Fib report on design of concrete members strengthened with externally applied reinforcement

The last decades, the introduction of fibre reinforced polymer (FRP) reinforcement has been proven instrumental for the strengthening and seismic retrofitting of a large number of ageing concrete structures. FRP reinforcement in the form of strips, sheets, fabrics and bars are used as externally applied reinforcement, by means of dedicated application techniques such as surface bonded reinforcement (often designated as externally bonded reinforcement), near surface mounted reinforcement (applied in grooves in the concrete substrate), textile reinforced mortar (jacketing with reinforced mortar layer), etc. Work by the International Federation of Structural Concrete (fib) resulted in a design guidance document (fib Bulletin 14) issued in 2001 for externally bonded reinforcement, and continued by the introduction of FRP reinforcement in Eurocode 8 (CEN 2005) and in the fib Model Code 2010 (fib 2013). Currently, also a CEN work group is active to introduce FRP reinforcement and strengthening of concrete structures with FRP in the next version of Eurocode 2 (CEN 2004). More recently, fib Task Group 5.1 issued an updated version of the fib design guideline (fib 2017), in succession of Bulletin 14 (fib 2001). In this new bulletin the scope is broadened to the before mentioned types of externally applied reinforcement. It covers the various FRP material and strengthening systems which have become apparent, the basic design approaches, the bond interaction, structural behaviour, practical execution, etc. Mainly those aspects are taken into account which form the majority of the design problems for persistent load situations. Moreover, seismic retrofitting is comprehended in a detailed manner. The new bulletin reflects the evolution in the design of concrete members strengthened with FRP, whereby this concrete strengthening technology has evolved from an emerging one, with first practical applications dating from the 1990’s, to a widely accepted technology, with nowadays thousands of applications worldwide.