Shear strength in reinforced concrete beams with cold joint
摘要
Cold joints in reinforced concrete (RC) beams can significantly impact shear behavior, influencing stress distribution and failure patterns. This study examines how delay times, compressive strength, and shear reinforcement affect the shear performance of RC beams with vertical cold joints. The goal is to understand the role of these factors in structural integrity and failure mechanisms. To achieve this, eighteen RC beams were tested and divided into two groups based on compressive strength (30 MPa and 50 MPa). Within each group, stirrup spacing was varied (50 mm, 75 mm, 130 mm, and no stirrups), and delay times at the cold joint were set at 0, 60, and 180 min. The experimental program evaluated shear capacity, crack propagation, and failure modes. The results reveal that cold joints create stress concentrations, consistently causing failure on the side opposite the joint. Beams with a 60-min delay showed better shear performance than those with a 180-min delay, indicating the importance of bond strength at the joint. Denser stirrup spacing (50 mm and 75 mm) effectively controlled diagonal crack growth, while wider spacing (130 mm) led to more extensive cracking. Additionally, higher-strength concrete (50 MPa) improved shear resistance and reduced the negative impact of cold joints compared to normal- strength concrete (30 MPa). These findings offer valuable insights into the behavior of RC beams with cold joints, emphasizing the need for careful design and construction practices in shear-critical regions to ensure structural safety and performance.