Shear Tests of Reinforced Concrete Beams with the Influence of Initial Shear Cracks

Cracks in reinforced concrete (RC) structures can result in a reduced load-bearing capacity if they grow beyond the limits, thus understanding the effects of cracks and including them in the structural health monitoring method is necessary. The influence of the cracks cannot only be quantified by the crack patterns or width, because of the complexity of the stress state and other factors. In particular, the impact of shear cracks on the structural performance of RC beams is yet to be studied in detail. This study focuses on the initial shear cracks and aims to investigate the correlations between the locations of shear cracks and the load-bearing capacity of beams. Beams with the same geometry design were divided into four groups. Each group of beams exhibited one type of initial shear cracks, including (i) reference beams with no cracks, (ii) beams with shear cracks in the bending span, (iii) beams with shear cracks in the shear span, and (iv) beams with pre-defined notches in the shear span. The initial cracks were carefully recorded. Then, all the beams were subjected to a four-point bending test. The load-bearing capacities of beams with initial shear cracks and notches were compared with that of reference beams. The results indicated that the initial cracks in the bending span had limited influence on the load-bearing capacity, while the cracks in the shear span significantly reduced the ultimate load of the beams. Also, the cracks in the shear span were likely to further propagate to become the dominant cracks, but the cracks in the bending zone may stay unchanged.