EXPERIMENTAL INVESTIGATION OF CONFINING THE COMPRESSION ZONE IN OVER-REINFORCED BEAMS

Over-reinforced concrete sections are restricted in most design codes to avoid the brittle compression failure of concrete, which occurs suddenly without warnings. In recent years, there have been significant improvements in construction industry that needs to use over-reinforced sections in huge projects such as, high-rise building and bridges. In over-reinforced concrete sections, a high percentage of reinforcement steel is added into concrete section to reduce the beam size and to provide adequate stiffness. Limited trials have been carried out to strengthen the over-reinforced section by using proper confinement in the compression zone, which restrains the lateral expansion and failure of concrete at the compression zone. This study investigates experimentally the effect of installing different configurations of confinement in the compression zone of over-reinforced concrete beams. These configurations contain distributed steel bars at the compression zone confined by square ties, circular ties, square spirals, or circular spirals. Six full-scale beams, 3000 mm long and 150×250 mm2 cross section, were tested under a four-point bending load. The results indicate significant enhancement in the flexural strength, ductility, and failure propagation of the beams especially when using the spiral confinement.