This research presents a novel self-centering fluidic viscous damper that incorporates preloaded ring springs to offer self-centering capability and a fluidic viscous damper for energy dissipation. A full-scale self-centering fluidic viscous damper was developed and subjected to low-cyclic reversed loading tests. The test results show the self-centering fluidic viscous damper has both displacement-dependent and velocity-dependent hysteric responses with self-centering capability. Fatigue tests further show that the self-centering fluidic viscous damper maintains a stable hysteretic response under reversed loading. An analytical model and a numerical model are developed for the proposed self-centering fluidic viscous damper and analyzed. Comparisons of test results and the numerical and analytical models show similar hysteric responses, thereby validating the accuracy of the numerical and analytical models to simulate the behavior of the proposed damper.

Bridge performance undergoes time-varying changes when exposed to aggressive environments. While much work has been done on bridge reliability under corrosion, little is known about the effects of creep and shrinkage on the reliability of concrete bridges. In this paper, the CEB-FIP model for creep and shrinkage is applied by using finite-element (FE) analysis in conjunction with probabilistic considerations. Verification is made by comparing the analytical findings with existing test data. More specifically, a time-dependent reliability assessment is made for a composite prestressed concrete (PSC) box-girder bridge exposed to a chloride environment. This realized via an advanced probabilistic FE method. The postcracking behavior of the thin-walled box girder is described using composite degenerated shell elements, and importance sampling is used to improve the efficiency of the reliability analyses. It is shown that concrete creep and shrinkage dominate during the early stages of bridge structure deterio...

Suspenders are crucial load-bearing members of suspension bridges, and they are prone to fatigue damage under repetitive vehicle and wind loads. Field observation shows that short suspenders at the midspan or the ends of bridges may be more vulnerable. This study investigated the influence of using rigid central clamps on the fatigue performance of short suspenders, and two finite-element models of a long-span suspension bridge, with and without central clamps, were developed for comparison. Results show that central clamps can significantly mitigate the bending stress of short suspenders by reducing the relative motion between cables and the girder. Although wind-induced stresses of suspenders are smaller in amplitude than those induced by the vehicle load, the wind loads also contribute significantly to fatigue damage of suspenders because of the large number of stress cycles. Based on a vehicle-load model and the wind spectrum developed from field-monitored data, a fatigue life evaluation procedure was developed, and the fatigue lives of suspenders of the bridges with and without central clamps were calculated, respectively. Results suggest that when there are no central clamps, suspenders may have fatigue lives shorter than the design value.

This paper presents the seismic upgrade of existing frame structures by using the self-centering (SC) concrete wall with friction dampers. Working principle, numerical simulation, and design procedure of the upgrade system are introduced, and application was made in the seismic resilience upgrade of a five-story reinforced concrete (RC) frame building located in a high-seismicity area in China. The original building, as a corridor, connects two adjacent buildings and was evaluated as seismically deficient. Three posttensioned concrete walls with friction devices were therefore used to provide self-centering capacity and supplemental energy dissipation. In situ vibration tests were conducted to obtain dynamic properties of the rehabilitated structure and to validate the numerical model. Dynamic nonlinear analyses of original and upgraded buildings subjected to the design-basis earthquake (DBE) and the maximum considered earthquake (MCE) are conducted, which confirm the design objectives and improved seismic resilience of the upgraded system. In addition, by controlling the deformation pattern of the frame, the weak story failure might be avoided.

Suspenders are critical force transmission components in suspension and arch bridges, which connect the girder to the main cable/arch. Field inspection indicates that short suspenders at the midspan or the ends of a bridge may be more prone to fatigue damage under cyclic traffic loads when coupled with the effects of corrosion. The damage has been frequently observed to occur at the lower ends of suspenders. To evaluate the safety of suspenders, a stochastic time-variant reliability assessment method is proposed, where the time-variant model for deterioration of steel wires and probabilistic critical limit states based on crack depth and failure area are integrated, so as to consider the combined effect of corrosion and cyclic loading. A case study on the suspenders of the Jiangyin Yangtze River Bridge was performed in which a finite-element analysis was conducted in conjunction with a comprehensive traffic model. The time-variant reliability indices of the short suspenders were obtained according to the proposed method, which resulted in recommendations for suspender maintenance and replacement.