• Journal of Korean Society of Steel Construction
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• v.15 no.1
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• pp.87-96
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• 2003

The Ssteel-Cconcrete (SC) Ccomposite Ccolumn is a new Ccomposite Ccolunin system, where hoops are welded between flanges of H-shapesd steel and concrete is filled in spaces between flanges are filled with con crete. Tests of SC composite columns were performed previously to determine their compression, bending and shear strength, and it showed good structural behavior. But sSince a column is usually subjected to an axial compression force, and bending it ihas needed to be bent forevaluate its structural behavior to be evaluated when its axial load and bending isaresimultaneously applied to the SC composite column. In this paper, tests were conducted to investigate the bending strength of SC composite columns subjected to axial compression force and bending moment. The parameters of the tests were concrete, a stud bolt, a hoop and a magnitude of axial compression. The test results showed that the maximum bending strength and ductility of an SC composite column were increased by 33-42% and 33-63%, respectively, comparinged to those of a bare steel column. Also, the results obtained bywith the Korean Limit State Design Code (LSD) presents a considerably safe side value compared to those of the Eurocode-4 and the Japan Code. However, wWhen the axial compression force is was increased, however, there awere considerable differences between the maximum strength obtained by the test and the LSD analysis. For this reason, it is recommended tothe use of the Eurocode-4 is recommended when calculates the strength of an SC composite column is being calculated, since the Eurocode-4 gives us a better estimation.

• Steel and Composite Structures
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• v.43 no.6
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• pp.773-784
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• 2022

This paper aims to investigate the axial compressive behavior of reinforced concrete (RC) columns strengthened with self-compacting and micro-expanding (SM) concrete-filled steel tubes (SM-CFSTs). Nine specimens were tested in total under the local axial compression. The test parameters included steel tube thickness, filling concrete strength, filling concrete type and initial axial preloading. The test results demonstrated that the initial stiffness, ultimate bearing capacity and ductility of original RC columns were improved after being strengthened by SM-CFSTs. The ultimate bearing capacity of the SM-CFST strengthened RC columns was significantly enhanced with the increase of steel tube thickness. The initial stiffness and ultimate bearing capacity of the SM-CFST strengthened RC columns were slightly enhanced with the increase of filling concrete strength. However, the effect of filling concrete type and initial axial preloading of the SM-CFST strengthened RC columns were negligible. Three equations for predicting the ultimate bearing capacity of the SM-CFST strengthened RC columns were compared, and the modified equation based on Chinese code (GB 50936-2014) was more precise.

• Structural Engineering and Mechanics
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• v.69 no.6
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• pp.627-635
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• 2019

In order to study the axial compression performance of sand-lightweight concrete-filled steel tube (SLCFST) stub columns, three circular SLCFST (C-SLCFST) stub column specimens and three SLCFST square (S-SLCFST) stub column specimens were fabricated and static monotonic axial compression performance testing was carried out, using the volume ratio between river sand and ceramic sand in sand-lightweight concrete (SLC) as a varying parameter. The stress process and failure mode of the specimens were observed, stress-strain curves were obtained and analysed for the specimens, and the ultimate bearing capacity of SLCFST stub column specimens was calculated based on unified strength theory, limit equilibrium theory and superposition theory. The results show that the outer steel tubes of SLCFST stub columns buckled outward, core SLC was crushed, and the damage to the upper parts of the S-SLCFST stub columns was more serious than for C-SLCFST stub columns. Three stages can be identified in the stress-strain curves of SLCFST stub columns: an elastic stage, an elastic-plastic stage and a plastic stage. It is suggested that AIJ-1997, CECS 159:2004 or AIJ-1997, based on superposition theory, can be used to design the ultimate bearing capacity under axial compression for C-SLCFST and S-SLCFST stub columns; for varying replacement ratios of natural river sand, the calculated stress-strain curves for SLCFST stub columns under axial compression show good fitting to the test measure curves.

• Journal of the Korean Society for Railway
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• v.3 no.1
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• pp.34-41
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• 2000

The analysis of static and dynamic characteristics of reinforced roadbed materials was performed through model and laboratory tests. The strength characteristic of reinforced roadbed materials such as HMS-25 and soil were investigated through the unconfined axial compression test, the model soil box test and the combined resonant column and torsional shear test. The unconfined axial compression strength of HMS-25 shows a steady increasement in strength due to the chemical hardening reaction between HMS-25 and water. The result of model soil box test reveals that railroad roadbed of HMS-25 is better than that of soil in several aspects, such as, bearing capacity and settlement. The combined resonant column and torsional shear test result indicates that shear modulus of HMS-25 and soil increase with the power of 0.5 to the confining pressure and linear relationship to normalized shear modulus and damping ratio.

• Steel and Composite Structures
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• v.22 no.2
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• pp.217-234
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• 2016

In order to investigate mechanical properties and load-bearing capacity of T-shaped Concrete-Filled Square Steel Tubular (TCFST) composite columns under eccentric axial load, three T-shaped composite columns were tested under eccentric compression. Experimental results show that failure mode of the columns under eccentric compression was bending buckling of the whole specimen, and mono column performs flexural buckling. Specimens behaved good ductility and load-bearing capacity. Nonlinear finite element analysis was also employed in this investigation. The failure mode, the load-displacement curve and the ultimate bearing capacity of the finite element analysis are in good agreement with the experimental ones. Based on eccentric compression test and parametric finite element analysis, the calculation formula for the equivalent slenderness ratio was proposed and the bearing capacity of TCFST composite columns under eccentric compression was calculated. Results of theoretical calculation, parametric finite element analysis and eccentric compression experiment accord well with each other, which indicates that the theoretical calculation method of the bearing capacity is advisable.

• Steel and Composite Structures
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• v.33 no.2
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• pp.181-194
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• 2019

This paper presents an efficient approach to generate a new empirical formula to predict the axial compression capacity (ACC) of circular concrete-filled tube (CCFT) columns using the artificial neural network (ANN). A total of 258 test results extracted from the literature were used to develop the ANN models. The ANN model having the highest correlation coefficient (R) and the lowest mean square error (MSE) was determined as the best model. Stability analysis, sensitivity analysis, and a parametric study were carried out to estimate the stability of the ANN model and to investigate the main contributing factors on the ACC of CCFT columns. Stability analysis revealed that the ANN model was more stable than several existing formulae. Whereas, the sensitivity analysis and parametric study showed that the outer diameter of the steel tube was the most sensitive parameter. Additionally, using the validated ANN model, a new empirical formula was derived for predicting the ACC of CCFT columns. Obviously, a higher accuracy of the proposed empirical formula was achieved compared to the existing formulae.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.9
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• pp.997-1002
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• 2012

With the increasing demand for lightweight materials to reduce fuel consumption, especially in the transportation industry, magnesium alloys are being widely studied. However, there are several limitations to the large-scale application of magnesium alloys in a structure because of their low formability and strong anisotropy. In order to take into account both the strong anisotropy and tension-compression asymmetry of AZ31 sheet alloy, the Cazacu-Plunkett-Barlat yield criterion (Cazacu, 2006) was adopted in material modeling. The variation of the anisotropic coefficients that describe the yield surface evolution of AZ31 is optimized using an interpolation function based on specific calibration results. It generates continuous yield surfaces, which makes it possible to describe different hardening rates in tension and compression as well as the tension-compression asymmetry of magnesium alloys. The performance of the CPB06 yield criterion for simulating an axial crushing test was tested and compared with that of the Hill (1948) yield criterion.

• Advances in concrete construction
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• v.9 no.3
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• pp.249-256
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• 2020

This paper aims at investigating the effect of crumb rubber size and content on compressive behaviors of concrete under axial compression. Concrete specimens are designed and produced by replacing natural aggregate with crumb rubber content of 0%, 5%, 10%, 15% and three different sized crumb rubbers (No. 20, No. 40, No. 80 crumb rubber). And the failure mode, compressive strength, elastic modulus, stress-strain curves, peak strain and ultimate strain are experimentally studied. Based on the test results, formulas have been presented to determine the compressive strength, elastic modulus, the relationship between prism compressive strength and cube compressive strength, stress-strain curves and peak strain of crumb rubber concrete (CRC). It is found that the proposed formulas agree well with the test result on the whole, which may be used to practical applications.

• Steel and Composite Structures
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• v.17 no.4
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• pp.431-452
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• 2014

The present study focuses on the mechanical behaviour of concrete filled double skin steel tubular (CFDST) stub columns confined by fiber reinforced polymer (FRP). A series of axial compression tests have been conducted on two CFDST stub columns, eight CFDST stub columns confined by FRP and a concrete-filled steel tubular (CFST) stub column confined by FRP, respectively. The influences of hollow section ratio, FRP wall thickness and fibre longitudinal-circumferential proportion on the load-strain curve and the concrete stress-strain curve for stub columns with annular section were discussed. The test results displayed that the FRP jacket can obviously enhance the carrying capacity of stub columns. Based on the test results, a new model which includes the effects of confinement factor, hollow section ratio and lateral confining pressure of the outer steel tube was proposed to calculate the compressive strength of confined concrete. Using the present concrete strength model, the formula to predict the carrying capacity of CFDST stub columns confined by FRP was derived. The theoretically predicted results agree well with those obtained from the experiments and FE analysis. The present method is also adapted to calculate the carrying capacity of CFST stub columns confined by FRP.

• Steel and Composite Structures
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• v.35 no.2
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• pp.159-169
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• 2020

Sandwich composite wall consists of concrete core attached by two external steel faceplates. It combines the advantage of steel and concrete. The appropriate composite action between steel faceplate and concrete core is achieved by using adequate mechanical connectors. This research studied the compressive behavior of the sandwich composite walls using steel trusses to bond the steel faceplates to concrete infill. Four short specimens with different wall width and thickness of steel faceplate were designed and tested under axial compression. The test results were comprehensively evaluated in terms of failure modes, load versus axial and lateral deformation responses, resistance, stiffness, ductility, strength index, and strain distribution. The test results showed that all specimens exhibited high resistance and good ductility. Truss connectors offer better restraint to walls with thinner faceplates and smaller wall width. In addition, increasing faceplate thickness is more effective in improving the ultimate resistance and axial stiffness of the wall.