Seismic Pushover Analysis (pushover) Research And Improvement

Compared with other seismic design methods, nonlinear static analysis (Pushover) has a lot of advantages, and more and more designers accept and use it, many countries have it included in their own design specification; but the base of the theory is not rigorous, there are many flaws that we need to improve. This paper has done some researches about the selection of the displacement shape vector and the definition of the plastic hinge for nonlinear static analysis method.Firstly, this paper has elaborated the research status, advantages with disadvantages and the direction of future research about Pushover; then has introduced the details about the basic principles and key steps of this method, and has done nonlinear static analysis and elastic response spectrum analysis to a neat steel frame structure through the form of hand-counted partly;Secondly, this paper has made improvements on selecting the displacement shape vector of the traditional Pushover analysis, the improved shape of the displacement vector considered the affect of high formation and stiffness after yielding, then it has used FORTRAN90 language to write the procedure for solving the target displacement with the method of capacity spectrum. Through the analysis and comparison of a case, I have known that the result of the nonlinear static analysis under the improved shape of the displacement vector is more close to dynamic nonlinear time history analysis than the traditional Pushover analysis;Thirdly, this paper has derived the N-M-φrelationship of reinforced concrete section on the base of the material constitutive in our own Concrete Specification, and then has discussed the affect of concrete strength grade, the configuration of tensile rebar and axial compression ratio to ductility factor, the results show that the reduction of concrete strength,the increase of tensile steel's reinforcement ratio and strength and the compoent's axial compression ratio will all reduce the ductility;Finally, this paper has used the N-M-φrelationship which was obtained in chapter four and the simplified formulas of rod ends'limit and yield rotation angles to define the M3 hinges of beam and the P-M3 hinges of column for a plane frame, then has input them to SAP2000 and done nonlinear static analysis, compared the obtained results with the results under the default hinges. The results show that it is necessary to customize the plastic hinges.