Resilient Hybrid Steel-Timber Structural Systems for Seismic Applications
Creators: Mowafy Saad, Ahmed Gamal Abdelnaser Mohamed
Publisher: name: University of Alberta Library
Year: 2023

<p>The Black Swan events of the 1994 Northridge and the 2010-2011 Christchurch earthquakes brought seismic design philosophy under scrutiny, emphasizing need for resilient structure that prioritize life safety and facilitate rapid post-earthquake recovery with minimal repair costs. Hybrid steel-timber structures offer resilient option and improved structural performance by combining steel&#39;s ductility with timber&#39;s lightness. This thesis presents a practical guideline to design a resilient hybrid steel-timber rocking braced frame. To achieve this, a novel connection system featuring U-shaped steel seismic fuses was developed to connect between a gravity load-resisting timber frame and a steel concentrically braced frame acting as the lateral load-resisting system with self-centring capability. <br>
This research study comprises three interconnected components that utilize extensive experimental testing, numerical modelling, and design optimization methods. The first component introduces a novel U-shaped steel seismic fuse employing a unique scissor-bending mechanism. Comprehensive experimental and numerical analyses highlight its potential for diverse applications, offering notable strength, stiffness, ductility, and energy dissipation capacity. The second component explores an innovative hybrid timber beam-to-steel column connection system, incorporating the proposed U-shaped steel seismic fuses. Comprehensive testing led to significant improvements in the initial joint design, yielding a connection system that demonstrated enhanced cyclic load resistance and stable load-displacement cycles, facilitating rapid post-earthquake recovery. Building on these results, the third component introduces a new low-damage, self-centring hybrid steel-timber rocking braced frame. The proposed design methodology was validated through in-depth numerical analyses, demonstrating the system&#39;s desired seismic performance with minimal post-earthquake residual deformations.<br>
This research has generated significant advances in understanding of the seismic resilience of hybrid steel-timber structures. The findings revealed that the U-shaped steel seismic fuse can safely dissipate seismic loads through a scissor bending mechanism. Further, an innovative hybrid timber beam-to-steel column connection system demonstrated improved ductile behaviour and no strength degradation in glulam beam member, opening the door to more retrofitting options. In addition, replaceable fuses, validated in the study, offer opportunities for flexible and effective structural upgrades post-earthquake. The novel hybrid steel-timber rocking braced frame effectively resisted seismic-induced demands, demonstrating self-centring capabilities, and staying within the code-specified drift limit. Significantly, the system remained elastic under design-level hazards, proving its resilience. These collective findings found practical application in the design of a five-storey prototype building, where a self-centring, chevron-type steel frame served as an effective lateral load-resisting system.<br>
This body of work substantially contributes to seismic design standards and promotes the broader use of timber in hybrid steel-timber structures.</p>