Assessment And Improvement Of Planar Nonlinear Static Analysis Method For Building Structures

In recent years , performance-based seismic design(PBSD) has been become the new direction of seismic design. The basic idea of PBSD is to define performance objectives for earthquake severity with specified limiting levels of damage. Which provides building structures of different performance objectives, so as to satisfy diverse performances requirements of society and owners. Therefore, as the important means for performance-based seismic design, the research and improvement of pushover analysis (nonlinear static analysis) is necessary.In this paper, pushover analysis has been studied more profoundly based on previous researches and the theory of PBSD. In order to enhance the accuracy of pushover analysis, a bar element model which reflects the effect of the reinforcing steel arrangement has been presented, and the related procedures have been programmed.In this paper, five structures and five lateral load distribution patterns(three fixed patterns ,two adaptive patterns) are utilized for Pushover analysis. The deformation and ductility (including the top drift and interstory drifts and plastic joints distribution) are used as measure for structural performance. The results of these five structures from inelastic time-history analysis have been regarded as credible dates for comparison with those from pushover analysis. Analysis results show that the pushover analysis can predict the seismic response well for the low and medium-rise structures. The lateral load profiles have obvious influence on the performance of structure. Generally speaking, the uniform distribution and inverted triangular distribution represent the two extreme cases, if the other conditions are same, the base shear of structure at the yield point under inverted triangular shapes will be smaller than the base shear under uniform shapes.At last, the model pushover analysis (MPA) is further improved, which provides performance analysis of structure with higher accuracy. Due to neglecting the coupling among modes, MPA procedure has some errors. But it is accurate enough for practical application. Moreover, a new pushover analysis has been developed based on the traditional accurate calculation method of structure, which can simplify the earthquake response analysis of structures greatly. The results of a numerical example demonstrate that this method is feasible for preliminary performance assessment of some regular structures.