Concrete Strength of Vertical Joints in the Cantilever-cast Segment of Prestressed Concrete Box Girders

Abstract

This study analyzed the influence of concrete compressive strength caused by vertical joints placed between cantilever-cast segments of various prestressed concrete (PC) box girder bridges. The vertical joints of two actual bridges and an interior model were examined to test their concrete strengths and load-carrying capacities. First, the concrete strengths of most vertical joints were found to be lower than that of a normal position of web under normal construction conditions. This phenomenon is primarily caused by the difficulty of vibration and the non-uniformity in the deposition of concrete, resulting in a concrete quality in a segment different from that in a normal position. Second, the tensile strength of concrete is affected by the roughness of the vertical joint, and the cracking moment of the concrete is lower than that of the entire box girder model. Therefore, the quality of a segment must be well controlled to improve the bond at the site where old and new concretes are combined during construction.