In-Situ Evaluation of Two Concrete Slab Systems. I: Load Determination and Loading Procedure
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Volume 22, Issue 4
Abstract
The primary objective of in-situ load testing is to assess the safety and serviceability of an existing structural system with respect to a particular load effect. At this time, the most appropriate loading level and procedure, as well as the associated evaluation criteria are being reconsidered in light of technological advances in construction methods, analytical tools, and monitoring instrumentation. The in-situ load test method for reinforced concrete systems described in the ACI Building Code Requirements for Structural Concrete, namely the 24–h load test method and its evaluation criteria, has been in use for several decades, but may no longer serve the needs of contemporary construction and engineering practices. As a result, other load test methodologies and associated evaluation criteria are under development. This paper and a companion paper describe the rationale and application of an alternative approach to the determination of load level, loading procedure, instrumentation requirements, evaluation criteria and outcomes for two field projects. The first case study is relative to a posttensioned concrete slab where many areas were characterized by tendon and reinforcement misplacement, resulting in inadequate flexural strength and inadequate shear/flexure transfer at column/slab intersections. The second case study is the structural evaluation of a typical floor bay of a two-way reinforced concrete slab system, presenting distributed cracking at the positive and negative moment regions. Finite-element-method models were created for both structures to aid the load test design. The numerical models validated the field observations.
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Acknowledgments
The ACI Concrete Research Council, the NSF Industry/University Cooperative Research Center on Repair of Buildings and Bridges with Composites and the UMR–University Transportation Center on Advanced Materials are gratefully acknowledged for their financial support to the research. Yizhuo Chen assisted with the load tests and data reduction and his assistance is greatly appreciated.
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© 2008 American Society of Civil Engineers.
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Received: Sep 10, 2007
Accepted: Jan 15, 2008
Published online: Aug 1, 2008
Published in print: Aug 2008
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