Browsing by Author "Kazemzadeh Azad, S"

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    Development of detachable replaceable links for eccentrically braced frames
    Bozkurt, MB; Kazemzadeh Azad, S; Topkaya, C
    Eccentrically braced frames (EBFs) can be repaired after a major earthquake by replacing the links. The link replacement is not a straightforward process and is influenced by the type of the link and the amount of residual frame deformations. The past decade has witnessed the development of different types of replaceable links such as end-plated links, web connected links, bolted flange and web spliced links, and collector beam and brace spliced links. All of the developed replaceable link details, except the web connected links, are not suitable for link replacement under residual frame drift. In this paper, a detachable replaceable link detail which is based on splicing the link at its mid-length is proposed. The detail is well suited for installation under residual frame drifts. In addition, the weight and size of the members to be transported and erected are reduced significantly, thereby facilitating the replacement procedure. Performance of this proposed replaceable link is studied by conducting six nearly full scale EBF tests under quasi-static cyclic loading. The link length ratio, type of end-plated mid-splice connection, and the amount of residual drift are considered as test variables. The test results revealed that the inelastic rotation capacity of the detachable replaceable links exceeds the requirements of the AISC Seismic Provisions for Structural Steel Buildings. No failures are observed in the end-plated mid-splice connections demonstrating the potential of the proposed details. The detachable replaceable links are investigated by numerical analysis as well to further validate their applicability and to develop design recommendations.
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    Low-Cycle Fatigue Testing of Shear Links and Calibration of a Damage Law
    Bozkurt, MB; Kazemzadeh Azad, S; Topkaya, C
    This paper experimentally studies the low-cycle fatigue (LCF) behavior of shear links in eccentrically braced frames (EBFs) with the aim of calibrating a convenient damage law for estimating the exhausted as well as remaining life of these members under any loading history. A total of 14 specimens are tested using a nearly full-scale EBF setup under constant-amplitude cycles as well as proportional and arbitrary loading histories. A generalized damage law is subsequently calibrated using results of the present study as well as a comprehensive data compilation of previous experiments for predicting the occurrence of link fracture under earthquake-induced loading histories. The approach forms a basis for the development of acceptance criteria based on cumulative measures which can be incorporated into the current performance-based design and evaluation procedures. For further validation, the procedure is applied to the case of EBF links fractured during the Christchurch earthquakes. Finally, the current standards for EBF shear links are discussed based on the findings of the LCF tests.