【正文】 附錄一論文原文ACI STRUCTURAL JOURNAL TECHNICAL PAPERTitle no. 107S61Creep Effects in Plain and FiberReinforced PolymerStrengthened Reinforced Concrete Beamsby M. M. Reda Taha, M. J. Masia, . Choi, P. L. Shrive, and N. G. ShriveThe longterm deflection behavior of two reinforced concrete (RC) beams with similar dimensions and material properties was monitored. One beam was externally strengthened with fiberreinforced polymer (FRP) strips, whereas the other was used as a control specimen. Both beams have been subjected to sustained loading for over 61/2 years. The objective of the experiments was to assess the significance of creep in the epoxy adhesive and whether such creep might allow the FRP strips to unload over time. Slip movements at the ends of the FRP strips were also monitored.The experimental deflections have been pared to deflection predictions using ACI 209R92 and CEBFIP MC 90. The creep deformations of the FRPstrengthened beam are not as predicted from the control beam. Two analytical approaches are used: a stepbystep intime analysis and finite element (FE) modeling. Both techniques demonstrate that creep of the adhesive layer can account for the differences observed between the predicted and actual behaviors of the beams.Keywords: creep。 deflection。 epoxy adhesive。 fiberreinforced polymer(FRP)。 reinforced concrete.INTRODUCTIONIn recent years there has been much research on the use of fiberreinforced polymers (FRPs) to strengthen existing concrete structures. One popular application, used widely in practice, is to bond FRP strips externally to the tension face of reinforced concrete (RC) beams to increase flexural capacity.The FRP strips are typically bonded directly to the prepared concrete surface using an epoxy adhesive. The strips may be anchored mechanically near their ends or supported by additional shear reinforcement, usually in the form of Ushaped FRP sheets. If the beam is subsequently loaded with sustained loads, creep in the epoxy adhesive could take place and would allow the FRP strips to unload, leaving them ineffective against the sustained load. Similarly, if the strips are prestressed as recently remended by some researchers (for example, Ye et ), creep in the epoxy may relieve some of the initial force. Hence, although the FRP strips can still assist in supporting additional live load, the increased sustained loads may exceed the capacity of what could effectively bee the original unstrengthened beam.Research into the timedependent behavior (creep and shrinkage) of concrete beams strengthened with externally bonded FRPs is scarce. Analytical models were verified against limited experimental observations of RC2 and timber3 beams externally reinforced with FRP strips. Similar approaches were used for a posite glass fiberreinforced polymer (GFRP) box girder with concrete in the pression flange and a carbon fiberreinforced polymer (CFRP) strip bonded to the tension In all of the aforementioned models, however, the effect of creep in the adhesive layer bonding the FRP to the tension face of the beams was neglected. That is, perfect bond and strain patibility was assumed between the substrate and the FRP. Recent experiments by Choi et demonstrated that significant creep under shear stresses occurs in the epoxy at the concreteFRP interfaces when loading is applied within 7 days of epoxy application.Herein, the results of an experimental investigation and acpanying analytical predictions of immediate and timedependent beam deflections are described. The construction of the RC beams and the experimental program for observing their timedependent deflection are presented. The measured deflections are pared to deflection predictions using the ACI and CEBFIP methods implemented according to the remendations of Hall and The longterm deflection data show that the timedependent (creep) deformation of the CFRPstrengthened beam is a larger proportion of its immediate deformation than the same deformation ratio for the unstrengthened beam. The creep of the beam with the FRP strips could not be predicted from the creep measured on the plain beam when creep of concrete alone was considered. Because CFRPs have not been observed to creep at the stress levels generated,7,8 the additional creep may have occurred in the epoxy adhesive bonding the FRP strips to the concrete.The creep mechanism is expected to be a simple flow of the epoxy under the shear stress,5 which develops to create tension in the FRP strip. While models exist for predicting longterm deformation of RC beams strengthened with FRP (for example, Charkas et ), these models do not account explicitly for creep of epoxy adhesives. Herein,