Low-Cost Friction-Based Force-Limiting Connection With Reduced Sensitivity to Machining Tolerances and Accelerated Repairability

Abstract

This paper presents a novel yet practical friction-based structural component design for low-damage earthquake-resistant structures. The proposed connection design is based on a conventional slotted-bolted configuration with the novelty being the use of loose steel washer plates to establish the friction-sliding interface. This design concept offers two key advantages: (1) The connection generates relatively constant sliding forces without the need for small geometric tolerances in the machined parts, and (2) the use of loose steel washer plates to establish the friction interface allows quick inspection and replacement of friction shims if needed. Eliminating the need for small geometric tolerances reduces the manufacturing cost and time. Reducing the inspection and potential repair time enhances the practicality of the connection in real applications and supports the long-term functionality of earthquake-resistant buildings equipped with it. To verify this design concept, a numerical simulation was first conducted to assess the expected kinematics and force-displacement response. A comprehensive experimental characterization program was conducted, which consisted of component-level connection tests and shaking table tests of a full-scale three-story re-centering steel braced frame with sliding slabs, in which the proposed friction-based connection was designed as the force-limiting connection between the steel frame and the sliding slab. It is observed that the proposed connection exhibited a stable force-displacement response and relatively low bolt load loss without enforcing small geometric tolerances when machining the parts of the connection. The replacement of the friction shim was performed after the completion of the shaking table test while the friction-based connection remained installed on the frame specimen, which hence demonstrated the repairability of this connection.