In-Plane Orthotropic Behavior of Timber Floor Diaphragms in Unreinforced Masonry Buildings
Publication: Journal of Structural Engineering
Volume 140, Issue 1
Abstract
A full-scale experimental program consisting of testing four as-built diaphragms and four retrofitted diaphragms in both principal loading directions is presented. As-built configurations were typical of those found in historic unreinforced masonry buildings in North America and Australasia, whereas retrofitted diaphragms consisted of plywood panel overlays with stapled sheet metal blocking systems (SMBS). Test results were characterized using bilinear representations to establish recognizable performance parameters such as shear strength, shear stiffness, and ductility capacity, which were then used for comparative analysis. The nonlinear and low stiffness behavior of as-built diaphragms was confirmed in each principal loading direction. The plywood overlay and SMBS dramatically improved as-built diaphragm shear strength and shear stiffness and were shown to perform satisfactorily from a serviceability perspective. The orthotropic nature of as-built diaphragms was proven, with perpendicular-to-joist shear stiffness being as low as 68% of the corresponding orthogonal value. A typical duly framed stairwell penetration and discontinuous joists with two-bolt lapped connections were shown to have no detrimental impact on tested diaphragm performance. Predicted diaphragm performance using state-of-art assessment documents was shown to be inconsistent with corresponding values established from testing. It is recommended that these assessment procedures be updated with revised performance parameters and provisions to address diaphragm orthotropic behavior.
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Acknowledgments
The authors wish to acknowledge the financial support provided by the New Zealand Foundation for Research Science and Technology (FRST) Grant No. UOAX0411. The tireless assistance of Nikolaus Hollwegs, Mark Byrami, and Jeffrey Ang throughout the experimental program is also gratefully appreciated.
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Information & Authors
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Published In
Journal of Structural Engineering
Volume 140 • Issue 1 • January 2014
Copyright
© 2013 American Society of Civil Engineers.
History
Received: Aug 21, 2012
Accepted: Feb 5, 2013
Published online: Feb 7, 2013
Published in print: Jan 1, 2014
Discussion open until: Feb 26, 2014
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