Time-Dependent Prestress Losses in Historic Clay Brick Masonry Walls Seismically Strengthened Using Unbonded Posttensioning
Publication: Journal of Materials in Civil Engineering
Volume 25, Issue 6
Abstract
Time-dependent prestress losses in historic unreinforced clay brick masonry (URM) walls strengthened using unbonded posttensioning were investigated, with a particular emphasis on masonry shortening resulting from creep and shrinkage. An experimental program was undertaken that involved continuous monitoring of masonry shortening occurring in prestressed URM wallettes over a period of 180 days. The test wallettes were extracted from a real historic URM building and were subjected to varying magnitudes of prestress, representing axial stresses that would be developed at the wall base when strengthened using unbonded posttensioning. A rheological model is proposed for predicting masonry creep shortening, which can subsequently be used to predict posttensioning losses. It was established that a prestress loss of up to 16.4% for normal threaded steel bars and up to 5.4% for sheathed greased seven wire strands can be expected in posttensioned historic URM walls when the tendons are posttensioned to a stress of .
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Acknowledgments
The Higher Education Commission of Pakistan provided funding for the doctoral studies of the first author. Financial support for the testing reported was provided by the New Zealand Foundation for Research Science and Technology. Reids Construction Systems supplied the posttenstioning materials. Ronald Lumantarna, Benoit Rozier, Anatole Weil, and Tek Goon Ang are thanked for their help with the testing program.
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Information
Published In
Journal of Materials in Civil Engineering
Volume 25 • Issue 6 • June 2013
Pages: 718 - 725
Copyright
© 2013 American Society of Civil Engineers.
History
Received: Dec 12, 2011
Accepted: Jul 10, 2012
Published online: Aug 27, 2012
Published in print: Jun 1, 2013
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