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Experimental and numerical study on the seismic performance of a self-centering bracing system using closed-loop dynamic (CLD) testing

机译:使用闭环动态(CLD)测试的自定心支撑系统抗震性能的实验和数值研究

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This study investigates the seismic performance of a newly developed self-centering bracing system using a novel experimental technique named as closed-loop dynamic (CLD) testing. The bracing, named piston-based self-centering (PBSC) apparatus, employs Ni-Ti superelastic shape memory alloy (SMA) bars inside a sleeve-piston assembly for its self-centering mechanism. During cyclic tension-compression loading, the SMA bars are only subjected to tension avoiding buckling and leading to flag-shaped symmetric force-deformation hysteresis. Initially, a braced frame building fitted with PBSC is seismically designed and the preliminary sizing of the brace is determined. For testing, considering the lab capability, the brace is fabricated at a reduced scale. The process of "Closed-loop dynamic testing" starts with the brace test (step 1) under strain-rate loading to characterize the numerical model parameters (step 2), which are then scaled-up as per similitude law and implemented in a finite element software, S-FRAME's PBSC brace model (step 3). Then the braced frame building is analyzed under an earthquake (step 4) and the axial force-deformation response of the brace under consideration is captured (step 5). In order to further understand and validate the actual response of the brace under earthquake type loading, the axial deformation obtained from S-FRAME is scaled-down (step 6) and used as input parameters for testing the reduced scale brace (step 7). The obtained response (step 8) is further scaled-up and used to match the S-FRAME's PBSC model for validation (step 9). Iterations from step 3 to step 9 will be required until the experimental and numerical results converge. Convergence criteria used for this validation include both the energy dissipation capacity and initial stiffness within 10% accuracy. Reasonable agreement between the numerical and experimental results is achieved in the closed-loop dynamic testing. The PBSC brace shows excellent self-centering capability under various earthquake loadings.
机译:这项研究使用一种称为闭环动态(CLD)测试的新型实验技术,研究了新开发的自定心支撑系统的抗震性能。该撑杆被称为基于活塞的自定心(PBSC)装置,其在套筒-活塞组件内采用Ni-Ti超弹性形状记忆合金(SMA)杆进行自定心。在循环拉伸压缩载荷过程中,仅对SMA棒施加张力,从而避免弯曲并导致旗形对称的力变形滞后。最初,对采用PBSC的支撑框架结构进行抗震设计,并确定支撑的初步尺寸。为了进行测试,考虑到实验室的能力,支架以缩小的比例制造。 “闭环动态测试”的过程始于在应变率载荷下的支撑测试(步骤1),以表征数值模型参数(步骤2),然后根据相似律将其放大,并以有限的方式实现元素软件,S-FRAME的PBSC支撑模型(第3步)。然后,在地震作用下分析支撑框架结构(步骤4),并捕获所考虑支撑的轴向力-变形响应(步骤5)。为了进一步理解和验证支撑在地震类型荷载下的实际响应,将从S-FRAME获得的轴向变形按比例缩小(步骤6),并用作测试减小比例的支撑的输入参数(步骤7)。获得的响应(步骤8)将进一步放大,并用于匹配S-FRAME的PBSC模型以进行验证(步骤9)。从步骤3到步骤9进行迭代,直到实验和数值结果收敛为止。用于此验证的收敛标准包括能量消耗能力和10%精度以内的初始刚度。在闭环动态测试中,数值结果与实验结果合理吻合。 PBSC支架在各种地震载荷下均具有出色的自定心能力。

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