Reliability Analysis of FRP-Confined Concrete at Ultimate using Conjugate Search Direction Method

Abstract

In this paper compressive strength and ultimate strain results in the current database of fiber-reinforced polymer (FRP)-confined concrete are used to determine the reliability of their design space. The Lognormal, Normal, Frechet, Gumbel, and Weibull distributions are selected to evaluate the probabilistic characteristics of six FRP material categories. Following this, safety levels of the database are determined based on a probabilistic model. An iterative reliability method is developed with conjugate search direction for evaluating the reliability. The results show that Lognormal and Gumbel distributions provide best probability distribution for model errors of strength and strain enhancement ratios. The developed conjugate reliability method provides improved robustness over the existing reliability methods owing to its faster convergence to stable results. The results reveal that the part of the database containing normal strength concrete (NSC) heavily confined (i.e., actual confinement ratio (flu,a/f’co) > 0.5) by low and normal modulus carbon fibers (i.e., fiber elastic modulus (Ef) ≤ 260 GPa) and moderately confined (i.e., 0.3 ≤ flu,a/f’co ≤ 0.5) by aramid fibers exhibits a very high safety level. The segments of the database with a low and moderate safety level have been identified as i) NSC moderately and heavily confined by higher modulus glass fibers (i.e., Ef > 60 GPa), ii) high strength concrete (HSC) moderately and heavily confined (i.e., flu,a/f’co > 0.3) by glass fibers, iii) HSC lightly confined (i.e., flu,a/f’co ≤ 0.2) by carbon fibers, and iv) HSC lightly confined by aramid fibers. Additional experimental studies are required on these segments of the database before they can be used reliably for design and modeling purposes.

From Probabilistic to Quantile-Oriented Sensitivity Analysis: New Indices of Design Quantiles

“…When the influence of input variables on the load action side approaches zero, the reliability is only influenced by the variables on the resistance side. In the presented case study, the corrections of [45,46], then the proposed concept cannot be used.…”

“…If σ F → 0, then C Ti of the variables on the load action side approaches zero naturally. If an extreme value distribution is used, such as a Gumbel or Weibull pdf [45,46], then the proposed concept cannot be used.…”

3D Finite Element Pseudodynamic Analysis of Deficient RC Rectangular Columns Confined with Fiber Reinforced Polymers under Axial Compression

“…or higher than 0.85 × f cc and lower than f cc if there is an abrupt FRP fracture. Based on this approach the corresponding ε cc and ε cu are defined at the same points, see also [17,19,53,58,63].…”

“…All these experimental investigations have led to the proposal of a large amount of semi empirical models trying to predict with accuracy the ultimate stress and strain behavior of concrete columns when subjected to monotonic axial loading [50][51][52][53][54][55][56][57][58] and few expressions have been proposed to predict the cyclic response [59][60][61][62]. Ozbakkaloglu et al [63] proposed a probabilistic model for the prediction of ultimate stress and strain of FRP confined columns. In addition to these, the behavior of FRP confined concrete in the microstructural level has been investigated through finite-element (FE) analysis focused on the analysis of solid FRP confined concrete cylinders and rectangular specimens as well [64][65][66][67][68].…”

Axial Strength of Eccentrically Loaded FRP-Confined Short Concrete Columns

“…Fiber reinforced polymer (FRP) jacketing or confinement has been widely adopted and used in rehabilitation work on concrete structures [ 1 , 2 , 3 , 4 ]. The confinement can not only enhance the strength and ductility of a concrete structure [ 5 , 6 ] but also increase the bond between the concrete and internal steel reinforcement [ 7 , 8 , 9 ].…”