A review of existing pushover methods for 2D reinforced concrete buildings

Student: Manuel Lopez
Supervisor: Dr R. Pinho

Abstract

It is well known, within the Earthquake engineering community, that the most accurate method of seismic demand prediction and performance evaluation of structures is nonlinear time history analysis. However, this technique requires the selection and employment of an appropriate set of ground motions and having a computational tool able to handle the analysis of the data and to produce ready-to-use results within the time constrains of design offices; clearly, a simpler analysis tool is desirable. One method that has been gaining ground, as an alternative to time history analysis, is the nonlinear static pushover analysis. The purpose of the pushover analysis is to assess the structural performance by estimating the strength and deformation capacities using static, nonlinear analysis and comparing these capacities with the demands at the corresponding performance levels. Traditionally, conventional (i.e. non-adaptive) has been used and implemented in design codes. Although it provides crucial information on response parameters that cannot be obtained with conventional elastic methods (either static or dynamic), this method is not exempt from some limitations such as the inability to include higher mode order effects or progressive stiffness degradation. Therefore, the need for a fully adaptive procedure that overcomes the above deficiencies is readily noted. A revision of the "non-conventional" pushover procedures recently proposed was carried out, from which advantages and disadvantages of each approach were identified. It was noted that adaptive pushover methodology constitute a viable option to nonlinear dynamic analysis since it solves the inherent deficiencies that conventional pushover analysis possesses. Additionally, the possibility of using an alternative modal combination to the quadratic modal combination rules (i.e. SRSS and CQC) has been proposed and assessed. The technique is named Direct Vectorial Addition, DVA. The feasibility of this alternative modal combination is tested by using case models of actual buildings. To verify the accuracy of the different pushover schemes the results obtained by these nonlinear static methods are compared to those from the nonlinear time history analysis and the standard error is used to evaluate the accuracy of the comparisons.

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