An Ехрerimental аnd Numeriсаl Study of Internаlly Torsional Strengthening of Bох Beams Made from SCC Cоncrete

This study investigates the torsional performance of reinforced Self-Compacting Concrete (SCC) box beams, internally strengthened with Framed Stiffening Ribs (FSRs) or Framed Steel Stiffening Ribs (FSSRs). The experiment consists of casting and testing seven beams, one reference without any reinforcement and six strengthened. The number and type of FSRs, opened or closed, are considered the main variables of the study. The experimental results indicate that adding one opened FSSR and five closed FSSRs enhances the ultimate strength of the beams by 32.71% and 122.42%, respectively. This reveals the superiority of closed FSSRs against the open ones. In addition, the percentage of increase in the ultimate torque (Tu) of the ratio closed to opened FSSRs is 9.8%, 10.3%, and 14.7% for the beam of 1, 3, and 5 FSSRs, respectively. ABAQUS software in conjunction with Finite Element Method (FEM) are used to assess the beams numerically. A robust connection is observed between the final torque and angle of twist (θ) derived from the modeled and experimental results. The mean and coefficient of variation for the ratio of FEM to experiment for Tu, are calculated to 1.038 and 2.785%, respectively.  Similarly for θ, they are 0.975 and 5.555%. Therefore, the simulation of the beams can be used to study the tortional behavior of such cases with less time, effort, and cost.