THE INFLUENCE OF SHEAR ON LAPPED SPLICES IN REINFORCED CONCRETE

The primary objective of this investigation was to study the effects of level of shear, amount of transverse reinforcement, and casting position on the strength of lapped splices. A limited number of tests were conducted to examine the influence of concrete strength, slump, and bar size on splice performance. In addition, an exploratory study is reported on the influence of high range water-reducing admixtures (superplasticizers) on splice performance. Twelve beam specimens containing both top and bottom splices were constructed providing a total of twenty-four separate tests. Ten specimens contained four #11 bars (22 in. lap length) and two contained five #9 bars (16 in. lap length). The concrete varied from 4025 psi to 5700 psi. The parameters of cover, spacing, edge distance, and lap length for a given bar size were kept constant in each group. The behavior of the beam specimens was studied in terms of the crack patterns and steel strain distributions. The measured average bar stresses are compared to evaluate the effect of the variables. The results provide additional data for evaluating design equations which have been recommended by ACI Committee 408 to change the ACI Building Code (ACI 318-77). The ACI Code is primarily intended for building design; however, AASHTO Code provisions closely follow the ACI Code and are applicable to bridges as well as other transportation structures. (FHWA)