Reinforced Concrete Beams with Drop-in- Ends of Vertical and Inclined Reinforcement and having Pockets Loaded by In-Plane Static Forces

Abstract

This research presents an experimental investigation on the behaviour of RC dapped end beams with loaded openings that have been strengthened initially with four different techniques including steel fibre concrete, inclined crossed bars, jacketing with steel plates and the composite section technique. Ten specimens with a rectangular opening at the midspan are tested under in-plane point load within opening. Such beams are categorized into two groups with five specimens per group. The dapped end zone of the first group is reinforced with standard vertical stirrups, while for the other groups inclined bar reinforcement has been used. Two main parameters have been considered which are the detailing of the reinforcement around the opening and the effect of inclusion of the dapped ends. The response has been discussed in terms the first cracking load, ultimate load, maximum deflection, failure modes, load-deflection curves, crack patterns, crack width, to recognize the optimum strengthening proposal of the opening. Results indicated that the modified reinforcement configurations of the dapped ends yielded better response and the ultimate load increased when adopting the composite section method in (21-23%) relative to the conventional beams.  Regarding strengthening by steel SFRC method, an improvement in load capacity by (8-10%) has been observed. Whereas, strengthening with crossed inclined bars yielded an enhancement of (8.5-11%). Furthermore, using steel plates increases the load capacity by about (11-13%)