电视塔三维非平稳随机地震响应特性

采用随机振动复模态理论，对北京电视塔模型三维非平稳地震激励下的响应应特性进行了计算研究。结果表明：塔下部结构与上部结构响应有较大的差别，塔身、塔楼、混凝土桅杆响应的演变谱密度主要分布系统的第二、第四频率上，而钢结构桅杆的前六阶频率上增有较大的不可忽视的响应变密度，因此对电视塔结构的抗震设计应根据响应的特点考虑高阶振型的影响。

On the Response Properties of TV Tower under Three Dimensional Non-stationary Random Seismic Exciation

Existing methods for analyzing the dynamic properties of tall TV tower under seismic excitation, such as the response spectrum method, can not be used either to analyze the cross spectral densities or to analyze structures with non classical damping. In this paper, based on the complex mode analysis theory of random vibration, we derived eqs.(3) and (4) for computing the response evolutionary spectral densities of tall TV tower. With these two equations, we overcome the shortcomings of the response spectrum method. To our best knowledge, we did not find anything like eqs.(3) and (4) in the open literatures. Using eqs.(3) and (4), we computed the structure of Beijing TV tower under three dimensional non stationary seismic excitation. Results (Figs.3 through 6) show that the evolutionary spectral densities of the responses of tower body and observation deck and reinforced concrete mast are mainly distributed on the second and the fourth system frequency, but the evolutionary spectral densities of the responses of steel mast are mainly distributed on the first six system frequencies. Therefore the influence of the higher order system frequencies of tall TV tower must be taken into account in the aseismatic design according to its response properties.