Eccentric compressive behaviour of horizontal circumferential joints in concrete wind turbine towers considering joint opening

Abstract

Horizontal circumferential joints are critical load-transfer regions in the concrete segments of steel–concrete hybrid wind turbine towers. However, existing studies and design methods generally treat the annular concrete section as a continuous member and do not explicitly consider the transition from full-section compression to partial joint opening under eccentric compression. To address this gap, this study investigates the eccentric compressive behaviour of horizontal circumferential joints in the concrete segment of steel–concrete hybrid wind turbine towers. A total of six concrete tower specimens were tested under eccentric compression with eccentricities of 0.67 e 0 and e 0 . The failure modes, load–displacement curves, stiffness degradation, and strain distribution at the horizontal joint were obtained. The test results show that all specimens failed by concrete crushing near the horizontal joint. Reinforcement improved the load carrying capacity and delayed crack development. However, once the eccentricity exceeded a critical value, joint opening occurred, leading to a marked reduction in capacity and stiffness. Finite element models were then developed and validated against the test results. Parametric analyses were conducted to examine the effects of material properties, cross sectional dimensions, and eccentricity. The results show that concrete strength, section dimensions, and eccentricity are the dominant factors affecting the eccentric compressive capacity. Evaluation of current design codes shows that they do not explicitly consider the interaction between joint opening and bending moment. A new design method is proposed by introducing a critical eccentricity to distinguish full section compression from partial joint opening. The proposed method gives an average predicted to measured ratio of 1.01 and a coefficient of variation of 0.021 against the experimental and numerical results.