Numerical investigation of reinforced-concrete beams with half-joints

The shape and dimensions of reinforced-concrete beams with half-joint or ‘dapped’ ends often represent a problem in structural design. If suitable geometry is not provided properly to the re-entrant corner, a diagonal tension crack may grow rapidly and failure will occur with little or no warning. In the study reported in this paper, two-dimensional finite-element analysis was adopted to investigate the effects of variation of some main parameters such as shear-span-to-depth ratio, the length ratio and the depth ratio. The analysis covered 29 specimens with half-joint ends, which had conventionally detailed reinforcement with an adequate development length of the longitudinal tension reinforcement beyond the re-entrant section. The structural behaviour of the specimens was compared and validated with previous experimental results from the literature. In addition, failure loads were compared with calculated values predicted by common codes and various equations. The results showed that shear capacity increases by reducing the nominal shear-span-to-depth ratio, reducing the length ratio or increasing the depth ratio. Moreover, the finite-element model was generally found to be in good agreement with previous test data.