Proposed Modifications to ACI 318-95 Tension Development and Lap Splice for High-Strength Concrete

Safety concerns and a lack of test data are responsible for the current upper limit of 100 psi (689,500 Pa) on the square root of the concrete compressive strength for use in calculating tension development and lap splice lengths. Based on recent research on the lap splice strength of reinforcing bars in high-strength concrete, modifications to current design criteria are formulated that will allow removal of the limit on the square root of the compressive strength, ensure adequate ductility and bond, and improve the overall safety of the tension development and lap splice criteria in American Concrete Institute (ACI) Standard 318-95 for concrete with strengths above 10,000 psi (68,950,000 Pa). The result of the analyses used to develop the new design criteria indicate that increasing lap splice length, without providing transverse reinforcement, does not provide an adequate level of ductility in high-strength concrete members. Adequate ductility can be achieved by using a minimum splice length, as defined by ACI 318-95 for beams without transverse reinforcement, plus a minimum quantity of transverse reinforcement over the tension development/lap splice length with an area equal to 50% of the area of the bars being developed/spliced.