MOST SIGNIFICANT RESEARCH CONTRIBUTIONS
- Development of Analytical Models and Analytical Tools for Concrete Structures:
a) Developed two analytical models for confined concrete with PhD student S. Razvi. The models (cited by over 1200 papers) are among the most frequently used confinement models for research, teaching and engineering applications worldwide.
b) Developed a rectangular stress block for high-strength concrete with PhD student T. Ozbakkaloglu, which was adopted by the ACI Innovation Technology Group 4.
c) Developed hysteretic models for dynamic inelastic response history analysis:
• Hysteretic model for moment axial force interaction effects.
• Hysteretic model for inelastic shear response of reinforced concrete structures.
• Hysteretic model for anchorage slip in concrete.
• Hysteretic model for FRP reinforced concrete elements.
d) Developed computer software with graduate students for the benefit of structural engineering community in Canada:Blast-resistant anchor design software (BRADS) with PhD student E. Jacques, which has been adopted by CSA S852-2018 as a design tool.
• Blast-resistant anchor design software (BRADS) with PhD student E. Jacques, which has been adopted by CSA S852-2018 as a design tool.
• Seismic screening software (SCREEN) with PhD student and PDF M. Shooshtari for Public Works and Government Services Canada as updated seismic screening tool for Canada.
• Dynamic analysis of reinforced concrete elements for blat assessment and design (RC-Blast) with PhD student E. Jacques.
• CanRisk software for seismic risk assessment of buildings in Canada, developed with PhD student S. Tasfamariam and MASc student A. Elsabbah.
2. Development of Design Codes and Standards; Design Handbooks and Guidelines:
a) Chaired CSA Technical Committee S852 and developed a new Canadian standard on “Blast-Resistant Window Anchor Systems” (the only standard on the topic worldwide).
b) Chaired the Subcommittee on Design of CSA Technical Committee S850 on Design and Assessment of Buildings for Blast Loads and contributed significantly to the design provisions.
c) Chaired the Subcommittee on Seismic Design of CSA Technical Committee S806 and developed seismic design provisions for FRP reinforced concrete structures.
d) Contributed towards the development of the seismic provisions of the National Building Code of Canada (2005, 2010 and 2015 editions).
e) Contributed towards the development of the relevant design provision in ACI 318 Design Code for use of high-strength transverse reinforcement (2008, 2011, 2014, and 2019 editions).
f) Currently serving as a member of the Canadian Standards Association CSA A23.3 and contributing towards the design requirements for reinforced concrete structures in Canada with specific emphasis on the use of high-strength reinforcement and seismic design.
g) Edited the first Metric Design Handbook for Reinforced Concrete Elements in Canada, and wrote two chapters of the handbook, which was published by the Portland Cement Association on behalf of the North American Cement Industry. The handbook evolved into the current Concrete Design Handbook, which is now published by the Cement Association of Canada (CAC). Wrote three chapters of the new handbook, which is currently used by the practicing engineers and universities across Canada.
h) Edited and coauthored the ACI SP17-2011 Design Handbook for Reinforced Concrete Elements, published by the American Concrete Institute. The handbook is used in the US, Central and South America, as well as different parts of the world.
i) Chaired the Task Group 2 of ACI Technical Committee 374 on Performance-Based Seismic Design of Concrete Buildings, and developed Displacement-Based Test Protocol published by the American Concrete Institute. A revised version of the document is currently being developed.
j) Contributed significantly to the Encyclopaedia of Natural Hazards, published in 2013 by Springer.
3. Development of Retrofit Technologies for Seismic Resistant Structures:
New techniques have been developed through experimental and analytical research for seismic retrofit and rehabilitation of existing seismically deficient structures and structural components. The following is a list of seismic retrofit methodologies developed:
• Buckling Restrained Brace (BRB): A new buckling restrained brace was developed with PhD Student Z. Al-Sadoon and Dr. Palermo for seismic resistance of reinforced concrete frames. The brace consists of a steel bar, enchased in a concrete filled steel tube, with special end pieces that allow compression and tension yielding without buckling with continuous buckling restraint along the core length without the standard gaps used in conventional BRBs (Patented in Canada, USA; patents pending for Pakistan and China). The technology is currently being marketed through Steel Canada Ltd. in the US and China.
• Lateral bracing of nonductile concrete frame systems with diagonal prestressing strands (with two PhD and one MASc student): A seismic bracing system was developed through experimental and analytical research, involving diagonally placed prestressing strands. The frames are either diagonally prestressed or braced with nonprestressed cables for enhanced lateral force resistance. The technology is currently improved by considering cables of different prestressing levels for sequential engagement in seismic response when needed.
• RetroBelt system of column retrofitting: A new technology, involving transverse prestressing of concrete columns, was developed with PhD student C. Yalcin. Transverse prestressing improves concrete confinement through active lateral pressure, while controlling diagonal tension cracks. The technology was patented in Canada, U.S.A, Europe, and South America.
• Concrete column retrofit by FRP wrapping: Developed a displacement-based seismic retrofit design methodology for concrete columns. The methodology was adopted by CSA Standards S806-02 and S806-12 for use by the structural engineering community in Canada.
• Seismic strengthening of masonry walls: A seismic strengthening technique was developed for concrete block and brick masonry infill walls enclosed in non-ductile reinforced concrete frames. The technique involves use of surface bonded Fibre-Reinforced Polymer (FRP) sheets for increased diagonal tension resistance. The research program has recently been extended to load bearing masonry walls with retrofit strategies consisting of surface bonded FRP sheets in combination with either externally applied FRP or steel sheet anchors or internally placed reinforcing bars or prestressing strands for flexural strength and ductility enhancements. The technology is currently being disseminated to the structural design practice through publications.
• Lateral bracing of non-ductile shear walls: A technique was developed with Dr. M. Bruneau and PhD student M. Taghdi for improving strength and inelastic deformability of brittle reinforced concrete, reinforced masonry and unreinforced masonry shear walls. The technology was developed through tests of large-scale concrete and masonry walls, combined with analytical research. It consists of the use of steel strips as vertical and diagonal elements.
4. Development of Blast Resistant Design and Retrofit Methodologies for Structures:
A unique Blast-Research Laboratory was established at the University of Ottawa with a “Shock Tube” (blast simulator) suitable for large-scale structural testing (the only such facility in Canada). Extensive experimental and analytical research was conducted to generate design information and methodologies for blast-resistant structural and non-structural components. Specifically, the effects of high strain rates on materials were established (for the first time for timber and reinforcement bond in concrete), contributions were made towards the development of the CSA Standards S850 and S852 on Blast-Resistant Design, while also developing retrofit strategies to mitigate blast risk, consisting of the use of FRPs, lateral bracings (tension and compression), and polyurea.
5. Development of Displacement-Based Design Method for Confined Columns:
A displacement-based design procedure was developed for column confinement, which was adopted by the ACI Innovation Task Group 4 as part of seismic design guidelines for high-strength concrete columns. The procedure was subsequently adopted by the Canadian Standards Association in three of its standards, addressing FRP reinforced concrete design and blast resistant design of buildings; CSA S806-02; CSAS806-12; and CSA S850-12. The results were also used to introduce high strength steel for column ties in the ACI 318 Building Code.It was first published in the Journal of Structural Engineering of the American Society of Civil Engineers (ASCE) and was recognized by the ASCE 2000 Raymond C. Reese Research Prize as “an Outstanding Contribution to the Application of Structural Engineering Research.”