مقاله انگلیسی رایگان در مورد رفتار ستون فولادی FRP پر شده از فولاد فیبر تقویت شده – الزویر 2018

The addition of internal steel fibers to concrete is a popular technique that is used for improving the inherent brittle behavior of plain concrete [1–4]. Likewise, lateral confinement of concrete results in a significant improvement in the ductility of concrete under compression [5–17]. Therefore, fiber-reinforced polymer (FRP)-confined steel fiberreinforced concrete (SFRC), as an ultra high-performance system, can be considered as a higher performance alternative with further enhanced mechanical properties to conventional FRP-confined plain concrete. As shown previously, the existence of steel fiber decreases isolated major crack formations in the concrete and results in a more even and controlled cracking [18]. In the case of FRP-confined SFRC, this in turn leads to reduced stress concentrations on the FRP jacket leading to higher FRP hoop rupture strains and ductility [19]. A number of experimental studies have been performed recently to understand the mechanical behavior of FRP-confined SFRCs [19–22]. Only the two of these studies experimentally investigated the mechanical behavior of FRP-confined SFRCs under concentric axial compression [19,20]. The remaining two were concerned with FRPconfined SFRC containing internal steel reinforcing bars under eccentric loading [21] and SFRCs confined by hybrid FRP tubes [22]. Existing studies have shown that steel fiber parameters (i.e. volume fraction (Vf) and aspect ratio (AR)) influence the stress-strain relationship of the concrete. It was shown that at a given Vf, an increase in AR leads to a decrease in the compressive strength (f′cc), ultimate axial strain (εcu), and hoop rupture strain (εh,rup) of concrete. On the other hand, an increase in Vf at a given AR results in an increase in f′cc, εcu, and εh,rup [19]. Finite element (FE) method has been extensively used to accurately model the mechanical behavior of confined plain concrete. Although a relatively large number of studies have been reported on the FE modeling of FRP-confined plain concrete [23–31], no study has been reported to date on the FE modeling of the FRP-confined SFRC. Furthermore, most of the existing FE models for FRP-confined plain concrete were based on an approach that was recently shown to be inaccurate, especially for high-strength concrete (HSC) [32,33]. Therefore, there is a clear need for additional numerical studies to better understand the constitutive behavior of FRP-confined SFRC. As discussed in detail in Refs. [31,34], concrete damage-plasticity approach, which was proposed by Lubliner et al. [35] and later modified by Lee and Fenves [36], provides a more accurate prediction of the constitutive behavior of confined concretes than the pure plasticity and damage approaches. In order to investigate the constitutive behavior of the FRP-confined concrete by damage-plasticity approach, it is required to establish experimental databases for both FRP-confined and actively confined concrete [31]. The review of the literature indicates that only two experimental studies have investigated the compressive behavior of actively confined SFRCs [1,37], the results of which would not be sufficient for the development of an accurate FE model. To address this research gap, in the current study additional experimental tests were performed on actively confined SFRCs to compile a reliable database that would enable FE modeling of FRP-confined SFRCs.