Strength and behavior of Mechanical Coupler Based on Laboratory Tests

Abstract

In reinforced concrete structures, it is inevitable to have splices. In general, structural engineers specify the splice method either by lap or welded splice. Nevertheless, many construction sites use the mechanical coupler as an alternative method. In such case, the product owner needs to test samples in the laboratory before use for the method specified in the drawing and specifications. This study collected test results of mechanical couplers around 200 samples for analyses. It is observed that all samples are of type A or double-sided coupler for deformed bars. Construction sites always want to test its tensile strength the same way as regular tensile test of reinforced steel. In particular, they want to know the point of failure either at the couple or at the steel bar and the location. An additional test requirement is for partial tightening of coupler. The tensile test results indicate that almost all samples failed at the steel bar at various distance depending on the size and tensile strength of the reinforced steel. It is unpredictable to figure out which bar will be failed. For partial tightening tests, the steel bars are not always failed at the loosen side. It can be concluded that tensile strength of splices by using mechanical coupler essentially depends on the strength of coupler and tightness. The tensile strength of mechanical coupler must be higher than the reinforced steel bar. The tightness of coupling should be designated by the standard torque. Most importantly, it must be tested under the simulated structural conditions before allow to be used in the project.