Shear performance of circular and rectangular concrete-filled double-skin steel tubes (CFDSTs)

Abstract

With the advancement of megawatt (MW)-level wind turbine towers, traditional steel pipe structures no longer meet the requirements for large-scale wind turbine towers. Concrete-filled double-skin steel tubes (CFDSTs) is a potential structural form with expanded sections, high bending stiffness, light weight, and good seismic performance. However, it is prone to experience shear, flexural, shear-flexural, and torsion complex loading conditions caused by accidental loads. Currently, experimental studies on the shear performance of CFDSTs are still few. The influence mechanisms of the hollow ratio (χ) and the shear-span ratio (m) are unclear, with immature calculation methods. Therefore, this paper investigates the shear performance of circular and rectangular CFDSTs. A total of 15 circular and 8 rectangular CFDSTs are tested. The experiments primarily examine the influences of χ and m on failure modes, load-displacement relationships, and strain. Experimental results demonstrate a transition from shear-dominated to flexure-dominated failure modes as m increases, with local buckling exacerbated by higher χ due to reduced concrete cross-sectional area. Shear capacity decreases with rising χ and m, though flexural stiffness partially mitigates this reduction at larger m. Simultaneously, corresponding finite element (FE) models are established to thoroughly analyze the shear capacity mechanism of CFDSTs by exploring the logarithmic strain distribution, load distribution of each component, and contact stress. Finally, the shear capacity calculation methods are provided for circular and rectangular CFDSTs, which considers χ, m, and the constraint effect factor (ξ).