Development of a novel connection method using expanded rib and spiral bars for reinforced concrete beams with cold joints

Abstract

A contactless coupler system was developed for the analysis of reinforced concrete beams, specifically for beams with non-contact joints. Beam tests were conducted on specimens with three types of reinforcing bars: continuous (CR), non-continuous expanded (NE), and simply non-continuous (NR). The test results indicated that both the CR and NE specimens demonstrated comparable levels of strength and flexibility. However, the NR specimens fractured in a brittle manner. The strain measurements revealed that the decline in the strength and stiffness of the contactless coupler influenced the beam's structural behavior. When this decline surpassed a certain point, the weakest part of the beam shifted from the cold joint to the connecting segment. This shift led to a modification in the manner in which the beam failed. The distinction between NE and NR becomes apparent through the enhancement in the bonding strength of the rebars, facilitated by the use of expanded ribs. These ribs contribute significantly to decreasing the development length needed for the rebars. Furthermore, a meticulous analysis of the failure modes and the transition zone of weakness has been conducted by leveraging numerical simulations. These simulations take into account the mechanical conditions intrinsic to the contactless coupler.