Nonlinear static procedures for analysis and retrofitting of existing buildings with dissipative braces

Abstract

Nonlinear Static Procedures (NSPs), often called pushover analyses, are deemed to be very practical tools to assess the nonlinear seismic performance of structures. The use of NSPs for the seismic assessment of plan regular buildings and bridges is widespread nowadays. The use of NSPs in the case of real existing structures, which are almost always irregular, has so far been studied by a limited number of authors. This fact limits the application of NSPs to assess current existing structures. In order to improve the use of NSPs in practical, the applicability of NSPs for analysis and retrofitting of existing buildings with dissipative braces is evaluated in this thesis. In this work, a more efficient incremental modal pushover analysis (IMPA) to obtain capacity curve of the structure to evaluate the seismic demand is proposed: the procedure allows defining the capacity curve based on the execution of a series of MPAs. The case studies chosen are a benchmark structure as the regular structure and a real existing reinforced concrete building, which shows a strong irregularity in plan and vertical.Comparative evaluation of the different commonly used NSPs, which are Capacity Spectrum Method (CSM) adopted in ATC-40, Displacement Coefficient Method integrated into FEMA356, and N2 method presented in Eurocode 8 and modal pushover analysis (MPA), to describe their relative accurancy and limitations. A displacement based design procedure of dissipative devices for seismic upgrading structures is applied to the exising builidng. The accuracy of the IMPA is evaluated by comparison with IDA curve for the regular and irregular structure. Force-based and displacement design procedure of passive energy dissipation devices are applied to retrofit a school building located in shanghai, the comparisons of the two design methods and the seismic behavior of the retrofitting structure with different passive energy dissipation devices are discussed.