实心砖石古塔动力特性与结构损伤分析

为研究“丝绸之路”起点世界文化遗产建筑兴教寺测师塔的动力性能及结构损伤，采用超低频动态测试系统进行了原位动力测试试验.在环境随机激励下，采集了该塔各楼层顶部水平振动的速度响应信号，经滤波后通过积分变换进行自谱及互谱分析，得到了结构沿水平方向的前2阶自振频率与振型.并依据结构测绘结果，建立测师塔数值模型，计算了弹性模量逐渐降低时的振动特性，并与测试结果进行对比，依据结构损伤参数识别的改进形法，进行了测师塔结构损伤分析.结果表明，该塔沿东西与南北两个水平方向的前2阶频率值相近，第1阶振型呈弯曲型，第2阶振型呈弯剪型；与无损砌体弹性模量的取值比较，测师塔结构的等效弹性模量降低较多，其结构整体损伤较为严重.因此，可通过确定无损砌体的弹性模量，采用动力测试及数值计算依据等效弹性模量进行残损砖石古塔结构损伤识别.

DAMAGE AND DYNAMIC CHARACTERISTICS ANALYSIS OF A SOLID STRUCTURE PAGODA

In order to study the dynamical characteristics and structure damage of Ceshi Pagoda in Xingjiao Temple, which is one of the world heritage of culture buildings, we conducted in-situ dynamical test by super low frequency dynamical test system. Stimulated by a random vibration, the velocity response data in the top of each floor is gathered after wave filtering. By self spectral and inter spectral analysis with integral transform, the first and second stage of frequencies and vibration modes are acquired along the horizontal direction. A finite element model of Ceshi Pagoda is constructed, based on the measured data. The vibration characteristics are calculated for decreasing elastic modulus. Then they are contrasted with the test results.The structure damage analysis is performed, based on Improvement Shape Method for damage parameter identification. The results show that the first and the second stage vibration frequencies are close to each other along NS and EW direction. The first stage vibration mode is bending type, and the second is bending and shearing type. The effective elastic modulus of Ceshi pagoda is much smaller than that of a masonry structure in good conditions. Therefore, the damage of masonry pagodas can be recognized from the results of dynamical test and numerical calculation, after the elastic modulus of complete masonry structures is defined.