Numerical analysis of special concentric braced frames using experimentally-validated fatigue and fracture model under s
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Numerical analysis of special concentric braced frames using experimentally‑validated fatigue and fracture model under short and long duration earthquakes Ali Hammad1 · Mohamed A. Moustafa1 Received: 12 March 2020 / Accepted: 27 October 2020 © Springer Nature B.V. 2020
Abstract Over the past decade, several long duration subduction earthquakes took place in different locations around the world such as Indonesia in 2004, China in 2008, Chile in 2010, and Japan in 2011. Long-duration and large-magnitude earthquakes are also possible to occur in the Cascadia subduction zone along the Pacific Northwest Coast of the United States. In this paper, numerical investigation was conducted to investigate the influence of earthquake duration on the structural response of steel special concentric braced frames (SCBFs). Calibration and validation of numerical models were achieved using results from recently completed shake table tests at the University of Nevada, Reno of three identical 1/2-scale one-story one-bay SCBFs under unidirectional short and long duration earthquakes. The objective of this paper is two-fold: (1) to use the experimental results to assess the suitability of current low-cycle fatigue models when incorporated into numerical models; (2) to utilize the calibrated numerical model in large number of simulations to extend and generalize the experimental results to quantify the effect of earthquake duration on SCBFs. For the latter, two suites of short and long duration ground motions were utilized to conduct incremental dynamic analysis (IDA) for the calibrated numerical models of the tested frames. The IDA, and resulting fragility curves, concluded that longer duration earthquakes result in 45% lower median displacement capacity, which could be regarded as premature low-cycle fatigue induced-failure of braces. Keywords Shake table tests · Special concentric braced frames · Low-cycle fatigue · Long duration ground motions · Incremental dynamic analysis
1 Introduction Special concentrically braced frames (SCBF) are known for their low fabrication and erection costs with respect to achieving certain drift performance level. SCBFs differ from ordinary concentric braced frames (CBF) mainly by the brace local and global buckling * Mohamed A. Moustafa [email protected] 1
Department of Civil and Environmental Engineering, University of Nevada, Reno, NV 89523‑0258, USA
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Bulletin of Earthquake Engineering
limits and special brace-gusset plates detailing. During extreme events, SCBFs meet the collapse prevention design criteria through developing brace plastic deformations, where the system behavior reaches high nonlinearity and inelasticity. The numerical modeling of SCBFs depends highly on several parameters, e.g. low-cycle fatigue and fatigue-induced rupture that requires careful validation. At the onset of the braces’ failure, most of the lateral capacity is lost causing noticeable drift ratios and depending on what drift ratios correspond to the failure versus what is intended from t
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