Study on the influence of reinforcement on the temperature field and stress field of concrete for offshore wind power platform

Abstract

The offshore wind turbine foundation is composed of massive reinforced concrete. Apart from its crack-limiting effect, steel reinforcement can also enhance the load-bearing capacity of the concrete structure and influence the development and distribution of the temperature field. The role of steel reinforcement cannot be neglected in the simulation analysis of the temperature and stress fields of the foundation. While the precise algorithm for simulating every steel reinforcement bar is computationally intensive, the average equivalent algorithm based on reinforcement ratio neglects the interaction between steel reinforcement and concrete. Therefore, an equivalent calculation method for thermal and mechanical parameters of massive reinforced concrete is proposed, aiming to reflect the macroscopic role of steel reinforcement while considering its local effects. Then the accuracy of these method in predicting the temperature and stress field changes of reinforced concrete were verified by using simplified models. Taking the Leting offshore wind turbine foundation as a case study, this paper compares the Equivalent Reinforced Concrete(ERC) model with the Plain Pile-cap Concrete(PPC) model to analyze the effect of reinforcement on temperature and stress changes in foundation concrete. Simulation result reveal that reinforcement can lower the maximum temperature of the foundation concrete, with a reduction of about 1.2℃ at the center of the foundation and more than 8℃ in areas with dense reinforcement, while also decreasing the internal-external temperature difference. The surface concrete of the foundation experiences tensile stress during the early stages of heating, and the internal concrete of the foundation develops tensile stress during the later stages of cooling. Under the influence of reinforcement, the former was reduced by 0.34 MPa, a reduction rate of 22.37%, and the latter was reduced by 0.87 MPa, a reduction rate of 24.79%. Acting as a low thermal resistance pathway, the reinforcement′s high thermal conductivity effectively lowers the maximum temperature and the internal-external temperature difference in the foundation concrete, reducing the stress induced by temperature. Additionally, the difference in the coefficient of thermal expansion between steel and concrete result in compressive stress in the surrounding concrete during the later stages of cooling, further decreasing the maximum tensile stress in the internal concrete areas of the foundation, thereby reducing the risk of cracking in the foundation concrete.

Keywords

offshore wind turbine foundations / mass concrete / reinforcement simulation / heat conduction / temperature stress / concrete / deformation / mechanical property