Reusability of damping behavior in friction damper using brake pads: Experimental evaluation under repeated loading without intervening maintenance

Abstract

Over the past decade, friction dampers have been increasingly integrated into structural components to mitigate seismic damage and reduce post-earthquake repair costs, aiming to enhance the seismic resilience of infrastructure. A critical demand in this context is the application of optimized friction shims that could prevent wear on the contacting metallic surface and exhibit reliable reusability of damping behavior under repeated loading without requiring maintenance. Inspired by the fact that brake pads do not damage the wheel surfaces, this study investigatesd the feasibility of using three types of brake pad materials as friction shim in friction damper: (a) Phenolic resins with aramid fiber (PRAF); (b) Phenolic resins with fine iron wire/steel fiber (PRIW); (c) Iron-based powder metallurgy (PM). These brake pads were installed in a symmetric friction damper and tested under two initial average contact pressures: 8.93 MPa and 14.88 MPa. Therefore, six specimens were assembled. A loading protocol with a constant loading velocity of 5 mm/s, including 42 loading cycles, was adopted. The loading protocol was executed twice to evaluate the reusability of the damping behavior in these specimens. Notably, there was a time interval between these two loading sequences during which no maintenance operations were performed to simulate mainshock-aftershock earthquake sequences. The bolt force fluctuation, temperature variation, and stability in the friction coefficient and friction strength across both loading sequences were examined. The results showed that: (a) These brake pads did not cause wear damage to the contacted metallic surface; (b) Compared with aramid fiber, the iron wire/steel fiber was more effective in improving friction coefficient; (c) The friction coefficient and friction strength of the specimens using PM was increasing gradually during the initial sliding due to the break-in phase. The specimens using PM exhibited the highest friction strength and energy dissipation after completing the break-in phase compared to those using PRAF or PRIW; and (d) Specimens equipped with PRAF or PRIW had satisfactory reusability in terms of friction strength, fatigue resistance, and energy dissipation.