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Calculation methods to evaluate the strength of tension lap splices are based primarily on nonlinear regression analysis of test results. While the results from these analyses are extremely useful, applicability of their results beyond the domain of the data is often questioned. The objective of this research was to develop an expression for the calculation of bond strength based on a physical model of tension cracking of concrete in the lap-spliced region. Two different types of failure modes are considered: horizontal splitting that develops at the level of the bars (side-splitting failure), and vertical splitting that develops along the bar on the face cover (face-splitting failure). The developed expression was verified using results from 203 unconfined and 278 confined beam tests where the splice region was subjected to constant moment.
Keywords: bond; reinforced concrete; splice; stirrup.
(ProQuest Information and Learning: ... denotes formulae omitted.)
INTRODUCTION
Because the performance of reinforced concrete structures depends on adequate bond strength between concrete and reinforcing steel, accurate calculation of splice strength is important. The ACI 318-02 (ACI Committee 318 2002) equation for development and splices of reinforcement is based on the expression for development length previously endorsed by ACI Committee 408 in ACI 408.1R-90 (ACI Committee 440 1990; Jirsa, Lutz, and Gergely 1979). This design expression is based on nonlinear regression analysis of test results available at the time. Since then, additional studies have been conducted that have investigated the behavior of lapped splices. With the increase of test data, new attempts have been made to better estimate splice strength based on statistical approaches incorporating the most recent data. To calculate bond strength more accurately, recent studies have included additional variables beyond those considered by ACI 318. Unfortunately, as more variables are added, the descriptive equations become more complex and cumbersome, especially for design applications.
RESEARCH SIGNIFICANCE
Although many studies on lap-spliced bars exist, a theory-based analysis procedure has not been developed. While additional test data have resulted in an increase in the accuracy of current statistical approaches, splice strength behavior remains not fully understood. Furthermore, the applicability of statistical approaches outside the domain of the data is often questioned. The objective of this study was to develop an expression for the calculation of bond strength based on...