Abstract:
The New Zealand Building Act of 2004 established a framework for assessing and managing earthquake-prone buildings in New Zealand, with the significance of this process being highlighted after the Canterbury earthquakes. The result of the assessment process is presented as a percentage of the New Building Standard (NBS), measuring how resilient the building is to seismic actions. The minimum requirement for existing buildings is 34%NBS, although 67% is often required by insurance companies. Fibre Reinforced Polymer (FRP) composites have been used extensively as Externally Bonded Reinforcements (EBR-FRP) since the Building Act was enacted, mainly due to the versatility of application, as well as the high strength and light weight nature of the material (which does not increase the seismic weight of the structure). In EBR-FRP systems, the fibres (typically carbon fibres, although glass fibres have also been used) are bonded to the external surface of the concrete structure with epoxy resin. One of the main shortcomings of EBR-FRP systems is premature FRP-to-concrete debonding as a result of the low tensile strength of concrete. One way to overcome the adverse effects of premature debonding and to ensure the continuity of the load path is to use FRP anchors, which are bundles of fibres saturated in epoxy and introduced into the concrete structure. Several design guidelines have been produced since FRP products were introduced in civil engineering applications, with a widely used design document being published by the American Concrete Institute, namely ACI440.2R-17 “Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures”. Other documents used include the Italian guideline CNR-DT200 and the fib Bulletin 14. While a design approach has been recently published by the authors, neither of these widely accepted codes include guidance on how to design FRP anchors. New Zealand engineers have typically relied on published research or have resorted to engineering judgement, often validates with proof-testing. A concise but comprehensive summary of the use of FRP anchors in the last decade has been summarised in this paper with a focus on innovative designs that required out-of-the-box thinking in order to develop creative solutions to difficult and complex problems. The works summarised herein have been obtained from a number of engineering firms, suppliers and installers. No specific engineer, products or companies are named in order to retain the neutrality and unbiased position of the authors.