With the continuous development of the ductility capacity concept for seismic design of bridges, the ductility capacity of many existing bridges does not meet the requirements of the current code for seismic performance because of the low reinforcement ratio and reinforcement corrosion of reinforced concrete (RC) piers. Because of their superior mechanical properties and low price, basalt fibre‐reinforced polymer (BFRP) sheets have potential application in the seismic retrofits field of existing bridges. To study the seismic strengthening effect of RC pier columns, scaled specimens with standard reinforcement ratios, with low reinforcement ratios according to the past code and with corroded reinforcements, were designed and manufactured and then wrapped and pasted with BFRP sheets on the plastic hinge areas. Pseudostatic tests were conducted to verify the seismic performance of the strengthened and unstrengthened specimens. Experimental results showed that the ultimate flexural capacity, deformation capacity, and energy dissipation capacity of strengthened RC pier columns were superior. Especially for strengthened specimens with low reinforcement ratios or corrosion reinforcement, their seismic performance could rival than that of columns with standard reinforcement ratios, which showed the advantage of BFRP sheets in the seismic retrofitting of existing bridge piers.

Particle dampers (PD) are safe, economical, and effective energy-dissipation devices for structures. However, the additional mass of PD must be sufficiently large to provide a better damping effect, and the initial movement condition of particles has a significant impact on the damping effect of PD. In this study, a particle-inertial damper (PID) is proposed to overcome these problems, and its mechanical model is established with and without considering particle collision. Subsequently, the influence of particle rolling friction and particle collision on the inertial amplification capacity as well as the dynamic response of a single degree of freedom (SDOF) structure with non-collision and collision PID (SDOF-PID) are systematically analysed. Finally, the control effects of a PID and a tuned mass damper (TMD) are compared based on two typical optimisation methods. The results indicate that particle rolling friction has little influence on the inertia amplification effect of a PID and the displacement response of a SDOF-PID. Under harmonic excitation, particle collision significantly affects the damping mechanism of a PID by its equivalent inertia coefficient, equivalent damping coefficient, and equivalent stiffness coefficient. The fixed-point theory and ‘performance-cost’ theory can be used to optimise the PID to a certain extent. The damping effect of a PID on the SDOF under the most severe seismic excitation is better than that of the PID under white noise excitation. With respect to the decreasing ratio of 40~50%, the additional mass of the PID is only one thousandth that of the TMD under the same damping capacity demand.

The possibility of blast impact loads acting on bridge structures is gradually increasing. The local and entire explosion response law of a concrete box girder bridge is still unclear, and anti-explode devices for reducing the entire explosion response of a bridge are scarce. In this study, a rotational inertia particle damper (R-IPD) and a 1:4 scale model of a typical three-span continuous-girder bridge were designed and manufactured. Subsequently, an explosion test of the bridge model with and without R-IPDs was conducted. The results showed that the local dynamic response (LDR) of the bridge model was more likely to occur under an explosion load. The local overpressure, strain, and acceleration responses of the box girder near the explosion centre were more significant than those at other locations or of other components. Moreover, the LDR of the box girder was similar in the middle and side spans. As the explosive equivalent (EE) increased, the entire displacement response (EDR) of the model bridge increased. Under the same EE conditions, a larger span suffered a larger EDR. After the R-IPD installation, the EDR of the bridge model decreased. Furthermore, the damping effect of the R-IPDs on the EDR of the bridge model increased with an increase in the EE, and the maximum vibration reduction rate was up to 12%. However, the damping effect of the R-IPDs on the LDR of the model bridge was not obvious. The damping effect of the R-IPDs depended on the relative displacement between the two ends of the damper and exhibited obvious hysteresis.