Model for rapid evaluation of corner crack widths in reinforced concrete dapped-end conections

Dapped-end connections are widely used in concrete infrastructure, and in particular in Gerber-type bridges and precast concrete buildings. The main vulnerability of such connections is the early opening of inclined cracks at the re-entrant corner of the dapped end. Such cracks are difficult to control as they propagate at low loads and open significantly before the occurrence of secondary cracks. The goal of this paper is to propose a rational model for rapid evaluation of the width of the corner cracks, including the effects of secondary cracking and, indirectly, the effect of restrained shrinkage at low loads. The model assumptions stem from detailed test observations of specimens with light and heavy reinforcement, arranged in orthogonal or diagonal layouts. The model is developed in two steps: 1) predicting the crack width at yielding of the connection, and 2) capturing the shape of the response from zero load up to yielding. A database of 42 tests with a broad range of variables is used to validate the model. It is shown that the main properties influencing the width of the corner crack are the amount and detailing of the reinforcement, and their effect is well captured by the model. It is also illustrated how the model can be used to design the reinforcement of dapped ends to meet crack width limits at service conditions.