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Steel and Composite Structures
  Volume 37, Number 2, October25 2020 , pages 175-191
DOI: https://doi.org/10.12989/scs.2020.37.2.175
 


Experimental study of failure mechanisms in elliptic-braced steel frame
Habib Ghasemi Jouneghani, Abbas Haghollahi and S. Bahram Beheshti-Aval

 
Abstract
    In this article, for the first time, the seismic behavior of elliptic-braced moment resisting frame (ELBRF) is assessed through a laboratory program and numerical analyses of FEM specifically focused on the development of global- and local-type failure mechanisms. The ELBRF as a new lateral braced system, when installed in the middle bay of the frames in the facade of a building, not only causes no problem to the opening space of the facade, but also improves the structural behavior. Quantitative and qualitative investigations were pursued to find out how elliptic braces would affect the failure mechanism of ELBRF structures exposed to seismic action as a nonlinear process. To this aim, an experimental test of a 1/2 scale single-story single-bay ELBRF specimen under cyclic quasi-static loading was run and the results were compared with those for X-bracing, knee-bracing, K-bracing, and diamond-bracing systems in a story base model. Nonlinear FEM analyses were carried out to evaluate failure mechanism, yield order of components, distribution of plasticity, degradation of structural nonlinear stiffness, distribution of internal forces, and energy dissipation capacity. The test results indicated that the yield of elliptic braces would delay the failure mode of adjacent elliptic columns and thus, help tolerate a significant nonlinear deformation to the point of ultimate failure. Symmetrical behavior, high energy absorption, appropriate stiffness, and high ductility in comparison with the conventional systems are some of the advantages of the proposed system.
 
Key Words
    elliptic-braced moment resisting frame; Failure mechanism; energy dissipation capacity; ductility; nonlinear analysis
 
Address
Habib Ghasemi Jouneghani and Abbas Haghollahi: Department of Civil Engineering, Faculty of Civil Engineering, Shahid Rajaee Teacher Training University, Tehran, Iran
S. Bahram Beheshti-Aval: Department of Civil Engineering, Faculty of Civil Engineering, K.N. Toosi University of Technology, Tehran, Iran
 

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