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In this study, the flexural bearing behavior of corroded reinforced concrete (RC) beams reinforced with U-type Textile Reinforced Concrete (TRC) was investigated using a four-point bending loading method. Nine test beams were produced: one original beam, three RC beams with corrosion alone, and five corroded beams strengthened with U-type TRC. The analysis focuses on assessing the impacts of the steel corrosion degree and the number of textile layers on various aspects of the bending behavior, such as failure modes, bearing capacity, and load displacement curves, in U-type TRC-strengthened corroded beams. The experimental results revealed three distinct failure modes in the U-type TRC-strengthened corroded beams. TRC effectively enhanced the bearing capacity. With sufficient textile layers, it can be restored to the level of the original RC beams. Moreover, in the cases of severe corrosion in RC beams, the bearing capacity increased more significantly. The TRC also enhanced the ductility. Finally, a calculation equation for the ultimate bearing capacity of U-type TRC-strengthened corroded beams was presented and validated, demonstrating consistent alignment with the experimental data. [ABSTRACT FROM AUTHOR]

Rotation capacity of reinforced concrete ( RC) beams is a vital property for its relationships with moment redistribution, energy absorbability, and so on. Evaluation of the rotation capacity has been one of the classic and intractable problems in structural engineering over the past decades. The precise prediction about rotational behavior of a RC beam is the primary basis of quantifying its rotation capacity. In this paper a displacement-based finite layer element method considering the factors of flexural cracks, concrete crushing, and pre-and postyield behavior of bond is presented to predict the rotational behavior. In conclusion, it shows good agreement between simulation results, implemented by the proposed method, and the test results in the literature. [ABSTRACT FROM AUTHOR]

End concrete cover separation is one of the most common failure modes for RC beams strengthened with external FRP reinforcement. The premature failure mode significantly restricts the application of FRP materials and could incur serious safety problems. In this paper, an innovative stress field-based analytical approach is proposed to assess the failure strength of end concrete cover separation and the conventional plane-section analysis is extended to evaluate the corresponding carrying capacity of FRP-strengthened RC beams. First, the dowel action of reinforcement and the induced concrete splitting, reflecting the interaction between concrete, steel and FRP, are considered in establishing the geometrical relationships of stress field for cracked concrete block. Then, the cracking angle and innovative failure criterion, considering the arrangement of steel and FRP reinforcement and cracking status of concrete and its softening effect, are derived to predict the occurrence of concrete cover separation and related mixed modes of debonding failure. Subsequently, an extended sectional analytical approach, in which the components of effective tensile strain of FRP resulted from flexural and shear actions are both considered, is presented to evaluate the carrying capacity of strengthened beams. Finally, the proposed calculational model is effectively validated by experimental results available in the literature. [ABSTRACT FROM AUTHOR]

Through proper arranging of a hybrid combination of longitudinal fiber reinforced polymer (FRP) bars and steel bars in the tensile region of the beam, the advantages of both FRP and steel materials can be sufficiently exploited to enhance the flexural capacity and ductility of a concrete beam. In this paper, a methodology for the flexural strength design of hybrid FRP-steel reinforced concrete (RC) beams is proposed. Firstly, based on the mechanical features of reinforcement and concrete and according to the latest codified provisions of longitudinal reinforcement conditions to ensure ductility level, the design-oriented allowable ranges of reinforcement ratio corresponding to three common flexural failure modes are specified. Subsequently, the calculation approach of nominal flexural strength of hybrid FRP-steel RC beams is established following the fundamental principles of equilibrium and compatibility. In addition to the common moderately-reinforced beams, the proposed general calculation approach is also applicable to lightly-reinforced beams and heavily-reinforced beams, which are widely used but rarely studied. Furthermore, the calculation process is properly simplified and the calculation accuracy is validated by the experimental results of hybrid FRP-steel RC beams in the literature. Finally, with the ductility analysis, a novel strength reduction factor represented by net tensile steel strain and reinforcement ratio is proposed for hybrid FRP-steel RC beams. [ABSTRACT FROM AUTHOR]

• A numerical model to predict flexural behavior of hybrid RC beams was proposed. • TCM was used to simplify the analysis of tension stiffening effect. • LSM was developed to simplify the description of softening behavior of concrete. • Simplified multilinear moment–curvature curve of hybrid RC beams was suggested. Hybrid fiber reinforced polymer (FRP)-steel reinforced concrete (RC) beams exhibit different flexural failure modes with different reinforcement ratios and the contributions from tensile region and compressive region of the beams to flexural behavior vary accordingly. Therefore, a general model to predict the global nonlinear behavior of hybrid FRP-steel RC beams featured by common flexural failure modes is critical to analysis and design. In this paper, flexural behavior of a hybrid FRP-steel RC beam is considered as the systematic combination of mechanical behavior of FRP and steel RC tension chords and concrete strut. The Tension Chord Model (TCM) for steel and its extended application for FRP, properly considering the bond performance between FRP/steel reinforcement and the surrounding concrete, are employed to represent the tension stiffening effect in tensile region; the Linear Softening Model (LSM), incorporating the compressive fracture energy and considering the confinement effect, is applied to predict the softening behavior of compressive concrete. Based on the primary principles of equilibrium and compatibility, the aforementioned two models are assembled to numerically evaluate the advanced moment–curvature relationship and flexural behavior. Due to the proper combination and application of mechanical models, the global evaluation process is significantly simplified and avoids the lengthy iterative calculations performed in conventional numerical methods. Finally, the proposed calculational model is validated by comparisons between the predictions and experimental results of hybrid FRP-steel RC beams with common flexural failure modes available in the literature. [ABSTRACT FROM AUTHOR]

Arranging a hybrid combination of longitudinal fiber reinforced polymer (FRP) bars and longitudinal steel bars in the tensile zone of a concrete beam is able to sufficiently exploit the superior properties of both FRP and steel materials to achieve a satisfactory ductility level. As the foundation of analysis and design of hybrid FRP-steel reinforced concrete (RC) members, study of tensile behavior of concrete chords with FRP-steel reinforcement is essential and necessary. In this paper, the average crack spacing of hybrid (Glass Fiber Reinforced Polymer-GFRP and steel) RC chords is analytically estimated. Subsequently, the Tension Chord Model (TCM) is extended to predict the tensile behavior of hybrid GFRP-steel RC chords. Finally, the presented models are effectively validated by experimental results of concrete chords reinforced with GFRP bars and steel bars in different combinations available in the literature, and detailed discussions about analytical and experimental results are also performed. [ABSTRACT FROM AUTHOR]