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It is one of the main methods of structural health monitoring to carry out regular or continuous strain monitoring on key components of the structure so as to judge whether the structure is overloaded or damaged. In order to resolve the problems of traditional structural strain monitoring methods, such as large amount of wiring, high cost of installation and maintenance, and poor reliability, etc., RFID strain sensor technology is proposed in recent years, so as to realize non-contact wireless strain measurement without the need of external power supply. Firstly, this paper introduces the basic theory of RFID technology, including its main hardware components and load modulation method for wireless transmission. The research progress of RFID strain sensor is classified and summarized from three aspects: sensor design scheme, sensor working frequency band and whether the chip is used. Further, this paper analyzes the key design ideas and technical difficulties of various kinds of RFID strain sensors, and expounds their advantages, disadvantages and application status. Finally, future research direction of RFID strain sensor design is discussed. [ABSTRACT FROM AUTHOR]

Cable vibration exhibits multi-mode characteristics. It is imperative to develop new measures for reducing vibration and design methods. Negative stiffness dampers have unique mechanical properties, which can efficiently dissipate vibration energy to achieve excellent vibration reduction effects. However, there is still a lack of optimization design methods to determine parameters reasonably. This study investigates the parameter optimization of negative stiffness dampers for multi-mode vibration of cables using theoretical analysis and numerical simulation methods. Nonlinear damping is taken into consideration. Firstly, dynamic equation of the controlled cable is derived, followed by an analysis of variation law of additional mode damping ratio under single mode to obtain the optimization process of damper parameters under multiple modes. Secondly, a numerical model of the controlled system is established. The proposed optimization design method for negative stiffness dampers is verified using a full-scale cable as an example, and the influence of nonlinear damping is analyzed. The research results indicate that the proposed vibration reduction optimization design method can easily determine the required optimization parameters for multi-mode vibration of cables. The optimized negative stiffness damper can effectively control the time history and frequency response of cables. Nonlinear damping can be utilized to achieve an economic design of dampers. [ABSTRACT FROM AUTHOR]

In this paper, the stochasticity of the response of the structure and the randomness of the limit state under earthquake are considered and the seismic-convex set model is applied to the fragility analysis of structure. The maximum inter-layer displacement and the maximum layer acceleration are used as two engineering demand parameters reflecting structural performance and non-structural performance, and both are treated as random variables that conform to the lognormal distribution. The thresholds of the two demand parameters are treated as convex variables. The threshold ellipsoid model and interval model are established respectively, and a two-dimensional joint limit state equation with both convex set variables and probability variables is established. According to the compatibility between the convex set model and the probabilistic model, a Monte Carlo method based on Kriging model is proposed to calculate the upper and lower bounds of the failure probability, and the fragility curve that reflects the upper and lower bounds of the failure probability is obtained. The research shows that the fragility curve established by the interval model is conservative. Without considering threshold randomness will underestimate the seismic capacity of the structure. [ABSTRACT FROM AUTHOR]