UC San Diego

Friction-based structural components have been developed and used in earthquake-resistant buildings for seismic response modification purposes. They can provide high initial stiffness, decoupled strength and stiffness, and energy dissipation, through relatively simple designs. If properly designed, they can be damage-free after earthquakes. However, their broader application requires further understanding at multiple levels. At the material level, the mechanical and tribological properties of composite friction materials remain insufficiently understood for earthquake structural engineering applications. At the component level, conventional friction-based components can be sensitive to machining tolerances, and friction shim inspection and replacement may require removal of external clamping parts, which can be time-consuming. In addition, friction-based components typically have near-zero post-elastic stiffness, which may lead to excessive connection displacement demands in specific applications. This dissertation investigates friction-based structural components through material-level experimental characterization and component-level development, testing, and assessment. At the material level, composite friction materials were characterized through tensile tests, bearing tests, bolt relaxation tests, and friction tests. The effects of material constituents, normal load, sliding velocity, displacement history, cumulative displacement, and dwell time were investigated. At the component level, two design concepts were studied. The first used initially loose steel washer plates in slotted-bolted friction-based components to reduce sensitivity to machining tolerances and to achieve accelerated repairability. The connection was evaluated through component-level tests and its implementation in a full-scale shaking table test of a three-story steel braced frame with sliding slabs. The second, termed the Modified Friction Device, was developed to generate predetermined discrete variable forces at target displacement levels. Its response was evaluated through reduced-scale and full-scale experimental testing. The material-level results of this dissertation provide information for selecting composite friction materials for use in friction-based components for structural engineering applications. Friction-based components with loose-washer-plates design concept generated stable Coulomb-type force-displacement responses without enforcing tight machining tolerances and allowed rapid friction shim replacement. The Modified Friction Device developed the intended discrete variable friction force at predetermined displacement levels, and tests validated its kinematics and design parameters adjustability. Overall, this dissertation improves the understanding, design, and performance of friction-based components for use in earthquake-resistant structures.