Unified model for evaluating ultimate strain of FRP confined concrete based on energy method

The energy balance method has been widely used in the extant literature to derive the ultimate axial strain of conventional confined concrete columns. However, researchers noted that this method yields unrealistic results compared to experimental data when it is applied to fiber-reinforced polymer (FRP) confined concrete columns. Therefore, it is deemed that the existing ultimate strain model based on the energy method cannot be directly applied to FRP-repaired concrete. With this model shortcoming in mind and through a theoretical analysis with proper calibration, the current study extended the energy balance approach to develop a generalized model to determine the ultimate strain of FRP repaired concrete columns. This proposed new model can be used to predict the ultimate strain of repaired columns under both concentric and eccentric loadings. Because this model is established in a unified form without any restrictions to the cross-sectional geometry, it is applicable to different shapes of repaired columns. On the other hand, although the energy balance method is unconservative for heavily damaged concrete, it exhibits a better performance with respect to the existing models when compared with the test result. K E Y W O R D Sconcrete structure, confinement, energy method, FRP, repairing, ultimate strain

U_{u} = v_{col} ([], \int_{0}^{ε_{italiccd}} f_{cd} italicdε + \int_{ε_{italiccd}}^{{\overset{ε}{true}}_{italiccuo}^{r}} f_{cd} italicdε) = v_{col} \int_{0}^{{\overset{ε}{true}}_{italiccuo}^{r}} f_{cd} italicdε,

where f cd is the peak remaining strength of unconfined repaired concrete. For simplicity, it is assumed that

{\overset{false˜}{ε}}_{cuo}^{r}

equals to 1.75 ε cd . The total energy absorbed U up up to the remaining peak strength of unconfined repaired concrete is:

U_{up} = v_{col} \int_{0}^{ε_{italiccd}} f_{cd} italicdε .

…”

Section: Energy Balance In Frp‐repaired Concrete Columnsmentioning

confidence: 99%

“…The tensile energy absorbed per unit volume by the confining material U f is:

U_{f} = v_{col} k_{f} \int_{0}^{ε_{f, rup}} f_{f} ((), ε) italicdε,

U_{f} = 0.5 v_{col} E_{f} k_{f} {(ε_{f, rup})}^{2},

where E f is the elastic modulus of FRP.…”

Section: Energy Balance In Frp‐repaired Concrete Columnsmentioning

confidence: 99%

ε_{f, rup} = k_{ε, f} ε_{f} .

…”

Section: Ultimate Strain Of Frp‐repaired Concrete Under Concentric Lomentioning

confidence: 99%

“…( k ε , f ) 2 and k s in Equation (13) are given in Equations , respectively. Adopting a similar approach to Wu and Cao, the ratio k s ( k ε , f ) 2 in Equation (13) is given as:

k_{s} {(k_{ε, f})}^{2} = α {(\frac{E_{l}}{f_{italicco}})}^{β} {(\frac{f_{30}}{f_{italicco}})}^{γ} {(\frac{2 r}{b})}^{η} {(\frac{h}{b})}^{χ} {(\frac{ε_{f}}{ε_{italiccd}})}^{μ} {(δ)}^{ω},

where α , β , γ , η , χ , μ , and ω are coefficients to be determined.…”

Section: Ultimate Strain Of Frp‐repaired Concrete Under Concentric Lomentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Energy balance method for modeling ultimate strain of fiber‐reinforced polymer‐repaired concrete

Tijani

Lim

2019

Effects of predamage and load cyclic on compression behavior of fiber reinforced polymer‐confined concrete

Cao

Hou

Liu

et al. 2021

Most existing studies on fiber reinforced polymer (FRP) confined concrete have focused on undamaged concrete that is subjected to uniaxial monotonic compression. However, FRP jackets are usually applied to concrete columns with existing material damage and potential future damage. This paper investigates FRP confinement on concrete with damage before and after FRP jacketing. A total of 32 FRP‐confined concrete specimens were tested under axial compression in this work. The prior damage before FRP jacketing was implemented as predamaging by applying preloading and then release on the plain concrete specimens. The post damage after FRP jacketing was performed by applying cyclic axial compression loading on FRP‐confined concrete specimens. The test results reveal that the concrete predamage levels have significant influences on the cyclic stress–strain curve and envelop stress–strain curve for FRP confined concrete under cyclic loading. Existing models on ultimate state, plastic strain, reloading and unloading moduli were evaluated and investigated in this work.

Analysis of a compressive strength model for FRP‐confined damaged concrete columns based on the Drucker–Prager yield criterion

Zhang

Xiong

Musa

et al. 2022

Fiber reinforced polymer (FRP) has been widely used in repairing and strengthening of damaged concrete columns due to its excellent material properties. Most of the existing compressive strength models for FRP-confined concrete columns have been established through regression analyses of experimental data, and only a few models were established based on theoretical derivation. Therefore, to extend these compressive strength models based on theoretical derivation, a new strength model based on the Drucker-Prager yield criterion was established in this article, which is suitable for predicting the strength of FRP-confined circular and square concrete columns with loaddamaged, fire-damaged and strain rate. To study the strength model of FRPconfined concrete columns, the author collected 675 test data from published literature and built a large database containing cross-section type, damage type, damage degree and strain rate. In this database, most of the existing strength models in the published literature and the model proposed in this article were evaluated. The evaluation results show that the model can accurately predict the compressive strength of FRP-confined circular and square concrete columns with undamaged, load-damaged, fire-damaged and strain rate.