Debra Gardiner
University of Canterbury
PhD Candidate
2007 – 2010
Supervisors: Prof Des Bull, Prof Athol Carr, Dr Richard Fenwick
External Funding: Haynes Willimason Fellowship - New Zealand Federation for Graduate Women, H J Hopkins Postgraduate Scholarship in Civil Engineering
PhD Research Topic:
The magnitude and paths of internal forces within suspended concrete floor diaphragms is considerably more complex than the simplistic methods employed in current design practice. Some of the methods produce outcomes that relate very poorly to real behaviour.
The concrete diaphragms (floors and roof) tie the vertical structural elements (walls and frames of various sorts) together so that the building can resist gravity and lateral forces that arise from wind and earthquakes for example. Issues that are related and will be investigation for this research include:
1) Magnitude of design forces in the structure and across the floor diaphragms.
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Comparison of current methods - technical review
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Verification of actions within diaphragms for a range of building types (frames, walls and combination of these) by non-linear time history (utilizing a range of appropriate earthquake records).
2) Review of current methods employed by design Standards for reinforcing and detailing of concrete diaphragms, including the recommendations “Strut and Tie” methods. Reviews on these methods indicated that these are not generally applicable to most of the architectural layouts employed in buildings.
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Realistic floor architecture involves quite complex layouts of structural elements (including penetrations in the floors for lifts, stairs and mechanical services). Recent concept development demonstrates that one viable and pragmatic solution to floor diaphragm design would be the extending of the Strut & Tie method.
2) Localised damage at the sites of plastic hinge zones in beams and local displacement damage at floor-to-wall connections are not accounted for in conventional methods.
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There will be a review of current methods and recent emerging research of this feature.
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Recommendations for the “Strut and Tie” solutions for diaphragm design, recognising that localised damage in the structure will dictate viable force paths through the structure.
These issues will be investigated in this research by carrying out numerous analytical studies using a variety of numerical programs. The aim of the research will be the production of recommendations for the design and detailing of concrete floor diaphragms to be used by practitioners.
Publications:
Gardiner, D.R., Bull, D. K., and Carr, A.J., 2008, Trends of Internal Forces in Concrete Floor Diaphragms of Multi-storey Structures During Seismic Shaking, Proc. of 14th World Conference on Earthquake Engineering (14WCEE) 2008 , Beijing, China. (Paper ID: 05-06-0178) pdf
Gardiner, D.R., Bull, D. K., and Carr, A.J., 2008, Investigation of the Magnitude of Inertial and Transfer Forces in Floor Diaphragms during Seismic Shaking, Proc. of 2008 NZC Conference, Rotarua, New Zealand. pdf
Gardiner, D.R., Bull, D. K., and Carr, A.J., 2008, Internal forces of concrete floor diaphragms in multi-storey buildings, Proc. of 2008 NZSEE Conference, Wairakei, New Zealand. pdf
Gardiner, D.R., Bull, D. K., and Carr, A.J., 2006, Analytical Verification of the Distribution of Seismic Forces in Diaphragms, 3rd Pro Project Report, University of Canterbury, Christchurch, New Zealand pdf [contact authors]
Contact details:
Debra Gardiner
Department of Civil and Environmental Engineering
The University of Canterbury
Private Bag 4800
Christchurch
New Zealand 8020
email:drg42@student.canterbury.ac.nz