Circular Columns Research Articles

Probabilistic curvature limit states of corroded circular RC bridge columns: Data-driven models and application to lifetime seismic fragility analyses

Reinforcement corrosion has been recognized as an influential factor in the seismic fragility, both demand and capacity models, of aging reinforced concrete (RC) bridges. For capacity models, accurate and applied prediction tools accounting for aging effects are yet to be well established. Current practices usually perform numerical analyses to obtain time-variant capacity models, which are time-consuming particularly when multi-source structural and environmental uncertainties are considered and sometimes even suffer computational non-convergence. To address these issues, this study leverages a rigorously optimized artificial neural network architecture to develop data-driven models for rapid estimates of probabilistic curvature capacity of corroded circular RC bridge columns with flexural failure modes. An extensive database of multi-level curvature limit states (i.e. slight, moderate, severe, and complete) is created through experimentally validated moment–curvature analyses. A new threshold for the moderate limit state is defined based on the strain of core concrete, rather than cover concrete, to account for the potential full erosion of the cover with drastic corrosion. The data-driven probabilistic capacity models are applied to aid the lifetime seismic fragility assessment of a typical highway bridge, where the spectral acceleration at 1.0 s (Sa-10), peak ground velocity (PGV), and Housner intensity (HI) are found consistently, for the first time, as optimal intensity measures for probabilistic demand modeling of RC columns with different extents of aging effects. For the ease of application, the database and code for the data-driven probabilistic capacity models are accessible at https://bit.ly/3uAa8EY .

Blast performance of RC columns with different levels of concrete grades and reinforcing ratios

AbstractThe present article aims to study the behavior of RC columns under blast loading. A nonlinear dynamic Three‐Dimensional (3D) Finite Element FE model‐based explicit solver available in ABAQUS Software is used. A parametric study is investigated to enhance the blast resistance of RC columns under three different scaled distances z of an explosion, that is, 0.23, 0.5, and 1.07 m/kg1/3 for close, intermediate, and Far in‐distance. In addition, three levels of concrete grades are used, which are Normal Strength Concrete (NSC), High Strength Concrete (HSC), and Ultra High‐Performance Concrete (UHPC). The study also considers Three reinforcement ratios for longitudinal and transverse reinforcement ratios of (ρL = 1.28%, 2.4%, and 3.1%) and (ρs = 0.6%, 0.9%, and 1.35%), respectively. Further, three different Axial Load Ratios, ALR = 0.01, 0.2, and 0.4, are considered to examine the effect of increasing ALR on the RC column under close explosion. For more investigation, the parametric analysis considers two geometrical shapes of RC columns (square and circular). The material behaviors of concrete and reinforcing steel bars are represented using Concrete Damage Plasticity (CDP) and Johnson–Cook (J–C) models, respectively, available in ABAQUS Software. The FE model has been initially validated against experimental study. The FE‐predicted deflection and damage were observed and agreed with the practical cases. In addition, the parametric study's results demonstrate that the RC column's blast deflection is significantly reduced with increasing reinforcement ratios. However, increasing concrete grade could efficiently reduce blast damage and deflection. Furthermore, compared with NSC, UHPC significantly reduced maximum damage and deflection by around 60% for square and 55% for circular columns, respectively.

Local buckling behavior and reinforced mechanisms of short circular timber columns confined with bamboo scrimber

Developing sustainable high-performance bamboo scrimber (BS) as structural and reinforcing materials is significant. BS was used as reinforcing material to increase ancient timber columns' load-bearing capacity and safety via a damage-free strengthening method. The BS panels were fastened to the surface of the wooden columns by spaced steel strips. The spacing of the steel strips was the important factor in balancing the appearance of the confined reinforced timber columns with maximizing the strength of the confined panels. In this study, eight short circular wooden columns reinforced with BS with varying spacing of steel strips were fabricated and tested under axial compression. Each specimen's damage characteristics, load-carrying capacity performance, and strain coordination were analyzed and compared. The reinforcement method has a significant effect, and the reinforcement system of all specimens provides an additional load-bearing capacity of more than 48.3 % with about 38 % increase in cross-section area. The load-bearing capacity decreases significantly with increasing the spacing of steel strips. When the steel strips' distance is more than 363 mm (the corresponding slenderness ratio is 41), the confined panel showed significant buckling behavior from the beginning of loading. In contrast, the confined panels of the other circular reinforced timber column showed buckling and load drop only near the peak load, which takes full advantage of the strength of the BS material. The strain growth trends of the confined panels and core column were similar, although the strain of the confined panels' bending offsets some of the compressive strain, which was evidence that they were synergistically stressed under axial compression. The part of confined slats between the steel strips was intercepted as a compression bar, and the commonly used equation for the load-bearing capacity of a flexible bar was introduced. Various flex rod equations based on material properties were calculated and compared to the test results. The calculations showed that the buckling equation suggested by Euler and CSA086-19 had the best agreement with BS materials with similar proportional limits and ultimate strength. BS as a flex rod was suggested with a slenderness ratio not exceeding 32, and a general equation for calculating the steel strip spacing considering the material thickness was proposed for construction reference.

Experimental study on the behavior of small-scaled circular and square RC columns under various loading conditions and corrosion effect

Reinforced concrete columns are vital load-bearing elements, responsible for transferring vertical loads and resisting lateral forces. While numerous factors govern column performance, this study pinpoints cross-sectional shape, transverse reinforcement configuration, and the corrosive threat as its primary areas of investigation. Thus, 20 small-scaled (1/8th scale) RC columns (square and circular, with ties or spirals) were tested under various loading conditions. Columns were divided into five groups. A preliminary test was conducted to determine individual axial load capacity through failure under axial compressive loading. The main test then explored their behavior under combined axial load and variable lateral drift compared to their behavior at two corrosion levels 15% and 25%. While corrosion levels were roughly achieved, uneven distribution due to the accelerated process concentrated pitting near construction joints, impacting reinforcement more than rebar. Results confirmed the efficacy of spirals in enhancing capacity, particularly for circular columns where they also increased lateral load capacity. However, spirals also amplified corrosion vulnerability in circular columns, suggesting a steeper decline in performance at higher corrosion levels. Two key models were derived from analyzing the recorded data: normalized total dissipated energy and normalized absolute peak load. Future research should prioritize exploring column behavior under a wider range of combined loads and corrosion levels to refine and validate these models.

Interaction and compatibility between steel and concrete of circular CFST stub columns with high-strength materials

To promote the application of high-strength-materials in concrete-filled steel tubular (CFST) columns, finite element modeling, and parametric analysis were conducted on circular CFST stub columns filled with normal-strength concrete (NSC) and ultra-high strength concrete (UHSC). For simulating properties of concrete under passive confinement, a three-dimensional constitutive model for NSC and UHSC was established, of which the stress-strain relation and evolution of dilation angle are both related to confining pressure and axial plastic strain. The model was verified by tests of CFHSST (concrete-filled high-strength steel tube) and UHSCFST (ultra-high-strength concrete-filled steel tube), demonstrating that the interaction between concrete and steel tube can be revealed correctly. Parameter analysis of CFST stub columns filled with NSC and UHSC was carried out, with the grade of steel tube covering from Q235 to Q890 and the D/t ratio ranging from 8.9 to 75. With the decrease of D/t ratio, the deformation capacity and post-peak performance of columns are improved. A recommended range of steel contribution ratio of UHSCFST was proposed for the consideration of cost and safety, which is 25% ∼ 63%. Based on the analysis of interaction between concrete and steel tubes, the compatibility of the two materials is recommended, of which the yield of steel tube occurs after contact with concrete and before the concrete reaches its peak strength. Besides, the formula in EC4 overestimates the load-bearing capacity of CFST stub columns with high-strength materials. Therefore, a modified formula was proposed that reduces the enhancement factor of concrete strength and enables a safer prediction of load-bearing capacity.

Predictive modeling of aramid fiber reinforced polymer confinement for improved compressive strength in circular concrete columns

Fiber Reinforced Polymers (FRPs) have gained significant attention in the field of structural engineering due to their high strength-to-weight ratio, corrosion resistance, and ease of application. Among various types of FRPs, Aramid Fiber Reinforced Polymers (AFRP) stand out for their exceptional tensile strength and durability, making them ideal for confining concrete columns to enhance their compressive strength. This study aims to leverage these benefits by predicting the compressive strength of circular concrete columns confined with AFRP using Artificial Neural Networks (ANNs). To develop and validate the ANN model, a comprehensive dataset consisting of 190 samples was employed during the training phase, while an additional set of 33 samples was used for validation. The performance and predictive capabilities of the ANN model were thoroughly assessed through extensive testing and direct comparison with experimental results, which demonstrated the model’s high accuracy and reliability. Moreover, a detailed parametric study was conducted to examine the influence of various input parameters on the compressive strength prediction. The findings from this study offered significant insights into the effects of various parameters on the predicted outcomes, including column diameter, unconfined concrete strength and strain, as well as AFRP confinement parameters such as thickness, tensile strength, elastic modulus, and strain. Notably, the sensitivity analysis underscored the profound impact of the tensile strength of AFRP on the ANN model's predictive accuracy. The research offers a robust tool for engineers, enabling them to estimate the compressive strength of AFRP-confined circular concrete columns accurately. Additionally, it provides crucial insights that are instrumental in optimizing the design and application of AFRP wrapping or tube-encased methods within the realm of structural engineering. Overall, this research marks a significant step forward in the field of structural engineering, providing a valuable predictive tool and offering insights that can lead to the development of more resilient and sustainable infrastructure.

Numerical investigation and design methods of the local buckling of WAAM stainless steel circular hollow section stub columns

3D printing is an advanced technology that has been used in biomedical and automotive engineering, and has raised a significant response in civil engineering. Wire and arc additive manufacturing (WAAM), a metal 3D printing technology, has prospective applications in steel construction because it can fabricate large-scale structural members at an acceptable cost and manufacturing efficiency. Fundamental studies are still urgently needed to realize its engineering application. However, due to the irregular geometric features, limited studies on the structural performance of WAAM components, particularly the numerical studies, have been carried out. To this end, a numerical investigation on the local buckling of WAAM stainless steel circular hollow section (CHS) stub columns under axial compression has been conducted and presented herein. The finite element (FE) models were established and validated against the existing experimental research. Parametric studies were subsequently carried out to broaden the cross-sectional resistance data pool using the developed FE models. The applicability of the cross-section design provisions specified in EN 1993-1-4:2006 + A2:2020, ANSI/AISC 370-21 and the continuous strength method (CSM) for the design of WAAM CHS was evaluated according to the experimental and FE results. Furthermore, a modified design method with improved accuracy was suggested.

Experimental behavior of axially loaded circular high-strength concrete-filled high-strength steel tubular stub columns after exposure to fire

The high-strength concrete-filled high-strength steel tubular (HCFHST) column is an innovative type of high-performance steel-concrete composite component, which has a broad prospect for engineering applications. To investigate the axial compressive behavior of post-fire HCFHST stub columns with circular cross-sections, twenty-five specimens were heated following ISO 834 standard fire and then loaded to failure under axial compression after being cooled. The effects of various heating durations, concrete and steel strength on the temperature distribution, spalling of the steel-concrete interface, post-fire ultimate bearing capacity and axial stiffness were analyzed. The residual ultimate capacity and axial stiffness of HCFHST stub columns experience a pronounced decrease as the heating duration increases. High strength steel has no significant contribution to the enhancement of the post-fire axial stiffness of HCFHST stub columns, and the effect level of high-strength concrete on the failure load of composite columns subjected to different heating durations is similar. Finally, the applicability of relevant equations for the residual compressive capacity of the ordinary strength CFST column to HCFHST stub columns was evaluated. The evaluation results revealed that available methods of conventional strength CFST stub columns cannot obtain accurate post-fire resistance predictions of circular HCFHST stub columns.

An analytical model for axially compressed circular concrete-filled steel tubular (CFST) short columns with varied confinement factors

Accurate evaluation of the load-strain behavior of axially compressed concrete-filled steel tube (CFST) short columns is pivotal for engineering structures, and depends on precise prediction of the hoop-axial strain response. This study introduces a two-stage hoop-axial strain relationship that incorporates the initial Poisson's ratio and elastic limit to account for the initial linearity of concrete, and a reduction coefficient to take into account the effect of concrete strength on lateral deformation properties, based on a widely used hoop-axial equation. Experimental validation across a definite concrete strength range of 28 MPa to 125.3 MPa reveals improved predictions for the dilation rate of CFST columns subjected to axial compression, particularly for those columns fabricated with high-strength concrete (> 100 MPa). Subsequently, an analytical model consisting of the proposed two-stage strain relationship, a confined concrete model with inflection-point strain and residual strength, and the biaxial stress-strain relationship of steel tube is then established to estimate the compressive behavior of circular CFST short columns. Experimental verification over a range of confinements (confinement factor from 0.289 to 2.138) demonstrates the ability of the proposed analytical model to accurately capture the load-strain curves of circular CFST short columns, especially the post-peak behavior of those with confinement factors less than 1. The performance of the established analytical model in assessing the axial load-carrying capacity of circular CFST stub columns is investigated using a database assembled from available studies.

Probabilistic Postearthquake Vertical Load-Carrying Capacity Loss Model and Rapid Functionality Assessment for Reinforced Concrete Circular Bridge Columns

Probabilistic Postearthquake Vertical Load-Carrying Capacity Loss Model and Rapid Functionality Assessment for Reinforced Concrete Circular Bridge Columns

Estimating the axial strain of circular short columns confined with CFRP under centric compressive static load using ANN and GRA techniques

This investigation introduces advanced predictive models for estimating axial strains in Carbon Fiber-Reinforced Polymer (CFRP) confined concrete cylinders, addressing critical aspects of structural integrity in seismic environments. By synthesizing insights from a substantial dataset comprising 708 experimental observations, we harness the power of Artificial Neural Networks (ANNs) and General Regression Analysis (GRA) to refine predictive accuracy and reliability. The enhanced models developed through this research demonstrate superior performance, evidenced by an impressive R-squared value of 0.85 and a Root Mean Square Error (RMSE) of 1.42, and significantly advance our understanding of the behavior of CFRP-confined structures under load. Detailed comparisons with existing predictive models reveal our approaches' superior capacity to mimic and forecast axial strain behaviors accurately, offering essential benefits for designing and reinforcing concrete structures in earthquake-prone areas. This investigation sets a new benchmark in the field through meticulous analysis and innovative modeling, providing a robust framework for future engineering applications and research.

Research on Mechanical Properties of Concrete-Filled Double-Skin Circular Steel Tubular Columns Stiffened by Perforated Steel Plates Under Axial Compression

Research on Mechanical Properties of Concrete-Filled Double-Skin Circular Steel Tubular Columns Stiffened by Perforated Steel Plates Under Axial Compression

Behavior of circular concrete-filled double-skin aluminum alloy tubular stub columns: Test, modeling and confinement-based design

Concrete-filled double-skin steel tubular members have been widely adopted in marine structures, thereby being constantly subjected to harsh corrosive environment. This has triggered the emergence of concrete-filled double-skin aluminum alloy tubular (CFDAT) members of late, wherein aluminum alloy tube is taken as an excellent corrosion-resistant material. Nevertheless, the design guidelines of CFDAT columns have not yet been incorporated into existing international standards due to the absence of relevant research, hindering their structural applications. To this end, this study aims to further investigate the behavior of circular CFDAT stub columns under concentric loading and to clarify the confinement mechanism of this member. In total, 12 CFDAT stub columns were axially tested and the corresponding experimental results were discussed. The research findings showed that the ultimate load of CFDAT specimens is significantly affected by the hollow ratio, concrete strength and diameter-to-wall thickness ratio of outer tube. Using the test results, finite element (FE) model was developed and then utilized to ascertain the confinement mechanism of CFDAT columns, followed by a comprehensive parametric study of such members. Subsequently, the feasibility of current design formulas for the design of CFDAT columns was evaluated against the experimental results and outputs of FE analysis, accompanied by an obvious prediction deviation. Accordingly, a new confinement coefficient reflecting the confinement effect of concrete strength in such members was suggested, which can reasonably capture the interaction between of aluminum alloy tubes and sandwiched concrete. Using this coefficient, a unified design model for estimating the ultimate load of CFDAT and CFAT members was suggested and has better predictive ability than existing design codes and empirical formulas.

Axial compression performance of rubberized concrete-filled steel tubular stub columns after fire exposure: Experimental investigation and calculation models

Rubberized concrete (RuC) has emerged as a promising eco-friendly solution for structural elements, offering improved energy dissipation, damping characteristics, and ductility. Incorporating rubber particles into concrete-filled steel tubular (CFST) columns presents an environmentally conscious alternative for various structural applications. However, understanding its performance post-fire is crucial for safe design application, an area currently lacking comprehensive research. This study investigates the structural behavior of sixteen axially loaded circular RuCFST columns after exposure to fire. The columns, with diameters of 219 mm and 377 mm, are filled with normal concrete and RuC, containing 5 %, 15 %, and 30 % replacement of natural fine and coarse aggregate with rubber particles. Following ISO-834 fire standards, the specimens undergo elevated temperatures and subsequent application of compressive axial loads to determine their post-fire behavior. Analysis includes examination of failure modes, temperature-time relationships, axial load-deformation curves, and strain and stress development in the columns. Microstructural analysis using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) is conducted to study internal morphology before and after exposure to high temperatures. Results indicate non-uniform and nonlinear distributions of maximum temperatures across cross-sections, with historical temperature affecting residual capacity more significantly with increased rubber content and decreased column size. Load-bearing capacities decrease by up to 30 % and 22 % for small and large RuCFST columns, respectively, after exposure to fire. Residual axial stiffness also declines, with reductions of nearly 55 % and 42 % for small and large columns, respectively. In contrast, ductility improves in fire-exposed specimens, with columns having a 30 % rubber replacement ratio showing the highest enhancement. A novel method for calculating post-fire residual load capacity based on the average historical maximum temperature is introduced, demonstrating high accuracy and offering a valuable tool for assessing and reinforcing RuCFST columns after fire exposure.

PERANCANGAN APLIKASI PERHITUNGAN KUAT NOMINAL KOLOM BETON BERTULANG BERBASIS APLIKASI ANDROID

Nowadays, the use of applications which is to analyze or to design in civil engineering are necessary. Besides being able to solve the analysis and design problem, the use of applications is an effective for computational time problems compared to manual calculations. Column is one of the most crucial elements in a building construction where the role of the column is to support and distribute the loads on the building structure. In general, in designing a column, column interaction diagram with a certain cross section is made and compare the capacity of the column sections (Pn and Mn) from the column interaction diagram with the required strength values (Pu and Mu). Android is an operating system on smartphones and is popular nowadays. The aim of this research is to develop an Android-based application using Android Studio with Java programming language to create a column interaction diagram of several types of columns, i.e. square column with 4 (four) side reinforcement, square column with reinforcement on 2 (two) sides, and circular columns. The results obtained from the developed application are compared with manual calculations (reference). The difference of result obtained is less than 1% which means that there is no significant comparison between the designed application and manual calculations (reference). Therefore, the developed application can be practically used as an alternative in designing columns.

Rainbow Trapping with Engineered Topological Corner States and Cavities in Photonic Crystals

AbstractThis work presents a pioneering photonic crystal (PC) heterostructure design exploiting tailored topological corner states and cavities to unleash a fascinating topological rainbow effect. This effect arises from the strategic integration of a nontrivial topological PC with sharp corners within a trivial PC matrix, resulting in a heterostructure rich in corner states and cavities. The critical innovation lies in manipulating the sector angle of circular columns, granting dynamic control over the rainbow effect and light localization. This manipulation induces distinct group velocities for different light frequencies, leading to their separation and localization at specific corner states. This remarkable “rainbow trapping” phenomenon manifests as highly confined light exhibiting exceptional resilience against disorder. These findings illuminate a pathway toward crafting next‐generation photonic devices boasting unparalleled functionalities. The reconfigurable rainbow trapping holds immense potential for applications in wavelength division multiplexing, optical sensing, and even venturing into quantum information processing.

Prediction of axial capacity of corrosion-affected RC columns strengthened with inclusive FRP

The primary cause behind the degradation of reinforced concrete (RC) structures is the propagation of corrosion in the steel-RC structures. Nowadays, numerous retrofitting techniques are available in the construction sector. Fiber-reinforced polymer (FRP) is one of the efficient rehabilitation measures that can be implemented on corroded structures to enhance structural capacities. However, the estimation of axial strength of FRP-strengthened columns affected by corrosion has been a challenging and tedious task in the laboratory as well as on the site. Considering such shortcomings, the prediction of axial capacity can be done using various analytical methods and artificial intelligence (AI) techniques. In this study, a comprehensive dataset of circular columns was extracted from the literature to predict the axial strength of FRP-wrapped and unstrengthened RC corroded columns. The laboratory results from the assembled dataset were compared to corresponding values estimated using relevant design codes provided by American Concrete Institute (ACI 440.2R-17 and ACI 318-19), and Bureau of Indian Standard (IS 456:2000). Five machine learning models were employed on columns to predict the axial load carrying capacity of FRP-strengthened and un-strengthened RC corroded columns. The results discovered that the extreme gradient boosting (XGBoost) model achieves superior accuracy with the least errors and could be used by the scientific community and FRP applicators to forecast the axial performance of corroded columns strengthened with and without FRP. The findings from the design codes revealed that prediction errors were available in high margins. Furthermore, feature importance analysis was conducted using the Shapley Additive exPlanation algorithm to know the contribution and influence of each input parameter on axial capacity. The feature analysis found that unconfined compressive strength of concrete plays an important role in deciding the axial capacity of columns. Moreover, to enhance the precision of axial capacity computation and improving the overall efficacy in engineering practice, a web-based user-friendly interface was developed for FRP applicators and engineers to simplify the process.

Axial compressive properties of intermediately slender circular ancient timber columns reinforced with high-performance bamboo-based composites

The use of circular, medium-length timber columns reinforced with high-performance bamboo-based composite (HPBBC) is a sustainable reinforcement method without damage. This study conducted axial compression tests on seven circular medium-length wooden columns strengthened using the sustainable reinforcement method with different HPBBC materials and reinforcement thicknesses. The test results revealed that bamboo scrimber with Sinocalamus affinis fibers (BSS) of 10, 20, and 30 mm thicknesses, respectively, increased the supplementary load-bearing capacity by 29.30 %, 85.74 %, and 153.68 % compared to unreinforced wooden columns. The transverse deformation of the wooden columns destabilized the reinforcement system when the high-stiffness BSS was used as reinforced materials. In contrast, the wooden columns were destabilized broken by the transverse deformation of the hollow structures made of laminated bamboo lumber (LBL) and bamboo scrimber with Moso bamboo fibers (BSM). Using reinforcing materials with good stiffness can prevent the destabilization of timber columns. Based on the damage model, an equation of the load-bearing capacity of sustainable reinforcement wood columns based on the buckling stress of the columns was proposed. The calculated results revealed that the equations proposed in this study agree with the test result when the Euler buckling stress is used.

Axial partial compressive behavior of round-ended concrete-filled steel tubular columns

The paper conducted 19 partially and 5 fully loaded tests on round-ended concrete-filled steel tubular (CFST) columns. These tests revealed that the ultimate strengths of round-ended CFST columns under partial load declined as the cross-sectional aspect ratio or partial compression area ratio increased. However, the use of a top plate effectively enhanced their ultimate strengths. In addition, a finite element model (FEM) was utilized to generate 487 large-size models to explore the confinement effect, stress distribution, and parametric effects. Since there are no specific design standards available for round-ended CFST columns, the paper has evaluated the applicability of design methods provided in Eurocode 4, AISC 360–16, and Chinese code GB50396 which are intended for circular, square, or elliptical CFST columns for round-ended CFST columns under partial load. However, these existing design techniques showed inaccurate and dispersed resistance predictions for round-ended CFST columns. Therefore, an effective simplified method for forecasting the resistance predictions of round-ended CFST columns under the partial load has been proposed based on the testing results and FEM analysis.

Novel prefabricated FRP bar reinforced UHPC shells for column strengthening: Development and axial compression tests

Reinforced concrete (RC) columns are vital components in the construction of large-scale coastal structures, including bridges and piers. Over time, exposure to marine and nearshore environments can lead to a significant deterioration of RC columns. This study introduces an innovative method for strengthening circular concrete columns using two semi-circular shells made from fiber-reinforced polymer (FRP) bar reinforced ultra-high-performance concrete (UHPC), referred to as FRU shells. These semi-circular FRU shells can be easily assembled on-site by connecting them with grouting sleeves, forming a circular tubular jacket that encloses the existing concrete columns. In this study, compression tests were conducted to assess the effectiveness of the proposed strengthening technique. The influence of external FRU jackets with different FRP spacing and various jacket heights was discussed. The results demonstrate that this strengthening approach significantly improves the initial stiffness, ultimate load-bearing capacity, and ductility of the existing circular concrete columns. A theoretical model for predicting the compressive strength of the strengthened columns is proposed and verified against the test results. The proposed prefabricated strengthening system has the potential to be implemented in an underwater environment and to streamline in-situ construction processes for strengthening of various kinds of columns.