Studies On Effects Of The Numbers And Spatial Positions Of Shear Walls On Seismic Performance Of Frame-wall Structures

Structural failures in recent earthquakes have exposed the weakness of current design procedures and shown the need for new concepts and methodologies for the seismic performance evaluation of structures. On the basis of the requirements, performance-based seismic design was developed. Frame-wall structures are studied emphatically in the paper. First of all, a method of performance-based seismic design for determining the optimal quantity of the shear walls is presented. Secondly, the influence of planar disposal of walls on structures torsion is discussed. At last, the effect of shear wall height on seismic performance is studied after ascertaining the numbers and planar disposal of shear walls.Based on a spatial elastic-plastic procedure PUSH&EPDA, frame-wall structures are studied with the pushover and time-history analysis methods. The ductility factor responses of frame structures are calculated for different the numbers of walls and base shear coefficient of frames. The results show that, for relatively small base shear coefficient of frames, shear failure of the walls result in large elastic-plastic displacement responses of the frames and even in failure of the structure in a strong seismic motion. An increase in the number of walls sometimes worsen the response of frame-wall buildings. However the response displacements decrease gradually as the numbers of wall increase for relatively large base shear coefficient of frames. After analyzing the results of the calculation, empirical formulas for the required base shear coefficients of the walls and frames which gave a target ductility factor response also are expressed. These equations should be of practical use in designing numbers of frame-wall buildings.The paper describes the need of controlling torsional vibration response and reviews a series of correlative principles on the Chinese Codes of Seismic Design. The studies on the effects of the accidental eccentricity on seismic responses of frame-wall structures and the pushover analysis of irregular structures are emphasized. The results show that the influence of accidental eccentricity and ability resisting horizontal shear forces are declining with the irregular extent increasing.The pushover analysis method and the time-history analysis that seismic input is bidirectional earthquake ground motion are applied to study the effects of shear wall height on frame-wall structures nonlinear response. Some parameters including shear force and turnovering moment distributions could be conducted with the different height of walls. The present numerical analysis shows that it is not necessary to extend the shear wall over the entire height of the structure for some frame–wall structures.