Research On Pseudo-Static Displacement And Aseismic Element Reliability Of Space Lattice Structures Under Multiple Support Excitations

Because of the complicated performance of space lattice structures under multiple support excitations, the pseudo-static displacement which is a part of total response is selected carefully to be investigated thoroughly. On the other hand, the element reliability obtained by multiple support excitations is compared to that analyzed by the simple support excitation. Meanwhile, The relationship between pseudo-static displacement and dangerous element is also studied.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, 2000m/s respectively are chosen to simulate the ground motion. On the basis of the time history response of space lattice structures under multiple support excitations, the rules of pseudo-static displacement development are summarized herein, which are related to structural span, apparent velocity and natural free-vibration period of structure. Moreover, the effect of structural form on pseudo-static displacement is analyzed, by which the conclusions obtained in the paper can be interpreted. The joints whose pseudo-static displacement are dominant in response are located near the support, and the effect of pseudo-static displacement on structure is decreased from edge to middle position. Apparent velocity has few effect on pseudo-static displacement, while structural span and natural free-vibration period of structure have various effect which meet the need of structural form. The directions of seismic wave have no effect on pseudo-static displacement.Based on the comparison of reliability index of above structures under the two patterns of excitations, the change of the amount of dangerous elements and the difference in their distribution are thoroughly analyzed, in which the effects of structural span, apparent velocity are also involved. The barrier value of structural span corresponding to the form of structure is presented, and the safety is insured within the span proposed in the paper while multiple support excitation is substituted by simple support excitation. The relationship between pseudo-static displacement and dangerous elements is investigated as also. The results show that the difference in amount of dangerous elements between the two patterns of excitations, as well as the degree of influence of the pseudo-static displacement on dangerous elements are closely related to the form of structure.