Abstract：The ancient Tibetan city wall has high historical and cultural value, but after hundreds of years of wind and rain erosion, its safety performance is significantly affected by some serious defects. To obtain the dynamic characteristics of the Tibetan ancient wall and accurately evaluate the performance of Tibetan ancient buildings, an ambient vibration test was carried out on an ancient Tibetan wall. Based on the ambient excitation data, the covariance-driven stochastic subspace method was used to conduct the identification of modal parameters. Furthermore, the accuracy of the method in identifying modal parameters was verified based on one classical case. By combining the covariance-driven stochastic subspace identification method and the random decrement technique, the frequency, mode shape and damping ratio of the out-of-plane vibration of the city wall were obtained. Finally, in view of the complex mechanism of the damping ratio and the large recognition error of identification, the damping ratio of the city wall was further accurately estimated based on the Cramer-Rao lower bound, and then the results of damping ratio with less variability were obtained. With the wall segment E taken as an example, the Cramer-Rao lower bound method produced the damping ratios with smaller dispersion than the stochastic subspace method based on the random decrement technique as well as the STD method, and the coefficient of variation was reduced from 0.273 and 0.290 to 0.046, respectively.
刘威 杨娜 白凡 常鹏. 基于环境激励的藏式古城墙动力特性研究[J]. 土木工程学报, 2021, 54(4): 45-56.
Liu Wei Yang Na Bai Fan Chang Peng. Research on the dynamic characteristics of Tibetan ancient city #br#
wall based on ambient excitation. 土木工程学报, 2021, 54(4): 45-56.
