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在古建筑结构保护中,无损伤或微损且便携快速的高精度检测手段以及识别结构损伤的方法一直是重要的研究课题。本文基于古塔结构的动力特性,建立了基于模态信息的古塔结构损伤识别方法,采用损伤前后结构的低阶模态信息差异进行损伤定位和损伤程度评估。首次用将该方法对典型砖木混合古塔结构——上海市松江方塔开展了研究。采用微动测试技术,获取损伤结构的动力特性参数(模态信息),采用数值方法计算获取结构未损伤模型的特征值。对测试参数及计算参数进行统一物理量的数据归一化处理后,利用结构的单元刚度矩阵作为诊断项,根据损伤表征向量进行了损伤定位及损伤程度评估。通过微动测试技术评价的结构整体损伤与以往的历史记录及测绘结果进行比较,得出结构7层、8层刚度损失最大,达到0.56,其次为第9层,达到0.78。
In the protection of ancient buildings, high-precision detection methods without damage or micro-damage, and fast and portable, as well as a method of identifying structural damage, have long been an important research topic. Based on the dynamic characteristics of pagoda structure, a damage identification method of pagoda structure based on modal information is established. The damage localization and damage degree are evaluated by the difference of low-order modal information before and after the damage. For the first time, this method was used to study the typical brick-concrete pagoda structure - Songjiang Fangta, Shanghai. The dynamic characteristic parameters (modal information) of the damaged structure are obtained by using the fretting test technique, and the eigenvalues of the undamaged structure are obtained by numerical method. After normalizing the test parameters and the calculated parameters, the unit stiffness matrix of the structure is used as the diagnosis item, and the damage localization and damage degree are evaluated according to the damage characterization vectors. Compared with the historical records and the mapping results, the total structural damage evaluated by fretting test technology is compared with the historical records and mapping results. The results show that the stiffness loss of the 7th and 8th floors is the largest, reaching 0.56, followed by the 9th, reaching 0.78.