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11.62: A numerical study on the seismic performance of experimentally‐tested steel single‐storey concentrically braced frames
Author(s) -
Penelov Chavdar,
Hadzhiyaneva Irena,
Belev Borislav
Publication year - 2017
Publication title -
ce/papers
Language(s) - English
Resource type - Journals
ISSN - 2509-7075
DOI - 10.1002/cepa.387
Subject(s) - opensees , brace , structural engineering , residual , braced frame , nonlinear system , earthquake shaking table , allowance (engineering) , seismic analysis , eurocode , numerical analysis , engineering , finite element method , mathematics , frame (networking) , mathematical analysis , algorithm , physics , mechanical engineering , telecommunications , quantum mechanics
The paper presents an overview on nonlinear modeling and numerical evaluation of the seismic response of two steel single‐storey concentrically braced frames with X‐brace configuration previously tested by other researchers. The numerical simulations included series of nonlinear time history analyses using OpenSees computational framework. The brace members were modeled with fiber frame finite elements with distributed plasticity taking into account their initial imperfections. The material model accounted for the low‐cycle fatigue effects based on the approach proposed by several other research works on the topic. The maximum response displacements of the investigated specimens were also evaluated following the procedure given in Annex B of EN 1998–1 (Eurocode 8). However, the previously conducted shake table testing and the herein presented numerical results indicated that this procedure may significantly underestimate the displacements of single‐storey dissipative short‐period CBFs designed with high values of the behaviour factor. It was also found that the numerical estimation of the maximum and residual lateral response displacements of the analyzed CBFs based on nonlinear time history analysis is very sensitive to small variations of the material properties and assumed damping model (damping matrix definition). Therefore the experimentally‐obtained response displacements can be realistically predicted only if the parameter variations are taken into account in the numerical analyses. The authors believe that the use of high values for the behaviour factor in the design of low‐rise CBFs may result in excessive residual displacements and low‐cycle failure of the brace members. It is suggested the further revisions of Eurocode 8 impose lower reference values of the behaviour factor for the short‐period steel CBFs with slender braces in order to reduce their ductility demand and related damage in strong earthquakes.