Nonstationary Random Seismic Response Of Lattice Shells Under Multi-Support And Multi-Dimensional Earthquake Inputs

This thesis presents a nonstationary random response study of lattice shells under multi-support and multi-dimensional earthquake excitations. First, the methods for multi-component seismic response analysis are summarized. Then, the multidimensional pseudo excitation method is developed for nonstationary random vibration analysis of lattice shells under multi-support and multi-dimensional earthquake inputs. This method is proved to be an accurate solution of random vibration equation, in which all cross-correlation items, either between earthquake inputs or between participant modes are involved naturally. Compared to conventional method, the computational efficiency of the developed method is much higher. It is found that the derived method is particularly suitable for random vibration analysis of long span lattice shells which are usually characterized with closely spaced natural frequencies and coupled vibration modes. After then, input parameters for random seismic model are discussed. Based on new seismic code "Code for Seismic Design of Buildings" (GB50011-2001), a method of selecting parameters and equivalent phase velocity of the earthquake wave for multidimensional analysis is suggested. Based on above research, a computer program has been developed for the random vibration analysis. The program is highly efficient and can deal with the influence of traveling wave effect and nonstationary seismic excitation. And then, random vibration analyses are performed for both double-layer cylindrical lattice shells and single-layer cylindrical lattice shells to investigate their seismic performance under multiple seismic inputs. And comparisons are made between stationary and nonstationary responses, multi-dimensional and single-dimensional responses, etc. Some valuable conclusions are drawn and the effects of different parameters on seismic responses of lattice shells are investigated. Finally, the response spectral method for earthquake resistant design of structures to multiple seismic ground motions is further studied. The combination formula for multidimensional response spectral approach is put forward and verified in terms of a concept of equivalent spectrum. The achievements of this thesis enrich the theory of multi-dimensional seismic response analysis and provide good reference for practical seismic design of structures.