Crack Resistance of RC Beams on the Shear

Most important parameter of serviceability limit state (SLS) for reinforced concrete (RC) beams is crack resistance. These include width of crack opening, cracking distribution, load at which is achieved limit and maximum width of crack opening. This is especially important for shear resistance. In this article, new data of crack resistance of rectangular RC beams are described. Changing parameters were shear span (acquiring values 1, 1.5, 2) and strengthening with FRCM (Fiber Reinforced Concrete Matrix) system in the supporting area. Eight samples for experimental researches were carried out: six once from them without strengthening but with different shear span and two once with composite system. Using the limit width of the crack opening as criteria of exhaustion of the bearing capacity can conclude that remains about 19-26% of load caring capacity before the danger of shear failure of the beam. When the shear span decreases on the 25% the maximum width of the crack opening decreases only on the 7% and on the 40$ when shear span decreased by 50%. External strengthening system reduced maximum crack opening on the 43%: from 0.75 to 0.43 mm and values exceed limit insignificant.