This study aimed at examining the feasibility of using fiber-reinforced polymer (FRP) rebars instead of steel ones in prestressed concrete beams (PCBs) with external FRP tendons. By applying an experimentally validated program, numerical tests were performed on simply supported PCBs, with investigated variables including rebars’ type and area. Three types of rebars were considered, i.e., carbon, glass FRPs (CFRP, GFRP), and reinforcing steel. The ratio of tensile rebars ranged from 0.22% to 2.16%. The results indicated that the beams with CFRP rebars exhibited better crack mode and higher ultimate load than the beams with GFRP or steel rebars. GFRP rebars led to considerably higher ultimate deflection and tendon stress increment than steel rebars. In addition, several models for calculating the ultimate stress in unbonded tendons were assessed. An analytical model was also proposed to predict the tendon stress at ultimate and flexural strength in externally PCBs with steel and FRP rebars. The model predictions agreed well with the numerical results.

This paper investigates the feasibility of replacing steel bars with carbon-fiber-reinforced polymer (CFRP) bars in continuous reinforced concrete (RC) beams. A numerical model is introduced. Model predictions are compared with the experimental results that are available in the literature. A comprehensive numerical investigation is then performed on two-span CFRP/steel RC beams with ρ_b2 = 0.61–3.03% and ρ_b1/ρ_b2 = 1.5, where ρ_b1 and ρ_b2 are tensile bar ratios (ratios of tensile bar area to effective cross-sectional area of beams) over positive and negative moment regions, respectively. The study shows that replacing steel bars with CFRP bars greatly improves the crack mode at a low bar ratio. The ultimate load of CFRP RC beams is 89% higher at ρ_b2 = 0.61% but 7.2% lower at ρ_b2 = 3.03% than that of steel RC beams. In addition, CFRP RC beams exhibit around 13% greater ultimate deflection compared to steel RC beams. The difference of moment redistribution between CFRP and steel RC beams diminishes as ρ_b2 increases. ACI 318-19 appears to be conservative, and it leads to more accurate predictions of moment redistribution in CFRP RC beams than that in steel RC beams.

The tendon stress in bonded prestressed concrete (BPC) beams is section-dependent while it is member-dependent in unbonded prestressed concrete (UPC) beams, leading to marked difference between these two structural systems. However, little work has addressed the bond effect of steel tendons. This research presents comparative investigations of BPC and UPC beams with various prestress levels. A numerical model is experimentally validated. Numerical assessments are conducted for simply supported and continuous scenarios, focusing on the effects of bond condition and prestress level. The results show that BPC beams exhibit better crack pattern (i.e., smaller crack width with larger crack zone) than UPC beams. The difference in ultimate loads or deflections between BPC and UPC beams depends heavily on the prestress level (the values of UPC beams are around 64% and 94% of those of BPC beams at prestress levels of 25% and 75%, respectively). Unbonded tendons produce greater moment redistribution in continuous scenarios than bonded tendons. It is also shown that the ACI code cannot well describe the bond impact of steel tendons on moment redistribution in continuous scenarios. A modified ACI equation is proposed, which can predict accurately the moment redistribution in both BPC and UPC beams.

Rammed earth construction is an ancient technique which has recently attracted renewed interest throughout the world. Although rammed earth is currently regarded as a promising material in the construction industry in the context of sustainable development, it is difficult to quantify its bearing capacity, mechanical performance, as well as retrofitting approach, which discourages people from large-scale application in architectural engineering. This paper is devoted to the study of these problems based on rammed earth wall model experimentation. Three different models are studied considering different material components as well as structural configurations. By measuring the strain and deformation of the rammed earth wall models subjected to uniformly-distributed vertical loading, their ultimate bearing capacities are tested based on experimental investigation. Then the method of cement mortar-steel fiber reinforcement (CMSF) is carried out to study the ultimate bearing capacity enhancement of the wall models. Results show that the method of cement mortar-steel fiber reinforcement can increase the ultimate bearing capacity of the rammed earth wall models significantly, which is of relevant engineering significance in practical application.

This paper assesses the impact of adopting carbon- or glass-fiber-reinforced polymer (CFRP or GFRP) instead of steel rebars on the redistribution of moments in prestressed concrete beams (PCBs) with external CFRP tendons. A numerical program is introduced, and numerical simulations are performed on two-span continuous beams with steel, CFRP or GFRP rebars of various areas, i.e., Ar2 = 360–3560 mm², and Ar1/Ar2 = 1.5, where Ar1 and Ar2 are areas of tensile rebars over the positive and negative moment zones, respectively. The results show the moment redistribution is contributed by concrete cracking only for the beams with fiber-reinforced polymer (FRP) rebars, and by concrete cracking and steel yielding for the beams with steel rebars. As a result, the use of FRP rebars leads to a substantially lower moment redistribution than in steel rebars. It is also demonstrated that Eurocode 2, CSA A23.3-04 and ACI 318-19 fail to reflect the rebar influence on moment redistribution in PCBs with external tendons. A simplified equation for the quantification of moment redistribution in externally PCBs with steel and FRP rebars is recommended, which yields accurate and conservative predictions.

The present investigation aims to identify the flexural performance of two-span concrete beams reinforced with hybrid carbon fiber reinforced polymer (CFRP) and steel bars. By applying a finite element analysis, a comprehensive numerical assessment is performed. The investigated variables are A_f/A_r (A_f = area of CFRP bars; A_r = total area of CFRP/steel bars), load pattern (symmetrical and unsymmetrical loading) and load type (center-point, third-point and uniform loading). The results show that beams with A_f/A_r of 0.25 show 16.0% and 11.3% higher ultimate load at symmetrical and unsymmetrical loading, respectively, than beams with A_f/A_r of 0.0 (i.e., beams with steel bars), but the change in ultimate load is not apparent when varying A_f/A_r between 0.25 and 1.0. Unsymmetrical loading causes 6.0–15.0% greater deflection capacities than the symmetrical one. When A_f/A_r increases from 0.0 to 1.0, moment redistribution at symmetrical loading is decreased significantly by 62%, while the redistribution variation is marginal at unsymmetrical loading. In addition, the applicability of two equations based on the ultimate strain in tensile bars for predicting moment redistribution is evaluated. It is generally shown that these equations can account for the influence of A_f/A_r and load type.