Analysis of cracking evolution mode of the monobloc sleeper

PurposeMonobloc sleepers have several problems related to bending cracking, especially longitudinal cracking and cracking at rail seat under preload release. Therefore, the purpose of this study is to describe the behavior and cracking mode of prestressed concrete railroad sleepers under static loads using the positive test. Experimental tests followed by 3-D numerical models were performed of the same test.Design/methodology/approachTwo steel supports were placed on the rail seat. During a progressive loading, the initiated cracks had approximately the same amplitude as those obtained from the numerical model. The type of cracking depends on the intensity of the applied static load and the loading rate. A validated three-dimensional digital model was established. The obtained results showed a perfect resemblance to the experimental tests. The final design was optimized and verified using a validated numerical simulation.FindingsAt low static loading levels, the first flexural shear cracks appeared at a vertical position located between the two steel supports. At higher static loading levels, bending shear cracks have occurred. The latter are inclined at the steel supports. It was proven that for higher loading levels, shear cracks were the primary mode of failure.Research limitations/implicationsOwing to the sensitivity of monobloc sleepers to technology production, the results are limited by the maximal loading and press used.Practical implicationsNumerical modeling greatly reduces uncertainties in laboratory testing and is an important tool for visualizing and quantifying rail seat cracks to understand behavior and predict collapse.Social implicationsEnsuring human life during rail operations is one of our the long-term priorities. This cannot be done unless the authors manage to master the manufacturing tool for sleepers while controlling the limitation of crack propagation.Originality/valueThe three-dimensional numerical established model has been checked and validated against the experimental results using the positive test to understand the behavior and the cracking mode of prestressed concrete railroad sleepers under static loads. The proposed numerical model has been more refined for a later more complex application by reducing the computation time.