Numerical investigation of parameters influencing fire evaluation tests of chemically bonded anchors in uncracked concrete

Abstract

European guidelines for fire performance evaluation of post-installed anchoring systems are limited to mechanical (e.g., expansive, undercut) mechanisms of load transfer and the steel failure mode, whereas the adhesive bond mechanism remains unaccounted for in chemically bonded anchors. Furthermore, current evaluation methods do not account for the influence of practical testing conditions on temperature profiles along the bonded depth. This paper presents 3D finite element thermal simulations of chemically bonded anchors in uncracked concrete exposed to ISO 834 fire conditions with comparisons to experimental specimens. Five parameters representing application and testing conditions are investigated to assess their influence on temperature profiles along the embedment depth of bonded anchors. A numerical model is proposed based on the results of the numerical simulations to determine thermal data necessary for predicting the load-bearing capacities of bonded anchors using the Resistance Integration Method. The model adopts Eurocode material properties for concrete and steel, with 3D analysis yielding conservative capacity prediction compared to physical fire tests. 3D and 2D simulation results are compared, demonstrating that modelling using 2D heat transfer analysis yields inaccurate temperature profiles compared to 3D modelling. After experimental validation of the proposed model, additional parameters are explored in a numerical parametric study: embedded depth, external length of the anchor element, insulation of the anchor element, and insulation of the concrete element. Results show that the embedded depth has a significant influence on temperature profiles along the bond. Moreover, the external length of the anchor influences temperature profiles, but not beyond 20 mm from the concrete surface.

Evaluation of PIRs Post-Fire Pull-Out Strength in Concrete Exposed to ISO 834-1 Fire

“…Standard metallic fixtures for such fire tests were used [ 16 ]. The influence of the loading systems on temperature profiles and resulting pull-out capacity of bonded anchors in the heating phase were investigated by [ 10 , 11 ] and found negligible. The steel of the loading system was insulated using a ceramic wool-based material to protect the steel from reaching failure and to induce a pull-out (bond) failure.…”

“…The 3D model considers the PIR as a perfect cylinder inside the concrete beam with an embedment depth of 160 mm of the steel inside the concrete, and 40 mm of extended length ( Figure 4 ). Al Mansouri et al [ 11 ] conducted a parametric study to investigate the influence of the extended length of the steel above the concrete surface and concluded that this external length influences temperature profiles between no extended length and 20 mm of extended length. Beyond 20 mm from the concrete surface, the influence is insignificant for a medium size anchor (M12).…”

“…The mass density of the carbon steel is considered constant equal to 7850 kg/m 3 with respect to temperature. The thermal properties of the insulating material considered in the 3D numerical analysis were the same that were defined by Al Mansouri et al [ 11 ]. The insulating material consisted of glass fiber with a thickness of 50 mm whose properties (conductivity, specific heat and mass density) are respectively presented in subfigures (1), (2), (3) of Figure 7 .…”

“…Previous pull-out tests at high temperature have shown that bond capacity decreases rapidly with temperature [ 6 , 9 ]. Al-Mansouri et al [ 10 , 11 ] have studied the influence of fire exposure conditions on the pull-out resistance of bonded anchors in concrete. Pinoteau et al [ 12 ] proposed a “bond Resistance Integration Method” using thermal calculations and bond resistance variation at different temperatures.…”

Fire Rating of Post-Installed Anchors and Rebars

“…The results were used as a basis for numerical simulations, using a shear lag model considering bond stress and displacement compatibility along the anchor [46]. Al-Mansouri et al used numerical simulations [47] and experimental tests [48] to investigate test parameters influencing the evaluated fire resistance.…”