Performance of Unreinforced Masonry Walls Retrofitted with Externally Anchored Steel Studs under Blast Loading
Publication: Journal of Performance of Constructed Facilities
Volume 25, Issue 5
Abstract
Six full-scale concrete masonry walls were tested under free-field blast loading using different charge sizes up to 250 kg of ammonium nitrate/fuel oil (ANFO) and at a constant stand-off distance of 15.0 m to cover a wide range of expected damage levels. Five walls were retrofitted with cold-formed steel studs anchored to the wall backs and were compared to the remaining as-built wall. Significant enhancement to the out-of-plane blast resistance of the retrofitted walls, compared to the as-built wall, was observed. This enhancement is attributed to the development of a tied-arch action in the retrofitted walls in which the masonry forms a compression strut while the steel studs serve as the tie. A simplified single-degree-of-freedom model was used to analyze the experimental results, and the model results agreed well with the observed damage levels and the resistances of the walls. In addition, the effectiveness of the proposed retrofit technique was evaluated in terms of strength enhancement and wall deflection reduction. The test results were also compared with those predicted by available blast damage assessment models for unreinforced masonry walls. However, it was found that available models, which do not account for the tied-arch mechanism, greatly underestimate the actual blast capacity of the retrofitted walls because of the assumption of a tensile flexural failure mode. Additionally, the proposed retrofit technique shifts the mode of failure from flexure to shear.
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Acknowledgments
The following organizations are gratefully acknowledged for their support towards this study: the Chemical, Biological, Radiological/Nuclear and Explosives Research and Technology Initiative (CRTI project UNSPECIFIED06-015TD) for the financial support; the Canadian Explosives Research Laboratory (CERL) for conducting the blast tests; the Canadian Armed Forces for the use of the test range; the Natural Sciences and Engineering Research Council of Canada (NSERCNSERC); the Canadian Concrete Masonry Producers Association (CCMPA) for donating the masonry blocks; the Canada Masonry Design Center (CMDC) for building the walls; Bailey Metal Products Limited for donating the steel studs; and the Center for Effective Design of Structures (CEDS) at McMaster University, funded through Ontario Research and Development Challenge Fund (ORDCF), a program of the Ministry of Research and Innovation (MRI), for their financial support.
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Information & Authors
Information
Published In
Journal of Performance of Constructed Facilities
Volume 25 • Issue 5 • October 2011
Pages: 441 - 453
Copyright
© 2011 American Society of Civil Engineers.
History
Received: Apr 29, 2010
Accepted: Dec 21, 2010
Published online: Dec 23, 2010
Published in print: Oct 1, 2011
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