Time Depending Thermo Mechanical Bond Behavior of Epoxy Bonded Pre-Stressed FRP-Reinforcement

ABSTRACT

The development of different pre-stressed epoxy bonded CFRPreinforcement systems for retrofitting RC-structures continues. In addition to requirements concerning the ultimate limit state (ULS) pre-stressed systems could satisfy demands in regard to the serviceability state (SLS) like crack limitation or fatigue. In comparison with the well known material behavior of concrete under sustained loading epoxy resins show material properties more sensitive to thermal effects, for example loss of strength or creep deformations. In experimental tests the influence of permanent load and temperature is examined. The pure epoxy resin adhesive was evaluated in lab-shear tests and the structural behavior of the system in the form of epoxy bonded pre-stressed near surface mounted CFRP-strips. The experiments reveal a significant influence of the epoxy resin adhesive behavior on the long-term structural behavior in service. To evaluate the effects with regard to designs relevant problems as long-term development of transfer lengths of pre-stressed reinforcement or of the slip between reinforcement and concrete under varying load and thermal conditions results of a simulation model are presented.

Keywords 

CFRP reinforcement; creep; epoxy resin; long-term behavior; pre-stressing; SLS; strengthening; sustained load; temperature