Abstract:

In order to study the mechanical behavior of 2-layer spiral strand under tension-bending coupling effect and the cooperative working mechanism of internal wires. Taking friction and slippage between wires into account, static equilibrium relationships of layer-wire segment on 2 typical conditions of inter-layer contact and coupled contact are established and derived analytically. An improved semi-refined finite element model is presented for numerical simulation and compare the results. Relative slip direction between wires on 2 contact conditions are obtained from the distribution of shear force on layer-wire, based on which the axial force limit of layer-wire after sliding is derived according to the equilibrium equation. The bending moment-local curvature relation of spiral strand is obtained by summing the bending moments contributed by each wire under tension-bending coupling effect, and a simplified bending moment-mean curvature relation is proposed to describe bending behavior of the spiral strand. The result shows that there are slip stagnation points on contact surface of adjacent wires because layer-wire rotates along the axis of spiral strand periodically, and relative slip direction on both sides of the stagnation point is opposite. The slip stagnation point and initial slip position on contact surface of layer-wire to layer-wire and layer-wire to core-wire are different. Ignoring internal slip spreading process, we have the same bending moment-mean curvature relation on 2 contact conditions of 2-layer spiral strand, the function image is a double broken line. The error of the bending deformation results before and after slipping between semi-refined FE model and analytical values is less than 4%, and the extracted relative slip results are in agreement with the analysis conclusions.

Key words: spiral strand, tension-bending coupling effect, slippage between wires, bending characteristics, contact conditions, semi-refined finite element model