【正文】 ter loading (recorded up to 2470 days) and as predicted for both beams using CEBFIP10 and ACI11 models.Fig. 3—Relative slip versus time at each end of one CFRP strip (Beam 2) as measured and as predicted using FE model.5. Some relative slip occurred between the concrete and CFRP strip at the strip ends soon after loading, as shown in Fig. 3. Since then, the movement at one end of the strip has essentially stabilized and only a relatively small gradual movement has occurred at the other end. The significant scatter in the slip readings, particularly late in the data record, is thought to result from temperature variations in the strain gauges between dates of reading (the beams are beside an airconditioning outlet) and repeated reconnection/disconnection of the measurement instrumentation for these gauges. The maximum relative slip at the ends of the gauged CFRP strip within 2470 days was in the order of mm ( in.)—an average of approximately 60 microstrain over the length of the strip—which implies an average loss of tensile stress of approximately 9 MPa ( psi) in the strips, and translates to an average loss of tensile force of approximately 1 kN ( kips) per strip. Fifty percent of this movement occurred in the first 3 weeks after loading. This observation agrees with those reported by Choi et al.,confirming that the majority of epoxy creep occurs in a relatively early time period.ANALYTICAL PREDICTION OF DEFLECTIONSAnalytical predictions of the beam deflections were made in an attempt to identify any features of the behavior not obvious from the experimental results alone. First, the simplified procedures of CEBFIP10 and ACI11 were used. These procedures focus on accurate modeling of concrete creep—and thus deflection—without considering the effect of creep of epoxy. A stepbystep intime analysis and an FE model were therefore developed to examine the bined effect of creep of the concrete and of the epoxy on the longterm deflection.Analytical prediction of deflections using CEBFIP and ACIApproaches based on the CEBFIP Model Code 1990 and the ACI Committee 209 remendations11 were used by Hall and Ghali6 with the former being shown to achieve good agreement with experimental results for concrete beams reinforced with steel bars and concrete beams with GFRP bars in place of the steel bars. Both approaches aim at estimating longterm deflections due to the effects of creep and shrinkage in the concrete. The methodologies are described in detail by Hall and Ghali6 and Masia et al. Fig. 4—Deflections predicted by stepbystep in time model versus experimentally measured deflections for Beam 1 (reinforced with steel only), including effect of concrete creep and tension stiffening of concrete (238。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。specimen. Two CFRP strips were bonded to the tension face of the second beam (Beam 2) using an epoxy adhesive. The strips are 100 mm ( in.) wide, mm ( in.) thick, and 2970 mm ( in.) long. Over the shear spans at each end of Beam 2, GFRP sheets were wrapped in a Ushape to cover the two side faces and the tension face of the beam. The CFRP strips are unidirectional with the fibers aligned along the length of the beam. The strips have a modulus of elasticity of 165 GPa (23,571 ksi) and a tensile strength of 2800 MPa (400 ksi) in the direction of the fibers (manufacturer’s data). Test setup and procedureThe beams were simply supported (pinroller) over a span of 3200 mm