ملخص البحث :

Openings in beams cause load path and stress discontinuities. Several research experiments have been conducted in recent years to improve the area surrounding the opening using various techniques. In this research investigate the effect of hybrid concrete (normal concrete and steel fiber reinforced concrete ) on the beams with transfer opening subject to combined loading (torsion and bending). Six specimens of reinforced concrete beams with the same dimension and reinforcement were tested. The variable where distance of hybrid area around opening (150, 225, 450 and 1500) mm. The opening in reference concrete beams was decrease in the ultimate twisting moment (18.28%) with respect to solid one (without opening). The ultimate twisting moment increases by (32-68%) as steel fiber reinforced concrete is used around the opening. Simultaneously, the twist angle was increased by about (27.6- 46.7%). In addition, relative to the control specimen, the first crack was delayed by bout (41.6-75) %.