Long-Term Behavior of Composite Beams under Positive and Negative Bending. I: Experimental Study
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VIEW THE REPLYPublication: Journal of Structural Engineering
Volume 136, Issue 7
Abstract
This paper presents an experimental program designed to examine the long-term behavior of composite steel-concrete beams under sustained loads. The test program consisted of two simply supported beams under positive bending moments and two cantilever beams under negative bending moments. Long-term deflections, strains, and the cracking behaviors of the specimen beams were monitored over a period of 3 years. The primary observations are: (1) the deflection of the simply supported beam under positive bending moment increased quite significantly over the time due to creep and shrinkage, with the midspan deflections after 3 years of loading reached 2.5 times of the initial deflections, and (2) the cracking of concrete occurred in hogging moment regions for cantilever beams due to the combined effects of concrete shrinkage and sustained negative bending moments. Current design codes were evaluated through a comparison between the calculations and testing results. It was found that the effective modulus method provides a satisfactory prediction on deflections and strains for beams under positive bending moments. But for beams under negative bending moment, the stiffness reduction due to cracking effect should be considered in calculation.
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Acknowledgments
The experimental investigation presented in this paper was carried out in the Engineering Structure Laboratory at Tsinghua University, and was financed by the Chinese National Science Foundation (Grant No. UNSPECIFIED50408001). The assistance of the laboratory staff and the financial support are gratefully acknowledged.
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Information
Published In
Journal of Structural Engineering
Volume 136 • Issue 7 • July 2010
Pages: 849 - 857
Copyright
© 2010 ASCE.
History
Received: Mar 12, 2009
Accepted: Dec 20, 2009
Published online: Dec 29, 2009
Published in print: Jul 2010
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