Search

Shaking table tests are performed on a one-bay one-story steel frame with superelastic Cu-Al-Mn shape memory alloy (SMA) tension braces. The frame is subjected to a series of scaled ground motions recorded during the 1995 Kobe earthquake, Japan. The test results demonstrate that the SMA braces are effective to prevent residual deformations and pinching. It is also shown that the time history responses observed from the shaking table tests agree well with the numerical predictions using a rate-independent piecewise-linear constitutive model calibrated to the quasi-static component tests of the SMA braces. This suggests that the loading rate dependence of Cu-Al-Mn SMAs as well as the modeling error due to the piecewise linear approximation can be neglected in capturing the global response of the steel frame. Numerical simulations under a suite of near-fault ground motion records are further performed using the calibrated analytical models to demonstrate the effectiveness of the SMA braces when the variability of near-fault ground motions is taken into account. A stopper, or a deformation restraining device, is also proposed to prevent premature fracture of SMA bars in unexpectedly large ground motions while keeping the self-centering capability in moderate to large ground motions. The effectiveness of the stopper is also demonstrated in the quasi-static component and shaking table tests. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a novel beam-to-column moment connection suitable for the column’s weak axis. The proposed system is developed in line with an idea to mainly utilize bolts with the number of welds minimized, thereby avoiding difficulties encountered in in situ welding. In this system, a wide-flange beam is joined to a wide-flange column by bolted splices at the top flange and newly invented hysteretic dampers at the bottom flange. The mechanical behavior of the damper and the whole connection system is described herein. The seismic performance of the proposed connection was verified through cyclic tests of six full-scale beam–column subassemblies, taking into account the effects of the geometry and arrangement of the dampers. The tests revealed that the proposed system is capable of achieving stable hysteresis behavior in a large deformation range. Yielding was limited only in the dampers while the beam and column remained essentially elastic until the ultimate state of the structure. [Copyright &y& Elsevier]

• Benefits of installing the LVEM-isolated floor in the first story of a two-story frame. • The frame lateral stiffness is basically not weakened by the floor-isolation. • A 40% reduction in the peak inter-story drift could be obtained via a regular design. • The ambient temperature notably influences the performance of the floor-isolation system. • Peak of the floor acceleration response spectra is notably mitigated by the floor-isolation. We introduce a novel floor-isolation system for mitigating the seismic responses of steel frames. In the system, the floors are connected to steel beams by the laminated visco-elastic material (LVEM). In this paper, we present the feasibility of installing the LVEM-isolated floors in the first story of a two-story steel moment-resisting frame. Firstly, we notice that the floor-isolation decouples the composite behavior between the floors and the beams, thus weakens the stiffness of the beams. Based on a generalized frame model, it is demonstrated that such a reduction in beam stiffness only yields a tiny decrease in the global lateral stiffness of the frame. Subsequently, the dynamic analysis model is established for the frame equipped with the LVEM-isolated floor. The LVEM isolators are simulated by a refined Kelvin-Voigt model, while the entire structure is modeled by a three-degree-of-freedom system. The accuracy of the numerical approach is validated by shaking table tests. Based on the established model, a large-scale numerical computation is conducted using 136 earthquake records. The results demonstrate that the structural displacement responses could be remarkably mitigated by the floor-isolation. In general, the reduction of the peak inter-story drift gets more pronounced when a larger mass-isolation ratio and a softer LVEM isolator are applied. For a regular structural design configuration (e.g., mass-isolation ration ν = 0.7, LVEM isolator stiffness ratio κ = 0.2), a 40% reduction in the peak inter-story drifts could be obtained via the floor-isolation. The ambient temperature notably affects the performance of the floor-isolation system. In many cases, a risen temperature amplifies the benefits of the floor-isolation while a fallen temperature abates such benefits. Meanwhile, the floor-isolation alters the form and the amplitude of the floor acceleration response spectrum (FARS). The peaks of the FARS are significantly mitigated by the LVEM-isolated floors. Quantitatively speaking, we could get a 50% reduction in the peak of FARS from the LVEM-isolated floor system for regular design configurations, say, ν = 0.7, and κ = 0.2. [ABSTRACT FROM AUTHOR]