Seismic and Blast Retrofit of Reinforced Concrete and Masonry Buildings

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The performance of physical infrastructure during recent earthquakes has clearly demonstrated that a large segment of existing building inventory is vulnerable to seismic excitations. Buildings designed prior to the enactment of modern seismic design guidelines of 1970's, as well as those built more recently without the appropriate seismic design and detailing practices pose particularly high seismic risk. It is economically not feasible and practical to replace these deficient buildings with new and improved structures. Therefore, seismic retrofitting (rehabilitation and strengthening) remains to be an effective and viable seismic risk mitigation strategy for civil engineering infrastructure. In addition to the seismic risk, critical infrastructure is vulnerable against accidental or maliciously intended deliberate explosions. Blast-resistant design is not common in Canada. The National Building Code of Canada does not require explicit blast-resistant design of buildings. Therefore, existing buildings and other physical assets are vulnerable to blast threats, especially if the charge weight is high (as in the case of car and truck bombs) and the proximity of explosions to buildings (standoff distance) is close. The objective of the proposed research program is to develop new and innovative seismic and blast retrofit methodologies for structurally deficient concrete and masonry buildings. The emphasis is placed on the development of cost effective and structurally sound retrofit techniques. The proposed research will be conducted by following two phases; Phase I research will consist of the development of seismic retrofit strategies. Innovative bracing systems will be developed for non-ductile reinforced concrete frames, either in the form of diagonal prestressing or buckling restrained braces. Surface bonded fibre reinforced polymer (FRP) systems with ductile steel sheet anchors will be developed for non-ductile concrete shear walls and unreinforced masonry walls (load bearing and non-load bearing). Phase II will include development of blast retrofit methodologies for tilt-up construction and unreinforced masonry walls. The use of polyurea with or without welded reinforcement fabric will be considered for the latter application. Combined experimental and analytical research will be conducted. Large scale frames and walls will be tested under simulated seismic loading at the Structures Laboratory, and large-scale concrete and masonry walls will be tested under simulated blast loads at the Blast Research Laboratory of the University of Ottawa. The experimental research will be complemented by dynamic inelastic analysis of buildings and building components. Fragility curves for seismic risk mitigation, and pressure-impulse curves for blast performance assessment will be generated.