International Concrete Abstracts Portal

An experimental study was conducted to compare the long-term performance of two partially prestressed concrete (PC) beams reinforced with either bonded CFRP tendons (CFRP-PC) or steel strands (steel-PC) under 1200-day sustained loading. The deflections increased rapidly during the first 200 days and then at a slower rate. The final-to-initial deflection ratio was 1.58 for the CFRP-PC beam and 1.45 for the steel-PC beam. The final-to-instantaneous maximum crack-width ratio was approximately 2.00 for both beams. Based on the age-adjusted effective modulus method (AEMM), a finite element analysis (FEA) program was developed and calibrated using the experimental results. Parametric simulations were subsequently performed on 14 beams. A modification of the suggested equation in ACI 440.1R-15 was proposed to predict the time-dependent deflection of PC beams, which exhibits an improved correlation with the experimental results as compared to the design standards.

This study investigates the bending performance of fiber-reinforced cementitious composite (FRCC) beams reinforced with fiber-reinforced polymer (FRP) bars through experimental and analytical programs. A one-sided cyclic bending test with controlled displacement for polyvinyl alcohol FRCC (PVA-FRCC) beams reinforced with aramid FRP and aramid FRCC (A-FRCC) reinforced with carbon FRP, and section analysis were conducted. Both beams were designed primarily to fail in compression to avoid a brittle failure due to FRP rupture. The load capacity of A-FRCC beams is found to be higher than that of PVA-FRCC beams. Both specimens showed ductile behavior after the peak. Compression tests of rectangular columns were also conducted to determine the section reduction factors compared to the cylindrical compression test. Using Popovics model on the compression side and tensile stress-crack width relationship on the tension side, the stress-strain relationships for the FRCCs are developed. The adaptability of the models is checked by section analysis, and it shows good agreement with the bending test results.

The influence of lap splices on the seismic behavior of low-rise reinforced concrete (RC) walls was studied through tests of four 1:2 length-scale bridge pier wall specimens subjected to constant axial load and a quasi-static cyclic loading sequence. The study parameters were horizontal reinforcement ratio (0.25 to 0.34%), splice length to shear span ratio (≈ 0.2 to 0.3), and wall-end confinement. Specimens lost 20% of maximum lateral strength at drifts between approximately 1.2 and 1.8%, increasing with horizontal reinforcement ratio, wall-end confinement, and splice length to shear span ratio. Splice failure, bar fracture, or their combination, caused abrupt strength loss and transition from flexure- to rocking-controlled behavior. Flexure-compression failure in the specimen with a splice length to shear span ratio of approximately 0.3 resulted in gradual strength degradation without transition to rocking. All specimens sustained drift demands of almost 2% without loss of axial load-carrying capacity.

To investigate the seismic behavior and resilience of reinforced concrete (RC) slit shear walls with either low-bond or debonded high-strength reinforcements, eight shear walls with different cross-sectional forms and types of longitudinal reinforcing bars were fabricated and subjected to both compressive loading and cyclic lateral loading. The experimental results indicate that the test shear walls with anchored infilled steel columns (ISCs) failed in flexure of the subshear walls due to the form of a vertical slit. The use of both low-bond high-strength reinforcing bar (SBPDN reinforcing bar) and an anchored ISC significantly increased the ductility of the shear wall without reducing the stiffness at the early deformation stage or the seismic resistance. Interestingly, the debonding of the longitudinal reinforcing bar reduced the strain of the transverse reinforcement. The debonding and low bonding of the longitudinal reinforcing bar increased the contribution ratio of deformation due to steel-bond slip but decreased the contribution ratio of shear deformation. Moreover, the anchorage of an ISC plays an important role in the contributions of shear and flexural deformation. The models proposed in the current provisions can be used to accurately predict the seismic resistance of shear walls with debonded and low-bond high-strength reinforcing bars.

Although grouted splice sleeve connectors (GSSCs) are notably used in precast concrete structures, steel sleeves are heavy and have corrosion issues. The bond characteristics in GSSCs using cylindrical and tapered fiber-reinforced polymer (FRP) sleeves, lighter alternatives, were investigated in this study. A series of pull-out tests for 144 specimens was conducted to evaluate the effects of FRP type, number of layers, shape, and length on the bond characteristics in GSSCs. The test results showed that for FRP GSSCs, tapered FRP sleeves effectively developed confinement compared with cylindrical FRP sleeves, leading to better bond strength and shorter development length. A design equation was proposed for estimating the tensile strength of FRP-based GSSCs, which predicted the test results well. The tapered FRP sleeves reduced the development length compared with the FRP cylindrical sleeves, implying greater FRP GSSC efficiency in precast concrete structures, which provides engineers with valuable insights for efficient FRP splice-sleeve design in precast concrete structures.