The Seismic Performance Of Tall Building Frame Structure With Vertical Step Back

The structure with vertical step back is a common high-level vertical irregularform, and there are two main forms: one is the upper of structure with vertical stepback; and the other one is that podium structure step back at the top of the podium.Because its vertical lateral force resisting members is discontinuity at the step backfloor, the lateral stiffness will be break at the step back floor. Although it’s not soserious as stiffness weakness that happens at the lower part of the frame structure withupper shear wall, the seismic performance of the structure with vertical step back isstill adversely affected. In this thesis, I will study whether the seismic performance ofthe structure with vertical step back that is based on10.6new provisions of Technicalspecification for concrete structures of tall building (JGJ3-2010) to be designed isimproved, as well as main factors that impact the seismic performance of structurewith vertical step back.In this thesis, two groups of models have been established: the first groupcontains2examples that are designed and calculated according as Technicalspecification for concrete structures of tall building（JGJ3-2002）；the second groupcontains24examples that are designed and calculated according as Technicalspecification for concrete structures of tall building（JGJ3-2010）. The sis exploreswhether the seismic performance of structure with vertical step back that be designedaccording as new specification is improvement by the contrast of the first group andsecond group of examples, and determines factors that impact the seismicperformance of structure with vertical step back by the contrast of the second group ofnumerical examples. The main contents in this thesis are as follows:1. The analysis models are established by using PKPM structural design analysissoftware developed by the China Academy of Building Research. Results contain theamount of reinforced bars in the frame, as well as vibration cycle, the elastic storydrift and column axial compression ratio and other factors.2. The amount of longitudinal reinforcement of the column can be determined byusing the software CRSC. In this thesis, we use the software RCM to calculatecolumns’ N-M curve, and then fit the curve by the software Origin. At the same time,RCM software is used to calculate the yield moment of the beam end. 3.In this thesis, we get the structural elastoplastic story displacement, the columnshear, beam-column plastic hinge and so on by the earthquake response of the modelsunder a actual earthquake wave, which obtained by the method of elastic-plasticdynamic time-history and using the plane structural dynamics response analysissoftware NDAS2D(Nonlinear Dynamic Analysis of Structures in2Dimensions).4. It is demonstrated that the seismic performance of the frame structure withvertical step back according as the new specification is better than the one accordingas the old specification by the contrast between the first group and the second groupof models. And It can be determined the factors that impact the seismic performanceof the frame structure with vertical step back by the contrast between the secondgroup of models.5. I deliver the conclusion by the analysis: the main factors that affect the seismicperformance of tall building frame structure with vertical step back contain thenumber of step back spans of tower, the storey high of podium, the number of tower’sspans. When the frame structure vertical step back small, it’s effect to promote theseismic level of vertical columns to improve the seismic performance of structure; butwhen the frame structure vertical step back greater, the elastic-plastic dynamictime-history method should be used to analysis the seismic performance of thestructure.