Seismic assessment of out-of-plane URM walls
Principal Researcher: Associate
Professor Jason Ingham
Students involved: Hossein Derakhshan, Aaron Wilson, Ronald Lumantarna.
Introduction:
In order to investigate the seismic behaviour of typical New Zealand unreinforced masonry (URM) walls when subjected to out-of-plane loading, a research project has been developed which includes international collaboration between The University of Auckland, University of Adelaide and University of British Columbia in Canada.
Objectives and scope of the Research:
Presentation of a simple tabular assessment tool, which can be used in place of the existing complicated New Zealand evaluation guidelines, is the ultimate objective of this research. The scope of the research includes experimental (static and dynamic shaking table) testing on two- and three-leaf unreinforced masonry (URM) walls. One-leaf URM walls are not considered in this research, but it is expected that results from ongoing research in Australia are included in the New Zealand study. The scope of the research also includes numerical modeling of one- and two-storey walls connected to flexible diaphragms. The numerical model will account for tri-linear force-displacement relationship of URM out-of-plane walls. Toward the objective of the research, a parametric study will provide the opportunity to examine different wall models subjected to different earthquake excitations. Analyses will represent different classes of wall/building height, seismicity and support flexibility. The conclusion of the parametric study will be a tabulated form of assessment for out-of-plane URM walls. A last study will investigate the behaviour of parapets, provide simplified assessment tool and proposes retrofit details of these elements.
Experimental Study:
Experimental study will include both static and dynamic shaking table testing of two- and three-leaf walls. A total of 10 static tests (Table 1) have been scheduled to be performed in laboratory alone. In-situ testing will also be performed to extend the results from lab-based tests. Of the 10 lab-based tests, 6 have been performed as of the date of this report, and the other 4 tests are to be completed by the first week of May, 2009. Table 1 shows the test matrix and the tests that have been completed so far. Figure 1 shows the setup used to perform all of the tests. Figure 2 shows the last of the walls (Walls 4 and 5) built with 3-leaf thickness and awaiting airbag tests on 1st of May, 2009.
Experimental study will also include in-situ testing of out-of-plane walls. In-situ tests are aimed at both one-way and two-way evaluations. Juxtaposed results of in-situ and lab testing of one-way walls enable this study to be used with more confidence. In addition, two-way in-situ testing evaluation will provide evidence on the extents by which two-way actions increase the strength and stiffness of out-of-plane walls. Although their effect on out-of-plane rocking behaviour is not yet understood, two-way actions are known to greatly increase initial stiffness and strength of out-of-plane walls in a linear elastic analysis. Figure 3 shows a setup used previously to perform two-way tests on a wall in Wellington.
The preliminary results from airbag testing performed recently in The University of Auckland can be found below:
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.
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.
Derakhshan, H. and Ingham, J. M. (2009). "Out-of-Plane testing of an unreinforced masonry wall subjected to one-way bending”, Proc. 2009 AEES Conference, Ballarat, Australia, November 21-23, 2008.
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.
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.
 |
 |
(a) Airbag testing setup |
(b) Test 3-A |
Figure 1 |
|
 |
Figure 2: Walls 4 and 5, awaiting airbag tests on 1st of May 2009 |
 |
Figure 3: Airbag testing being performed on a two-way one-leaf URM wall located in a Wellington building |