【正文】 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, we use two different approaches to determine if creep in the epoxy can account for the different behaviors observed in the beams: a stepbystep intime analysis allowing incremental creep of concrete and epoxy in each time step and enforcing equilibrium at the end of the time step, and finite element (FE) modeling with shear flow allowed in the epoxy adhesive layer.RESEARCH SIGNIFICANCEThe potential effects of creep on RC beams strengthened with externally applied FRP strips are considered. It was thought that creep in the epoxy resin might relieve stress in the FRP, making the FRP less effective from a serviceability point of view under sustained loads. Thus, FRP strips used to strengthen a beam, which was then subject to increased sustained load, might end up with the extra sustained load being carried by the original concrete and steel reinforcement, not the FRP. The experimental and analytical work performed revealed that the situation is more plex. Nevertheless, creep deflections are greater than predicted from the creep of concrete alone, indicating contributions from creep of the epoxy. The reported experimental program was designed to identify the existence of epoxy creep rather than replicate a practical retrofit scenario. The results highlight the potential for epoxy creep to affect the longterm performance of FRP retrofits in practice.EXPERIMENTAL PROGRAMTest specimens and materialsTwo similar RC beams were cast from the same concrete batch (Fig. 1). Each beam was 3500 mm ( in.) long, 280 mm ( in.) wide, and 180 mm ( in.) high, reinforced with four longitudinal bars (Canadian mm [ in.] diameter, 100 mm2 [ ] area) at an effective depth of 135 mm ( in.) from the top surface of the beam. Seven 10M stirrups were spaced uniformly in each shear span of each beam. The 28day pressive strength of the concrete, as determined from 100 mm (4 in.) diameter, 200 mm (8 in.) high cylinders—cast from the same batch of concrete as the test beams—was 177。 epoxy adhesive。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