Finite Element Modeling and Experimental Verification of CFRP Confined CFST Columns Under Compression

1. Introduction

Concrete-filled steel tube columns are widely used in structural engineering because they combine high load-carrying capacity with relatively compact cross-sections, but their performance under compression is often limited by local buckling of the steel tube, especially in thin-walled, high-strength, or slender members [1]. Carbon fiber-reinforced polymer confinement has emerged as a practical strengthening technique for these composite columns because it can enhance strength and ductility, delay outward deformation of the tube, and mitigate local buckling-related deterioration [2]. This strengthening strategy has attracted attention across several related composite systems, including stainless-steel CFST columns, double-skin members, rectangular and circular sections, and offshore-oriented columns, which reflects the broader engineering relevance of confinement-based strengthening under compressive loading [3].

Experimental evidence shows that CFRP confinement can improve axial compression behavior and restrain local buckling, but the gain is not uniform because it depends on section shape, tube geometry, material strength, loading condition, and wrapping configuration [4]. Increasing the number or thickness of CFRP layers often increases axial resistance, with one numerical study reporting gains from 8.5% for a single 1.2 mm sheet up to 44.5% for four sheets, although other studies show that the effect of CFRP layers can be secondary to parameters such as outer tube width-to-thickness ratio, tube diameter, or steel strength [5]. Partial or discontinuous wrapping reduces strengthening efficiency because local buckling tends to develop in unconfined regions, indicating that confinement continuity is a major variable in column response rather than a minor detailing choice [6,7].

Evidence from eccentric and combined-loading studies also shows that increasing eccentricity or slenderness reduces ultimate load and strain capacity, even when CFRP is present, which confirms that confinement improves behavior but does not eliminate geometric sensitivity [8]. Ref [9] indicate that further indicate that the main strengthening mechanism is not a direct increase in the axial capacity of the steel tube itself, but an indirect confinement effect that improves the response of the concrete core and delays instability in the composite section [10]. Even adjacent work on hollow steel columns reaches a similar conclusion, showing that CFRP gives only modest improvement to yield capacity but can provide more substantial gains in ultimate capacity within an effective confinement range [11].

Although the beneficial role of CFRP confinement is now well established, the internal stress transfer, contact behavior, and confinement interaction among the steel tube, concrete infill, and FRP jacket remain difficult to observe directly in laboratory tests [12,13]. For this reason, finite element modeling has become a central research tool in the analysis of CFRP-confined CFST columns, since it enables the full loading process, material interaction, and local instability to be studied in detail beyond the limits of physical instrumentation [14]. Across the literature, ABAQUS is commonly used to construct three-dimensional nonlinear models of confined composite columns, and these models are routinely verified against experiments using failure modes, load-displacement or load-shortening curves, and strain development [15].

This modeling framework typically incorporates constitutive laws for concrete, steel, and CFRP together with material, geometric, and contact nonlinearities, and in some cases includes initial imperfections derived from buckling modes to better reproduce the actual behavior of tested specimens [16]. Validated numerical models are then used not only to reproduce observed behavior, but also to clarify stress distribution, component interaction, contact pressure evolution, and the relative contribution of each material to the column’s axial resistance [17]. They also support broad parametric studies that would be difficult to perform experimentally, covering variables such as concrete compressive strength, steel tube thickness, CFRP thickness or number of layers, confinement length, slenderness, eccentricity, and section dimensions [18]. These parametric investigations repeatedly show that material and geometric properties act together, with tube diameter, tube thickness, outer tube strength, concrete strength, and steel yield strength often exerting stronger influence on ultimate capacity than CFRP quantity alone [19]. The outputs of experimentally verified finite element studies are also frequently translated into simplified analytical or empirical design models, including axial capacity equations, interaction relationships, and practical prediction formulas for engineering use [20].

Against this background, the purpose of the present study is to develop reliable finite element models for CFRP-confined CFST columns subjected to axial compression and to verify those models against experimental observations so that the structural response of the composite columns can be simulated with confidence. The study adopts ABAQUS to represent the behavior of the concrete core, steel tube, and FRP confinement through appropriate constitutive models, with validation based on the agreement between numerical and experimental results in terms of load-displacement response, ultimate strength, and observed failure modes. Within this framework, the research is directed toward evaluating how confining pressure and key material and geometric parameters influence the uniaxial behavior of the columns, with particular emphasis on different infilled concrete compressive strengths, steel tube thicknesses, and CFRP layer thicknesses. The objectives are therefore threefold: (1), to establish and experimentally verify a nonlinear finite element model capable of reproducing the compressive behavior of CFRP-confined CFST columns; (2), to assess the effectiveness of CFRP confinement in improving strength, stiffness, and failure performance under axial loading; and (3), to use the validated model to interpret the structural mechanics of the confined composite section and provide evidence that can support practical analysis, design, and strengthening applications. In this way, the study addresses the continuing need for experimentally grounded numerical tools that can explain the confinement mechanism more clearly and predict the compressive performance of CFRP-confined CFST columns more reliably for engineering practice.

2. Methodology

2.1. Finite Element Modeling

The finite element method was employed to investigate the axil behavior of concrete-filled steel tube (CFST) columns confined with CFST sheets as Figure 1, thereby reducing the dependence on full- scale experimental testing and enabling systematic parametric studies. In this work, nonlinear simulations were carried out using ABAQUS, and the numerical model were calibrated to reproduce both the pre peak and post-peak response of confined concrete, local buckling of the steel tube, and the composite interaction between the different constituent material. Under axial compression, the concrete core tends to expend laterally due to Poisson’s effect, but in CFST columns this expansion is restrained by the surrounding steel tube (and CFRP, when present), generating radial contact pressure at the interfaces and placing the concrete in triaxial compressive stress state. This confinement increases both compressive strength and strain capacity and delays crack initiation and propagation, thereby enhancing overall ductility and energy abortion. Simultaneously, the literal pressure exerted find the concrete induces hoop tension in the steel tube, getting to biaxial stress state that improve composite action and increases the axial carrying capacity of the member beyond the peak load.

In the finite element model, the concrete core and steel-tube wear discretize it using eighth-node Rajesh integration solid elements (type C3D8R), while the CFRP sheet was modeled using four-node reduced integration shell element type S4R which are suitable for thin orthotropic laminate layers. The structural domain discretizes it into small elements connected at nodes to form a computational mess and ABAQUS was used to define the geometry generate, the mesh assign material properties and perform nonlinear analyses [21]. The equilibrium equation for each element was assembled into a global system and solve it to obtain their structural response under the specified loud and boundary condition. Appropriate contact interaction we’re defining between the steel tube and concrete core and between there CFRP and steel surface to realistically capture radio confinement and composite action. Model accuracy was evaluated by comparing numerical dedication with experimental load, displacement curves, ultimate axial strength and observed failure modes. Good agreement between simulation and test result was used as a primary creation for model validation before conducting parametric analysis [22].

2.2. Concrete Material Modeling

The nonlinear behavior of concrete was modeled using the Concrete Damage Plasticity (CDP) model available in ABAQUS. This constitutive model is based on the plastic-damage theory originally proposed by Lubliner et al. [23] and subsequently extended by Lee and Fenves [24] to account for cyclic loading effects in concrete structures. The CDP model combines isotropic damaged elasticity with isotropic tensile and compressive plasticity to represent both in elastic deformation and progressive defense protection due to cracking and crushing. To fully characterize the material response, four aspects must be defined: (i) the compressive and tensile stress–strain relationships, (ii) the damage evolution law, (iii) the yield function, and (iv) the plastic flow rule.

Under uniaxial compression, concrete exhibit an initial liner elastic response up to the First field yield, followed by non-liner hardening up to the peak stress and subsequent softening as microcracking and crushing develop. Under uniaxial tension, the response is liner elastic up to the tensile strength, after which cracking occur Stiffness rapidly degrades. In the CDP model, these phenomena are represented through compressive and tensile damage variables, $d_c$ and $d_t$, which range from 0 for undamaged material to 1 for fully damaged material, and through separate definitions of inelastic and plastic strains in compression and tension. The initial elastic modulus of undamaged concrete is denoted by E_o, while ${\epsilon }_c^{in}$and ${\epsilon }_c^{pl}$ represent compressive inelastic and plastic strains, respectively. Similarly, ${\epsilon }_t^{ck}$and ${\epsilon }_t^{pl}$ denote tensile cracking and plastic strains.

Figure 2. Concrete Damage Plasticity material: uniaxial response in compression (a) and tension (b) [Redrawn based on ABAQUS/CAE Documentation].

Figure 2. Concrete Damage Plasticity material: uniaxial response in compression (a) and tension (b) [Redrawn based on ABAQUS/CAE Documentation].

The yield surface in the CDP model is controlled by the ratio of biaxial to uniaxial compressive strength (${\sigma }_{bo}/{\sigma }_{co}$) and the ratio of the second stress invariant on the tensile and compressive meridians (Kc). In this study, the default ABAQUS values of ${\sigma }_{bo}/{\sigma }_{co}$ = 1.16 and Kc = 2/3 were adopted. A non-associated plastic flow rule based on the Drucker–Prager hyperbolic potential function was employed. The flow rule was defined using a dilation angle (ψ), eccentricity (ε), and a viscosity parameter. The default eccentricity value of 0.1 was used, while a dilation angle of 30° was adopted in accordance with previous studies. A small viscosity parameter was also introduced to improve numerical stability and convergence during the nonlinear analysis.

The elastic properties of concrete were defined by its modulus of elasticity (Ec) and Poisson’s ratio. In this study, Poisson’s ratio of 0.20 was adopted, while the modulus of elasticity was calculated according to the provisions of ACI 318 as follows:

$$E_s=4700\sqrt{f_c^{\prime }}$$

The material modeling of concrete considers the effects of confinement during axial compression. When subjected to loading, plain concrete exhibits lateral expansion, but in concrete-filled steel tubes, this expansion is restricted by the surrounding steel, resulting in a triaxial stress condition. Since concrete behavior is pressure dependent, confinement enhances its strength and ductility by raising compressive resistance and postponing the onset of cracking. The model introduced by Tao et al. [28] incorporates confinement effects into the concrete stress-strain relationship by applying a confinement factor (ξ_c), which modifies the stress-strain curve to reflect the triaxial stress state.

$${\xi }_c={\displaystyle \frac{A_S{f}_y}{A_c{f}_c^{\prime }}}$$

(1)

Where A_s and A_c denote the cross-sectional areas of the steel tube and concrete, respectively. f_y is the steel yield stress, and f'_c is the concrete compressive strength.

The stress-strain model proposed by Tao et al. [25] is shown in Figure 3. The ascending branch of the stress-strain curve follows the model of Samani and Attard [26]. The following expressions were used:

$${\displaystyle \frac{\sigma }{f_c^{\prime }}}={\displaystyle \frac{A.X+B.X^2}{1+\left(A-2\right)X+(B+1)X^2}}$$

(2)

Where $X=\epsilon /{\epsilon }_{co};A={\displaystyle \frac{E_c{\epsilon }_{co}}{f_c^{\prime }}}$ $;B={\displaystyle \frac{{(A-1)}^2}{0.55}}-1$

$${\epsilon }_{co}=0.00076+\sqrt{\left(0.626f_c^{\prime }-4.33\right)\times {10}^{-7}}$$

(3)

Where $f_c^{\prime }$ is expressed in MPa. Ec is concrete modulus of elasticity. The strain at point B is determined as follows:

$${\displaystyle \frac{{\epsilon }_{cc}}{{\epsilon }_{co}}}=\exp \left(k\right),k=\left(2.9224-0.00367f_c^{\prime }\right){\left({\displaystyle \frac{f_B}{f_c^{\prime }}}\right)}^{0.3124+0.002f_c^{\prime }}$$

(4)

where$f_B$ is the confining stress at point B, which can be calculated as follows:

$$f_B={\displaystyle \frac{0.25\left(1+0.027f_y\right)exp\left(\frac{-0.02\sqrt{B^2+D^2}}{t}\right)}{1+1.6\times {10}^{-10}{\left(f_c^{\prime }\right)}^{4.8}}}$$

(5)

Where B and D are the dimensions of the steel tube.

The descending branch of the concrete model is characterized by the equation introduced by Binici [27]:

$$\sigma =f_r+\left(f_c^{\prime }-f_r\right)exp\left[-{\left({\displaystyle \frac{\epsilon -{\epsilon }_{cc}}{\alpha }}\right)}^{\beta }\right]$$

(6)

Where $f_r$ represents the residual stress, while α and β determine the form of the softening branch. According to Tao et al. [28], these parameters are optimized through various trial values to achieve the best agreement between experimental and numerical results. The value of β is set at 0.92 for rectangular columns and 1.2 for circular columns. The definitions of α and $f_r$ provided in Eqs. (7a) and (7b), respectively.

$$\alpha =0.005+0.0075{\xi }_c$$

(7a)

$$f_r=0.1f_c^{\prime }$$

(7b)

A comparison between experimental and numerical data showed that the residual stress model effectively captures the post-peak response of the CFST columns subjected to loading. Therefore, the residual strength of the concrete was determined using the formula suggested by Susantha et al. [28].

That means Concrete does not immediately lose all its strength after reaching peak stress. Even after significant cracking and crashing, it retains some load-carrying capacity known as residual strength. The residual stress model accounts for this remaining strength and enables a more realistic simulation of concrete behavior after peak stress. For CFST columns, the contact interaction between the steel tube and concrete core was modeled to accurately capture the confinement effect. The radial pressure exerted by the steel tube induces a triaxial compressive stress state within the concrete, thereby increasing its strength and strain capacity while mitigating crack formation. In ABAQUS, model development proceeded with mesh generation (see Figure 4). Various meshing techniques, including structured, unstructured, and adaptive approaches, were employed to control element distribution and enhance simulation accuracy [29].

The analysis was performed in ABAQUS by applying displacement loading conditions to simulate the structural response. In CFST models, the steel tube and concrete core interact to produce a confinement effect that limits the lateral expansion of concrete under axial compression, generating triaxial compressive stresses and enhancing both strength and ductility. Concurrently, the steel tube develops circumferential tensile stresses that improve the composite action and load-carrying capacity of the member.

2.3. Parametric Analysis

A parametric analysis was conducted using the validated finite element model to investigate the influence of key material and geometric variables on the axial behavior of CFRP-confined CFST columns. The parameters considered in this study were the concrete compressive strength, steel tube thickness, and CFRP layer thickness. The structural response was evaluated in terms of load–displacement behavior, ultimate axial strength, and failure mode. The material properties adopted for the analysis are summarized in Table 1, Table 2 and Table 3.

Finite element modeling has been widely applied to structural analysis, heat transfer, and fluid–structure interaction problems [22,30]. This approach provides an effective means of predicting structural performance and assessing design adequacy. Additional references on finite element theory and modeling procedures may be consulted for further guidance and best practices [31,32]. The material properties adopted in the present study are summarized in Table 1, Table 2 and Table 3

3. Result and Discussion

3.1. Experimental Database, Specimens, Materials, and Constitutive Models

A total of seventy-two tested columns, including eighteen CFST and fifty-four CFRP confined CFST columns, were considered to verify FEM analysis results. FRP layers (nf) were 0, 1, 2, or 3. The steel tube thicknesses were 1.8, 2.8, or 3.8 mm, and the nominal compressive strengths for the infilled concrete were 20, 30, or 40 MPa. Concrete mixtures were prepared both with and without polypropylene fiber and silica fumes. For each mixture, three concrete cylinder specimens were tested to determine the actual compressive strength used in the numerical model.

Well-graded crushed coarse aggregates were utilized. Maximum particle size was 25 mm and fineness modulus of 4.93 were employed, while the fine aggregate was river sand, with a maximum size 4.75 mm and a fineness modulus 3.46. Ordinary Portland cement was used in all mixtures. Silica fume was add in slurry form, with approximately 50% solids by mass.mAll column specimens had a length-to-diameter ratio of 2, while different diameter-to-thickness ratios were considered through steel tube thicknesses. Coupon testing was used to assess the steel tube's properties. The steel tube's yield strength (fy) and elastic modulus (Es) were found to be 307 MPa and 230 GPa, respectively.

The columns were externally wrapped with carbon fiber sheets bonded using an epoxy resin. Flat coupon tests on the CFRP provided an elastic modulus (Ef) = 230 GPa, ultimate strain (εfu) = 2.1%, the tensile strength (ft) = 4900 MPa, and the nominal thickness (tf) = 0.34 mm. The epoxy resin was a solvent-free, two-component composition. Components A (resin) and B (hardener) mixed at a weight ratio of a 4:1. According to the manufacturer, the epoxy had an elastic modulus, tensile strength, and shear strength were 15 GPa, 35 MPa, and 13 MPa. The experimental program and test setup are described in detail by Mohammed and Güneyisi [33]. Figure 5 shows a typical failure mode of the CFRP confined CFST column after testing, illustrating the characteristic crushing and buckling pattern under axial compression.

3.2. Overview of FEM Validation and Notation

Model validation was conducted using the experimental results reported by Mohammed and Güneyisi [33]. The influence of the number of CFRP layers, infilled concrete properties and steel tube thickness on the axial load-shortening response and failure modes was examined. The predictive capability of the finite element model was evaluated in terms of the ultimate load capacity and overall load-deformation behavior.

The notation adopted in the figures and tables is as follows. The prefix ‘CF’ denotes CFST layers, and the following digit indicates the number of CFRP layers. The letter ‘t’ followed by numeral specifies the steel tube sickness in millimeters. The designations ‘C’ and ‘CFS’ indicate concrete without and with silica fume and Polypropylene fibers, respectively, and the subsequent number denotes the nominal concrete strength in MPa. For example, CF0t3.8C30 refers to a CFST column with a 3.8 mm steel tube and concrete of nominal strength 30 MPa without silica fume or fibers, whereas CF0t1.8CD20 refers to a column with 1.8 mm steel tube thickness and concrete containing silica fume and polypropylene fiber with nominal strength 20 MPa.

Figure 6 and Figure 7 present representative axial load-shortening curves for specimen with different CFRP confinement level and concrete string including comparison between finite element predictions experimental results and analytical model. Figure 8 illustrated typical filer mode and stress distribution from the numerical simulations for unwrapped CFST specimens, specimens confine only by the steel tube, and specimens confined by both steel tube and CFRP. Table 4 summarizes the compassion between experimental ultimate load capacities $N_{u,\mathrm{e}\mathrm{x}\mathrm{p}}$ and finite element predictions $N_{u,\mathrm{F}\mathrm{E}\mathrm{M}}$ for all 72 columns.

3.3. Effect of CFRP Confinement Level (CF0–CF3)

Figure 6 and Figure 7 show how the number of CFRP layers affects axial load-shortening behavior.

For the C30 specimens with 3.8mm steel tubes (Figure 6), all configurations (CF0–CF3) exhibit an initial linear elastic response, followed by a nonlinear stage as the load approaches the peak capacity. The unconfined specimen CF0t3.8C30 reaches its peak load at a relatively small axial shortening and then it shows a noticeable reduction in load-carrying capacity, indicating the onset of local buckling of the steel tube and crushing of the concrete core. With the addition of CFRP confinement, the peak load increases significantly. CF1t3.8C30 exhibits a moderate improvement in strength and maintains a relatively stable post-peak response. Further increase in confinement in the CF2t3.8C30 and CF3t3.8C30 specimens leads to higher ultimate loads and improved deformation capacity. CF3t3.8C30 demonstrates the highest load capacity and a more gradual post-peak decline, indicating enhanced confinement and delayed damage propagation.A similar trend was reported by Ref [35], who found that increasing the number of CFRP layers reduced post-peak softening and produced smoother axial load-strain curves in square CFRP-steel tube confined concrete specimens.

For the C40 specimens (Figure 7) The axial load–shortening curves display a similar trend. Increasing CFRP confinement level from CF0 to CF3 improves both axial strength and ductility, as evidenced by higher peak loads and larger axial shortenings before failure. The CF0t3.8C40 specimen, without CFRP, shows the lowest peak load and experiences a gradual reduction in load after reaching the maximum capacity, reflecting limited confinement provided only by the steel tube. CFRP confined specimens CF1t3.8C40 and CF2t3.8C40 specimens exhibit improved strength and a relatively stable load plateau after yielding. CF3t3.8C40 achieves the highest axial load and maintains load capacity over a larger range of axial shortenings, demonstrating the most effective confinement.The FEM results also agree well with the experiments, particularly in the pre-peak range, showing that the model captured the main confinement behavior of the CFRP-strengthened specimens [36,37]

Overall, both experimental and FEM results clearly show that increasing the number of CFRP layers enhances axial strength and deformation capacity. The finite element model successfully reproduces these confinement effects, with numerical curves closely tracking the experimental curves, particularly in the pre-peak region.

3.4. Influence of Concrete Strength and Steel Tube Thickness

The axial behavior is also significantly affected by concrete strength and steel tube thickness. Comparing the C20, C30, and C40 specimens forgiven confinement level show that higher nominal concrete strength leads to higher Peak load capacity, as expected from their greater compressive resistance of the core. The axial load shortening core from 40 MPa concrete exhibit higher ultimate load than those 20 and 30 MPa concretes, while retaining the characteristic pattern of an initial liner stage followed by nonlinear hardening and softening.

Steel tube thickness controls confinement efficiency and resistance to local buckling for a fixed concrete stranded and CFRP level, increasing tube sickness from 1.8 mm to 3.8 mm results in higher axial capacity and more ductile post-peak behavior. For example, columns CF3t1.8C30, CF3t2.8C30, and CF3t3.8C30 show progressively higher peak load and improve its softening as steel thickness increases reflecting enhanced confinement by the thicker tube. Similar trend is observed for other concrete strength and CFRP level.

The finite element model reproduces these parametric effects with good accuracy. Numerical peak loads increase with both concrete strength and steel tube thickness and the axial load shortening curves exhibit higher initial sickness and improved ductility for stronger concrete and thicker tube. The combine it influence of internal confinement steel tube and concrete properties and external confinement CFRP layer is well captured by the simulation also the numerical curves remain in the experimental curves due to idealized material and interference modeling.

3.5. Failure Modes and Stress Distribution in FEM

Figure 8 present typical failure mode as stress distribution obtained from the finite element simulation:

Unwrapped CFST specimens fail through extensive concrete crushing and local buckling of the steel tube, leading to a relatively sudden loss of load crying capacity. Stress concentration develops near mid height for regional geometric imperfection, causing localized instability. In specimens confined only by steel tube, confinement improves strength and delays buckling, but once local buckling initiates, capacity decrease Sharpley and damage remain concentrated.

Adding CFRP wraps changes the failure mode significantly. The CFRP layer restrains outward deformation of the steel tube and concrete, promoting a more uniform stress distribution and delaying buckling and crushing. CFRP confined specimens exhibit more distributed cracking, reduced local buckling and a more gradual post peak softening, indicating enhanced ductility and energy absorption. The simulated failure patterns and stress field are consistent with experimental observation, supporting the validity of the adopted material models and interaction definitions.

3.6. Accuracy Assessment of FEM Prediction (Table 4)

Table 4 presents the comparison between experimental ultimate load capacities $N_{u,\mathrm{e}\mathrm{x}\mathrm{p}}$ and finite element predictions $N_{u,\mathrm{F}\mathrm{E}\mathrm{M}}$ for all 72 CFRP-confined CFST columns:

The Table 4 presents a comparison between experimental ultimate load capacity (N_u.exp) and finite element model predictions (N_u.FEM) for axially loaded CFRP-confined CFST columns having different properties. Generally, the results show a strong agreement between FEM and experimental results, indicating that the numerical model is reliable for predicting structural behavior. The ratio N_u.exp/N_u.FEM ranges approximately between 0.83 and 1.08. This narrow range demonstrates that the FEM model could accurately capture the load-carrying capacity with some deviations. In most cases. the ratio is slightly less than 1.0, meaning that the FEM tends to slightly overestimate the strength, which is common due to idealized material properties and perfect bonding assumptions in simulations. The effect of CFRP layers (CF0 to CF3) is clearly reflected in both experimental and FEM results. As the number of CFRP layers increases, the ultimate load capacity consistently rises. This confirms the effectiveness of CFRP confinement in enhancing the axial strength prominently. Besides, the FEM model successfully reproduces this confinement effect. It is also noted that increasing the steel tube thickness of 1.8 mm to 3.8 mm leads to higher load capacities. The FEM predictions follow the same trend as the experimental data, indicating that the interaction between steel tube confinement and CFRP wrapping is well captured in the numerical model, and this trend is reproduced by the FEM model [37]. Additionally, for higher concrete strength of 40 MPa compared to that of 20 MPa, both experimental and FEM results show increased load capacity. It is clearly observed that the FEM model demonstrates high accuracy and consistency in predicting the axial capacity of CFRP-confined CFST columns. It effectively captures the influence of CFRP confinement, steel thickness, and concrete strength with only minor deviations that remain within acceptable limits.

4. Conclusions

Nonlinear finite element models developed in ABAQUS accurately reproduce the axial response of CFRP- confined CFST columns across a board experimental set. Comparison with 72 tested specimens demonstrates strong agreement in pre-peak stiffness, ultimate capacity and observed failure patterns, with Nu,exp/Nu,FEM ratio clustering near unity. CFRP confinement consistently enhances peak load, post-peak ductility and energy absorption and increasing the number of CFRP layers produces progressively higher ultimate loads and more gradual softening. However, parametric results confirm that concrete compressive string it and steel tube thickness frequently control axial capacity to a comparable or greater degree than CFRP quantity, hence CFRP is most effective when combine it with adequate tube geometry and concrete properties. Stress and deformation filed from the simulation show that CFRP primarily restrain outward information of the steel tube improving core trixail stress and delaying local buckling the validated Fe models therefore provide a reliable tool for interpreting confinement mechanism and performing efficient parametric and design studies future work should extend model to eccentric login long term effects and interface bonding tool broaden applicability in design practice.