Search Results (211)

In order to study the mechanical properties of L-shaped columns of recycled aggregate concrete-filled steel tubes (L-RACFST) with a recycled aggregate concrete (RAC) coarse aggregate replacement rate of 100%, three L-RACFST columns with a RAC coarse aggregate replacement rate of 100% were made to carry out axial compression and two-way bias point load tests. The finite element numerical model was verified on the basis of the test. ANSYS was used to investigate the influence of steel strength, steel thickness, width-to-thickness ratio, and eccentricity on the mechanical properties of L-RACFST columns. Results show that: (1) The eccentricity significantly affects the compressive bearing capacity of L-RACFST columns. Compared with the axial compression specimens, the ultimate bearing capacity of the specimens with eccentricities of 40 mm and 80 mm decreases by 18.67% and 24.84%, respectively. (2) An eccentric load will exacerbate the comprehensive bending deformation of the test specimen. (3) During parameter design, eccentricity has a significant effect on the compressive load-bearing capacity of L-RACFST columns with a 100% RAC replacement ratio. However, increasing the steel’s thickness and strength and reducing the width–thickness ratio can effectively compensate for the loss of compression performance caused by eccentricity. The findings of this study provide guidance for the engineering design and application of steel tube RAC composite special-shaped columns with a high replacement rate. Full article

This study investigates the compressive performance of fiber-reinforced polymer (FRP) rebar-reinforced Seawater and Sea Sand Concrete (SSC) columns through an integrated approach combining finite element analysis, theoretical derivation, and machine learning. Finite element models were developed to quantify the influence of key parameters on the ultimate bearing capacity and lateral deflection. The results indicate that the compressive capacity decreases significantly with increasing eccentricity and slenderness ratio. Columns reinforced with steel rebars demonstrated superior load-bearing and anti-lateral displacement capabilities compared to their FRP-reinforced counterparts. A theoretical formula for predicting the compressive capacity was derived; however, it systematically overpredicted the experimental measurements by approximately 36%. To develop data-driven predictive models for the ultimate load capacity of FRP–SSC columns, four machine learning models, backpropagation neural network (BPNN), bootstrap aggregating BPNN (Bagging-BP), genetic algorithm-optimized BPNN (GA-BP), and gradient boosting regression trees (GBRT), were employed. Using sectional dimension, concrete strength, reinforcement parameters, eccentricity, and slenderness ratio as inputs, the validation sets of the models achieved R-values of 0.942, 0.918, 0.933, and 0.990, respectively. Feature importance analysis based on SHAP identified eccentricity as the most influential parameter. Results from this work can help to understand the behavior of FRP–SSC columns under compression. Full article

Concrete-filled steel tube (CFT) columns have been widely used in high-rise buildings and bridge structures due to their excellent composite performance. In practical applications, CFT columns inevitably experience eccentric loading due to structural imperfections, asymmetric load distributions, and seismic actions, particularly in corner columns of seismic-resistant structures where biaxial eccentric compression may occur. However, despite extensive studies on the local buckling behavior of CFT columns under axial compression and uniaxial eccentric compression, the behavior under biaxial eccentric compression remains insufficiently understood. In this paper, a theoretical study on the local buckling behavior of rectangular CFT columns subjected to biaxial eccentric compression is presented. Based on classical elastic stability theory and the energy variation method, an analytical model is developed by assuming that both the loaded and unloaded edges of the steel tube are elastically restrained against rotation and selecting an appropriate deflection function satisfying the boundary conditions and compatibility requirements. The relationship of local buckling strength of rectangular CFT columns subjected to biaxial eccentric compression and width-to-thickness ratios under different stress gradient coefficients is obtained. The results indicate that the local buckling strength σ_cr of steel tubes decreases significantly with the increasing width-to-thickness ratios b/t when the stress gradient coefficient α₀₁ and α₀₂ remain unchanged, and the local buckling strength of the broad face is much lower than that of the narrow face. As the stress gradient coefficient increases, the local buckling strength σ_cr of steel tubes increases. When the stress gradient equals 0, the steel tube is subjected to axial compression and the minimum of the local buckling coefficient can be obtained. When the stress gradient equals 2, the steel tube is subjected to pure bending and the maximum of the local buckling coefficient can be obtained. The proposed model provides a rational prediction of local buckling strength under different biaxial eccentric compression conditions. Finally, recommended width-to-thickness ratio limits for steel tube plates with different steel grades and stress gradient coefficients are proposed, which can provide practical guidance for preventing premature local buckling and improving the material utilization efficiency of rectangular concrete-filled steel tube columns. Full article

Coastal and offshore steel infrastructures such as transmission towers and wind turbine towers are prone to coating degradation after long-term exposure to salt fog, high humidity, and ultraviolet radiation. The subsequent uniform corrosion significantly reduces the cross-sectional load-carrying capacity and threatens structural safety. This paper presents a numerical parametric analysis on the compression behavior of circular steel tube (CST) members subjected to uniform corrosion induced by coating failure, based on 18 accelerated corrosion tests. The effectiveness of the wall thickness reduction method for simulating uniform corrosion after coating degradation is verified, and the influence of key parameters on load-carrying capacity degradation is systematically investigated. A simplified formula for elastic local buckling of corroded CSTs is derived, and a direct strength method (DSM) calculation framework considering both global buckling and local–global interactive buckling is established. The results show that the uniform corrosion ratio is the dominant factor affecting load-carrying capacity degradation, while sectional dimension, slenderness ratio, and eccentricity have negligible influence. The proposed DSM method achieves a prediction error within 5% compared with test and numerical results. It is primarily applicable to uniformly corroded steel tubes represented by equivalent wall thickness loss, and its applicability to scenarios with localized corrosion, pitting corrosion, weld-zone corrosion, or non-uniform wall thickness reduction requires further validation. This method provides a rapid and accurate tool for residual load-carrying capacity assessment and life cycle management of coastal steel infrastructures after coating failure. Full article

This study investigates the buckling behaviour of extruded aluminum square and rectangular hollow section (SHS/RHS) members under compression and combined loading. An experimental programme was conducted to examine the response of aluminum members subjected to eccentric compression. The experimental results were used to validate detailed finite element models developed in Abaqus, which were subsequently employed in an extensive parametric study. The outcomes of this study are intended to support the development of new design rules based on the Overall Interaction Concept (O.I.C.). Full article

This article presents a complete cost-optimized design for rectangular isolated footings (RIFs) under biaxial bending with a partially compressed contact area (PCCA) and an eccentric column, i.e., part of the base is in contact with the soil (generating compression), and the other part is not in contact with the soil (generating neither compression nor tension), and the soil pressure behaves linearly. The proposed model is presented by integration to find the moments in the critical sections, the bending shears in the critical sections and the punching shear acting on the RIF, and these are compared with those that must be resisted according to the standards (ACI 318-19) Some articles show complete designs for RIFs with a fully compressed contact area (FCCA) and an eccentric column, and other articles show only the minimum area (A_min) for RIFs with a PCCA and an eccentric column. The main contributions of this article are as follows: (1) the A_min is determined from the loads and moments, assuming that the loads and moments it resists must be greater than or equal to those acting on the RIF; (2) the minimum cost (C_min) is determined. Three numerical studies are described to demonstrate the advantages of this study over other models. The results indicate that, according to the studies presented in this article, savings of up to 45.99% for A_min and 93.62% for C_min can be achieved using the model proposed in this article (MPA); this occurs when the pressure acting on the foundation does not reach the maximum available soil pressure (p_max). Therefore, this paper could be of great use to engineers dedicated to the construction of foundations. Full article

With the continuous advancement of urban renewal and the renovation and utilization of existing buildings, a large number of existing reinforced concrete slender columns face challenges in capacity evaluation. Quick and accurate calculation of their stability capacity, which represents the upper limit of member capacity, holds significant importance. These columns often exhibit plastic characteristics such as concrete cracking and steel yielding. Moreover, the bracing restraint provided by adjacent columns typically falls between that of a sway frame and a non-sway frame, classifying them as elastically restrained sway frame columns. Current design codes lack appropriate effective length factor tables for such columns, while the stiffness degradation induced by material nonlinearity is difficult to quantify accurately. To address these issues, the frame column is isolated from the overall structure and modeled as a rigid compression member system with three springs. The influence of bracing stiffness on the column’s critical load is revealed, leading to a formula for the elastic critical load of elastically restrained sway frame columns. Based on tests of reinforced concrete columns under compression, the influence mechanisms of eccentricity ratio and longitudinal reinforcement ratio on flexural stiffness degradation are elucidated. The obtained elastoplastic stiffness is then integrated into the stability calculation framework for elastically restrained sway frame columns, resulting in a method for determining the elastoplastic stability capacity of reinforced concrete columns that accounts for both geometric and material nonlinearities. This method avoids solving complex transcendental equations and offers a straightforward calculation process, providing a simple and practical hand-calculation tool for evaluating the stability capacity of reinforced concrete columns in existing buildings. Full article

To overcome the inherent drawbacks of cast-in-place reinforced concrete bracing—such as long construction periods and difficult demolition—as well as the relatively high construction cost of steel structure bracing, while fully incorporating the respective technical advantages of these two traditional support systems, this paper proposes a novel hybrid prefabricated reinforced concrete (RC)–steel structure foundation pit bracing system. In order to investigate the overall bearing capacity variation in the standard components of this structure under complex external forces in foundation pits, a numerical model was established using the finite element software ABAQUS. The study examines the trend of the axial compressive bearing capacity of a single standard beam segment as the steel thickness of its external stiffening sleeve varies, as well as the effects of eccentric loading, oblique loading, and the presence or absence of auxiliary supports on the structural bearing capacity of multi-segment beam assemblies. The numerical analysis results show that the bearing capacity of a single beam segment exhibits a strong correlation with the variation in sleeve thickness, and a fitting curve of compressive strength as a function of thickness was derived. For the multi-segment assembly, an increase of 1 mm in the load eccentricity in the Y and Z directions reduces the ultimate peak load by approximately 20.95 kN and 23.94 kN, respectively; in the XY and XZ planes, an increase of 1° in the eccentric angle of the oblique load reduces the peak ultimate bearing capacity by about 6.02 kN and 9.67 kN, respectively. Auxiliary supports have a relatively minor influence on the structural bearing capacity. This research thoroughly explores the bearing capacity of the prefabricated steel–concrete composite and steel structure foundation pit bracing under complex working loads, providing strong support for engineering design and demonstrating broad application prospects. Full article

Background/Objectives: The morphology of the glenoid cavity is increasingly recognized as a key factor influencing joint mechanics and clinical outcomes, particularly in the context of shoulder instability. However, the specific effects of glenoid shape on the contact pressure distribution and humeral head displacement remain insufficiently explored. This study examined the impact of five glenoid morphotypes—pear, oval, teardrop, calabash, and inverted comma—on contact pressure patterns and humeral head displacement. Methods: Using three-dimensional models of the glenoid cavity derived from anatomical landmarks, we simulated cartilage compression and computed pressure fields using an elastic foundation model under a 700 N joint reaction force applied in various orientations. Results: Our results demonstrate that the glenoid morphology significantly influences both the magnitude and spatial distribution of contact pressures, particularly under eccentrically directed loads. Notably, pressure and humeral displacement were more pronounced when the force was inclined in the antero-posterior direction compared with the supero-inferior axis. Discussion: Among the morphotypes, the pear-shaped glenoid, the most prevalent in the general population, exhibited the greatest susceptibility to variations in glenohumeral loading. This suggests a potential evolutionary trade-off in shoulder morphology, favoring increased mobility at the expense of joint stability. Conclusions: These findings underscore the biomechanical relevance of patient-specific glenoid anatomy and advocate for its consideration in diagnostic and therapeutic strategies targeting shoulder instability and cartilage degeneration. Full article

Fabricated reinforced concrete columns are important components of reinforced concrete structures. During the design reference period, columns are prone to degradation in mechanical and deformation properties, which affects the normal service of the structure. Based on compressive tests of fabricated reinforced concrete columns, this paper uses ABAQUS 2021 finite element analysis software to explore how factors such as column damage and CFRP sheet layout affect the compressive performance of fabricated concrete columns under eccentric compression in order to investigate their mechanical properties and the confinement effect of CFRP sheets on such columns. The results indicate that the change trend of the bearing capacity of the finite element model is largely in agreement with that of the test specimens, and the ultimate bearing capacity error is below 3%, thereby confirming the validity of the finite element model. Compared with strip confinement, full-wrap confinement achieves a greater improvement in ultimate bearing capacity, and two to three layers are recommended as the ideal number of CFRP sheets for strengthening. The maximum increase in ultimate bearing capacity can reach 19.18%. When the strip width is constant, the smaller the spacing, the smaller the concrete strain in the compression zone. When the net spacing is constant, reducing the strip width increases the number of cracks and decreases crack width, but reduces the ultimate bearing capacity of the column accordingly. Strengthening with CFRP sheets can enhance the ultimate bearing capacity, deformability, and ductility of columns with initial damage under both small and large eccentric compression. The maximum increase in ultimate bearing capacity can reach 8.31%. The results obtained in this paper are conducive to promoting the reinforcement and reconstruction of fabricated reinforced concrete columns and reinforced concrete structures. Full article

This paper presents a preliminary numerical investigation on the mechanical behavior under eccentric compression of T-shaped steel tube-steel reinforced concrete columns. A refined finite element (FE) model was developed in ABAQUS 2021 and validated against published axial compression test results. The effects of three key parameters (eccentricity, outer steel tube thickness, and built-in steel skeleton size) on the bearing capacity, failure mode, stiffness degradation, and stress distribution of the studied members were systematically analyzed via finite element analysis, followed by comparative calculations and an applicability analysis of the calculation of eccentric compression bearing capacity. All eccentric compression results presented herein were obtained through numerical simulation and have not been directly verified by physical tests. The results show that the ultimate bearing capacity decreases by more than 57% as the eccentricity increases from 0 mm to 75 mm, with the failure mode transitioning from axial compression failure to flexural failure. Within the studied parameter range, the 4 mm-thick outer steel tube exhibits superior comprehensive performance, including bearing capacity, stiffness, and ductility. Increasing the built-in steel skeleton size effectively enhances the flexural stiffness and ductility, and delays stiffness degradation. The existing code-specified formula demonstrates good accuracy (relative error < 6%) for e ≤ 50 mm but yields significant errors for e = 75 mm. An empirical expression for the equivalent eccentricity influence coefficient α is proposed, which reduces the overall average error from 4.89% to 2.26% within the parameter scope of this study. Full article

Hollow glued bamboo scrimber (HGBS), as a novel sustainable engineered bamboo material, exhibits considerable potential for structural engineering applications. To clarify the influence of slenderness ratio on the eccentric compression behavior of HGBS columns, an experimental and numerical investigation was conducted. A total of six HGBS specimens were tested under axial and eccentric compression to obtain their failure modes, load–displacement responses, and strain distribution characteristics. A detailed finite element model was developed in ABAQUS, in which bamboo scrimber was modeled as an orthotropic elasto-plastic material, while cohesive elements were employed to simulate the adhesive interfaces. The results indicate that HGBS columns subjected to eccentric compression exhibit pronounced axial force–bending moment interaction behavior. The average ultimate load under eccentric compression was only 17% of that under axial compression, demonstrating that the eccentric bending moment and second-order effects play a dominant role in reducing the load-carrying capacity. The finite element predictions agreed well with the experimental results, with deviations within 10%, confirming the reliability of the numerical model. Parametric analyses revealed that, as the slenderness ratio increased (corresponding to an increase in column height from 300 mm to 3000 mm), the ultimate load decreased from 104.17 kN to 28.20 kN, while lateral deformation and global instability became increasingly significant. The study elucidates the key influence of slenderness ratio on the eccentric compression performance of HGBS columns and provides a useful analytical basis for the design and application of engineered bamboo columns. Full article

As a structural material characterised by low density, high strength, excellent corrosion resistance and recyclability, aluminium alloy tubes are finding increasingly widespread application in the construction sector. However, there is currently a lack of research on the prediction of the bearing capacity of aluminium alloy square tube columns. To investigate the failure behaviour of aluminium alloy square tube columns under axial and eccentric compression, this paper first designed 10 thin-walled aluminium alloy square tube column specimens with varying lengths, cross-sectional dimensions and wall thicknesses. Axial and eccentric compression tests were conducted, and the loading process and failure modes were analysed. Building on this, a hybrid load-bearing capacity prediction model combining Multi-Objective Particle Swarm Optimisation (MOPSO) with the Gaussian process regression (GPR) algorithm was proposed. This model is capable of automatically learning and capturing 236 sets of experimental data. Subsequently, using the established prediction model, the contributions of high-sensitivity parameters and cross-sectional influence parameters to the load-bearing capacity were determined. Based on the prediction results, a correction factor for the diameter-to-thickness ratio was introduced into the eccentric compression bearing capacity formula of the Chinese code to establish an improved calculation formula. Compared with the implicit formula provided by machine learning models, the explicit formula proposed in this paper is more suitable for practical engineering design. The results show that the prediction results agree well with the experimental results and can accurately predict the ultimate bearing capacity of aluminium alloy square columns. Compared with the bearing capacity calculation methods in existing codes, the proposed formula reduces the root mean square error (RMSE), mean absolute error (MAE) and coefficient of determination (R²) of the dataset by 70.91%, 70.85% and 64.27%, respectively, whilst increasing the coefficient of determination (R²) from 0.8107 to 0.9830 (a relative improvement of 21.25%). Full article

High-performance fiber-reinforced cementitious composite (HPFRCC) has shown considerable potential as a strengthening material for improving the crack resistance, integrity, and deformation capacity of masonry structures. In aging concrete hollow block masonry walls subjected to long-term eccentric compression, material degradation may lead to premature cracking, local crushing, stiffness deterioration, and reduced safety margins, thereby adversely affecting structural reliability and service performance. However, studies on the eccentric compression behavior of HPFRCC-strengthened concrete hollow block masonry walls with simulated material degradation remain limited. In this study, experimental, finite element, and theoretical analyses were conducted on three HPFRCC-strengthened specimens with an eccentricity ratio of 0.5y, namely a 30 mm double-sided strengthened specimen, a 45 mm double-sided strengthened specimen, and a 30 mm single-sided strengthened specimen. The failure modes, load–displacement responses, lateral deformation, strain development, and DIC strain distribution characteristics were investigated. The results showed that, under the test conditions considered in this study, the double-sided strengthened specimens exhibited higher load-bearing capacity, greater stiffness, and better structural integrity than the single-sided strengthened specimen. Among them, the 45 mm double-sided strengthened specimen reached the highest peak load of 1643 kN, whereas the 30 mm double-sided strengthened specimen exhibited a gentler post-peak response, more dispersed crack development, and better deformation compatibility. The finite element results were generally consistent with the experimental results; the ratios of the experimental to numerical peak loads ranged from 0.96 to 1.01, while the corresponding peak displacement ratios ranged from 1.02 to 1.09. Within the parameter range considered in the numerical analysis, increasing the strengthening thickness was generally beneficial to the eccentric compression capacity. The proposed preliminary sectional bearing capacity model showed acceptable agreement with the test results for the specimens considered in this study; however, its broader applicability requires further validation using additional specimens. Full article

Limited research exists on the behavior of square CFDST slender columns, especially under the consideration of the relation global buckling and confinement effect. This study evaluates square concrete-filled double-skin steel tubular (CFDST) columns using nonlinear finite element analysis (FEA) to simulate structural behavior under axial and eccentric loads until failure. Parametric analyses of extensive specimens of square CFDST pin-ended columns evaluate various parameters, providing design insights for engineering applications. The study was conducted over a wide range of slenderness ratios. Four concrete varieties with compressive strengths were tested: normal concrete (NC), engineered cementitious composites (ECCs), high-strength concrete (HSC), and ultra-high-strength concrete (UHSC). Parametric variables included inner to outer steel tube thickness ratios, hollow ratios with a wide range, inner tube steel grades, and load eccentricities. An increasing slenderness ratio reduced the axial capacity, causing failure to change from yielding to buckling. By increasing the inner thickness, the capacity increased for intermediate columns compared to very long (i.e., slender) columns. The ideal hollow ratio is ($\overline{\chi }=0.638$) for short columns compared to ($\overline{\chi }>0.7$) for slender columns. UHSC improved short columns. Concrete’s performance was impacted by eccentric loading, which decreased the capacity, particularly in long columns. Designers should take into consideration the diminished efficacy of material strength enhancements under eccentric loading and prioritize stability in long, slender columns. The design formula was modified to enhance the strength estimates of square CFDST columns. Full article