振型对结构动力特性影响显著;结构竖向刚度的非连续性改变了层地震力的分布,转换层及其上部结构层间位移角突变,主体结构与钢桁架平面外变形差异较大;地震波的频谱特性引起主体结构对El Centro波地震响应最强烈,而转换钢桁架局部对人工波地震响应最强烈。

According to a construction project of tall building with transfer steel trusses located at a higher lever, a three- dimension calculating model considering the in-plate elastic deformation of floor is built, in which the high-precision finite element method with beam and shell elements is used. To study the seismic performance of the structure, mode-frequency analysis with Ritz solution, single-point acceleration response spectrum analysis and time history analysis are applied. It is indicated that some modes corresponding to the maximum of earthquake force are principal, but others produced by steel trusses are local because of the weakness of theirs joints. Higher-modes can affect the dynamic performance of the structure evidently when transfer steel trusses are located at a higher level. The saltation of earthquake force along the height of building is caused by the discontinuous stiffness of the structure, which leads the story drift angle of structure to increase. The deformation difference between the main structure and steel trusses in Y direction is distinct under earthquake waves. In the seismic responses of main structure caused by artificial wave, site wave and E1 Centre wave, that caused by E1 Centre is the most intense one, but in the seismic responses of transfer steel trusses, that caused by the artificial wave is the most intense one, which are caused by the spectrum characteristics of earthquake waves.