Seismic Behavior And Element Reliability Of Space Lattice Structures Under Multi-Dimensional And Multi-Support Excitations

The seismic excitation of space lattice structures is not only multi-dimensional but also multi-support, so ground motions are very complicated. The dynamic behavior under multi-dimensional and multi-support excitation is analyzed and the comparisons are made with the structure response under multi-dimensional and simple-support excitation. On the other hand, the element reliability obtained by multi-dimensional and multi-support excitation is studied based on reliability index. Besides, a simplified method to calculate member forces under multi-dimensional and multi-support excitation is presented.The Harichandran model is used as horizontal coherency function and Dr. Liu's model is used as vertical coherency function. Horizontal and vertical acceleration ground motions, being true of the above coherency functions, are generated through the WAWS(weighted amplitude wave superposition)method, which is improved through FFT(fast fourier transform) technique by Prof. Ye. Based on the above theories, several parameters are set reasonably in application. Six grades whose apparent velocity is 50m/s, 100m/s, 200m/s, 300m/s, 500m/s respectively are chosen to simulate the ground motion.The dynamic behavior of space lattice structures subjected to multi-dimensional and multi-support excitation, as well as to multi-dimensional and simple-support excitation are thoroughly analyzed based upon time history method. The characteristic of the distribution of member forces under these two kinds of earthquake motions is studied and some differences are reached. Furthermore, the effects of the structural span and the apparent wave velocity on these differences are also suggested.The aseismic reliability subjected to multi-dimensional and multi-support excitation, as well as to multi-dimensional and simple-support excitation are thoroughly analyzed based upon the fast multi-support response spectrum method. The aseismic reliability obtained by the multiple support excitation is compared to that investigated by the simple support excitation, such as the difference in the distribution and the amount of dangerous members. The relationship between the dangerous members and the span, as well as the apparent velocity is studied as also.Applying with above theories, Laoshan bicycle-gymnasium for the Olympic games is analyzed in detail.The differences of structural response between multi-dimensional excitation and simple- dimensional excitation are analyzed, based on which this paper presents a simplified method to calculate member forces under multi-dimensional and multi-support excitation. After learning the member forces under multi-dimensional excitation, simple-support excitation and multi-support excitation, we can know the member forces under multi-dimensional and multi-support excitation through the simplified formula. The time of simulation of ground motions in simplified method is shortened to 1/2. Numerical results show the method decreases the consuming time and is simple and accurate.