Calculation of thermal state stress of the wind turbine’s foundation slab for the improvement of the quality and crack resistance

Abstract

The thermal stress state of massive concrete and reinforced concrete structures during the construction period is characterized by the risk of large tensile stresses and, as a result, temperature cracks that violate the integrity of the structure. These defects are unacceptable for crack-resistant structures. The process of concrete hardening is accompanied by the release of a large amount of heat as a result of the hydration reaction of cement. The most dangerous cases are with uneven temperature distribution within the block body. Significant gradients can lead to stresses that exceed the stresses from operational loads. The thermal stress state is also influenced by temperature fluctuations of the surrounding environment, solar radiation, cooling rate of the block, initial and boundary conditions, and the possible cutting of a massive structure into separate concrete blocks. The latter factor is the subject of the research reflected in this study. The article establishes that, despite the possible increase in the construction time cutting the foundation plates into separate blocks by height can make the thermal stress state of the plate significantly more favorable in terms of ensuring crack resistance. In some cases, cutting can be such a successful method of combating temperature cracks that it will allow for the abandonment of special thermal insulation on the surface of the structure. The study shows the effectiveness of the cutting method depending on the number of blocks for the improvement of foundation slab quality.