Study On 3d Linear And Nonlinear Seismic Response Analysis Method For Reinforced Concrete High-rise Building

With the development of economy and society, the social wealth accumulates greatly, so the financial loss caused by intense earthquake becomes heavier and heavier. The current seismic design concept,which aims to protect people's lives,does not work well on controlling the damage of structures and on decreasing the wealth loss. In order to control the response of structures in earthquakes, the idea of performance-based seismic design was developed the first time by the American scholars in early 1990s, then it got widespread acceptance in the world. The linear dynamic analysis method, the nonlinear static analysis (pushover analysis) and the nonlinear dynamic analysis, as the key tools of practicing the performance-based seismic design, were widely developed and improved. In this dissertation, based on the forerunner's works, the author studies the 3D seismic response analysis methods of linear dynamic analysis and pushover analysis of irregular concrete reinforced spatial structures systematically. The main work is as follows:1,Study and improvement on mechanic models of concrete reinforced columns, beams and beam-column joints.The 3D fibre model of concrete column is proposed in different type from the forerunner's model.Based on the deformation characteristic of columns, it is assumed that column's plastic deformation occurs evenly in the plastic hinge zones, and the column is divided into three parts, which are elastic zone in the middle and the plastic hinge zones with certain length in both ends. The elastic 3D column element is used to simulate the middle part, and the plastic 3D column element is used to simulate the plastic hinge zone. The column's stiffness matrix is computed by condense the structural matrix of the super-column-element with three substructures.The multi-segment model of plane beam is improved in this dissertation. In this model, the beam is divided into some parts and the sum can be adjusted freely, the section stiffness in each part is computed by cross-section analysis, and the beam's stiffness matrix is calculated by condensing the assembly matrix of all parts. Slippage of a rebar in the beam-column joints is studied by numerical simulating method. According to the result of slippage analysis and the result of the beam's cross-section analysis,the method of computing the relation between bending moment and slipping rotation on the beam end is proposed.A model of evaluating the slipping effect, in which two rotation springs are added on the beam ends, is developed, in which the two springs and the beam constitute the super beam element. 2,The multiple vertical-line element model of shear wall is improved in this dissertation. In author's work, the axial stiffness of vertical-line is calculated by two-parallel component model, in which the stiffness of concrete and the steel bar components is determined based on their constitutive relationship. The stiffness of shear spring is determined by softened-truss model. A new procedure considering the flexual deformation of the wall influencing its shear stiffness is proposed based on the wall's horizontal crack length and its crash length.This method is not only simple in calculation, but also effective in considering the wall's flexual deformation reducing its shear ability. A new method evaluating the effect of fixed-end rotation of the wall is developed, in which the fixed-end rotation is considered as the slippage of the longitudinal reinforcement in the foundation of the wall's column. The improved multiple vertical-line element model of shear wall is used to computed the two test walls, the load result is beyond the test result about 20% in terms of rectangular section wall, and agrees well with the test result in terms of wall with edge columns.3,Study on the 3D linear seismic response analysis method. Based on the rigid slab assumption, two types of 3D analysis model, which are the plane substructure model and the spatial pole-component-system model, are developed as the structural analysis model. The difference between the two types of 3D model and the reasons, studying by the dynamic analysis of a 9-story frame structure and a two-tower 20-story frame-tube structure, are discussed. Aiming at the deficiency of the plane substructure model, improvements at two perspectives are proposed, the improved model is more accurate.4,Study on the 3D nonlinear static pushover analysis method and making of computing procedure. N2 method and modal pushover analysis method (MPA) are studied. Based on the models developed in this dissertation, a 3D pushover analysis computing procedure is developed with MATLAB language. Then the N2 method and MPA method are used to evaluate the seismic performance of two irregular spatial frame structures with the computing procedure. The difference between the two pushover methods are examined. The influence of rebar slippage in the beam column joint is assessed, and the result shows that the target displacement and the story drifts increase due to rebar slippage.5,The accuracy evaluation of the 3D nonlinear static pushover analysis method. The accuracy of the 3D pushover method is evaluated from their target displacements, story drifts and story torsion rotations based on the average results of elasto-plastic time history analysis with multi earthquake waves, which use the common computing procedure CANNY as the analytical tool. The common drawbacks of 3D pushover method are disclosed, which are, (1) the seismic response in structural upper story is overestimated,and the seismic response in structural lower story is underestimated, (2) the deformation in the weaker story can not be discovered correctly.6,The improvements of the 3D pushover method. Two improved procedures are developed for N2 method, and they are: (1) pushing in x and y direction simultaneously N2 method. The combination of pushing loads in x and y direction, which leads to maximal torsion rotation, is given to the structure at same time. With this modification, the story torsion rotations improve effectively. (2)multi modal N2 method. The pushover analysis in x and y direction is performed with multi modal load pattern in this method, so the maximal story drifts and story torsion rotation improve greatly. Three improved methods are proposed for MPA method, and they are: (1) positive-and-negative MPA method. The disadvantageous effect of the modal load combination in positive and negative direction is considered in this method. For the slight irregular structure, the result of this method is much the same as that of MPA. But for the severe irregular structure, the result of this method is larger than that of MPA. So the disadvantage of the structural load or deformation in earthquake is discovered appropriately. (2) modal target displacements ratio MPA method. The higher modal target displacements are calculated based on the target displacements of"basic mode group"with a coefficient in this method. For one thing, the difficult caused by the odd higher mode pushover curves is solved, for another, the calculation of higher modal target displacements is simplified.And the accuracy of this method is as that of MPA, so it is a effective improvement.(3)load dependent Ritz vector (LDR) MPA with magnified higher modal target displacements. In this modification method, the load dependent Ritz vectors are used as the modal vectors in lieu of the exact eigenvectors, and the higher modal target displacements are magnified base on the truncation modal participating mass. This improvement leads to good result.