Seismic Performance of a Full-Scale Steel Structure Using Resilient Slip Friction Joints

Abstract

The fundamental objective of this thesis is to facilitate the use of a self-centring damper called Resilient Slip Friction Joint (RSFJ) in steel structures of seismically active regions for providing low-damage structural solutions. To achieve this purpose, real-scale experimental tests should verify the performance of the damper under simulated earthquake conditions and design guidelines should be developed so that engineers can incorporate the damper in building design. The RSFJ was developed previously to provide energy dissipation, self-centring, and response repeatability characteristics in one package. Three different structural systems common to steel frame construction have been investigated in this work where the RSFJ has been adopted deliberately for each of these systems to enhance their seismic performance by adding energy-dissipation and self-centring characteristics while keeping the initial seismic functionality of those systems. These systems are RSFJ Tension-Only Brace (RSFJ TO-Brace), RSFJ Tension-Compression Brace (RSFJ TC-Brace), and RSFJ Moment Resisting Frame (RSFJ MRF). The contributions of this thesis are therefore encapsulated in the next paragraphs. First, the RSFJ TO-Brace was developed and tested at the component level and then in a full-scale system level. RSFJs were added to the end of the bracing members and due to the type of connections devised, no compression force exists on bracing members and their connections. Therefore, bracing members are rods or similar components due to the absence of buckling issue. RSFJs and frame were designed to undergo displacements and forces which may happen under a Maximum Considered Earthquake (MCE). Quasi-static and dynamic loadings were applied to the frame. The results showed that the performance of the frame under different loading regimes is self-centring, energy dissipative, and repeatable. Moreover, suitability of the system for retrofitting purposes was probed by numerical analyses. Second, the RSFJ TO-Brace was investigated under earthquake conditions which would expand the RSFJ beyond its ultimate level. Loading of the RSFJ beyond its ultimate level may be allowed at the discretion of the design engineer or can be triggered by unexpectedly large earthquakes. Therefore, it is important to encourage a ductile failure mode. Three RSFJs were designed to have a ductile failure mode and were tested beyond their ultimate capacity up to the rupture. RSFJs with the same characteristics were then used in a full-scale steel frame and the frame was pushed quasi-statically beyond the ultimate level. The results showed that the failure mechanism is ductile as intended, the self-centring characteristic is still maintained, while the response is not fully repeatable due to the reduction in the pre-stressing force of the bolts. Equations were proposed to predict the elongation and over-strength of the joints and frame, which were verified with the test results. The observed elongation and over-strength of the joints and frame were reported as well. Third, a full-scale three-story three-dimensional steel structure was designed to include three structural systems using the RSFJ, RSFJ TO-Brace, RSFJ TC-Brace, and RSFJ MRF. A three-dimensional shaking table test can capture the dynamic effects on the performance of the RSFJ systems and the whole structure. The studied structure was two bays by one bay in plan and with an inter-story height of 3m. The structure was designed to be configurable i.e., the connections vital for the intended performance of each system were designed to be easily replaced, with no structural invasion, to permit changing from one to another system. The same beams, columns, and floors were used for all systems. For each system RSFJs, connections, and members were designed to undergo no damage under Ultimate Limit State (ULS) and MCE shaking levels. The design procedure used starts with force-based Equivalent Static Method (ESM) and continues with the pushover and Nonlinear Time-History Analysis (NLTHA) methods. The connections and members in all systems were designed and detailed to be deformation compatible. The earthquake record selected to represent the seismic intensity of the selected site was Imperial Valley 1940 earthquake. For the sake of extended numerical analysis, 7 more earthquake records were selected and then scaled to the site target spectrum. In the next step, 56 RSFJs were manufactured and tested to ensure the designed performance is achieved. Also, beams, columns, and floors were manufactured. The next steps including construction of the structure on the shaking table test and shaking it with the selected earthquake record and assessing the results were left uncompleted. This is due to the inevitable circumstances incurred by COrona VIrus Disease-2019 (COVID-19) on this study. This international project is planned to happen at the International Joint Research Laboratory on Earthquake

Engineering (ILEE), Shanghai, China, after international flights and collaborations and border restrictions are lifted.