Development and dynamic performance of multi-stage adaptive viscoelastic-friction seismic isolation and energy dissipation devices

To improve the seismic performance of reinforced concrete (RC) frame stairs, avoid serious damage during earthquakes that would affect evacuation of personnel and rescue activities, a multi-stage adaptive viscoelastic-friction isolator (MSAVF) was developed in this study. The structure and working mechanism of MSAVF were analyzed in detail. The influence of excitation frequency, displacement amplitude, surface radius, spring stiffness, spring preloading length and friction coefficient on the dynamic mechanical properties of MSAVF was revealed by studying the dynamic mechanical properties of full-size MSAVF under different loading conditions. The research results showed that the proposed MSAVF could effectively adapt to the different requirements of the lengthwise and crosswise mechanical properties of the stair structure, and its multi-stage and variable friction design significantly improved the seismic performance and seismic adaptability of the stair structure. MSAVF showed stable energy dissipation capacity under different excitation frequencies and displacement amplitudes, which met the seismic requirements under different intensity earthquakes. The radius of the curved surface significantly affected the crosswise energy dissipation performance of MSAVF, and the lengthwise friction characteristics remained stable. The spring stiffness, spring preloading length and friction coefficient were the key factors affecting the performance of MSAVF, which had significant effects on the equivalent stiffness, single-cycle energy dissipation, equivalent damping ratio and equivalent friction coefficient. It provided sufficient theoretical and experimental basis for further optimization and engineering application of devices.