Research on the Mechanical Properties and Reinforcement Approach for Cold Joints in Onshore Wind Turbine Spread Foundations

The spread foundation is the most commonly used cast-in-place foundation type for onshore wind turbines， requiring a large volume of concrete to be poured at one time. Due to factors such as limited site accessibility or adverse weather conditions， construction cold joints may occur during the foundation pouring process as a result of interruptions. Considering that the existence of construction cold joints may have an adverse effect on the safety performance of the wind turbine foundation， this paper takes a 5 MW wind turbine spread foundation as an example and analyzes the mechanical properties of the foundation with construction cold joints. Cold joints are considered at locations such as the base slabs， truncated cones， and columns. A refined finite element model of the wind turbine foundation with and without cold joints was established. The overall performance and interfacial stress conditions of the foundation with and without cold joints were analyzed under extreme conditions， and the fatigue life of the concrete and rebars in the foundation was verified under fatigue conditions. A reinforcement approach was applied for the cold joint interface. The results showed that， compared to the foundation without cold joints， the compressive stress in the concrete of the foundation with cold joints increased but remained within the safe range. Fatigue verification demonstrated that both the concrete and rebars in the foundation with cold joints could meet the 20-year service life requirement. For the base slab cold joints， the slip displacement at the interface exceeded the elastic limit； however， after implementing reinforcement measures， the interfacial slip displacement was maintained within the elastic stage， proving the effectiveness of the approach.