Influence of Temperature on the Longitudinal Cracking in Multipurpose Precast Concrete Sleepers Prior to Their Installation.

Prestressed monoblock railway sleepers are concrete elements with almost no reinforcement apart from the prestressing wires, which makes them very sensitive to any stress variation that can induce tensile stresses. In recent years, severe longitudinal cracking has been observed in a number of sleepers in hot regions of Spain, even before these elements were put in service. This work studies the problem while considering the thermal variation as the main factor affecting this cracking phenomenon. A non-linear static load-step analysis is applied on a non-linear finite element model to reproduce the problem and, after its experimental validation, the influence of three design parameters of the sleepers are studied: the nature of concrete aggregates, the dowel thickness, and the dowel material. The results show that all these three parameters may have significant influence on the problem, with the dowel material being the most important parameter. When the dowels are made of a material with a high elastic modulus and a high thermal expansion coefficient, the crack opening induced by a realistic thermal variation can reach significant values and result in longitudinal crack propagation. The changes of humidity are not considered in this study because they are beyond the scope of this work.