Parametric study of factors influencing the thermal distribution and load-bearing capacity of bonded anchors directly exposed to fire

Abstract

Pull-out has been proved to occur more often for bonded anchors under tensile loads at high temperatures than at ambient temperature. The existing evaluation method of bonded anchors under fire only covers steel failure mode. Due to the absence of guidelines for evaluating the pull-out of bonded anchors directly exposed to fire, only the evaluation method for mechanical anchors (without resin) is applicable. This paper presents an experimental study on the influence of different parameters linked to the existing evaluation method by means of pull-out fire tests. Additional unloaded fire investigation tests were conducted to compare different configurations of pull-out fire tests. This paper highlights the level of accuracy of load prediction using the resistance integration method based on temperature profiles of bonded anchors directly exposed to a standard ISO 834 fire. Results showed that parameters such as the existence of metallic fixtures on the rod barely influence the predicted load-bearing capacity and failure time. However, parameters such as adopting concrete element temperature along the thickness instead of steel temperature along the embedment depth, and the existence of insulation around the fixture have a greater influence and may result in a false estimation of the load-bearing capacity and failure time.