Effective Strain of BFRP for Confined Heat-Damaged Concrete Cylinders

Abstract

It is widely accepted that concrete columns confined with fiber-reinforced polymer (FRP) jackets exhibit significant increases in strength and ductility with reference to the unconfined case. Existing experimental studies have indicated that the hoop rupture strains measured in the FRP jackets are significantly lower than the material strain capacity determined by the flat coupon tensile tests. An FRP efficiency factor is then usually used to define the ratio of the average hoop rupture strain to the material strain capacity of the FRP jackets, which governs the lateral FRP confinement as well as the peak strength and ultimate strain of the FRP-confined concrete under axial compression. FRP jackets are also expected to be a promising solution to repair damaged RC columns after fire exposure. However, there is lacking research on the behavior of FRP-confined fire or heat-damaged concrete columns. In particular, the FRP efficiency factor of FRP-confined fire or heat-damaged concrete columns has not yet been established. The study presents the results of an experimental study aimed to investigate the effects of the historical high temperature and the layer of basalt FRP (BFRP) jackets on the efficiency factor of BFRP for the confined heat-damaged concrete cylinders. A sum of 51 standard concrete cylinders is prepared and tested under axial compression. The parameters varied between tests are the historical high temperature (200°C, 400°C, 600°C, or 800°C) that is used to produce the heat damage of concrete cylinders and the number of layers of BFRP jackets (2, 3, or 4). The test results have indicated that the efficiency factor of BFRP jackets increases with the historical high temperature but decreases slightly with the increase in the BFRP layers. A new temperature-dependent design equation for the BFRP efficiency factor of the confined heat-damaged concrete is proposed to consider the effects of the parameters mentioned above and can be used for practical design.

Nonlinear bond-slip model for fiber-reinforced polymer laminates externally bonded to thermally damaged concrete

“…FRP composites offer several advantages over traditional strengthening materials, including high strength-to-weight ratio, corrosion resistance, ease of application, and minimal changes in structural dimensions (Bisby et al, 2011). The use of FRP laminates has proven effective in the repair and strengthening of thermally or fire-damaged concrete (referred to as “thermally damaged concrete” for brevity) and RC members, including columns (Al-Kamaki et al, 2015; Bisby et al, 2011; Ouyang et al, 2021a, 2021b; Shayanfar et al, 2023; Song et al, 2021; Yaqub and Bailey, 2011) and flexural members such as slabs and beams (Alshannag and Alshenawy, 2020; Haddad et al, 2011; Xu et al, 2019). For example, Haddad et al (2011) conducted an experimental study using carbon FRP (CFRP) and glass FRP (GFRP) laminates to strengthen thermally damaged high-strength RC slabs.…”

Fire Performance of FRP-RC Flexural Members: A Numerical Study

“…In the literature, a large number of studies have been conducted on the performance of FRP bar-reinforced concrete (referred to as FRP-RC for simplicity) members at ambient temperature [1][2][3][4], and the related design provisions have been specified in the current design guidelines [5,6]. However, the FRP-RC members are likely to Polymers 2022, 14, 346 2 of 22 be exposed to fire hazards during their service life, especially when these members are used in indoor applications (e.g., in buildings) [7][8][9][10]. Under high-temperature exposure in a fire, the material properties of FRP bars and concrete as well as the bond behavior between them will usually be significantly reduced [11,12], possibly leading to a significant reduction in the load-carrying capacity of the FRP-RC members [13,14].…”