Use of 8mm Deformed Bars Stirrups in RC Beams


In reinforced concrete (RC) beams, steel stirrups are provided, primarily to resist the imposed shear and also to hold the tension/compression reinforcing bars in place.  Use of stirrups is necessary to prevent shear failure in RC beams which is normally exhibited by diagonal cracking in the RC beams. Diagonal cracks are the primary mode of shear failure in RC Beams near beam supports in the high-shear zone.

As per ACI Code 318-14, the minimum diameter of stirrups reinforcement to be used in RC beams is #3 (10 mm) diameter stirrups.  For lightly reinforced concrete (RC) beams, the main tension reinforcement may consist of #4 (13 mm dia.) bars with #3 (10 mm dia.) bars as compression reinforcement. Thus, the use of #3 (10 mm dia.) bars seems to be on the heavier side and much more than needed to prevent shear failure in lightly loads RC beams.  The Indian Code IS 456-2000 allows the use of 8 mm diameter stirrups as shear reinforcement. Therefore it seems plausible that for lightly reinforced RC beams like in residential construction in Pakistan, the use 8 mm diameter stirrups (if found to provide adequate shear resistance) may be economical as it saves the amount of shear reinforcement to be used.

The objectives of this work are:

  1. To ascertain the effectiveness of using #2.5 (8 mm dia.) bars as stirrups in the lightly loaded Reinforced Concrete (RC) beams, instead of #3 (10 mm dia.) bars
  2. Prediction of shear strength of shear critical RC beams by use of Equations in different building codes.
  3. Development of an analytical model (Response 2000 program) for predicting the shear strength of shear critical RC beams and comparing the results with available experimental results.
  4. Conducting a parametric study to ascertain the effects of various influencing parameters on the shear strength of RC Beams.