Local Plate Buckling Research Articles

Local buckling of 800 MPa high strength steel welded T-section columns under axial compression

Local buckling behavior of welded T-section column, which was fabricated from 800 MPa high strength steel (HSS), was investigated in this study. An experimental study consisting of eleven welded T-section columns under axial compression was carried out. The failure mode characterized by local buckling of plates was found, and different load-displacement curves of specimens were established. Embedding coefficients including the effect of flange on the web buckling and the effect of web on the flange buckling were suggested. A finite element (FE) model for predicting the ultimate load of specimens was developed, which was then verified by test data. Comparison of width-thickness ratio limits for flange and web between various specifications and test data were made. Chinese Specification GB50017-2017 overestimated the ultimate load, and American Specification ANSI/AISC 360-10 was a little underestimated. A new model modified from Chinese Specification GB50017-2017 was proposed for estimating the ultimate load of 800 MPa high strength steel welded T-section columns under axial compression, and a good agreement between the proposed model and test data was made.

Hysteretic model for steel piers considering the local buckling of steel plates

The pier is a vital structural component of bridges and thus critically considered in the seismic design. In order to provide an accurate and efficient methodology in the analysis of seismic response, a hysteretic model considering the effect of local buckling of steel plates is proposed for steel piers. In the hysteretic model, the Giuffre-Menegotto-Pinto hysteresis model is employed to establish the hysteresis curve equation, and the energy-based Ibarra-Krawinkler degradation rule is followed to describe the deterioration rule of structural bearing capacity and stiffness. In this study, a widely used Chinese steel Q345qC was taken as an example to illustrate the proposed model for steel piers. At first, the seismic performance of steel piers under horizontal cyclic load was analyzed. Then, the empirical formulae of the vital limit state points for evaluating the structural seismic performance were established, and further the identification of the decisive parameter (degradation parameter) of the hysteretic model was carried out. Morever, the verification on the effectiveness of the proposed model was verified, and the results showed its applicability and accuracy for steel piers under horizontal cyclic loads. Finally, the application of the proposed model in the seismic calculation of steel piers was interpreted.

Numerical analysis of axially loaded rectangular concrete-filled steel tubular short columns at elevated temperatures

Elevated temperatures significantly reduce the local buckling strengths of steel tubes and the ultimate strengths of rectangular concrete-filled steel tubular (CFST) columns exposed to fire. No fiber-based models have been developed that include local buckling effects on the fire-resistance of rectangular CFST columns. This paper presents a new fiber element model for the fire-resistance predictions of axially loaded rectangular CFST short columns at elevated temperatures considering local buckling. The thermal analysis problem of a CFST column is solved by the finite difference method to determine the temperature distribution within its cross-section including an air gap, concrete moisture content and the emissivity of exposure surfaces. The nonlinear stress analysis of axially loaded short CFST columns under fire recognizes the stress-strain behavior of concrete and steel at elevated temperatures. The expressions for initial local buckling and effective widths of steel plates are incorporated in the computational model to include the effects of local and post-local buckling on the fire responses of CFST columns. The existing experimental and numerical results are utilized to examine the accuracy of the fiber-based model. The fiber model developed is used to undertake parametric studies on the effects of local buckling, geometric and material properties and loading ratio on the thermal and structural responses of CFST short columns and the load distribution in steel tube and concrete. The numerical model proposed is demonstrated to simulate well the fire and structural performance of axially loaded CFST short columns under fire. Moreover, computational solutions presented provide a better understanding of the thermal and structural responses of CFST columns in fire.

Local Buckling of Steel Plates in Composite Structures under Combined Bending and Compression

Local Buckling of Steel Plates in Composite Structures under Combined Bending and Compression

Effect of width–thickness ratio on capacity of pultruded square hollow polymer columns

Width–thickness ratio is an important geometric parameter in the local buckling of plates and, therefore, also for columns with square hollow sections (SHS). This paper reports on an investigation into the effects of width–thickness ratio (b/t) on the failure modes and load-carrying capacities of SHS columns made from pultruded glass fibre reinforced polymer (PFRP). Two SHS columns, with b/t = 10·7 or 15·9 were examined under axial compression. The experimental results revealed that local buckling occurred in the 15·9 section but not in the 10·7 section. From a theoretical analysis, a formulation of critical width–thickness values was established at the boundaries between failure modes of the columns under compression, considering the different boundary conditions of the side plates. It is commonly understood that global buckling occurs in columns with higher non-dimensional slenderness. This is only true when the width–thickness ratio is less than the derived critical value. The experimental results from this study and previous works are consistent with the developed theoretical estimations of the failure modes and load-carrying capacities for PFRP SHS columns, considering the effects of both non-dimensional slenderness and width–thickness ratio.

Seismic behaviour of double skin composite shear walls with overlapped headed studs

This paper proposes a type of double skin composite (DSC) shear walls with boundary columns to make solutions to improve ductility of high-rise buildings. In this DSC shear wall system, overlapped headed studs were used to achieve composite action between the steel face plate and concrete core. Seven DSC shear walls were tested under combined axial compressive force and horizontal cyclic loads to evaluate the seismic behaviours of this DSC shear wall. Key parameters in this test program include height of overlapped headed studs, axial force ratio, introducing steel tubes in boundary columns, and aspect ratio of the DSC shear wall. The test results exhibited that the tested seven specimens failed in flexure mode characterized by local buckling of steel face plate, tensile fracture of steel boundary column, and concrete crushing. Test results also show that using higher headed studs in DSC shear walls improved their deformation capacity and energy dissipation capacity. Increasing axial force on the DSC shear walls did not compromise their energy dissipation capacities but slightly reduced their ductility. Introducing steel tube in the DSC shear walls significantly improved the ultimate resistance, ductility, and energy dissipation of the DSC shear walls. Decreasing the aspect ratio from 2.0 to 1.0 nearly doubles the ultimate resistance and energy dissipation capacity of the DSC shear walls. Theoretical models were also developed to predict the ultimate load carrying capacity of the DSC shear walls under horizontal loads. The validations of the predictions by the developed analytical models against 14 test results confirm the accuracy of the developed theoretical models.

A refined model for local buckling of rectangular CFST columns with binding bars

This paper presents a refined model for local buckling of rectangular concrete-filled steel tubular (CFST) columns with binding bars under axial compression due to a deficiency in the previous model i.e. the influences of horizontal spacing and diameter of binding bars were not considered. The influences of longitudinal spacing, horizontal spacing and diameter of binding bars on the critical local buckling stress can be reasonably considered in the proposed model, which is applicable to both elasto-plastic phase and elastic phase. The refined model is verified against the experimental results, showing better agreement than the previous model. Then, the proposed model is employed to investigate the influences of longitudinal spacing, horizontal spacing, diameter of binding bars and cross-sectional aspect ratios on the critical local buckling stress. It is found that the critical local buckling stress increases considerably with the decrease of the spacing of binding bars. Furthermore, the influence of longitudinal spacing of binding bars on the critical local buckling stress is more significant than that of horizontal spacing. It is also found that the critical local buckling stress increase modestly with the increase of diameter of binding bars in the case of small spacing of binding bars. In addition, the cross-sectional aspect ratio have little influence on the critical local buckling stress, which can be ignored. Aiming at delaying the occurrence of local buckling of steel plates in rectangular CFST columns with binding bars, it is suggested that decreasing longitudinal spacing as an efficient measure has priority over other measures.

Structural behavior of cold-formed thick-walled rectangular steel columns

Cold-formed rectangular steel columns with large and thick walls are increasingly applied in engineering recently. The section dimension and wall thickness have increased continuously to 800 and 22 mm, respectively, which causes the significant differences of cold-formed effects between cold-formed rectangular steel columns with thin and thick walls. Therefore, the mechanical performance and design method of cold-formed rectangular steel columns with thick walls should be studied. In this study, two section dimensions (700 mm × 20 mm and 600 mm × 16 mm) were selected for the axial load test and analysis of cold-formed rectangular steel columns with large and thick walls. The conclusions are as follows. (1) The indirect cold-formed rectangular steel columns have lower cold-formed effects than direct cold-formed rectangular steel columns. (2) Cold-formed rectangular steel columns with large and thick walls have high-bearing capacity under axial loads, which are manifested by local plate instability. (3) Calculation formula of ultimate bearing capacity with considerations to local plate buckling is proposed. The calculated and test results are in accordance with numerical simulation results.

Local buckling of steel plates in concrete-filled steel tubular columns at elevated temperatures

Local buckling remarkably reduces the strength of steel plates in rectangular thin-walled concrete-filled steel tubular (CFST) columns at ambient temperature. This effect is more remarkable at elevated temperature. However, there have been very limited experimental and numerical investigations on the local and post-local buckling behavior of steel plates in CFST columns at elevated temperatures. This paper presents numerical studies on the local and post-local buckling behavior of thin steel plates under stress gradients in rectangular CFST columns at elevated temperatures. For this purpose, finite element models are developed, accounting for geometric and material nonlinearities at elevated temperatures. The initial geometric imperfections and residual stresses presented in steel plates are considered. Based on the finite element results, new formulas are proposed for determining the initial local buckling stress and post-local buckling strength of clamped steel plates under in-plane stress gradients at elevated temperatures. Moreover, new effective width formulas are developed for clamped steel plates at elevated temperatures. The proposed formulas are compared with existing ones with a good agreement. The effective width formulas developed are used in the calculations of the ultimate axial loads of rectangular CFST short columns exposed to fire and the results obtained are compared well with the finite element solutions provided by other researchers. The initial local buckling and effective width formulas can be implemented in numerical techniques to account for local buckling effects on the responses of rectangular thin-walled CFST columns at elevated temperatures.

Local buckling of thin plate on tensionless elastic foundations under interactive uniaxial compression and shear

ABSTRACT This paper uses a mathematical method to develop an analytical solution to the local buckling behaviour of long rectangular plates resting on tensionless elastic Winkler foundations and under combined uniform longitudinal uniaxial compressive and uniform in-plane shear loads. Fitted formulas are derived for plates with clamped edges and simplified supported edges. Two examples are given to demonstrate the application of the current method: one is a plate on tensionless spring foundations and the other is the contact between the steel sheet and elastic solid foundation. Finite element (FE) analysis is also conducted to validate the analytical results. Good agreement is obtained between the current method and FE analysis.

Elastic and inelastic buckling of square and skew FGM plates with cutout resting on elastic foundation using isoparametric spline finite strip method

The elastic buckling of square and skew thin functionally graded material (FGM) plates with cutout resting on an elastic foundation is investigated using the isoparametric spline finite strip method. It is assumed that the material properties of FGM plates vary smoothly through the thickness according to the power law model. The elastic foundation is simulated by the Winkler and two-parameter Pasternak models. The isoparametric spline finite strip method is also applied to investigate initial inelastic local buckling loads of skew homogenous plates with cutout based on the Ramberg–Osgood representation of the stress–strain curve using the deformation theory of plasticity. The critical buckling load of the plate is achieved by minimizing its total potential energy and solving the corresponding eigenvalue problem. In addition, the effects of elastic foundation coefficients and hole size on the local buckling of plates with different boundary conditions are determined and discussed.

Assessing the reliability of local buckling of plates for mild and high strength steels

In the current Eurocode 3-1-5 [1] for local buckling, the resistance curve used to represent the reduction factor of plated elements due to local failure is based on the so-called Winter-curve, derived on a semi-empirical approach by George Winter in 1947. This design curve represents the mean reduction values achieved in the experiments conducted by Winter and other researchers.However, when applying the safety concept of EN 1990 [2], an additional safety factor γM is necessary to ascertain a defined level of failure probability. Currently, this factor is set to 1.0 for applications in building structures. In this paper 34 stub column tests on welded, squared box sections of steel grade S500 up to S960 are described. In combination with an experimental database on stub column tests summarised in Ref. [3], a new, optimised resistance curve is derived which could act as an alternative to the Winter curve. Additionally, both functions are evaluated in regard to the safety standard EN 1990 [2] with focus on the resulting γM.As γM represents the safety factor for the actual material and geometric properties, which are not known by the designer, the more decisive safety factor is γM*. This factor is used throughout Eurocode and refers to the nominal material and geometric properties. Its derivation and the influencing parameters are discussed and evaluated in the study at hand.

12.11: Experimental and numerical studies on Q690D welded Box‐section columns under cyclic loading

ABSTRACTTo evaluate hysteretic performance of Q690D high‐strength steel (HHS) welded box‐section columns, cyclic tests and numerical studies have been carried out. Firstly, cyclic loading tests were performed on two box‐section Q690D HSS welded columns with nominal axial compression ratio of 0.35. Failure modes were observed as elastic‐plastic local buckling of plate. The hysteretic curves and skeleton curves of the test specimens were produced and show that the tested columns have good energy dissipation capacity. It also shows that second order effect cannot be neglected for HHS welded columns. Then a finite element model has been built to simulate the cyclic loading tests. Comparison of numerical and test results verified the effectiveness of the built numerical model, which can then be used for further parametric analysis.

03.17: Design of haunches in structural steel joints

ABSTRACTThe paper presents research into the advanced design of stiffeners in structural steel joints. Experimental results of six specimens of haunches with and without flanges are presented. Three specimens are without flanges and three specimens are supported by additional flanges. Flanges differ in stiffness to observe the increase of haunch resistances and its effect on buckling shapes.Haunches with and without flanges are validated by numerical model to tests and resistances are calculated and evaluated. The research finite element model (RFEM) is studied by material and geometrical nonlinear finite element analysis with imperfections under the actual stress conditions and validated on the measured experimental data. The quality of prediction is demonstrated on the comparison of load‐deflection curves and failure modes. The stability analysis of a joint with a haunch is used for design Component Based Finite Element Models (CBFEM) of complex joints. RFEM allows verifying the design FEM model (DFEM) and component based FEM model (CBFEM) developed for the design of complex joints in steel structures. To avoid local buckling of slender plates in CBFEM a design procedure is proposed and verified on research finite element model (RFEM). It is proposed to use a combination of material nonlinear analysis without imperfections with buckling analysis in CBFEM. The verification is shown on an example of a haunch in a welded portal frame joint. The stiffener is studied by numerical analysis, resistances and critical loads are determined in RFEM and CBFEM and results are compared. A numerical study illustrates the effect of the haunch's thickness on the joint's resistance.

05.26: Reliability assessment for local buckling of plates

ABSTRACTIn the current Eurocode 3‐1‐5 [10] for local buckling, the resistance curve used to represent the reduction factor of plated elements due to local failure is based on the so‐called “Winter‐curve”, which was derived using a semi‐empirical approach by George Winter in 1947. This design curve reproduces the mean reduction values achieved in the experiments conducted by Winter and other researchers. However, when applying the safety concept of the Eurocode (EN 1990) [8], an additional safety factor is necessary to ascertain a defined level of failure probability. Currently, this factor is set to 1.0 for applications in building structures.In the study at hand, 131 stub column tests on welded, squared box sections from steel grades S275 up to S960 were evaluated to assess a realistic safety factor in conformity with the safety standard EC0 [8]. A considerable amount of tests where thereby classified as high strength steel. The results showed to be comparable for all steel grades in dependence of their local slenderness.The evaluation of test results revealed a considerable scatter, which is partly attributed to the stability failure mode, but could be also found to be originated from lack of information concerning unintended eccentricities in the experimental test setups. Therefore, the data set was divided into two sets, one consisting of all data, and one including only tests where these information were available and thus had reduced scatter. The second set lead consequently to a more favourable safety factor than the first one.For all sets using the procedure to derive a safety factor, assumptions have to be made regarding the property‐specific Coefficients of Variation (CoVs). Standard values often given in literature, although correct for their specific applications, cannot be simply adjusted when including high strength steel material. Additionally, as the resistance function for local buckling is complex, the impact of e.g. the thickness has to be taken into account carefully. Different approaches and variations are presented in this paper, leading to scientifically justified ‐values.

Experimental investigation into high strength Q690 steel welded H-sections under combined compression and bending

This paper presents a systematic experimental investigation into high strength Q690 steel welded H-sections under combined compression and bending. A total of 8 slender columns with four sections of different cross-sectional dimensions were tested successfully under eccentric loads. All columns failed in overall buckling about the minor axes of their cross-sections with significant material yielding. In some cases, plastic local plate buckling in the flange outstands became apparent at failure. After tests, all the columns were inspected closely, and no fracture in welding was found. As expected, these high strength Q690 steel welded H-sections were demonstrated to behave in various ways similar to those of conventional strength steel welded H-sections. Hence, these tests may be regarded to be confirmatory tests to structural behavior of Q690 steel welded H-sections under combined compression and bending.It should be noted that the measured failure loads were compared with the predicted resistances of these H-sections based on their measured geometrical and material properties according to various design rules given in EN1993-1-1, ANSI/AISC 360-16 and GB 50017-2003 respectively. Among all these three sets of design rules, EN1993-1-1 is shown to be effective and efficient in predicting resistances for high strength Q690 steel welded H-sections under combined compression and bending with properly selected parameters. Hence, EN1993-1-1 should be readily adopted by design and construction engineers in designing these Q690 steel welded H-sections under combined compression and bending.

Strength of double skin steel-concrete composite walls

Double skin steel-concrete composite walls have been increasingly used in civil engineering applications. However, the advantages of these walls have not been fully recognized due to the lack of appropriate technical guidelines for capacity design. In this paper, the local buckling strength of steel plate were firstly reviewed in terms of specifications incorporated in several modern codes. A methodology to predict the strength of steel plate with restraint of both concrete and shear studs was proposed based on the explicit solution for local buckling of steel plate in composite shear walls subjected to uniform axial compression and with elastically rotational restraint at loaded and unloaded edges. The results were compared with various previous experimental data and good agreement was observed. Furthermore, the load carrying capacity of composite walls was derived from the superposition of the contribution of steel plate and concrete. The predicted values from the proposed equations, together with the resulted determined from modern codes, were compared with the experimental results. It was found that both the proposed method and JEAG 4618 offer reasonable predictions while AISC 360 and KEPIC-SNG always underestimate the actual values.

Minimum cost design of overhead crane beam with box section strengthened by CFRP laminates

An overhead travelling crane structure of two doubly symmetric welded box beams is designed for minimum cost. The rails are placed over the inner webs of box beams. The following design constraints are considered: local buckling of web and flange plates, fatigue of the butt K weld under rail and fatigue of fillet welds joining the transverse diaphragms to the box beams, fatigue of CFRP (carbon fibre reinforced plastic) laminate, deflection constraint. For the formulation of constraints the relatively new standard for cranes EN 13001-3-1 (2010) is used. To fulfill the deflection constraint CFRP strengthening should be used. The application of CFRP materials in strengthening of steel and concrete structures are widely used in civil engineering applications due to their unique advantages. In our study, we wanted to show how the mechanical properties of traditional materials can be improved by the application of composite materials and how advanced materials and new production technologies can be applied. In the optimization the following cost parts are considered: material, assembly and welding of the steel structure, material and fabrication cost of CFRP strengthening. The optimization is performed by systematic search using a MathCAD program.

Structural Performance of Composite Shear Walls under Compression

In order to research the effect of different layout forms of steel plate on the axial compression behavior of a steel plate-concrete composite shear wall, this paper presents the experimental results and analysis of the axial compression behavior of a composite shear wall, with different layout forms of steel plate. A total of three tests were carried out, composed of two composite walls with built-in steel plate, and one composite wall with two skins of steel plate. The gross dimensions of the three specimens were 1206 mm × 2006 mm × 300 mm. Experimental results show that the composite wall with two skins of steel plate has an optimal ability of elastic-plastic deformation, and the maximum axial compressive bearing capacity among the three specimens. Using the energy method, the critical local buckling stresses of steel plate were calculated, and compared with the yield stresses. According to different confined actions of concrete, concrete constitutive models were proposed, and the axial compressive strengths of confined concrete were calculated. Considering the local buckling of steel plate and confined concrete, the calculation formula of the axial compression of the composite wall was put forward, and the calculated results were in good agreement with the test results. Therefore, the different layout forms of steel plate have a great influence on its buckling, and on the concrete inhibition effect, which can affect the axial compressive bearing capacity of the composite wall.

Theoretical and experimental studies of battened buckling-restrained braces

A new type of core-separated buckling-restrained braces, namely a core-separated battened buckling-restrained brace (B-BRB) has been proposed. Its load-carrying capacity and hysteretic response are investigated theoretically and experimentally in this paper. The B-BRB has a remarkable advantage over a common buckling-restrained brace (BRB), in which the newly formed cross-section of the B-BRB is spread outwards by spacing two cores, hence resulting in higher material utilization efficiency in its structural design. In addition, the two independent all-steel BRBs, each having a single plate core simply in-filled in a narrow hollow section, are connected by longitudinally distributed battens rather than continuous plates. Based on the elastic-plastic FE analysis of a B-BRB under monotonic compressive load, its ultimate resistance and failure modes are investigated numerically, considering the effect of its overall initial geometric imperfection. An interaction formula between normalized slenderness ratio and buckling factor of the B-BRB is proposed for predicting its ultimate load-carrying capacity. Consequently, the hysteretic response of the B-BRB is explored through elastic-plastic FE analysis. The maximum normalized slenderness ratios of the B-BRBs required for a load-bearing type and an energy-dissipation type are proposed in their strength designs, respectively. Ultimately, hysteretic responses of five B-BRB specimens have been experimentally investigated. The experimental results are compared with the FE numerical analysis, which considers plate local buckling of all components of the B-BRBs. The comparison has verified the rationality of the proposed design method.