Analytical and Experimental Investigation of Thermal Expansion Mechanism of Steel Cables

Different countries adopt different values of thermal expansion coefficients for steel cables in their design specifications, which results in the inconsistency for the design of prestressed structures. Therefore, a systematic study was conducted analytically and experimentally on thermal expansion mechanism of steel cables in this paper. First, the thermal expansion mechanism of steel cables was proposed, and the evaluation approach on the linear thermal expansion coefficient of steel cables was developed. The study identified the parameters that significantly affected the thermal expansion coefficient. After that, six types of steel-wire rope cables were tested by a thermal expansion coefficient measuring instrument. The identified parameters of the thermal expansion coefficient for these steel-wire rope cables were examined to show the effectiveness of the proposed approach. The analytical analysis further showed that the linear thermal expansion coefficients of these steel cables decreased with the lay pitch of the steel wires increasing, but the coefficients increased with the diameter of the steel wires increasing. Because the explicit expression of the analytical formula for the thermal expansion coefficients was very complicated, an advanced nonlinear finite-element model (FEM) was established to evaluate the thermal expansion coefficients of steel cables under idealized conditions by using the ANSYS software package. The analysis showed that the test result, the analytical result, and the numerical result were consistent, which exhibited that the FEM was effective to simulate the expansion of steel cables. In addition, 14 types of steel cables were tested. The tested steel cables included steel-wire rope cable, steel strand cable, and steel tendon cable. The thermal expansion coefficients were as follows: the steel-wire rope cable was $1.92\times {10}^{-5}/°\mathrm{C}$; the steel strand cable was $1.38\times {10}^{-5}/°\mathrm{C}$; the steel tendon cable was $1.87\times {10}^{-5}/°\mathrm{C}$; and the steel rod was $1.19\times {10}^{-5}/°\mathrm{C}$. The analytical and experimental results can provide a guideline for the relevant study on prestressed structures.