Behaviour of RC Beams with Strengthened Web Openings under Vertical Loads

Abstract

This study aims to investigate experimentally the behavior of self-compacting reinforced concrete beams with in-plane loaded openings strengthened with different techniques in the opening zone. The experimental program consists of testing five specimens with a rectangular opening at the midspan, one of the beams serves as a control beam (without strengthening), and four beams are strengthened at the opening zone with several methods including steel fibers, semi-rhombus crossed bars, jacketing with steel plates, and utilizing the composite section technique. The response has been discussed in terms of the first cracking load, ultimate load, maximum deflection, failure modes, loading history, crack patterns, toughness value, ductility index, and crack width to recognize the best strengthening proposal opening. Test results indicate that the technique of strengthening the WT-rolled steel recorded an increase in the ultimate load capacity, toughness, and ductility of about 21%, 91%, 44 %, respectively, relative to the control beam. However, the beam strengthened by steel fiber reinforced concrete around the opening yielded an increase in the cracking and the load-carrying capacity of about 33.3%, 10.95%, respectively. Concerning the specimen strengthened by the crossed steel bar making a semi-rhombus shape around the opening yields a slight enhancement in the loading capacity of about 8.5%. Furthermore, strengthening the opening with steel plates increases the beam’s load-carrying capacity by about 11.23% compared to the control beam.