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In order to improve the seismic performance of damaged reinforced concrete joints, a new retrofitting method using viscoelastic materials and steel plates is proposed. A reversal cyclic loading test was carried out on four T-shaped RC joints to investigate the reliability of this method. Seismic performance, including the strength, stiffness, ductility, and energy dissipation capacity of the original non-damaged joint and different repaired and retrofitted joints are then compared. The results show that this new method can significantly improve the strength of the retrofitted joints, and the joints can be loaded to a larger displacement value. After retrofitting, the energy dissipation of the joints increases, and the stiffness degradation decreases. The test results indicate that the retrofitting method is effective in repairing seismically damaged RC joints.

Micro structures of viscoelastic materials (VEM) play an important role in their mechanical properties and energy dissipation capacities. This work shows a mathematical modeling of VEMs considering...

In this work parameters are optimized for a proposed precision platform with a well-designed vibration isolation and mitigation (VIM) system, in which VIM devices, magnetorheological (MR) dampers and viscoelastic (VE) dampers are adopted to mitigate vibration responses. The optimization method is on the basis of the Non-dominated sorting genetic algorithm (NSGA-II), in which the dynamic responses as well as the maximum damping forces of MR dampers of the platform are chosen as objective functions. The optimization parameters, the constrain conditions and the objective functions are determined in accordance with the characteristics of the VIM system. Finally, a series of Pareto solutions are obtained and one Pareto solution is selected to compare with a preliminarily well designed VIM system. Numerical results show that the optimization method can effectively mitigate the vibration of the precision platform and reduce the maximum control forces of MR dampers simultaneously, which will lead to the miniaturization of MR dampers.

Aiming at the difficult problem of on-site real-time vibration responses monitoring and remote data transmission of the civil engineering structures, based on LabVIEW a remote data acquisition and ...

Viscoelastic dampers are a kind of classical passive energy dissipation and vibration control devices which are widely utilized in engineering fields. The mechanical properties and energy dissipation capacity of the viscoelastic damper are significantly affected by ambient temperature. In this work, dynamic properties tests of the sandwich type viscoelastic damper at different environmental temperatures are carried out. The equivalent fractional Kelvin model which can characterize the mechanical behavior of the viscoelastic damper with varying frequencies and temperatures is introduced to describe the dynamic properties and energy dissipation capability of the sandwich viscoelastic damper. The self-heating phenomenon of the sandwich viscoelastic damper is studied with a numerical simulation, and the dynamic properties and energy dissipation variation of the viscoelastic damper with self-heating processes are also analyzed. The results show that the dynamic properties of the viscoelastic damper are significantly affected by temperature, excitation frequency and the internal self-generated heating.

The bridge stay cable, one of the most critical components in cable-stayed bridges, is vulnerable to vibrations owing to its low inherent damping capacity. Thus effective vibration control technology for bridge stay cables is extremely critical to safe operations of cable-stayed bridges. Several countermeasures have been presented and/or implemented to mitigate this vibration; however the passive method can only add a small amount of damping to the cables, excessive energy demand of active control devices severely limits its practicality, the semi-active control methods still have the drawbacks of complex state estimation module and a large amount of control algorithm calculation. This paper proposes a practical magnetorheological pseudo negative stiffness (MR-PNS) control system coupled with control strategy for bridge stay cables. The current reference point is introduced in the dynamic modeling of the MR-PNS control system to characterize the current control strategy. This paper investigates the adjustable of MR-PNS control system performance and energy consumption caused by different current strategies. Taking the vibration control of the Nanjing Second Yangtze River Bridge J20 cable as an example, the simulation results highlight the advantages of the MR-PNS control system that the failure area is small, the quasi-optimal area is wide, and it can still keep sort of vibration damping performance in the degenerate area. The model cable vibration control test proves the feasibility and efficiency of the single input MR-PNS bridge stay cables control method.

The earthquake excitation is a kind of complicated multi-dimensional motion. It is not safe and accurate enough if only considering the horizontal earthquake excitation, especially for complex and important engineering structures. Therefore, anti-earthquake measures for engineering structures considering multi-dimensional excitations have become an extremely important research topic. In this paper, a new multi-dimensional earthquake isolation and mitigation device (MEIMD) is developed and tested under different cases at both horizontal and vertical directions. Effects of excitation frequency and displacement amplitude on both horizontal and vertical properties of this device are considered. At the same time, a modified equivalent standard solid model is proposed, which can effectively describe the effects of frequency and displacement on the horizontal and vertical properties of the device. Research indicates that the MEIMD possesses high-energy dissipation capacity at both horizontal and vertical directions and the proposed model can accurately simulate the value of the storage modulus and the loss factor.