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This study employs a novel beam-type wavelet finite element model (WFEM) to fulfill an adaptive-scale damage detection strategy in which structural modeling scales are not only spatially varying but also dynamically changed according to actual needs. Dynamical equations of beam structures are derived in the context of WFEM by using the second-generation cubic Hermite multiwavelets as interpolation functions. Based on the concept of modal strain energy, damage in beam structures can be detected in a progressive manner: the suspected region is first identified using a low-scale structural model and the more accurate location and severity of the damage can be estimated using a multi-scale model with local refinement in the suspected region. Although this strategy can be implemented using traditional finite element methods, the multi-scale and localization properties of the WFEM considerably facilitate the adaptive change of modeling scales in a multi-stage process. The numerical examples in this study clearly demonstrate that the proposed damage detection strategy can progressively and efficiently locate and quantify damage with minimal computation effort and a limited number of sensors. [ABSTRACT FROM AUTHOR]

As a practical and effective seismic resisting technology, the base isolation system has seen extensive applications in buildings and bridges. However, a few problems associated with conventional lead-rubber bearings have been identified after historical strong earthquakes, e.g., excessive permanent deformations of beatings and potential unseating of bridge decks. Recently the applications of shape memory alloys (SMA) have received growing interest in the area of seismic response mitigation. As a result, a variety of SMA-based base isolators have been developed. These novel isolators often lead to minimal permanent deformations due to the self-centering feature of SMA materials. However, a rational design approach is still missing because of the fact that conventional design method cannot be directly applied to these novel devices. In light of this limitation, a displacement-based design approach for highway bridges with SMA isolators is proposed in this paper. Nonlinear response spectra, derived from typical hysteretic models for SMA, are employed in the design procedure. SMA isolators and bridge piers are designed according to the prescribed performance objectives. A prototype reinforced concrete (RC) highway bridge is designed using the proposed design approach. Nonlinear dynamic analyses for different seismic intensity levels are carried out using a computer program called "OpenSees". The efficacy of the displacement-based design approach is validated by numerical simulations. Results indicate that a properly designed RC highway bridge with novel SMA isolators may achieve minor damage and minimal residual deformations under frequent and rare earthquakes. Nonlinear static analysis is also carried out to investigate the failure mechanism and the self-centering ability of the designed highway bridge. [ABSTRACT FROM AUTHOR]

This study presents a novel precast reinforced concrete (RC) wall system using shape memory alloy (SMA) bars and replaceable energy dissipating (ED) devices to achieve earthquake resilience (hereafter referred to as SMA-based RC wall). The major advantages of this structural system include (1) self-centering (SC) capability provided by the unbonded superelastic SMA bars used in the bottom boundary zones of the wall, (2) concentrated energy dissipation and damage in the replaceable steel angles, and (3) an earthquake resilient design that requires minimal repair even after strong earthquakes. The structural details and design considerations of the SMA-based RC wall were first introduced. Subsequently, the mechanical behavior of the SMA bars and ED angles was investigated through cyclic loading tests. The seismic performance of the SMA-based RC walls was computationally investigated using various parameters of interest in seismic applications and evaluated in terms of strength, stiffness, and SC and ED capabilities. The proposed SMA-based RC walls exhibited satisfactory and stable flag-shaped hysteretic loops with excellent SC and satisfactory ED capabilities. Compared with conventional RC walls, the proposed SMA-based RC walls provide a promising solution for high-performance structural systems required by modern resilient and sustainable civil infrastructure. [ABSTRACT FROM AUTHOR]

This paper systematically investigates the dynamic behavior of stay cables with passive negative stiffness dampers (NSD) installed close to the cable end. A passive NSD is modeled as a combination of a negative stiffness spring and a viscous damper. Through both analytical and numerical approaches, parametric analysis of negative stiffness and viscous damping are conducted to systematically evaluate the vibration control performance of passive NSD on stay cables. Since negative stiffness is an unstable element, the boundary of passive negative stiffness for stay cables to maintain stability is also derived. Results reveal that the asymptotic approach is only applicable to passive dampers with positive or moderate negative stiffness, and loses its accuracy when a passive NSD possesses significant negative stiffness. It has been found that the performance of passive NSD can be much better than those of conventional viscous dampers. The superior control performance of passive NSD in cable vibration mitigation is validated through numerical simulations of a full-scale stay cable. [ABSTRACT FROM AUTHOR]

Flexible bridge stay cables are often vulnerable to problematic vibrations under dynamic excitations. However, from an energy perspective, such excessive vibrations denote a green and sustainable energy source to some electronic devices (such as semi-active dampers or wireless sensors) installed on the same cables. This paper presents an experimental study on a novel dual-function system called electromagnetic damper cum energy harvester (EMDEH). The proposed EMDEH, consisting of an electromagnetic device connected to an energy-harvesting circuit (EHC), simultaneously harvests cable vibration energy and provides sufficient damping to the cables. A fixed-duty-cycle buck–boost converter is employed as the EHC, which emulates a resistive load and provides approximately optimal damping and optimal energy harvesting efficiency when operating in discontinuous conduction mode. A 5.85 m long scaled stay cable installed with a prototype EMDEH is tested in the laboratory under a series of harmonic and random excitations. The EMDEH can achieve a control performance comparable to passive viscous dampers. An average electrical power of 31.6 and 21.51 mW is harvested under harmonic and random vibrations, respectively, corresponding to the efficiency of 16.9% and 13.8%, respectively. Moreover, this experimental study proves that optimal damping and energy harvesting can be achieved simultaneously, which answers a pending question regarding such a dual-objective optimization problem. Self-powered semi-active control systems or wireless sensor networks may be developed for bridge stay cables in the future based on the proposed concept in this study. [ABSTRACT FROM AUTHOR]

This communication presents the design principle and experimental validation of two novel configurations of magnetic negative stiffness dampers (MNSDs), both of which are composed of several permanent magnets arranged in a conductive pipe. The MNSD, as a passive device, efficiently integrates negative stiffness and eddy-current damping in a simple and compact design, in which the negative stiffness behavior depends on the different arrangements of the permanent magnets. When applied to structural vibration control, passive MNSD may achieve a performance comparable with semi-active or active control in some applications. Laboratory experiments of small-scale prototypes successfully verified the proposed MNSD design concept. [ABSTRACT FROM AUTHOR]

This paper examines the suitability of superelastic copper-aluminum-beryllium (Cu-Al-Be) alloy wires for the seismic protection of bridges in cold regions. Experimental results for the mechanical properties of superelastic Cu-Al-Be alloy wires at a variety of temperatures and loading rates are presented. This research is motivated by the recent use of shape memory alloys for bridge restrainers subject to harsh winter conditions, especially in cold regions. Bridge restrainers made of superelastic Cu-Al-Be wire strands are expected to be used for protecting bridge decks from excessive displacement when subjected to strong earthquakes. Using a temperature chamber, superelastic Cu-Al-Be wires with a diameter of 1.4 mm were tested under uniaxial cyclic loading at various loading rates and cold temperatures. The test results from 23 to [?]50 °C demonstrate that Cu-Al-Be exhibits superelastic behavior at cold temperatures down to [?]85 °C. It is also found that with decreasing temperature the transformation plateau stress is reduced while its fatigue life increases under cyclic testing. [ABSTRACT FROM AUTHOR]