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FROM:
Nitin Kumar, P.C. Ashwin Kumar and Dipti Ranjan Sahoo (Civil Engineering, Indian Institute of Technology Delhi),
“Optimum range of slenderness ratio for braces in special concentric braced frames”, Fifth Asia Conference on Earthquake Engineering, October 16-18, 2014
ABSTRACT: Special concentric braced frames (SCBFs) are commonly used to resist the lateral forces in structures located in high-seismic regions. Steel braces undergo inelastic axial deformations and thus provides an adequate level of structural ductility and hysteretic energy dissipation capability to the frame under cyclic loading. Past studies have shown that the slenderness ratio and the width-to-thickness ratio of braces are primarily responsible for achieving enhanced seismic response in SCBFs. An increase in the brace slenderness ratio results in a reduction in its energy dissipation capacity along with a simultaneous increase in the ductility nearing its fracture. Currently, no guidelines are available for the lower limit of slenderness ratio and since both energy dissipation capacity and ductility of braces are essential parameters in quantifying the enhanced seismic performance of SCBFs, there is a need of establishing the optimum range of brace slenderness ratio and width-to- thickness ratio. Therefore, the main objective of this study was to find an optimum range as well as the lower limits of these parameters. An extensive finite element (FE) parametric study has been conducted on a wide range of parameters of hollow circular braces using a commercial software package ABAQUS. A validated simulation model which had the inelastic characteristics of braces and the fracture behavior incorporated was created. The results of simulation models matched very well with the past experimental results with respect to the four performance points, namely, global buckling, local buckling, fracture initiation, and complete fracture. This model paved way for the parametric study which resulted in a deep understanding of the influence of structural parameters on the behavior of braces.
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