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A compound-driven magnetorheological (MR) valve is designed to cope with the low reliability and high energy consumption of traditional MR valves. The operating magnetic field of the valve is applied by both the excitation coil and ring magnet, maintaining excellent pressure drop performance even at zero current. To analyze the performance and obtain the variation law of the magnetic flux density and pressure drop, a pressure drop mathematical model and a magnetic field simulation model are established. The key parameters of the MR valve are also optimized using non-dominated sorting genetic algorithms-II. A dynamic performance test system is built, and the influence of the load on the pressure drop and hysteresis characteristics of the MR valve is studied. The results show that the optimized pressure drop and adjustable coefficient are improved by 4.7% and 8.6% respectively. The pressure drop grows nonlinearly with the electric current and reaches saturation at a current of 1.5 A, and a pressure drop of 1485 kPa is still generated at zero current. The output damping force of the compound-driven MR valve-controlled damper can be continuously adjustable, indicating that the dynamic performance of the damper can be controlled by adjusting the input current.

CDC (Continuous Damping Control) shock absorber is the typical representative of the stepless valve-controlled type, which has the advantages of low cost and stable performance. Based on the throttling characteristics of the CDC valve, the damping force mathematical model of the CDC shock absorber is established. Through simulation analysis, the indicator characteristics and speed characteristics of the CDC shock absorber under different input currents and speeds are obtained. A CDC shock absorber testbed is built to study damping characteristics, and the results are compared with the simulation results. The results show that the indicator diagram obtained by simulation and experiment is smooth without distortion, and the speed characteristic diagram is smooth without a large mutation point. The experimental values of damping force are slightly larger than the simulation values. The relative error between the simulation data and the experimental data is basically less than 10% and the model has high accuracy. When the input current is the same, the damping force increases with the increase of piston rod speed. When the speed of the piston rod is the same, the damping force of the rebound and compression stroke decreases with the increase of input current.

A life-cycle cost analysis (LCCA) was conducted on prestressed concrete bridge superstructures using carbon fiber reinforced polymer (CFRP) bars and strands. Traditional reinforcement materials of uncoated steel with cathodic protection and epoxy-coated steel were also considered for comparison. A series of deterministic LCCAs were first conducted to identify a range of expected cost outcomes for different bridge spans and traffic volumes. Then, a probabilistic LCCA was conducted on selected structures that included activity timing and cost random variables. It was found that although more expensive initially, the use of CFRP reinforcement has the potential to achieve significant reductions in life-cycle cost, having a 95% probability to be the least expensive alternative beginning at year 23–77 after initial construction, depending on the bridge case considered. In terms of life-cycle cost, the most effective use of CFRP reinforcement was found to be for an AASHTO beam bridge in a high traffic volume area.

This paper presents a life-cycle cost analysis of prestressed concrete highway bridges using carbon fiber-reinforced polymer (CFRP) reinforcement bars and strands. Side-by-side box beam and AASHTO beam bridge structures were considered over several span lengths and traffic volumes. The results show that despite the higher initial construction cost of CFRP reinforced bridges, they can be cost-effective when compared to traditional steel-reinforced bridges. The most cost-efficient design was found to be a medium-span CFRP reinforced AASHTO beam bridge located in a high-traffic area. A probabilistic analysis revealed that there is greater than a 95% probability that the CFRP reinforced bridge will become the least expensive option between 20 and 40 years of service, depending on traffic volume and bridge geometry. The break-even year between CFRP and steel reinforcement is typically at the time of the first major repair activity on the steel-reinforced concrete bridge.