No 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.

The results of research initiated in the early 1980s led to the replacement of plasticity-based design guidelines for the load-carrying capacity of headed anchors embedded in concrete with those developed using fracture mechanics. While provisions are available in the design codes that account for the presence of tensile fields causing concrete cracking, no provisions are available for anchors embedded in prestressed concrete. This paper presents the results of linear elastic fracture mechanics ͑LEFM͒ analyses and of a preliminary experimental investigation of the progressive failure of headed anchors embedded in a concrete matrix under compressive or tensile prestress. The model predicts an increase ͑decrease͒ in load-carrying capacity and ductility with increasing compressive ͑tensile͒ prestress. It is shown that despite neglecting the dependence on size of concrete fracture toughness, LEFM predicts with remarkable accuracy the functional dependence of the ultimate capacity on prestress.

A combined experimental and computational study shows that the pullout capacity of anchors embedded at small depths in prestressed concrete is associated with the strongest possible (linear elastic fracture mechanics) size effect. A design formula is proposed that reflects the effects of embedment depth and the nondimensional parameters that quantify the level of prestressing and the characteristic length of the matrix