An analytical study of bond strength associated with splitting of concrete cover

Bonding between reinforcement and concrete may be idealized as a shear force along the surface of the reinforcement. Most predictions on bond strength have been empirical and based on statistics methodology. Thus, these equations are highly dependent on the test data used, which may limit their validity in different situations. Through analytical study on splitting bond mechanisms, which is the most common bond failure mode in real structures, an analytical model is proposed. The prediction values agree well and consistently with a large body of test data. More importantly, the analytical model provides insight into the interfacial bond mechanisms: factors that have been experimentally verified to have influences on bond strength are reflected and applied through theoretical analysis into the model. For practical design purposes, a simplified equation for development/splice length was proposed and compared with the current ACI 318 code. The proposed design equation shows much better overall results when evaluated by the test data available. Comparing with ACI 318, on average, it requires 10% longer development/splice length with significantly improved safety margin and data distribution.