Influence of the Cross-Sectional Shape and Corner Radius on the Compressive Behaviour of Concrete Columns Confined by FRP and Stirrups

Abstract

Axial compression tests were carried out on 72 FRP (fiber reinforced polymer)–stirrup composite−confined concrete columns. Stirrups ensure the residual bearing capacity and ductility after the FRP fractures. To reduce the effect of stress concentration at the corners of the confined square−section concrete columns and improve the restraint effect, an FRP–stirrup composite−confined concrete structure with rounded corners is proposed. Different corner radii of the stirrup and outer FRP were designed, and the corner radius of the stirrup was adjusted accurately to meet the designed corner radius of the outer FRP. The cross−section of the specimens gradually changed from square to circular as the corner radius increased. The influence of the cross−sectional shape and corner radius on the compressive behaviour of FRP–stirrup composite−confined concrete was analysed. An increase in the corner radius can cause the strain distribution of the FRP to be more uniform and strengthen the restraint effect. The larger the corner radius of the specimen, the better the improvement of mechanical properties. The strength of the circular section specimen was greatly improved. In addition, the test parameters also included the FRP layers, FRP types and stirrup spacing. With the same corner radius, increasing the number of FRP layers or densifying the stirrup spacing effectively improved the mechanical properties of the specimens. Finally, a database of FRP–stirrup composite−confined concrete column test results with different corner radii was established. The general calculation models were proposed, respectively, for the peak points, ultimate points and stress–strain models that are applicable to FRP−, stirrup− and FRP–stirrup−confined concrete columns with different cross−sectional shapes under axial compression.

Modeling and Calculation of Improved Centrifuged Reinforced Concrete Columns with Variotropic Structure

“…There are square or round, as well as solid or hollow sections [58][59][60]. In [61], the influence of the cross-sectional shape and the corner radius on the behavior of prototype columns reinforced with a fiber-reinforced plastic shell during compression was determined. The cross section of the samples changed from square to round as the corner radius increased.…”

“…It was noted that an increase in the radius of curvature led to a decrease in the stress concentration at the corners of the samples, as a result of which the confining effect of the shell increased and the deformations were more uniform. The highest was the strength of the round section [61]. Particularly interesting for this study are the works devoted to theoretical analysis and numerical modeling of the structural heterogeneity of concrete.…”

Evaluation of the strain response of FRP partially confined concrete using FEM and DIC testing

“…To reinforce concrete structures, researchers have used a variety of FRP materials, including carbon fiber, glass fiber and basalt fiber (Liang et al, 2019;Pantelides et al, 2013). The primary focus of research has been on various stress-strain models that correspond to various reinforcement structures, such as the type and thickness of FRP as well as the crosssectional shape, dimensions and corner thickness and strength of concrete columns (Ouyang et al, 2013;Jamatia and Deb, 2017;Parvin and Jamwal, 2006;Wei et al, 2022). These models, IJSI 15,2 262 Data availability statement: All data generated or analyzed during this study are included in this published article.…”

“…The primary focus of research has been on various stress–strain models that correspond to various reinforcement structures, such as the type and thickness of FRP as well as the cross-sectional shape, dimensions and corner thickness and strength of concrete columns (Ouyang et al. , 2013; Jamatia and Deb, 2017; Parvin and Jamwal, 2006; Wei et al. , 2022).…”