Hossein Derakhshan
University of Auckland
PhD Candidate
2007 – 2010
Supervisor: Associate Professor Jason Ingham, Professor Michael Griffith
Research Synopsis:
Introduction
Out-of-plane stability of URM walls is investigated, and recommendations are provided for seismic evaluation
of these components. The study is based on previous simplified analytical models extended to
represent a broader range of seismic scenarios with more accuracy. The extension includes incorporating
effects of a flexible diaphragm support on wall top, accounting for different wall cracking patterns,
and adopting material properties data that better represent New Zealand URM construction than quantities
assumed elsewhere. Numerical modelling is utilised to conduct parametric studies, which assist in
developing a simplified wall assessment procedure.
Experimental study: A set of 13 laboratory and 15 field tests was completed between October 2007 and November 2009, which included airbag testing of two- and three-leaf walls. Figure 1 shows the setup used to perform all of the lab-based tests. Figure 2 shows the last of the walls (Walls 4 and 5) built with 3-leaf thickness and tested on May, 2009. The in-situ tests were designed so that the obtained data assisted in evaluation of the lab testing results. In addition, two-way in-situ testing evaluation provided evidence on the extents by which two-way actions increased the strength and stiffness of out-of-plane walls. Figure 3 shows a setup used to perform twoway tests on a wall in Wellington.
Analytical and numerical study: Simplified analytical equations derived from elastic and rocking mechanics of out-of-plane walls were calibrated against lab-based experimental data, and the resulted empirical relationships was proposed to be used in out-of-plane seismic wall assessment. Further numerical investigation is being conducted to understand the influence of flexible diaphragm support, and this study will form the final part of the out-of-plane URM wall study. The numerical study is based on time-history analysis of URM wall models, which include a flexible diaphragm at top support.
Selected Publications:
1. Derakhshan, H., Griffith, M. C., Ingham, J. M. (2011). “Airbag testing of unreinforced masonry walls subjected to one-way bending”, ASCE Journal of Structural Engineering. Under review. 2011.
2. Derakhshan, H., Griffith, M. C., Ingham, J. M. (2011). “Out-of-plane behaviour of cracked one-way URM walls”, ASCE Journal of Engineering Mechanics. Under review. 2011.
3. Derakhshan, H., Dizhur, D., Lumantarna, R., Cuthbert, J., Griffith, M. C., Ingham, J. M. (2010). “In-field simulated seismic testing of as-built and retrofitted unreinforced masonry partition walls of the William Weir House in Wellington”, Structural engineering Society New Zealand (SESOC) Journal (submitted February 2010)
4. Derakhshan, H., Lumantarna, R., Dizhur, D., and Ingham, J. M. (2010). " In-situ airbag testing of unreinforced masonry walls”, 8th International masonry conference (8IMC), Dresden, Germany, July 04-07, 2010.
5. Derakhshan, H., Ingham, J. M. and Griffith, M. C. (2010). “Effects of unreinforced masonry wall slenderness ratio on out-of-plane post-cracking dynamic stability”, Proc. 2010 NZSEE Conference, Wellington, New Zealand, March 26-28, 2010.
6. Derakhshan, H., Ingham, J. M. and Griffith, M. C. (2009). “Tri-linear force-displacement models representative of out-of-plane unreinforced masonry wall behaviour,” 11th Canadian Masonry Symposium, Toronto, Canada, May 31-June 3, 2009.
7. Derakhshan, H., Ingham, J. M. and Griffith, M. C. (2009). “Out-of-Plane Assessment of an Unreinforced Masonry Wall: Comparison with NZSEE Recommendations”, Proc. 2009 NZSEE Conference, Christchurch, New Zealand, April 3-5, 2009.
8. Derakhshan, H. (2008). "Airbag Testing of a one-way out-of-plane unreinforced Masonry (URM) wall-testing with pre-compression load”, Department of Civil and Environmental Engineering Test Report, The University of Auckland, New Zealand, July, 2008.
9. Derakhshan, H. (2008). "Airbag testing of a one-way out-of-plane unreinforced masonry (URM) wall”, Department of Civil and Environmental Engineering Test Report, The University of Auckland, New Zealand, July, 2008.
Contact details:
Hossein Derakhshan
Department of Civil and Environmental Engineering
The University of Auckland
Private Bag 92019
Auckland
New Zealand
ph: +64 9 373 7599 x84521
email: hder004@ec.auckland.ac.nz