This paper proposes a novel damping model with negative stiffness known as the half-cycle negative-stiffness damping model. Analysis of a single degree of freedom (SDOF) system demonstrated that the half-cycle negative-stiffness damping model has negative stiffness and energy dissipation. The equivalent negative stiffness of the model was derived from the frequency response analysis of the system. An alternating transmission system and a one-way friction system were developed to assemble a half-cycle negative-stiffness damping device (HCNSDD), which can generate a half-cycle negative-stiffness damping model. A mechanical model was developed to represent the force-displacement relationship of the proposed HCNSDD. A HCNSDD specimen was manufactured and examined using experimental tests. The HCNSDD exhibits half-cycle negative-stiffness damping and stable mechanical properties, demonstrating the feasibility and effectiveness of the proposed HCNSDD. Finally, a finite element simulation approach for HCNSDD was presented, and the performance of seismic vibration control of HCNSDD was evaluated using a multidegree-of-freedom system.

A new type of negative stiffness friction damping device (NSFDD) was developed in this study, which can solve the problem of poor energy dissipation of the existing passive negative stiffness damping device. The friction force is generated by squeezing the friction plate with the preloaded nitrogen spring vertically. When the NSFDD is working, the friction plate causes the nitrogen spring to rotate and negative stiffness force and friction force are generated. The results of the performance test show that the NSFDD can achieve negative stiffness in the hysteretic model. Comparing with the existing negative stiffness device, the NSFDD has larger stroke, more stable negative stiffness and better energy dissipation capacity. The finite element software has been used to simulate the low cycle reciprocation of a structure, and the results show that the NSFDD reduces the stiffness of the structure while increasing the damping of the structure. The results of the simulation and analysis of the shock absorption plan of the NSFDD show that the NSFDD reduces the stiffness of the floor, thereby effectively control on the shear force, displacement and acceleration response of the structure.

A passive double triangular damping (DTD) device with equivalent negative stiffness is proposed in this study. The DTD device consists of transmission systems and triangular damping systems. A mechanical model was developed to describe the force–displacement relationship of a triangular damping system, while the feasibility of both the system and model was evaluated using experimental tests. The theoretical analysis demonstrated that DTD was a form of damping with equivalent negative stiffness, and the equivalent expressions were generated. Finally, the prospect of application in the DTD-controlled isolation system was explored using numerical simulation. The results revealed that DTD was more effective than a lead–rubber bearing in reducing isolator displacement and rooftop acceleration when subjected to ground motions.

In this study, the antiwhip capability of high‐energy piping in nuclear power plants was investigated based on the basement structure of a conventional island in a nuclear power engineering project. A lead extrusion impact damping device was developed, and its mechanical performance was validated through uniaxial static loading tests. A 1:4 scaled‐down test model was designed and fabricated using traditional energy‐dissipating steel beams, lead extrusion impact damping, and concrete blocks as three types of antiwhip restraining devices. Impact test studies were conducted supplemented by destructive impact tests without antiwhip restraining devices. Finite element models were established using Ansys LS‐DYNA simulation software, and simulations were conducted for these four scenarios. The antiwhip performances of different antiwhip measures were evaluated by comparing the test and finite element simulation results and considering factors such as the impact force, wall displacement, wall acceleration, and crack distribution and development. The results indicate that while traditional energy‐dissipating steel beams continue to provide some antiwhip effectiveness, the lead extrusion impact damping solution exhibits a significantly improved performance with better control of the structural dynamic response. In contrast, the concrete block solution demonstrated a poorer performance, leading to severe damage in structures like those without antiwhip restraining devices.

This study investigates the aerodynamic characteristics and flow mechanisms of two tandem rectangular columns with varying width-to-thickness ratios using wind tunnel tests and large eddy simulations. The width-to-thickness ratio (B/D, streamwise width to transverse thickness) varied from 1/4 to 1/1, and the spacing ratio (L/B, spacing to width) ranged from 0.2 to 20. The Reynolds number (Re) was fixed at 5.32 × 104. Four distinct flow states, namely, single bluff body, reattachment, bistable, and co-shedding, were identified with increasing L/B. As B/D decreases, flow state transitions occur at larger L/B values, and the bistable range expands. Under the single bluff body state, a significant amplification effect is observed in both the mean drag coefficient of the upstream column and the Strouhal number of the two columns at specific B/D and L/B configurations. Under the reattachment state, the enlarged recirculation bubble between the two columns and the weakened core negative pressure reduce the mean drag coefficient of the upstream column. However, the amplification effect in the Strouhal number of the two columns still persists. Under the co-shedding state, the reduction effects in both the mean drag coefficient and the Strouhal number of the two columns gradually diminish as L/B increases.