钢筋对海上风电承台混凝土的温度场及应力场的影响研究

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

摘要

海上风电承台为大体积钢筋混凝土，钢筋除具有限裂作用外，还可提升混凝土结构的受力性能、影响温度场的发展及分布，在对承台进行温度场、应力场仿真分析时钢筋的作用不容忽视。模拟每根钢筋的精细算法计算量过大，而按配筋率进行平均等效的算法又忽略了钢筋和混凝土之间的相互作用。提出一种针对大体积钢筋混凝土的热学与力学参数等效计算方法，旨在反映钢筋宏观作用的同时，体现钢筋的局部作用。利用小尺寸有限元模型验证了该方法在预测钢筋混凝土的温度场与应力场变化上的有效性。利用提出的算法，以乐亭海上风电承台为例，通过比较等效钢筋混凝土(ERC)模型与不考虑钢筋的混凝土(PPC)模型，详细分析了钢筋对承台混凝土温度和应力演变的作用。仿真结果揭示，钢筋能降低承台混凝土的最高温度，承台内部中心处降低约1.2℃,在钢筋密集区域处的最高温度降低超过8℃,其内外温差也明显降低。承台表面混凝土在升温前期产生拉应力，内部混凝土在降温后期产生拉应力。在钢筋作用下，表面拉应力降低了0.34 MPa,降低率达到22.37%,内部拉应力降低了0.87 MPa,降低率达到24.79%。钢筋作为低热阻通道具有较强的导热能力，有效降低了承台内部混凝土的最高温度及承台内外温差，减少了承台混凝土的温度应力。其次，钢筋和混凝土的线膨胀系数差异，使周围混凝土在降温后期产生压应力，进一步降低了承台内部混凝土区域的最大拉应力，降低了承台混凝土的开裂风险。

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.

关键词

海上风电承台 / 大体积混凝土 / 钢筋仿真 / 导热作用 / 温度应力 / 混凝土 / 变形 / 力学性能

Key words

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

基金资助

国家重点研发计划项目(2021YFC3090102)

中国三峡新能源(集团)股份有限公司科研项目(FQHX/0052-2020)