An Evaluation On The Effect Factor And Investigation On The Improving Method Of The Model Pushover Analysis

Pushover analysis is extensively used gradually and recommended by the new national code of seismic design of buildings as a simplified method for structure seismic evaluation.The selection of the lateral-force distribution is one of the critical issues in Poshover analysis,which directly affect the accuracy of Poshover analysis especially when the higher mode effect of structure is obvious.For the structure with no obvious higher mode effect,pushover with the lateral force distribution which is used extensively presently can offer better accuracy.By contraries,the reliability of pushover analysis need more investigation for the structure with obvious higher mode effect.The development of Modal Pushover based on structural dynamics theory provide a new methed in solving that problem.The principal objective of this paper is to develop a precedure of improved Modal Pushover analysis.the key of the investigation includes the following parts:The first part is to evaluate pushover and Modal Pushover Analysis completely and to evaluate the influence of the structure natural period of vibration and the nonlinear degree of structure on pushover analysis.The second part is to evaluate influence of the higher mode to the whole response of structure.The third part is that based on the conclusion that the nonlinear degree of structure affects the pushover anasysis obviously,The third part is to develop a plan about deducing the structure element stiffness to improve the MPA.The main conclusions obtained from above research are as follows:(1) The upper floor responses of POA are larger than the results of Time History Method, but the lower floor responses are overestimated in a different degree. The descending order of error is model A, D, B, C, and the order is out of the influence of structure. The four POA lost in the judgment of the plastic hinge's location of the upper beams and columns. On the other hand, The MPA of which mass participation ratio reaches 95% is better than POA,but it tend to overestimate story shear. It is the most important that MPA can find the plastic hinge's location more accurately, and the numerical error is restricted within a reasonable level.(2) The influence of natural period of vibration on the accuracy of POA is significant, and with the increase of period, the overestimation of upper floor is further amplified. MPA is affected limitedly by period and the primary influence is changing overestimation for underestimation in upper floor.(3) In the whole analysis, the effect of the nonlinear degree of structure on the drift in pushover analysis is obvious, and with the increase of nonlinear degree, Errors are increased in a some degree.(4)Both of the stiffness-reduction methods can improve the results of MPA, especially in the global reaction, and the improvement of the second method is not affected by nonlinear degree of structure and the period.