Eccentric Compression Loading Research Articles

Lateral deflections of slender RC columns under eccentric compression loading with different end conditions

AbstractIn the literature, several methods have focused mostly on determining the lateral deflection of columns with pinned end conditions. This paper presents a powerful method that allows the calculation of lateral deflection for columns of different end conditions, with particular attention to reinforced concrete (RC) columns. By utilizing the moment–curvature relations, a numerical procedure to compute slopes and deflections of pin‐ended columns is proposed, in which the slopes and deflections are corrected via an efficient and fast technique. Accordingly, slopes and deflections of columns with different end conditions are determined via procedures that rely on a simple searching technique. The second‐order analysis is individually included in the calculations; therefore, the complexity arising from the direct impact of the axial load on the lateral deflection is averted. Therefore, the method has the potential for inclusion in many numerical models for different structural members. The equations derived via the developed method have identical responses to the expressions obtained via the exact methods. A series of numerical examples are presented to illustrate the applicability of the proposed method to RC columns with different loadings and end conditions. Finally, the proposed method is evaluated, and its accuracy is demonstrated via parametric verification. As the axial load increased, the lateral displacement increased somewhat. The greater the eccentricity is, the greater the lateral displacement. As the eccentricity increased, the failure mode of the RC column changed from compression failure to bending failure.

Mesoscopic analysis on the coral aggregate reinforced concrete column under axial and eccentric compression

Coral aggregate concrete (CAC) has been identified as a promising building material for reef engineering construction, yet its practical application remains challenging due to incomplete research on the mechanical behaviors of the CAC beam and column components. In this study, a 3D mesoscale modeling approach considering the heterogeneity of CAC was utilized to investigate the mechanical performance of coral aggregate reinforced concrete columns (CARCCs) under axial and eccentric compression. Through numerical delineation of failure processes and damage mechanisms at the mesoscale, comprehensive parametric analysis integrating both numerical simulations and experimental validations were executed to assess the load-bearing capacity of CARCC. Results indicate that the mesoscale model has significant reliability in simulating the deformation and cracking failure behaviors and analyzing the load-displacement relationships of CARCC under axial and eccentric compression loads. When under axial loads, macroscopic cracks in CARCC primarily develop in an oblique manner, precipitating significant concrete spalling and extensive cracking failure along the longitudinal axis. Under eccentric loads, failure advances from crack initiation at load points to abrupt vertical fractures in stressed zones, manifesting a decrement in the load-bearing capacity with escalating eccentricity. Furthermore, the strength grade and reinforcement ratio exert a profound influence on the load-bearing capacity, with disparate impacts under varied loading conditions. It is concluded that reinforcement strategies tailored to specific loading conditions have significant implications for the design and safety of reinforced concrete structures in reef engineering projects.

Eccentric load capacity of ultra-high strength concrete-filled steel tubular lattice short columns

To explore the behavior of ultra-high strength concrete filled steel tubular (UHSC-FST) lattice short columns under eccentric compressive loads, experimental analyses on four specimens and 276 finite element models using ABAQUS were conducted. The study focused on the effects of steel tube wall thickness, concrete strength, steel tube strength, and load eccentricity on failure modes, load-displacement curves, and ultimate load-bearing capacity. Results showed that for columns with minor eccentricity-induced compressive failure, the reduction coefficient of ultimate load capacity has a weak correlation with the parameters. However, for columns with significant eccentricity-induced tensile failure, the reduction coefficient increases with steel tube thickness and strength and decreases with concrete strength. The center-to-center distance of the columns has a minor effect. Based on these findings, a comparative analysis of existing standards was conducted, leading to the development of an accurate method for calculating the ultimate load-bearing capacity of eccentric CFST lattice columns. This method is applicable to various cross-sectional dimensions, material strengths, and steel tube wall thicknesses, with calculation errors within 10 %, ensuring it meets engineering precision requirements.

Structural Behavior of Reinforced Concrete Columns Fully and Partially Reinforced with GFRP Bars Tested Under Concentric or Eccentric Compressive Loads

Concrete columns reinforced with glass fiber-reinforced polymer (GFRP) bars have been greatly interesting recently. The distinct properties of GFRP bars, such as high tensile strength and low modulus of elasticity compared to steel bars, as well as the linear stress-strain behavior, make the study of GFRP-reinforced concrete (FRP-RC) columns important. This paper investigates the structural behavior of column specimens reinforced by fully and partially GFRP bars subjected to concentric and eccentrically applied Compressive loads. 12 columns were reinforced by (36%, 64%, and 100%) of the GFRP bars ratio, and the control specimen was reinforced by conventional steel rebars; all specimens were tested under different eccentric ratios (e/h) 0, 0.66, and 1. The failure mode, the relation between the axial load and the average axial displacement, and a comparison between the experimental results and the theoretical interaction diagram for columns were presented and discussed. The results show that most of the failure in specimens occurs as a compressive failure, and it fails in the weakest region by crushing concrete, as well as kinking in GFRP bars. Using GFRP bars significantly increases the axial displacement values compared to the steel rebars in longitudinal reinforcement and decreases the failure load for specimens with an increase in the ratio of GFRP bars. The average axial displacement value for columns specimens tested under eccentric load at e/h equal to 0.66 and 1 decreases by 75% and 94.4% compared with the control specimen.

Behavior of randomly pitted Q690 high-strength steel H-section members under eccentric compression

Six Q690 high-strength steel H-section specimens with pits were tested under eccentric compression loads. The results showed that the pits changed the failure modes of the members under eccentric compression by inducing local buckling, which resulted in a significant reduction in the ultimate resistance, reaching 31.7 % when the volume loss ratio was 15 %. A numerical study was then conducted, which revealed that the ultimate resistance loss ratio varied with the volume loss ratio and the eccentricity ratio, but not with the slenderness ratio. Finally, the existing rules for determining the ultimate resistance were modified by using the equivalent residual thickness, and the applicability of the modification was assessed.

Design-oriented method for the load-bearing capacity of RC columns jacketed by octagonal and spiral stirrups under axial and eccentric compression

The purpose of this study was to develop the design-oriented calculation method for the load-bearing capacity of RC columns jacketed by octagonal and spiral stirrups under axial and eccentric compression load. Based on the result of sixteen full-scale jacketed concrete columns which subjected to axial compression load, the judging method for the axial load-bearing capacity ultimate state of jacketed RC columns was determined. Then the design-oriented method for the axial load-bearing capacity of jacketed columns was proposed according to the axial load-bearing capacity ultimate state of jacketed RC columns. In addition, based on the six full-scale jacketed concrete columns which subjected to lateral cyclic load, the design-oriented calculation model for the relative compression zone height of jacketed RC columns under eccentric compression was proposed. And the calculation methods for evaluating the load-bearing capacity of jacketed RC columns with large eccentricity and small eccentricity were proposed, respectively. Furthermore, the predicted results from proposed method fitted well with the test results, which indicated that the proposed design-oriented methods were suitable for evaluating the load-bearing capacity of jacketed RC columns under axial and eccentric compression.

Investigation the behavior of LWAC encased steel columns after exposure to elevated temperature

AbstractThis paper presents experimental and numerical investigations on the behavior of eccentrically loaded lightweight aggregate concrete encased steel (LWACES) columns after exposing to elevated temperatures. Sixteen concrete encased steel (CES) columns were considered in the study, 12 of which were exposed to elevated temperature then eccentrically loaded up to failure at different eccentricity ratios. The effect of temperature on the load–displacement relationships, failure load, and failure modes of the concrete encased steel (CES) columns was monitored and evaluated. Experimental results have shown that as the temperature increases, the load bearing capacity of the CES columns decreased. It has also been showed that, at high temperature, the normal‐weight concrete encased steel (NWCES) columns experienced larger degradation of the load bearing capacity compared to that of LWACES columns. Also, this study presents a numerical simulation of the behavior of LWACES columns at elevated temperatures with eccentric compressive load. The numerical model was implemented in conducting parametric study to understand the effect of temperature distribution, concrete cover, eccentricity ratio, and high temperature levels on the behavior of the thermally exposed (CES) columns. Numerical results have revealed that, at temperature value of 500°C, the ultimate capacity of LWACES with eccentricity ratios of 0.75, and 1 has decreased by 17%, and 23%, respectively, compared to that of the column with eccentricity ratio of 0.5.

Verification of the P–delta effect for fiber reinforced UHPC short columns

The P–delta effect, i.e., second–order (nonlinear) effect, can lead to large lateral displacements hence resulting in premature failure of structural members under axial loading conditions. This study aims to verify the P–delta effect in ultra–high performance concrete (UHPC) short columns considering fiber contribution. Fourteen UHPC short columns with a slenderness ratio of 17.5 were tested under eccentric compressive loading. The results show that increasing the content of steel fibers in UHPC can improve the resistance of both the compression zone and the tension zone, which therefore delayed the crushing failure and effectively reduced the flexural cracks. For the columns under the eccentricity of 110 mm, the ultimate bearing capacity increased by 3.6 %–4.9 % when the fiber content increased from 1.0 vol% to 2.0 vol%, and the increase was at 17.1 % when the fiber content was up to 3.0 vol%. The moment magnifying coefficients for UHPC were calibrated through the theoretical analysis. The calibrated coefficients agreed well with the experimental results with a ratio of 0.97. The proposed analytical models for the ultimate bearing capacity also agreed well with the experimental results. The average ratios of the calculated axial load to the experimental result were 1.02 and 0.97 for the compression and tension–controlled models, respectively. By the first and second–order analysis, their average deviation of the analytical models was 6.2 %. The analytical model considering the second–order effect gave a more accurate prediction on the bearing capacity.

Mechanical comparison of straight and pre-bent interlocking nails used for the stabilization of a tibial gap fracture model.

To compare the mechanical behavior of straight (STRT) and pre-bent (BENT) I-Loc angle-stable interlocking nails (AS-ILN) used for stabilization of canine mid-diaphyseal tibial fractures. In vitro experimental study. Tibial gap fracture models (n = 5/group). Tibial models simulating a comminuted mid-diaphyseal fracture were stabilized with either a STRT or BENT I-Loc AS-ILN. Bent nails were contoured to match the 10° tibial recurvatum of a mid-size dog. Constructs were subjected to cyclic eccentric compressive loads followed by ramp load until failure. Construct compliance, maximum compressive load and resistive torque, yield load and angular deformation at 450 N were statistically compared using t-tests (p < .05). Failure modes were described. Compliance was 45% lower in BENT than STRT groups (p < .0001). Constructs in the BENT group sustained ~20% and 34% greater maximum and yield loads, respectively, than STRT constructs. Maximum resistive torques were similar between groups (p = .16). At 450 N, sagittal plane angular deformation increased from 0° to 4° in procurvatum (STRT group) and decreased from 10° to 8° in recurvatum (BENT group-p < .0001). Construct yield failure occurred at the nail isthmus in both groups. These results demonstrated that, in a tibial gap fracture model, pre-bending I-Loc AS-ILNs provided mechanical advantages by increasing their ability to resist bending resulting from eccentric compressive loads. Pre-bending may reduce the occurrence of tibial nail yield failure. Surgeons should therefore consider pre-bending tibial I-Loc nails to match the bone anatomical recurvatum prior to implantation.

Stability of Prestressed Stayed Steel Columns Under Eccentric Compression

Prestressed stayed steel columns (PSSCs) are structural components notable for their exceptional stability and load capacity. However, their behavior under eccentric compression remains poorly understood compared to their performance under axial compression. This study conducted tests and finite element analysis (FEA) to investigate the stability of PSSCs under eccentric compression loading. The study focused on examining the overall stability, buckling modes, and ultimate load capacity of PSSCs under various scenarios. The findings revealed that PSSCs exhibit significantly higher stability and load capacity than conventional columns. However, when subjected to eccentric compression, they experience a substantial decrease in stability. The results of the linear and nonlinear buckling analyses suggest that interactive buckling may occur under certain conditions, thereby influencing the buckling load. These findings clarify the correlation between stability and eccentric compression, offering valuable insights for future research and practical engineering applications.

Eccentric compressive behavior of T-shaped welded multi-partition composite members

Six T-shaped welded multi-partition composite members were tested under eccentric compression loading by considering the influence of eccentricity and eccentric angle. The test results showed that no weld tearing occurred when the specimen was damaged, indicating that the two vertical welds could ensure the overall working performance of the specimen. The specimens exhibited the smallest bearing capacity when failing along the asymmetric axis, which was the most dangerous situation. The parametric analysis is conducted by a verified finite element model considering the influence of the slenderness ratio, section height-to-width ratio, section depth-to-width ratio, concrete and steel grade, steel ratio, and eccentric angle. If concrete contributes a larger proportion to the bearing capacity, the interaction curve of axial force and bending moment tends to protrude. Conversely, the interaction curve of axial force and bending moment gradually shrinks as the slenderness ratio increases. Based on this observation, a calculation method of T-shaped welded multi-partition composite members under eccentric compressive loading along the asymmetric axis is proposed by considering the effect of the slenderness ratio. Formulas for bearing capacity under biaxial eccentric compression are proposed based on the results of the parametric analysis.

Compressive behavior of RC columns strengthened with FRP and prefabricated UHPC blocks

The combined strengthening method of cross-sectional shape-modification and lateral FRP confinement has been proven to be capable of significantly improving the compressive behavior of RC column and the FRP confining efficiency. However, the traditional shape-modification method using a cast-in-place concrete jacket has a complicated construction process and a long curing period. Additionally, the application of normal concrete substantially increases the cross-sectional area and weight of the column, resulting in poor seismic performance of the strengthened column. In this study, a novel strengthening method using FRP and modular prefabricated ultra-high performance concrete (UHPC) blocks is proposed for strengthening RC columns. An experimental study was conducted to investigate the axial/eccentric compressive behavior of RC columns strengthened with this novel method. The test results demonstrated the high efficiency of the proposed method in enhancing the load-carrying and deformation capacities of the RC columns under axial or eccentric compressive loads. The significant roles of the strengthening components in the novel method in improving the compressive behavior of columns were also verified.

Eccentrically compressed behavior of UHPC columns considering the P-delta effect

Eccentric compression is a critical behavior observed in arches and columns, particularly in structures constructed with ultra-high performance concrete (UHPC). Compared to normal concrete structures, those made with UHPC exhibit distinct behaviors that need to be clearly investigated. This study comprehensively investigates UHPC columns under eccentric compression load through experimental study and theoretical analysis. Various experimental parameters, including slenderness ratio, eccentricity distance, fiber content, and stirrup ratio, were examined across 26 UHPC columns. Failure modes were evaluated using digital image correlation (DIC) methods. The load-displacement responses indicated that slender columns subjected to significant eccentricity exhibited load decreases during yielding stages, whereas short columns experienced load increases. This discrepancy in yielding stages was attributed to P-delta effects. In addition, theoretical models were developed to determine the ultimate bearing capacity of columns experiencing compression-controlled and tension-controlled failures, considering the P-delta effect caused by the different slenderness ratios. The moment magnifying coefficients for UHPC were calibrated based on theoretical analyses of the limit curvature of eccentric compression members. The proposed theoretical models agreed well with the experimental results, with an average ratio of 1.02. The second-order effect for the case of UHPC short column with a slenderness ratio of 5 can be ignored as per Eurocode 2, which is less than 10 % of the corresponding first-order effect.

Experimental and analytical study on eccentrically loaded Fiber concrete columns reinforced longitudinally with GFRP bars

In this paper, experiments were carried out to analyze the behavior of the square columns reinforced longitudinally by GFRP bars along with different ratios of hooked end fibers under eccentric compressive loading. Eight short square columns with a cross-section dimension of 150x150mm and a height of 1200 mm, were fabricated to conduct the experimental program. A 150 mm enlargement in column-cross at both ends was considered to develop an eccentric axial load. The columns were tested under different load eccentricity ratios (0.26, 0.5, 1). Different tie spacings (50, 100, 120) mm. Different ratios of steel fibers 0 %, 0.5 %, and 1 % were incorporated into the concrete mix. It was observed that columns with steel fibers demonstrated good characteristics, including higher ultimate load, increased ultimate deflection, and enhanced ductility and toughness compared to the columns without steel fibers due to multiple cracking behaviors. The ductility of the columns reinforced with GFRP bars was enhanced by 46.8 %, and 68 % for steel fiber volume ratios of 0.5 % and 1 %, respectively. The energy absorption was increased by 42 % and 77 % for steel fibers ratios of 0.5 % and 1 %, respectively. When GFRP bars were used as longitudinal reinforcement, there was an improvement in the bond behavior between the concrete and the GFRP bars. All concrete columns reinforced by GFRP bars failed due to flexure-compression failure. There was no observed rupture of GFRP bars during the experimental test and the maximum strain did not reach 40 % of their ultimate strain capacity. Nonlinear Finite Element analysis was conducted to simulate the behavior of tested columns. The equations from previous studies and the codes were established to predict the nominal peak capacity of columns considering all parameters. In general, there was a reasonable level of agreement observed between the experimental data and the theoretical results determined for seventy-column specimens in the current study and from previous studies in the literature.

Eccentric Compression Performance of Core-Steel Tube with T-Shaped Steel Reinforced Concrete Column

This paper introduces a novel steel–concrete composite column referred to as the core-steel tube with T-shaped steel reinforced concrete (CSTRC) column, which is composed of a core steel tube with T-shaped steel embedded in a reinforced concrete column. To investigate the mechanical performance of the CSTRC column under eccentric compressive load, the load–deformation response, stress, and strain distribution of CSTRC columns under eccentric load are analyzed by finite element software. Furthermore, the effects of slenderness ratio, concrete and steel strength on the eccentric compression performance of CSTRC columns are also discussed. Finally, a set of formulas for predicting the ultimate strength of the CSTRC columns is proposed. The study results reveal that: (1) The established finite element model accurately predicts bearing capacity and strain development. (2) When the eccentricity is 0.2, the specimen exhibits characteristics indicative of small eccentricity failure. Conversely, when the eccentricity is 0.8, the specimen demonstrates traits associated with large eccentricity failure. Furthermore, as the eccentricity increases, there is a notable decrease in the bearing capacity of the specimen. (3) The slenderness ratio affects the failure mode of the CSTRC columns, with consideration for second-order effects necessary when the ratio exceeds 22. (4) Increasing the concrete strength, steel strength, and steel ratio significantly enhances the ultimate load values of the CSTRC columns. (5) A comparison between calculated and simulated values demonstrates good agreement, validating the accuracy of the proposed method.

Behavior and design of eccentrically compressed hybrid steel and GFRP reinforced concrete columns at elevated temperature

AbstractThis study presents analytical model for the analysis of hybrid (steel and fiber reinforced polymers (FRP)) reinforced concrete (RC) columns at elevated temperature under eccentric compressive loads. The bending moment resistance of the (RC) columns at elevated temperature is formulated based on force equilibrium and strain compatibility of the concrete column section under combined bending moment and axial force. Deterioration the mechanical properties of concrete, steel, and FRP bars due to the rise of temperature has been taken into account using equations proposed by previous studies. Validating the suggested model was carried out by comparing the analytical results with corresponding experimental and numerical results in terms of axial load‐lateral displacement relationships, axial load‐bending resistance interaction diagrams, and failure modes. Validation results have shown the accuracy of the suggested analytical model. A parametric study has also been conducted using the proposed analytical model to investigate the effect of some parameters on the axial load‐bending resistance interaction diagrams of hybrid steel and FRP‐RC columns under elevated temperature. These parameters include the effect of higher temperature values, the effect of reinforcement material, and the effect of reinforcement configuration. Parametric study results have revealed some interesting conclusions that may be implemented in the design of hybrid RC columns at fire.

Synergistic Effects of CFRP and Steel Fiber in Slender RC Columns Under Eccentric Compressive Loads: Experimental and Predictive Analysis

Synergistic Effects of CFRP and Steel Fiber in Slender RC Columns Under Eccentric Compressive Loads: Experimental and Predictive Analysis

Nonlinear finite element and machine learning modeling of tubed reinforced concrete columns under eccentric axial compression loading

There is still insufficient data on the behavior of tubed-reinforced concrete columns (TRCCs) under the eccentric compression. Thus, this research work comprehensively examines the eccentric compression behavior of TRCCs using nonlinear finite element modeling and machine learning (ML). To do this, numerical simulation and parametric analysis based on existing investigations were conducted. In addition to the existing 22 specimens with limited test variables, additional 188 specimens were developed to cover a wide range of parameters, including the load eccentricity, transverse reinforcement spacing, columns’ slenderness ratio, yield strength of steel, and outer steel tube diameter. Additionally, six ML models were created to estimate the ultimate load results. The results indicated that increasing the outer steel tube yield strength and diameter, and reducing the load eccentricity, slenderness ratio, and spacing of the transverse reinforcement enhanced the load-carrying capacity of the columns. The Gaussian process regression model demonstrated superior performance metrics in comparison to other ML models, with the highest R2 values (0.998613 in training and 0.99823 in testing stages) and lowest root mean square error values (0.007213 in training and 0.008471 in testing stages). To save money, time, and resources compared to laboratory testing, an online-based prediction program is finally presented to predict the columns’ ultimate load.

Stability properties of 6061-T6 aluminum alloy members with double-layer H-type sections under eccentric compression loads

The stability properties of double-layer H-section aluminum alloy members were studied under eccentric compression loads in this paper. Firstly, six double-layer members were designed and tested under a set of eccentric compression loads with different eccentric distances; as a contrast, six single-layer members were also tested under the same loading conditions; based on the test results, it was compared that the ultimate bearing capacity and buckling modes of the single-layer and double-layer members with different load eccentricity ratios. The experimental results indicated that the stability properties of double-layer H-section aluminum alloy members were better than corresponding single-layer members, but the ultimate strengths of double-layer members were less than the twice of that of single-layer members. A numerical simulating method for single-layer and double-layer H-section aluminum alloy members was established and validated against the experimental results.

Resistance of natural stone masonry wallettes under centred and eccentric compressive loading: Experimental and numerical approaches

Masonry walls are typically subjected to eccentric compressive loadings in common buildings. However, the design of walls towards this type of solicitation remains very empirical, often leading to oversizing the structure. This is especially true for natural stone masonry, for which experimental data are quite scarce. This paper presents an experimental campaign on 15 natural stone masonry wallettes subjected to centred and eccentric compression until failure. Different values of the eccentricity of the load, ranging from h/12 to h/4 (where h is the thickness of the wallette) were investigated, highlighting the noticeable effect of such a value on the compressive failure load. During the tests, the displacements were recorded by a Digital Image Correlation system, providing insights into the different failure mechanisms that depend on the value of the eccentricity. The so-obtained experimental failure loads are then compared to the predictions of Eurocode 6. Finally, a finite-element yield-design analysis of these tests is proposed which shows that this modelling framework is suitable to find the ultimate bearing capacity of a masonry wallette.