Experimental Investigation of In-Plane Cyclic Response of Unbonded Posttensioned Masonry Walls
Publication: Journal of Structural Engineering
Volume 142, Issue 5
Abstract
This paper reports on an experimental study on four unbonded posttensioned masonry walls (PT-MWs). All walls had identical thickness, height, and length of 190, 2,000, and 1,400 mm, respectively, and were constructed using concrete masonry units (CMUs) and mortar type N, and were fully grouted. Different horizontal spacing values of 400, 600, and 1,200 mm were used between the posttensioning bars in the walls. Only Wall W4 had horizontal bonded reinforcement, located in the fourth and seventh courses. Two different levels of posttensioning force corresponding to an average posttensioning compressive axial stress on the masonry of 1.35 and 2.7 MPa were applied to the walls. Different initial posttension stresses in the bars ranging from 0.32 to 0.63 of the yield stress of each bar were applied to the walls. The walls were subjected to incrementally increasing in-plane lateral displacement cyclic load applied to the top of each wall. The experimental results including damage pattern, force displacement response, residual drift ratio, masonry compressive strain, wall rotation, damping, stiffness, stiffness degradation, and displacement ductility of the tested walls are presented and discussed in detail. The accuracy of ignoring the elongation of post-tensioning bars in predicting the strength of the tested walls is investigated based on the experimental results. The experimental tests showed that PT-MWs having the same total initial PT force but different stress levels in the PT bars displayed different lateral strengths. Doubling the total initial PT forces in the bars resulted in insignificant increases in the wall lateral strength. Finally, using bonded horizontal steel improved the lateral displacement capacity of the test specimen. Specimens that had horizontal reinforcement did not suffer postpeak shear cracking and hence were able to reach higher level of lateral displacement.
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Acknowledgments
The authors gratefully acknowledge the support of the Australian Building Code Board (ABCB), Bianco Precast Pty Ltd, Boral Pty Ltd, and the University of South Australia to support the experimental work. Special thanks to Mr. T. Golding, Mr. W. Penney, and Dr. H. Senko and the technical support staff from the Concrete Laboratory at the University of South Australia, for their dedication and assistance before and during the tests.
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Published In
Journal of Structural Engineering
Volume 142 • Issue 5 • May 2016
Copyright
© 2015 American Society of Civil Engineers.
History
Received: Dec 31, 2014
Accepted: Oct 2, 2015
Published online: Dec 17, 2015
Published in print: May 1, 2016
Discussion open until: May 17, 2016
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