Monotonic and Cyclic Axial Compressive Behavior of CFRP-Confined Rectangular RC Columns

Isleem, Haytham F.; Wang, Zhenyu; Wang, Daiyu; Smith, Scott T

doi:10.1061/(asce)cc.1943-5614.0000860

Cited by 48 publications

(49 citation statements)

References 45 publications

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“…Besides, it was reported that specimens with higher aspect ratios exhibited smaller FRP strains at peak load. Comparison of the test results of specimens with varying aspect ratios is shown in Figure 2, in which the FRP strain is found to decrease as the sectional aspect ratio increase, as it has been reported in several tests on confined concrete columns with rectangular sections [12,[16][17][18]24]. Based on regression of the specimens results, Equation 5 with 2 value of approximately 91% is introduced.…”

Section: Overview Of Experimental Test Resultsmentioning

confidence: 77%

“…When the R is greater than the value of 0•02, then cc ′ c ′ ⁄ > 1.0, which means the cc ′ is greater than c ′ , and as a result, the confined specimen experienced enhancement in their strength and finally an ascending stress-strain response. Conversely, when the value of R is less than 0•02, a second post-peak softening component occurs in the stress-strain response as reported in several tests conducted on columns in the literature (Isleem et al [16][17][18]). Table 1 In the next section, the overall performance of the proposed and existing models of peak strength and strain of FRP-confined rectangular columns were evaluated against the results of columns with elliptical sections (Table 1).…”

Section: B' B B a R A 'mentioning

confidence: 89%

“…It was concluded that the FRP jackets are not able to effectively improve the compressive behavior of square and rectangular columns exhibiting a softening behavior. Recently it has been confirmed by Isleem et al [16][17][18] for rectangular columns of larger-sized cross-sections that the confinement provided by the FRP wraps resulted in a significant improvement in axial strains but only a little improvement in axial strengths. In their study, the results of tests have shown that only the sufficiently confined specimens with the aspect ratio of 1.5 reached higher strengths as compared with that of the unconfined concrete cylinder, while no strength enhancement was achieved for larger-sized specimens with the aspect ratio of 2.0.…”

Section: Introductionmentioning

confidence: 92%

“…In the studies, the confinement pressure was the sum of the confinement provided by the FRP wraps and that of the internal hoops. In earthquake-prone regions, a large number of RC columns, particularly of rectangular cross-sections, that were built based on the out-of-date codes may not have adequate lateral reinforcement to resist high seismic load levels (Isleem et al [18]). As a result, they are subjected to major damages causing a total collapse of the building (Ilki et al [50]).…”

Section: Amount Of Frp For Sufficiently Confined Concretementioning

confidence: 99%

“…. The majority of the existing studies have focused on modeling the stress-strain behavior of FRP-confined concrete in circular cross-sections under axial compression, while only limited studies considered FRP-confined concrete in rectangular cross-sections [11][12][13][14][15][16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

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Axial Compression Model for FRP Confined Concrete in Elliptical Cross Sections

Z¹,

Isleem²

2018

Preprint

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Most of the existing studies conducted on FRP-confined concrete considered circular and square concrete columns, while limited studies were on columns with rectangular sections. The studies have confirmed that the circular cross-sections exhibited higher confinement effectiveness, whereas in the case of non-circular cross-sections the efficiency of FRP confinement decreases with an increase of the sectional aspect ratio and there is no significant increase, particularly for columns with the aspect ratio of 2.0. As recently suggested by the researchers, to significantly increase the effectiveness of FRP-confinement for these columns is by modifying a rectangular section to an elliptical or oval section. According to the literature, most of the existing confinement models for FRP-confined concrete under axial compression have been proposed for columns with circular and rectangular cross-sections. However, modeling the axial strength and strain of concrete confined with FRP in elliptical cross-sections under compression is most limited. Therefore, this paper provides new expressions based on limited experimental data available in the literature. For a sufficient amount of FRP-confinement, the threshold value was proposed to be 0.02. Finally, the accuracy of the proposed model was verified by comparing its predictions with the same test database, together with those from the existing models.

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Section: Overview Of Experimental Test Resultsmentioning

confidence: 77%

Section: B' B B a R A 'mentioning

confidence: 89%

Section: Introductionmentioning

confidence: 92%

Section: Amount Of Frp For Sufficiently Confined Concretementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Axial Compression Model for FRP Confined Concrete in Elliptical Cross Sections

Z¹,

Isleem²

2018

Preprint

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Assessment of analytical stress and strain at peak and at ultimate conditions for fiber‐reinforcement polymer‐confined reinforced concrete columns of rectangular sections under axial cyclic loading

Fanaradelli

Rousakis²

2020

Structural Concrete

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Confinement with fiber‐reinforcement polymer (FRP) materials is a technique, which can increase adequately the axial strain ductility of concrete. Plain and reinforced concrete columns, with circular, square and rectangular cross sections, confined with FRP materials, subjected to monotonic or cyclic compressive load, have been extensively studied over the last 35 years. Also, a lot of predictive expressions for peak and ultimate axial strength and strain, suitable for the available concrete sections, have been proposed. However, it is proven that it is difficult to accurately model and predict the behavior of the noncircular confined concrete columns, especially in the presence of internal longitudinal and transverse steel reinforcement, which is the real case for the majority of existing reinforced concrete structures. The presented study gathers all the available test results on square and rectangular reinforced or plain concrete columns confined with FRP materials and other novel techniques, subjected only to cyclic axial loading. It also assesses the performance of four significant expressions published in literature for the prediction of column load and deformation, proposed for the peak and ultimate conditions.

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Machine learning and nonlinear finite element analysis of fiber‐reinforced polymer‐confined concrete‐steel double‐skin tubular columns under axial compression

Isleem,

Qiong,

Chukka

et al. 2024

Structural Concrete

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Fiber‐reinforced polymer (FRP)‐confined double‐skin tubular columns (DSTCs) are an innovative type of hybrid columns that consist of an outer tube made of FRP, an inner circular steel tube, and a concrete core sandwiched between them. Available literature focuses on hollow DSTCs with limited research on DSTCs made with inner steel tubes filled with concrete. Overall, DSTCs have many applications, highlighting the importance of studying the effects of concrete filling and strength on the composite system. To address this gap, finite element models (FEMs) and both traditional and innovative machine learning (ML) techniques were used to develop accurate models for predicting load‐bearing capacity and confined ultimate strain under axial loads. A comprehensive database of 60 experimental tests and 45 FEMs simulations of columns was analyzed, with five parameters selected as input variables for ML‐based models. New techniques like gradient boosting (GB), random forest (RF), convolutional neural networks, and long short‐term memory are compared with established algorithms like multiple linear regression, support vector regression (SVR), and empirical mode decomposition (EMD)‐SVR. Regression error characteristics curve, Shapley Additive Explanation analysis, and statistical metrics are used to assess the performance of these models using a database containing 105 FEMs test results that cover a range of input variables. While EMD‐SVR and GB perform well for confined ultimate strain, the suggested EMD‐SVR, GB, and RF models show superior predictive accuracy for confined ultimate load. To be more precise, for confined ultimate load prediction, EMD‐SVR, GB, and RF obtain values of 0.99, 0.989, and 0.960, respectively. The values for GB and EMD‐SVR at confined ultimate strain are 0.690 and 0.99, respectively. However, design engineers are limited by the “black‐box” nature of ML. In order to solve this, the study presents an open‐source GUI based on GB, which gives engineers the ability to precisely estimate confined ultimate load and strain under various test conditions, enabling them to make well‐informed decisions about mix proportion.

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Monotonic and Cyclic Axial Compressive Behavior of CFRP-Confined Rectangular RC Columns

Cited by 48 publications

References 45 publications

Axial Compression Model for FRP Confined Concrete in Elliptical Cross Sections

Axial Compression Model for FRP Confined Concrete in Elliptical Cross Sections

Assessment of analytical stress and strain at peak and at ultimate conditions for fiber‐reinforcement polymer‐confined reinforced concrete columns of rectangular sections under axial cyclic loading

Machine learning and nonlinear finite element analysis of fiber‐reinforced polymer‐confined concrete‐steel double‐skin tubular columns under axial compression

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