Today, especially older steel structures with poor detailing are vulnerable to local member buckling and thereby system-wise instability, due to overloads such as earthquakes or other extreme events prior to reaching the required plastic rotation capacities specified for new buildings. Furthermore, even higher levels of plastic rotations than those specified in AISC and Eurocode-8 may also be needed for buildings in soft soils and important facilities. In addition, repair of beam local buckles is an expensive and challenging application. Therefore, mitigation of inelastic instabilities is an important task, which will not only improve the structural ductility and energy dissipation capacity of the structure, but will also minimize cumbersome repair works in the aftermath of extreme events.
This study will investigate the enhancement of ductility in existing steel special moment frame (SMF) connections through the use of externally bonded glass fibre reinforced polymer (GFRP) composite materials. The investigation will be both experimental and analytical in nature. In the proposed study, it is aimed to effectively utilize the unique material properties of GFRP to brace flange/web local buckles during plastic hinge formations in I-beams. Cantilever beams with/without GFRP will be constructed and tested under reversed cyclic loading. GFRP has a much smaller modulus than that of steel, typically one order of magnitude less, which limits its use in strengthening applications. However, this modulus mismatch is an asset when the primary goal is to stabilize inelastic local buckling with least possible strength increase in the section.
This investigation will provide a scientific base for the use of GFRP reinforcement in plastic hinge region of steel members by utilizing experimental and finite element analysis studies, and can also lead to relaxation of web/flange compactness limits. The GFRP-steel hybrid composite system has also the potential to be used in new constructions.
Fields of science
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