Uniaxial Bending Research Articles

Elastoplastic analysis of reinforced concrete space frames using the uniaxial and biaxial bending method

The scope of the work involves reinforced concrete frame structures with variations in structural design conception for columns with biaxial bending or uniaxial bending. The beams are designed with simple bending criteria for singly or doubly reinforced beams, or uniaxial bending. The analysis and design criteria are according to NBR 6118:2014. Structure analysis in elastoplastic regimen with the incremental analysis method is performed to detect plastic hinge formation order, collapse load factor, displacements, and rotation capacity of cross sections with the criteria established in the current building codes. The study evaluates the influence of the defined concepts on the structure’s elastoplastic behavior. The biaxial and uniaxial bending method is presented as an important formulation for obtaining the collapse load factor using the elastic stiffness matrix with modifications. The algorithms presented enable the development of research without the need for expensive commercial software licenses.

Laser Shock-Induced Nano-Twist of Transition Metal Dichalcogenides.

Mechanical strain, such as stretching, compression, bending, and rotation, significantly alters the photonic and electronic properties of 2D materials. The laser shock process, which allows 2D materials to deform at an ultrahigh strain rate, is a promising technology for alleviating the low strain transfer efficiency caused by the low interfacial bonding strength of the layered 2D materials. However, the mechanical strain introduced by shock waves is currently limited to uniaxial compression or bending deformation, and the monotonic strain patterns constrain the strain diversity and performance expansion space of 2D materials. This work proposed a novel strategy for nano-twist manufacturing using laser shock processing, based on partial interfacial decoupling behavior. Apart from the conventional uniaxial strain, we demonstrated experimentally and theoretically that the manufacturing of nano-twist allows the introduction of interlayer tensile and rotational strains in TMDCs. The microstructure and properties of the strained 2D materials were investigated. Furthermore, the dynamic deformation response of WSe2 during the shock process was studied using molecular dynamics simulations. The correlation between the laser shock-induced dynamic loading process, interfacial behavior, and deformation behavior of 2D materials was comprehensively explored. The primary contribution of this study lies in the introduction of diversified strain modes through nano-twist manufacturing by the laser shock process, which is expected to provide a convenient nano-twist fabrication process for the strain engineering and twistronics fields.

Self-powered, high sensitivity printed e-tattoo sensor for unobtrusive arterial pulse wave monitoring

Self-powered, highly unobtrusive, low-cost and accurate arterial pulse wave monitoring devices need to be developed to enable cost-efficient monitoring of entire cardiovascular disease risk groups. We report the development of a scalable fabrication process for a highly unobtrusive piezoelectric ultra-thin (t ~ 4,2 µm) e-tattoo arterial pulse wave sensor which utilizes only transparent and biocompatible polymer-based materials. The ferroelectric performance of the ultra-thin P(VDF-TrFE) material layer is optimized through the use of crosslinked PEDOT:PSS electrodes; this results in ~70 % and ~34 % improvements in remanent polarization (Pr) and coercive field (Ec), respectively, when compared to the sensors with pristine PEDOT:PSS electrodes. The ultra-thin form factor enables access to the high bending mode sensitivity of the P(VDF-TrFE) material layer; the maximum sensitivity value achieved in uniaxial and multiaxial bending is ~1700 pC N-1, which is ~50 times higher than the measured normal mode sensitivity. The increased sensitivity is linked to a specific set of direct piezoelectric coefficients using combination of experimental results, statistical analysis and finite element modeling. Finally, the accuracy of the e-tattoo sensor is demonstrated in the non-invasive measurement of radial artery pulse wave by comparing the signal to that obtained with reference device from 7 study subjects.

Deformation behavior of lightweight clad sheet: Experiment and modeling

In this study, three-layer Al/steel/Al clad metal sheets, which form a heterostructure comprising separate soft (Al) and hard (steel) domains, were fabricated using aluminum and low-carbon steel to investigate the enhanced mechanical properties of multilayered composites. The heterogeneous deformation mechanism was analyzed by combining experimental and computational approaches. The in-situ deformation behavior of the clad sheets was explored at micro/macro scales through uniaxial tensile and bending tests with a developed physics-based constitutive model by considering the evolution of geometrically necessary dislocations at the Al/steel interface. The experimental results were used to determine the appropriate parameters for the proposed modeling method. The modeling approach introduced in the study was successfully validated, thereby demonstrating its applicability for predicting the different mechanical properties of clad sheets under various deformation modes.

Understanding room-temperature deformation behavior in a dilute Mg–1.52Zn–0.09Ca (mass%) alloy sheet with weak basal texture

The deformation behavior of a weakly textured Mg–1.52Zn–0.09Ca (mass%) alloy sheet during room-temperature uniaxial tensile and bending tests was thoroughly investigated using the electron backscattered diffraction technique and crystal plasticity finite-element method. The sheet exhibited a high elongation to failure of 46.1% along the transverse direction because of the easy activation of basal slips, prismatic slips, and tensile twinning. Although the activities of the basal slips and tensile twinning were suppressed during the tensile deformation along the rolling direction, the sheet showed a satisfactory elongation to failure of 28.2% owing to the activation of the prismatic slips. Notably, the sheet exhibited excellent stretchability with a limiting dome height of 10.1 mm. This was attributed to a small fraction of the basal texture component, which facilitated the basal slips during the stretch formation. However, during the bending deformation, the prismatic slips and tensile twinning became less active than during the uniaxial tension, affording inferior bendability to that of automotive-grade Al alloy sheets. This may help to establish microstructural design guidance for the development of room-temperature formable Mg alloy sheets.

Mechanical properties of fully recycled coarse aggregate concrete with polypropylene fiber

Incorporating polypropylene fiber as an additive material into the mixture can effectively improve the mechanical properties of concrete. In this paper, in order to investigate the mechanical properties of fully recycled coarse aggregate (FRCA) concrete with PP fiber, four groups of specimens with different volume ratio of PP fiber were designed and manufactured to conduct experiments of uniaxial compression and bending respectively. Based on the test results, the influence of volume ratio of PP fiber on the compressive and flexural mechanical properties of FRCA concrete were analyzed. The results showed that the integrity of compression specimens with PP fiber was better after failure and the flexural failure of the specimens without fiber or with PP fiber was brittle after the peak value. Moreover, with the increase of volume ratio of PP fiber, the slump of specimens presented a downward trend, the cube compressive strength increased continuously, and the cylinder compressive strength first decreased and then increased. Besides, with the increase of volume ratio of PP fiber, the static pressure elastic modulus increased as a whole, and the flexural strength increased.

Experimental Investigation of Behavior of Reinforced Concrete Columns Strengthening with Carbon Fiber Reinforced Polymer Under Axial and Uniaxial Bending Loadings

Betonarme kolonlar, yapının yaşlanması, çevresel etkiler, deprem vb. gibi durumlardan dolayı güçlendirilmesi ya da onarılması gereken en önemli yapısal elemanlardır. Bir yapı elemanı güçlendirilirken hangi etkilere maruz kaldıklarını tespit etmek oldukça önem arz etmektedir. Betonarme kolonlar da çoğu kez eş merkezli yüklemelere maruz kalsalar da özellikle kenar kolonlar dış merkezli olarak da yüklemelere maruz kalarak eğilme momentleri tesiri altında eksenel yük taşımaya çalışmaktadır. Bu çalışma kapsamında eş merkezli ve dış merkezli olarak yüklenen betonarme kolonların karbon fiber takviyeli elyaf kumaş (KFTEK) şeritler ile güçlendirilmesinin deneysel olarak incelenmesi amaçlanmıştır. Bu amaçla 6 adet büyük ölçekli deney elemanı üretilmiştir. Bu deney elemanlarından 2 adeti referans olarak seçilmiştir. Geriye kalan 4 adet deney elemanı is KFTEK şeritler ile güçlendirilmiştir. Yükleme tipi (eş ve dış merkezli) ve ankraj kullanımı değişkenler olarak belirlenmiştir. Şerit genişliği ve aralığı ise sabit tutulmuştur. Gerçekleştirilen deneysel çalışma sonucunda deney elemanlarının maksimum yük taşıma kapasitesi, başlangıç rijitliği, sünekliği ve enerji tüketim kapasitesi hesaplanarak sonuçlar karşılaştırılmıştır.

An analytical solution to estimate the critical buckling load of doubly-curved laminates under a combined load of uni-axial compression, in-plane shear and bending moment

Curved panels are structural elements that form the skin of wings, fuselages and tail booms in aircraft. Buckling of these structures would adversely affect aircraft performance. Due to this, the problem of buckling has been extensively researched in the past. Most of the research has been restricted to the analysis of flat composite panels and analysis of curved panels through simplifications involving geometry, material properties and boundary conditions. The present study aims to develop an analytical solution that can predict the critical buckling load for a wider range of problems. An analytical solution was developed in order to obtain the critical buckling load for a doubly-curved composite laminate under compression, shear, moment or any combination of the three loads. The assumptions of the classical laminate plate theory were used in order to obtain the displacement fields as well as strains of the laminate. The energy method was employed in order to obtain the critical buckling load for various load cases. The values obtained through the analytical solution are compared to the critical buckling loads obtained through finite element analysis (FEA). The highest deviation of critical buckling load from FEA was calculated to be 16.55%. Variation of the critical buckling load with respect to the radius of curvature, boundary conditions and stacking sequence was analyzed. The developed solution was also found to be valid for cases when radii of curvatures are unequal as well as when the length and breadth of laminate are unequal.

The effect of loading methods on the microstructural evolution and degree of strain localization in Cu50Zr50 metallic glass composite nanowires: A molecular dynamics simulation study

In this work, the Cu50Zr50 metallic glass composite nanowire (MGCNW) is subjected to uniaxial tensile, bending, and cyclic deformation. The effect of loading methods on the microstructural evolution and degree of strain localization is investigated. The simulations are performed using molecular dynamics (MD) code. The embedded atom method (EAM) is used to model the interactions between Cu–Zr atoms. The model for the study is created by embedding spherical copper nanocrystallites (diameter = 50 Å) in the Cu50Zr50 metallic glass matrix. Uniaxial tensile simulations have been carried out at strain rates in the range of 106 s−1 to 109 s−1. Three-point bend tests are carried out at different loading rates (1 m/s to 10 m/s). Finally, a strain-controlled cyclic deformation test is carried out at a strain amplitude of 0.02. All the tests are carried out at a temperature of 300 K. Atomic clusters of high shear strain are observed at the yield that later develops into bands with increasing strain. The degree of strain localization is observed to be higher in the bend tests as compared to the tensile and cyclic deformations. Also, it increases with decreasing strain rate. Voronoi polyhedral analysis reveals the breakdown of (0, 0, 12, 0) icosahedral clusters during plastic deformation, which is prominent during tensile deformation.

Effect of Graphene Nanoplatelets on Mechanical Performance of GFRP Composites

The carbonaceous nanofillers such as graphene nanoplatelets (GN) due to their unique properties have been increasingly used as nanofillers to improve the mechanical properties of FRP composites. In the present study, unidirectional glass fiber reinforced polymer (GFRP) composites and GFRP composites with graphene nanoplatelets (GN-GFRP) are fabricated using vacuum bag process and hand layup method. The percentage of GN added in GN-GFRP composites is 0.1% and 0.5% in case of hand layup method and 0.5% in case of vacuum bag process. The specimens are tested under uniaxial tension and three-point bending to study the effect of GN on the tensile and flexural performance of GFRP composites. In case of composites fabricated using hand layup method, the tensile strength of GFRP composites increased by 35.8% and 40.4% with the addition of 0.1% and 0.5% GN respectively. The tensile modulus of GN-GFRP composites with 0.5% GN decreased by 11.8% compared to GFRP composites. The flexural strength of GN-GFRP composites with 0.1% and 0.5% GN are found to have increased by 6.5% and 5.3% respectively compared to GFRP composites. The flexural modulus of GN-GFRP with 0.1% GN increased by 11% and the same for GN-GFRP with 0.5% decreased by 8.2% compared to GFRP composites. The tensile strength and modulus of GN-GFRP composites fabricated using vacuum bag process decreased by 24.4% and 7.7% respectively compared to GFRP composites. Scanning Electron Microscope (SEM) investigation reveals that poor adhesion of resin with the fibers caused delamination in GN-GFRP composites fabricated using vacuum bag process resulting in reduction of tensile properties.

Microstructure characteristics and deformation behavior of tin bronze/1010 steel bimetal layered composite by continuous solid/liquid bonding

The tin bronze (TB) and steel (SAE 1010) bimetal layered composite (BLC) plate was prepared by continuous solid-liquid bonding. Microstructures and interdiffusion between Cu and Fe in the obtained BLC were characterized by optical microscope, electron probe micro-analysis and electron back scattering diffraction. Mechanical properties were analyzed by the uniaxial tensile and bending tests. Moreover, in order to study the deformation behavior of the two materials, the clad ratio and mechanical properties of the BLC after rolling were also performed. The results show that the TB/1010 steel BLC with excellent metallurgical bonding and homogeneous microstructure is obtained. The ultimate tensile strength of the BLC (512.3 MPa) is located between the TB (376.2 MPa) and 1010 steel (536.3 MPa), and it is 56.0 MPa larger than the calculated value by the rule of mixture, which is attributed to the synergetic strengthening of the interface. The plastic instability strain is calculated according to the long-wavelength prediction combining the strain hardening index n and work hardening coefficient k of TB and 1010 steel. The generation of twins in TB and the reduction in grain size caused by rolling result in an increase in yield strength of the BLC. The results of the bending tests further show that the strength of interface is larger than that of the TB because the crack propagation is located at the TB and the interface is always tightly bonded.

The Effect of Low-Processing Temperature on the Physicochemical and Mechanical Properties of Bovine Hydroxyapatite Bone Substitutes.

Bovine bone grafts (BBX) require protein removal as part of the manufacturing process to reduce antigenicity and, in consequence, to be safely used in humans. Deproteinisation may have direct effects on the characteristics of the bone material and on in vivo material performance. This research aimed to comprehensively study the physicochemical and mechanical properties of BBX processed at low deproteinisation processing temperatures. Cubes of bovine bone (8 mm3) were treated with temperatures between 100 °C and 220 °C at 30 °C intervals and with pressures ranging from 1.01 to 24.58 Bar. The samples were characterised topographically and mechanically using scanning electron microscopy (SEM), atomic force microscopy (AFM), and uniaxial bending tests. The organic content and the chemical composition were determined using thermogravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FTIR). X-ray diffraction (XRD) and FTIR were also used to quantitatively determine the specimen crystallinity. Increasing temperature/pressure was associated with decreasing protein levels and compressive strength and increasing surface irregularities and crystallinity. The findings suggest that low-temperature processed bone is likely to exhibit a rapid in vivo degradation rate. The deproteinisation temperature can be adjusted to tailor the graft properties for specific applications.

MORI-A: Soft Vacuum-Actuated Module With 3D-Printable Deformation Structure

Many soft robots are made of polymeric materials such as silicone, urethane, and gel. These soft matter-based robots can be designed to have soft functionality by controlling the deformation, elastic modulus, and other properties of the flexible material. However, updating the shape of a soft robot once it is developed is not considered to be highly effective. It has to be redesigned whenever different functions are required. The body of a modular robot is composed of connected voxel units, and the model and behavior of the robot can be altered conveniently by recombining the module groups. This study proposes a reconfigurable and vacuum-actuated soft matter modular block: MORI-A. It can realize different behaviors of uniaxial bending, shear deformation, and non-deformation depending on the 3D-printed structure contained in a unit. In addition, MORI-A can display elastic anisotropy that depends on the density of the 3D structure it contains and the trajectory it adopts during fabrication. This study quantitatively verifies the load capacity and bendability of MORI-A. We then show that the combination of deformable shapes can improve the diversity of soft modular robot designs by simultaneously developing many curved deformations. These designs include characters. soft modular grippers, applications for underwater swimming robots using curvature, and artificial muscles for dolls made of cloth or cotton that are not supposed to move spontaneously.

The investigation of additive manufacturing and moldable materials to produce railway ballast grain analogs

The size and shape of individual grains, play an important role in the mechanical behavior of granular materials such as the strength and stability of railway ballast. The aim of this research is to study materials from which uniform, reproducible grains with irregular convex geometry can be created by molding and additive manufacturing technologies in order to create reproducible artificial assemblies that can be used in experiments. Packings with determined grain shape results more controlled investigations contrarily to using natural grains with random geometry. Specimens were made from railway ballast materials, materials used in the construction industry, additively manufactured and molded polymers, and certain low-strength materials. Uniaxial compression and bending tests were conducted on these specimens. The mechanical properties of typical railway ballast materials (basalt and andesite) were compared with the properties of artificially produced materials. The results show that for grain reproduction the molding technology is recommended with the use of polyester-crushed stone composite and ceramic powder. Furthermore, the additive manufacturing was recommended with PolyJet or Multi Jet Fusion technology as they have the feasibility to produce grains with similar material properties to the properties of basalt and andesite.

Determination of uni-axial bending resistance of reinforced fly ash concrete columns

As a by-product from coal burning of thermal power plants, fly ash has appropriate physical properties and chemical composition that can be utilised for the concrete industry, in a form of a fine-mineral additive to reduce cement up to 25% by mass and to enhance the workability of concrete. However, the negative effect of fly ash on the strength of reinforced concrete (RC) members has not been considered in current design provisions. Hence, the determination of uni-axial bending resistance of a basic member - RC column - having 20% cement weight replaced by fly ash is presented in this paper in the following research steps: (i) Experimental investigation on a number of 8 RC column specimens; (ii) Validation of test results with a number of code provisions including Eurocode 2, ACI 318-19, and TCVN 5574:2018; and (iii) Proposal of a simplified justification approach for TCVN 5574:2018 to be capable of modelling the reduction and predicting the uni-axial bending resistance of reinforced fly ash concrete columns.

Experimental study on seismic behavior of welded H-section stainless steel beam-columns

Previous studies have shown that structural stainless steel material has significant cyclic hardening characterized by strain amplitude dependence and unsaturation under cyclic loadings, which could have a remarkable impact on the seismic performance of stainless steel structures. Whether the current stainless steel structure design codes based on their static performance can accurately predict the seismic capacities of stainless steel structural members is worth studying. This paper investigates the hysteretic behavior of welded H-section stainless steel members under combined constant compression and uniaxial cyclic bending. A total of 24 specimens were tested, which covered a variety of test variables including stainless steel grade, section slenderness, axial compression ratio and loading history. Residual stresses of the welded H-sections considered in this study were measured. Then, the failure mode, hysteretic response, ductility coefficient and energy dissipation of welded H-section stainless steel beam-columns were fully obtained from the tests. Cyclic hardening was observed at the structural member level in the tests. The effect of loading history on seismic behavior was thoroughly discussed. It was found that various loading histories can obviously influence the strengths and deformation capacities of welded H-section stainless steel beam-columns resulting in their discrete seismic behavior, mainly due to the unsaturated cyclic hardening feature of stainless steels. Moreover, the current design codes including European Code, American Specification, Australia/New Zealand Standard and Chinese Specification underestimate the seismic capacities of welded H-section stainless steel beam-columns.

Testing, characterization and numerical prediction (uni-axial tension and bend test) of Double-side TIG welded SS321 plate for pressure vessel application

This study reports the welding of SS321 nuclear grade stainless steel employed for pressure vessel industries using the novel Double-side tungsten inert gas (DS-TIG) welding. The optimization technique (Taguchi-based Grey relational analysis (GRA)) used in this research will give firsthand knowledge to the industry concerning the process variables to produce quality weldments using the DS-TIG welding method. The optimized combination of input variables was noted to produce a butt joint with SS321 plate having 6 mm thickness: Arc length (Al) 3 mm, Arc current (I) 220 Amps, and Traverse speed (S) 120 mm/min. The Analysis of variance (ANOVA) table was created to estimate the significance of the input process variables in the weldments. The impact of process variables on the Depth of penetration: DoP and Bead width: BW in relation to the heat input was evaluated. The microstructural features and mechanical integrity of the DS-TIG weldment made with the optimized combination of input process variables were analyzed utilizing Optical microscopy, Electron back scattered diffraction (EBSD), Tensile, Hardness, Impact, and Bend tests. A Finite element (FE) model of uni-axial tension and bend test was developed to predict the tension strength (base and weld metal) and stress distribution during bend test of DS-TIG specimen. A good agreement between the experimental and predicted results was noticed (error less than 5%) in terms of stress vs. strain plot (uni-axial tension) and load vs. displacement plot (bend test).

Investigation of Reinforced Concrete Column Containing Metakaolin and Fly Ash Cementitious Materials

Nowadays, high-performance concrete is employed in the building sector all over the world. For a strong and durable construction, high performance appears to be a better option. These specially designed types of concrete are made using both conventional and unique materials to fulfill a combination of performance requirements. The objective of this experiment is to investigate the behaviour of short and long columns made of high-performance concrete (HPC). In this study, HPC was manufactured by essential denominators such as cement, fine aggregate, coarse aggregate, water, and mineral admixtures such as metakaolin and fly ash at different replacement levels. The high-performance concrete (HPC) was designed with compressive strength (CS) of about 60 N/mm2. The mixture was developed under the guidelines in modified ACI 211.4R-93. All combinations have the same 0.30 water binder ratio (W/B) and are utilized to achieve improved workability with the addition of a superplasticizer for a chemical admixture, namely, CERAPLAST 300. Seven proportions are cast with 0%, 5%, 7.5%, and 10% replacement of cement with metakaolin and another set of specimens with 5%, 7.5%, and 10% replacement with metakaolin along with a constant 10% replacement of fly ash. For the investigation of strength properties, specimens (cube, prism, and cylinders) such as compressive strength (CS) (3, 7, 28, 56, and 90 days), flexural (FS) and tensile strength (STS) (28 days) and modulus of elasticity were cast (28 days). Totally 14 columns, 7 for short and long columns, were cast, each cured for 28 days. These specimens have been tested in the 1000 kN loading frame. All small columns were tested with concentrated compression, whereas long columns were investigated with little concentration and uniaxial bending. The compressive strength of HPC with 7.5 percent metakaolin and 10 percentage fly ash (MR6) is 59 MPa, 7.34% greater than the compressive strength of reference concrete.

Testing, numerical analysis and design of stainless steel equal-leg angle section beams

The stability and design of stainless steel equal-leg angle section members subjected to uniaxial bending are studied herein. An experimental investigation, comprising material testing, initial geometric imperfection measurements and physical tests on hot-rolled austenitic stainless steel equal-leg angle section beams is first presented. The test results are then used to validate shell finite element models developed within ABAQUS, which are in turn used to undertake numerical parametric studies that consider both hot-rolled and cold-formed equal-leg angle section beams in austenitic, duplex and ferritic stainless steel with a wide range of slenderness values. Recent studies have shown that for angles under major-axis bending, both lateral-torsional and local buckling can arise, while under minor-axis bending, lateral-torsional buckling and Brazier-type flattening can occur. When designing for major-axis bending according to Eurocode 3, both local and lateral-torsional buckling are considered; it is shown herein that equal-leg angle sections under major-axis bending can be designed using a normalised slenderness based on the minimum of the local and lateral-torsional elastic buckling moments, while also considering their ratio. Under minor-axis bending, however, in comparison with the current provisions in Eurocode 3 that only require cross-section checks, it is shown that both safer and more accurate resistance predictions can be achieved when account is taken for lateral-torsional buckling and Brazier-type flattening. New design proposals for stainless steel equal-leg angle section beams, covering both major- and minor-axis bending, are therefore developed. The proposed design rules offer substantially more accurate and consistent resistance predictions compared to existing codified design rules. The reliability of the new design provisions, with a recommended partial safety factor γM1=1.1, is verified following the procedure provided in EN 1990.

Eccentric compression behaviour of rectangular concrete-filled steel tube columns with self-compacting lower expansion concrete

The use of a self-compacting lower expansion concrete in a concrete-filled steel tube (CFST) structure not only promotes the quality of concrete pouring but also improves the bond behaviour between the steel and the concrete. In combination with the actual stress state of the columns in the engineering structure, it is necessary to study the eccentric compression behaviour of the column. In this study, experimental studies involving both uniaxial and biaxial bending tests of rectangular self-compacting lower expansion CFST columns were carried out. The variation laws of the load–displacement curves, the lateral deflection curves and the stress–strain curves during the loading phase were analysed. Furthermore, the failure modes and the mechanical properties of the specimens under eccentric compression loads were investigated. Subsequently, the numerical models of CFST columns with self-compacting lower expansion concrete were considered and established. In order to verify the rationality of the finite element modelling, the numerical calculation results were compared with test results. Then, a parametric analysis of the compression and the bending bearing capacities of each column was carried out by changing the eccentricity of the load, and the N–M curves or N-Mx-My surfaces describing the ultimate bearing capacity of the column were obtained. Finally, by the parametric finite element analysis of the rectangular CFST columns regarding to the bearing capacity under the same eccentricity, a conclusion was obtained: when the expansion agent content γ of a specimen increased from 0% to 10%, the bearing capacity of the columns increases significantly, but when continue increasing the expansive agent content, the expansion agent content has little effect on the compression–bending bearing capacity.