PRESTRESSED BEAMS WITH OPENINGS AND NO STIRRUPS UNDER TORSION AND BENDING

Test results of 17 axially prestressed concrete beams without stirrups and containing a transverse circular opening are presented. Mainly, b eams having two different opening diameters were subjected to various combinations of torsion and bending. Test results show that the bendin g moment has a beneficial effect and increases the torsional strength for beams with high T/M ratios. For beams with low T/M ratios; however , the torsional strength decreases rapidly with increasing the bending moment. Strength equations to predict the torsional strength at initi al cracking are developed. Based upon the initial cracking strength, e mpirical equations are suggested to predict the ultimate torsional str ength for all combinations of torsion and bending. The proposed equati ons predicted closely the torsional strength of the test beams. Compar ison of similar prestressed concrete beams with and without stirrups s hows that the introduction of stirrups promotes the development of a c onsistent failure pattern and increases the ductility and the torsiona l strength considerably.