Experimental and Numerical Investigation of Cold Joint Effects on Intermediate Concrete Moment Frame Under Cyclic Loading

Abstract

This study investigates the seismic behavior of reinforced concrete flexural frames with a focus on the impact of cold joints (CJs). Three one-bay concrete frames, scaled to 2:3 according to ACI 318-19(22), were tested under axial and cyclic loading. The frames included a control frame without CJs, a frame with CJs, and a frame with CJs reinforced with fiber-reinforced polymer (FRP) sheets. Initially, the difference between the frame without CJs and the frame with CJs was examined, revealing a 10% reduction in cumulative energy dissipation, a 24% reduction in ductility, and an 18% reduction in lateral load capacity for the frame with CJs. Additionally, the stiffness in frames with CJs has decreased. Subsequently, the frame with CJs was reinforced with FRP sheets, leading to a 33% increase in cumulative energy dissipation and a 54% increase in lateral load capacity. However, the FRP sheets, while increasing load capacity, introduced brittleness, which reduced ductility. Crack patterns varied, with the frame without CJs showing vertical cracks near connections at 3% drifts, and the frame with CJs exhibiting tension and compression vertical cracks at 1% drifts. After validating the numerical models, two structural designs have been proposed to mitigate the negative effects of CJs in reinforced concrete structures. These designs are intended to improve seismic performance and enhance the structure's resistance to cyclic loads.