Behavior and analysis of inverted T-shaped RC beams under shear and torsion

• Pilot testing of RC inverted T-beams under torsion and shear was conducted.
• The shear–torsion interaction has a significant effect on the behavior of the T-beams.
• The proposed analytical model showed good agreement with the experimentally observed behavior.

The 1998 ASCE-ACI Committee 445 on shear and torsion identified researching combined shear and torsion as well as giving physical significance for torsion design as an upcoming challenge (ASCE-ACI Committee 445 on shear and torsion, 1998). Most of the previous experimental studies were focused on reinforced (RC) beams under flexure, shear or torsion. The behavior of inverted T-shaped beams with both web and flange closed stirrups are not fully explored. In this research paper, an innovative test setup capable of simulating the behavior of inverted T-shaped beams under combined shear and torsion was developed and implemented. The behavior of three inverted T-shaped beams tested under different values for the ratios of the applied torque to the applied shear force is discussed. The value of the torque to shear ratio significantly affects the behavior of the inverted T-shaped beams in terms of cracking pattern; failure mode; strut angle of inclination; cracking and ultimate torque; post-cracking torsional rigidity; cracking and ultimate shear; flange and web stirrup strain. The flange stirrup is more efficient in resisting torsion moment over shear forces. A model capable of predicting the behavior of flanged beams under combined actions was developed and implemented. The model showed good agreement with the experimental results from three different experimental studies.