Transient temperature distribution in pre-tensioned anchors of cable-supported structures under ISO834 fire

Abstract

Anchors of steel cables consist of steel wires and filling materials, which provide wedge effect when the connected steel cable is in tension. The performance of steel cables and cable-supported structures significantly depends on the behavior of anchors, which becomes more serious when subjecting to fire. This paper investigates the transient temperature distribution in anchors exposed to ISO834 fire to provide references for predicting the mechanical behavior of anchors and steel cables at elevated temperatures. Firstly, experiments are conducted to determine the specific heat and thermal conductivity of filling materials such as zinc copper alloy for hot-cast anchors and mixture of epoxy resin and steel shot for cold-cast anchors. These measured thermal properties are then used for analytical calculation and numerical simulation. A formula to calculate the transient temperature distribution of fillers in hot-cast anchors is derived based on lump capacitance equilibrium and verified against numerical results. Numerical analyses of heat transfer in hot-cast and cold-cast anchors show that the heating rate of fillers is significantly lower than that of the socket wall. The temperature decreases along the longitudinal axis of anchors. The cross section of socket wall of hot-cast anchors has a non-uniform temperature distribution, while the filler part has a uniform temperature distribution. For cold-cast anchors, the socket wall has a uniform temperature distribution, while the filling materials have a significantly non-uniform temperature distribution. The geometry size of anchors has a minor effect on the heating rate of hot-cast anchors but significantly affects that of cold-cast anchors. The filling material of unprotected hot-cast and cold-cast anchors will reach its melting point less than 30 min when exposing to ISO834 fire.