http://yetl.yabesh.ir/yetl1/handle/yetl/18998 2026-07-16T22:57:39Z http://yetl.yabesh.ir/yetl1/handle/yetl/4309315 Axial Stress–Strain Model of LRS-FRP–Confined Rectangular Concrete Prisms Allowing for the Size Effect and Its Application in Flexural Analysis of Beams Xin-Kai Hao; Qin-Ye Zhu; Liu-Feng Zhong; Zhi-Tao Zhan; Qian Feng; Jian-Jun Zheng Large rupture strain fiber-reinforced polymer (LRS-FRP) composites exhibit a large rupture strain exceeding 5%, thereby enhancing the ductility and strength of concrete as a confinement reinforcement with notable energy dissipation capability. Nevertheless, available approaches are empirically derived from small-sized specimens, which renders them unsuitable for practical structures with larger sizes or aspect ratios. In this study, a passive stress–strain model for concrete wrapped by LRS-FRPs under concentric loading is proposed by incorporating partial interaction shear friction and bond-slip mechanisms. This model accommodates the size effect and a corresponding design equation is proposed to ensure the strain-hardening behavior of LRS-FRP-wrapped concrete prisms. The proposed passive stress–strain model is then employed in the segmental analysis to simulate the behavior of LRS-FRP-wrapped concrete beams considering the size effect and the confinement effect. Finally, a parametric study is conducted to investigate the effects of LRS-FRP thickness and longitudinal reinforcement on the behavior of beams. 2025-01-01T00:00:00Z http://yetl.yabesh.ir/yetl1/handle/yetl/4309314 Seismic Analysis of Precast and Post-Tensioned Column-to-Footing Connections with Steel–GFRP Bars and GFRP Spirals Duc Q. Tran; Suman Neupane; Chris P. Pantelides A numerical model simulating the seismic behavior of precast concrete columns confined with a glass fiber–reinforced polymer (GFRP) spiral reinforced with longitudinal steel or a combination of steel and GFRP bars was developed. Four column specimens confined with GFRP spirals longitudinally reinforced with either only steel longitudinal bars (all-steel) or a combination of steel and GFRP longitudinal bars (hybrid) were tested under cyclic loads. Two columns, one hybrid and one all-steel, were post-tensioned using high-strength steel bars. For the post-tensioned columns, carbon fiber–reinforced polymer (CFRP) jackets were applied externally at the column end. The columns were connected to the footings using grouted duct connections. A computational model using OpenSees is presented to analyze the cyclic response of the precast reinforced/post-tensioned concrete columns with grouted ducts reinforced with a hybrid arrangement of steel and GFRP bars. The numerical model incorporates plastic hinge length, buckling, bond slip, and low cycle fatigue of intentionally debonded steel reinforcing bars. Material models for confined concrete by two layers of GFRP internal spirals and CFRP external jackets, reinforcing steel bars, GFRP bars, and post-tensioned high strength steel bars proved their effectiveness in simulating the experiments. Satisfactory agreement between the model and experiments was observed. The numerical model predicted bar fracture during the same drift ratio as the experiments. The cumulative hysteretic energy of the numerical models deviated from the experiments by <6.0%. The difference in peak post-tensioning force between the numerical model and the experiments was <5.0%. 2025-01-01T00:00:00Z http://yetl.yabesh.ir/yetl1/handle/yetl/4309313 Experimental and Theoretical Investigation of Shear Transfer Mechanisms in GFRP-RC Deep Beams without Stirrups Zhe Li; Wei-Jian Yi; Ye Li; Hui Chen This study focuses on the shear transfer mechanisms of glass fiber–reinforced polymer (GFRP)-RC deep beams without stirrups and proposes a unified shear model applicable to both steel- and FRP-RC deep beams. Seven concrete deep beams reinforced with GFRP and steel bars were tested under four-point bending. The influences of reinforcement material, shear span-to-depth ratio, reinforcement ratio, and effective depth on the shear performance of the beams were studied. The test results indicated that, after the formation of the critical shear crack, the shear force was directly transferred from the loading point to the support, creating a strut-and-tie action. GFRP-RC deep beams without stirrups exhibited a significant size effect on shear strength. The contributions of different shear transfer mechanisms were quantified based on the kinematics of the critical shear crack measured using two-dimensional digital image correlation. At the peak load, the total contributions of aggregate interlock, dowel action, and residual tensile stresses in the fracture process zone to the shear strength of both GFRP- and steel-RC deep beams were <4%. A large amount of the shear force was transferred through the concrete strut. Because of the influence of the critical shear crack, concrete crushing in the pure bending region of the GFRP-RC deep beams occurred at loads lower than the flexural capacity. A unified shear model was established to predict the shear strength of both steel- and FRP-RC deep beams. The model was validated by comparing its predictions with the test results of 265 beams. The unified shear model accurately predicted the shear strength, with a mean value of the tested-to-predicted shear strength ratio of 1.04 and a coefficient of variation of 0.23. Furthermore, the proposed model effectively reflected the influence of the shear span-to-depth ratio and the effective depth on the shear strength. 2025-01-01T00:00:00Z http://yetl.yabesh.ir/yetl1/handle/yetl/4309312 Assessing Compressive Properties of GFRP Bars: Novel Test Fixture and Statistical Analysis Alireza Sadat Hosseini; Pedram Sadeghian This study investigates the compressive behavior of thermoset glass fiber–reinforced polymer (GFRP) bars across different grades, sizes, and length-to-diameter (L/db) ratios using a novel testing fixture. A total of 61 specimens were subjected to testing, encompassing bars in three sizes, three grades, and three L/db ratios. The new testing fixture, informed by insights from previous methods and initial investigations, easily adaptable to different bar diameters, and eliminates the need for resin, grout, or permanent attachment, allowing for reuse. Using this testing method, consistent measurements of compressive strengths were obtained for L/db = 2, reaching approximately 0.86 of their average measured tensile strength. These measurements exhibited a low standard deviation (SD) of 0.047 and a low coefficient of variation (CoV) of 5.4%. Additionally, the elastic modulus in compression closely aligned with the tensile modulus, with a ratio of 0.97, and minimal variation in measurements (SD = 0.032 and CoV = 3.3%). Increasing the L/db ratio of bars from 2 to 6 escalated result variability and reduced the compressive to tensile strength ratio (ffc/fft) from 0.86 to 0.63, mainly due to increased susceptibility to buckling as observed in the experiments. However, the elastic modulus ratios (Efc/Eft) remained consistent around 1.0. The results of a comparative statistical analysis using data from studies over the last decade highlighted a decreasing trend in ffc/fft ratios with increasing L/db ratios, having an average of 0.7. However, Efc/Eft remains stable at around 1.0 across different L/db ratios. 2025-01-01T00:00:00Z