Thermal stress analysis of cracks around the joints of the side wall of cast-in-place reinforced concrete open channels

Joint cracks are a type of characteristic crack that occurs in the side walls of cast-in-place reinforced concrete open channels. In this study, thermal stress analysis was performed to analyze the cause and timing of joint cracks in the side walls of such channels. The distribution of maximum principal stress indicated that previously placed spans restrain subsequently placed spans, increasing the risk of generating joint cracks. This suggests that the waterstops buried in the previously placed spans restrain the deformation of the subsequently placed spans due to the difference in strength caused by the material ages. In addition, the risk of generating joint cracks increased with the increase in the casting intervals. The maximum principal stresses exceeded the tensile strength of the concrete around the joint sections for both summer and winter construction. Thus, joint cracks may occur at both early and long-term material ages, regardless of construction season. To obtain a more realistic thermal stress analysis, outside temperature models capturing the features of temperature data in Japan were proposed, and these models gave appropriate analysis results.