EOTA Approach to Qualification and Design of Post-Installed Adhesive Anchors for Fire Exposure

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Title: EOTA Approach to Qualification and Design of Post-Installed Adhesive Anchors for Fire Exposure

Author(s): Werner Fuchs and John Silva

Publication: Special Publication

Volume: 283

Issue:

Appears on pages(s): 1-8

Keywords: EOTA TR 020, post-installed anchors, resistance to fire, design

Date: 3/1/2012

Abstract:
The best fire protection strategies for structural components are useless if connections lack the necessary fire resistance. Many current European Technical Approvals for anchors in concrete provide details on duration of fire resistance based on EOTA Technical Report 020 – Evaluation of Anchors in Concrete Concerning Resistance to Fire – published in 2004. This report delineates testing, evaluation and design requirements for anchors subject to fire exposure. It addresses post-installed mechanical anchors, adhesive anchors and plastic anchors and includes a simplified design approach that considers all relevant concrete failure modes as well as pull-out failure and the steel resistance. The failure modes relevant for normal service conditions also apply under fire exposure. Nevertheless, as temperatures increase the yield point of steel drops significantly. Stainless steels exhibit superior resistance to elevated temperature over carbon steels; however, in general, the reduction in the steel strength is greater than that associated with concrete breakout or pull-out failure. Thus, in most cases, steel failure is the governing parameter in the design, although concrete failure may control in case of shallow embedment, anchor groups or close to the edge. The simplified design method to determine the steel capacity under fire exposure provided by the EOTA Technical Report 020 and by the pre-standard CEN/TS 1992-4 ‘Design of fastenings for use in concrete’ yields often very conservative results. Therefore the leading brands in fastening technology perform fire tests according to the regime given in TR 020, which result in design values which are sometimes as much as three times as high as the values according to the simplified prediction.