Influence of Shear Span-to-Depth Ratio (a/d) on the Mechanics of Crack Formation and Failure of Reinforced Concrete Beams on Inclined Sections

One of the key points when calculating the strength of inclined sections (displacement calculation) is the issue of the design model. To create it, it is necessary to know not only the failure pattern, but also the order of crack formation and propagation during loading of structures. After the formation of cracks, a reinforced concrete beam has a complex structure that does not correspond to such systems as the arch or truss. The pattern of formation and propagation of diagonal cracks differs significantly from that of vertical cracks, which are the reason for the stretching stress or moment. Diagonal cracks are more dangerous, as they can be formed suddenly and the time interval between the crack formation and failure is considerably shorter than for pure bending. In this case, the strength of the vertical section is not achieved. This paper discusses the features of crack formation and failure of reinforced concrete beams on inclined sections with the shear span to effective depth ratio a/d = 0.5 and a/d = 1. The dynamics of propagation and width of opening of destructive diagonal cracks depending on the load is shown. The analysis of the studies revealed the specifics of formation and propagation of diagonal cracks in the zone of impact of the shear force and moment. The various loading patterns used for experimental samples revealed the specific pattern of the influence of positive and positive/negative moment diagrams on the crack formation and propagation.