• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.6
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• pp.270-278
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• 1999

This paper describes the collapse characteristics of the rectangular tube under eccentric compressive load. Overall buckling stress and bifurcation criterion (slenderness ration)are investigated. modified secant formula(MSF) is proposed to decide overall buckling stress. The bifurcation criterion which can distinguish between the local and overall buckling mode shapes is suggest by equating the local and overall buckling stresses. Additionally the effect of initial imperfection on bifurcation criterion is investigated.

• Proceedings of the Korean Nuclear Society Conference
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• 2002.10a
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• pp.415.2-415
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• 2002

• Structural Engineering and Mechanics
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• v.65 no.6
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• pp.679-687
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• 2018

In composite materials technology, the fiber-reinforced polymers (FRP) have opened up new horizons in infrastructural engineering field for strengthening existing structures and components of structure. The Carbon fiber reinforced polymer (CFRP) sheets are well suited for RC columns to this application because of their high strength to weight ratio, good fatigue properties and excellent resistance to corrosion. The main focus of present experimental work is to investigate effect of shapes on axial behavior of CFRP wrapped RC columns having same cross-sectional area and slenderness ratio. The CFRP volumetric ratio and percentage of steel are also adopted constant for all the test specimens. A total of 18 RC columns with slenderness ratio four were cast. Nine columns were control and the rest of nine columns were strengthened with one layer of CFRP wrap having 35 mm of corner radius. Columns confined with CFRP wrap were designed using IS: 456:2000 and ACI 440.2R.08 provisions. All the test specimens were loaded for axial compression up to failure and failure pattern for each shaped column was investigated. All the experimental results were compared with analytical values calculated as per the ACI-440.2R-08 code. The test results clearly demonstrated that the axial behavior of CFRP confined RC columns is affected with the change in shapes. The axial deformation is higher in CFRP wrapped RC circular column as compared to square and rectangular columns. Stress-strain behaviour revealed that the yield strength gained from CFRP confinement was significant for circular columns as compare to square and rectangular columns. This behaviour may be credited due to effect of shape on lateral deformation in case of CFRP wrapped circular columns at effective confinement action.

• Advances in concrete construction
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• v.8 no.4
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• pp.335-349
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• 2019

To investigate the axial compressive performance of the recycled aggregate concrete (RAC) filled glass fiber reinforced polymer (GFRP) tube and profile steel composite columns, static loading tests were carried out on 18 specimens under axial loads in this study, including 7 RAC filled GFRP tube columns and 11 RAC filled GFRP tube-profile steel composite columns. The design parameters include recycled coarse aggregate (RCA) replacement percentage, profile steel ratio, slenderness ratio and RAC strength. The failure process, failure modes, axial stress-strain curves, strain development and axial bearing capacity of all specimens were mainly analyzed in detail. The experimental results show that the GFRP tube had strong restraint ability to RAC material and the profile steel could improve the axial compressive performance of the columns. The failure modes of the columns can be summarized as follow: the profile steel in the composite columns yielded first, then the internal RAC material was crushed, and finally the fiberglass of the external GFRP tube was seriously torn, resulting in the final failure of columns. The axial bearing capacity of the columns decreased with the increase of RCA replacement percentage and the maximum decreasing amplitude was 11.10%. In addition, the slenderness ratio had an adverse effect on the axial bearing capacity of the columns. However, the strength of the RAC material could effectively improve the axial bearing capacity of the columns, but their deformability decreased. In addition, the increasing profile steel ratio contributed to the axial compressive capacity of the composite columns. Based on the above analysis, a formula for calculating the bearing capacity of composite columns under axial compression load is proposed, and the adverse effects of slenderness ratio and RCA replacement percentage are considered.

• Steel and Composite Structures
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• v.13 no.4
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• pp.367-382
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• 2012

This paper is dedicated to the buckling behaviors of strengthened perforated plates under edge shear loading, which is a typical load pattern of steel plates in civil engineering, especially in plate and box girders. The square plates considered each has a centric circular hole and is simply supported on four edges in the out-of-plane direction. Three types of strengthening stiffeners named ringed stiffener (RS), flat stiffener (FSA and FSB) and strip stiffener (SSA, SSB and SSC) are mainly discussed. The finite element method (FEM) has been employed to analyse the elastic and elasto-plastic buckling behavior of unstrengthened and strengthened perforated plates. Results show that most of the strengthened perforated plates behave higher buckling strengths than the unstrengthened ones, while the enhancements in elastic buckling stress and elasto-plastic ultimate strength are closely related to stiffener types as well as plate geometric parameters including plate slenderness ratio and hole diameter to plate width ratio. The critical slenderness ratios of shear loaded strengthened perforated plates, which determine the practical buckling pattern (i.e., elastic or elasto-plastic buckling) of the plates, are also studied. Based on the contrastive analyses of strengthening efficiency considering the influence of stiffener consumption, the most efficient cutout-strengthening methods for shear loaded perforated square plates with different slenderness ratios and circular hole diameter to plate width ratios are preliminarily identified.

• Advances in Computational Design
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• v.3 no.1
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• pp.71-86
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• 2018

Thin-walled cross-sections can be optimized to enhance their resistance and progress their behaviour, leading to more competent and inexpensive structural system. The aim of this study is to afford a methodology that would facilitate progress of optimized cold formed steel (CFS) column section with maximum ultimate strength for practical applications. The proposed sections are designed to comply with the geometrical standards of pre-qualified column standards for CFS structures as well as with the number of industrialized and practical constraints. The stiffening evaluation process of CFS lipped channel columns, a five different cross section are considered. The experimental strength and behaviour of the proposed sections are verified by using the finite element analysis (FEA). A series comprehensive parametric study is carried out covering a wide range of section slenderness and overall slenderness ratio of the CFS column with and without intermediate web stiffeners. The ultimate strength of the sections is determined based on the Direct Strength Specification and other design equation available from the literature for CFS structures. A modified design method is proposed for the DSM specification. The results indicate that the CFS column with complex edge and intermediate web stiffeners provides an ultimate strength which is up to 78% higher than standard optimized shapes with the same amount of cross sectional area.

• Journal of the Korean Society of Safety
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• v.16 no.1
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• pp.59-64
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• 2001

Even though there is a guideline for the required strength of pipe support in inspection, it does not mean the nominal strength which can be used for the form work design. And, Concrete Specification defines that the pipe support should be designed according to the steel design guidelines but the design details are not provided, such as buckling length and the sectional modulus, etc. For the better prediction of strength of pipe support, the slenderness ratio of support which reflects the boundary condition should be considered. In this paper, the elastic buckling formula based on the slenderness is derived. The formula contains the strength reduction factor that consider the strength deduction caused by initial lateral deformation and is 0.65 consistently regardless of boundary conditions. And the coefficient of effective buckling length is calculated from the experiment.

• Advances in concrete construction
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• v.7 no.2
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• pp.65-74
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• 2019

This paper reports on the results of a parametric study, which examines the effects of varying aspect ratios on the dynamic response of cylindrical silos directly supported on the ground under earthquake loading. Previous research has shown that numerical models can provide considerably realistic simulations when it comes to the behavior of silos by using correct boundary conditions, appropriate element types and material models. To this end, a three dimensional numerical model, taking into account the bulk material-silo wall interaction, was produced by the ANSYS commercial program, which is in turn based on the finite element method. The results obtained from the numerical analysis are discussed comparatively in terms of dynamic material pressure, horizontal displacement, equivalent base shear force and equivalent bending moment responses for considered aspect ratios. The effects experienced because of the slenderness of the silo in regards to the seismic response were evaluated along with the effectiveness of the classification system proposed by Eurocode in evaluating the loads on the vertical walls. Results clearly show that slenderness directly affects the seismic response of such structures especially in terms of behavior and the magnitude of the responses. Furthermore the aspect ratio value of 2.0, given as a behavioral changing limit in the technical literature, can be used as a valid limit for seismic behavior.

• Advances in concrete construction
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• v.9 no.3
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• pp.289-299
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• 2020

To investigate the long-term behavior of eccentrically loaded RC columns, which are more realistic in practice than concentrically loaded RC columns, long-term eccentric loading tests were conducted for 10 RC columns. Test parameters included concrete compressive strength, reinforcement ratio, bar yield strength, eccentricity ratio, slenderness ratio, and loading pattern. Test results showed that the strain and curvature of the columns increased with time, and concrete forces were gradually transferred to longitudinal bars due to the creep and shrinkage of concrete. The long-term behavior of the columns varied with the test parameters, and long-term effects were more pronounced in the case of using the lower strength concrete, lower strength steel, lower bar ratio, fewer loading-step, higher eccentricity ratio, and higher slenderness ratio. However, in all the columns, no longitudinal bars were yielded under service loads at the final measuring day. Meanwhile, the numerical analysis modeling using the ultimate creep coefficient and ultimate shrinkage strain measured from cylinder tests gave quite good predictions for the behavior of the columns.

• Steel and Composite Structures
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• v.22 no.6
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• pp.1487-1505
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• 2016

This paper presents the results of an experimental study on the behavior of a new type of composite FRP-concrete-steel member subjected to bi-axial eccentric loading. This new type of composite member is in the form of concrete-filled square steel tube slender columns with inner CFRP (carbon fiber-reinforced polymer) circular tube, composed of an inner CFRP tube and an outer steel tube with concrete filled in the two tubes. Tests on twenty-six specimens of high strength concrete-filled square steel tube columns with inner CFRP circular tube columns (HCFST-CFRP) were carried out. The parameters changed in the experiments include the slenderness ratio, eccentric ratio, concrete strength, steel ratio and CFRP ratio. The experimental results showed that the failure mode of HCFST-CFRP was similar to that of HCFST, and the specimens failed by local buckling because of the increase of lateral deflection. The steel tube and the CFRP worked together well before failure under bi-axial eccentric loading. Ductility of HCFST-CFRP was better than that of HCFST. The ultimate bearing capacity of test specimen was calculated with simplified formula, which agreed well with test results, and the simplified formula can be used to calculate the bearing capacity of HCFSTF within the parameters of this test.