Lateral Buckling Behavior Research Articles

The effect of longitudinal reinforcement ratio on the lateral buckling behavior of R/C walls modelled using prism elements

Studies on buildings subjected to earthquake action have shown that failure due to lateral buckling can cause structures to collapse. Therefore, transverse instability, its characteristics, and the mechanical factors that affect it need to be investigated to ensure the safety of structures. In the current experimental and analytical study, 22 tests were conducted using 11 column specimens constructed at a scale of 1:3 to simulate the boundary edges of structural walls. These specimens had varying ratios of longitudinal reinforcements (from 1.79% to 10.72%). The degree of tensile strain applied before compressive loading was 30‰ for all specimens. The present study examines the influence of the percentage of longitudinal reinforcement on the ultimate compressive capacity, deformation (axial and transverse), failure modes, and out-of-plane behavior of reinforced concrete seismic walls under earthquake loading conditions. It has been found that increasing the reinforcement ratio is not sufficient, by itself, to inhibit transverse instability, although it does affect its characteristics. It has also been discovered that rebar arrangement affects lateral buckling characteristics.

Analytical and numerical study on lateral buckling of imperfect subsea pipelines with nonlinear lateral pipe-soil interaction model

The nonlinear pipe-soil interaction model and the initial imperfections are predominantly factors that affect the lateral buckling behaviour of subsea pipelines with a high-temperature. In this study, mathematical models, taking these two factors into account, are proposed to simulate lateral buckling of subsea pipelines. Analytical solutions are derived from the assumption of rigid-plastic pipe-soil interaction, while numerical results are obtained when considering nonlinear pipe-soil interaction. The analytical and numerical results have an excellent agreement except for the negligible discrepancy in the pre-buckling state. The discrepancy is induced by the difference of mobilisation distance in rigid-plastic and elastic-plastic pipe-soil interaction models. After the analysis of snap-through phenomenon, the influence of breakout resistance, amplitude and half-wavelength of imperfection on the post-buckling behaviour is studied. Finally, the upper and lower bound critical temperature differences are discussed as well. The results show that the hysteresis cycle between pre-buckling and post-buckling states may appear under cyclic thermal loading. The snap-through phenomenon and the hysteresis cycle can take place more easily for large breakout resistance, small amplitude and large wavelength of imperfection. In the post-buckling state, the maximum stress uplifts with increasing breakout resistance or amplitude of imperfection, while it reduces with escalating wavelength of imperfection.

The structural efficiency of tapered steel section with perforation under lateral torsional buckling behaviour

Purpose Tapered section can resist maximum stress at a single location while the stresses are considerably lower at the rest of the member; therefore, it could have higher structural efficiency compared to conventional section. It could also satisfy functional requirements while reducing weight and cost in many fields of civil construction. Perforation in the steel section also eases the integration of Mechanical and Electrical (M&E) services such as ventilation pipes and electrical cables within the structural depths of the beam. In this analysis, the structural efficiency of tapered steel section with perforation under lateral-torsional buckling behaviour is investigated. Design/methodology/approach A total of 81 models are analysed using LUSAS software and five variables are investigated which involved perforation sizes, perforation shapes, perforation layout, tapering ratio and flange and Web thickness. Buckling moment is obtained from the analysis results in LUSAS software, while self-weight and structural efficiency are manually calculated. Findings Perforation size of 0.75 D has the highest structural efficiency, although it can withstand a smaller buckling load. This is due to its lower self-weight compared to other perforation sizes. The square perforation shape also has the highest structural efficiency compared to circular perforation and diamond perforation. An increment of percentage in structural efficiency of the square perforation shape with 0.75 D is the highest at 3.07%. The circular perforation shape with 0.75 D (Open-Open-Open perforation layout) has the highest increment of percentage in structural efficiency which is 2.37%. The tapering ratio of 0.3 is the most efficient and an increment of percentage in structural efficiency is 114.36%. The flange thickness of 0.02 m and Web thickness of 0.015 m has the highest structural efficiency at 45.756 and 29.171, respectively. Originality/value In conclusion, a section should be able to resist the large buckling moment and has a lower self-weight to achieve high structural efficiency.

Lateral torsional buckling of ultra-high-performance fibre-reinforced concrete girders

Ultra-high-performance fibre-reinforced concrete (UHPFRC) is a relatively newly developed construction material that not only has high compressive strength (greater than 150 MPa), but also high tensile strength (10–20 MPa). The use of UHPFRC enables the design of slender structural members; hence, instability could become a major governing failure mode. However, the estimation of buckling strength for a concrete structure is not easy, owing to its material characteristics. In this paper, the lateral torsional bucking behaviour and strength of ultra-high-performance concrete I-beams are discussed. A methodology is introduced to obtain the effective moment of inertia of UHPFRC I-beams, considering tensile cracks. By using the effective moment of inertia, the linear elastic buckling strength can be calculated. In addition, the inelastic lateral torsional buckling behaviour is investigated through finite-element analysis. A generalised buckling strength curve with a slenderness parameter is discussed. As a result, the limitations for classification of compact and non-compact members are defined, and lateral torsional buckling strength equations are suggested for a simply supported UHPFRC I-girder subjected to centre point loading. Several experimental studies were also conducted, and the results are applied to verify the final results.

Investigation of the Torsional Effects on the Lateral Buckling of a Pipe-Like Beam Resting on the Ground under Axial Compression

This paper deals with the lateral buckling behavior of an axially compressed beam interacting with the ground on which it is resting. Such a simple model is supposed to reproduce the same trends as observed during the lateral buckling of offshore pipelines on the seabed. In such practical analyses, the pipe-soil interaction relates the ground to the neutral axis of the pipeline. It is shown that, although such a constraint significantly affects the buckling behavior of the pipeline, it cannot reflect the torsional component of the buckling modes. However, this component is encountered in practice and may further modify the critical loads. Therefore, in this present preliminary study, the interaction between the beam in hand and the surrounding ground is modeled by a connection (a continuous distribution of lateral springs) related to the bottom line of the beam. In this way, the real contact between the soil and the bottom line of a pipe is mimicked, allowing for both flexural and torsional deformations in the buckling response. The problem is investigated analytically using an Euler–Bernoulli beam model with an isotropic linear elastic constitutive law and also an elastic interaction law. Original analytical solutions are derived and compared to numerical results obtained through finite element computations. In comparison with classical solutions (with the connection related to the neutral axis), new types of buckling modes may appear when considering torsional effects, depending on the boundary conditions, with generally much lower critical loads. These first results are certainly representative of some features of the global/localized lateral buckling of offshore pipelines, indicating that torsional effects should also be taken into account in such more comprehensive analyses.

Stability performance of thin-walled pultruded beams with geometric web-flange junction imperfections

The current paper investigates the role of initial imperfections at web-flange junction on the lateral torsional buckling behavior of pultruded fiber reinforced polymeric beams. This study is based on experimental and numerical results, which are developed in two main steps: perfect beams and beams with initial imperfections at the web-flange junction. In the first step, small-scale tests are carried out to calculate the mechanical properties of the composite section. Perfect and imperfect pultruded I- and C- shaped beams are subjected to full-scale experimental tests under an applied four-point bending load with a total lengths varying from 1500 to 3000 mm, and 2500–3500 mm for the I- and C-beams, respectively. The end conditions of all beams studied are simply supported. Perfect beams are tested to investigate their dominant failure mode, as well as the impact of lateral bracing on the failure modes. While, imperfect beams are tested to determine the effect of initial imperfections on the lateral-torsional buckling capacity and failure mechanisms.

The Lateral Torsional Buckling Behavior of Laminated Glass Beams

In this paper, the lateral torsional buckling (LTB) behavior of multi-layered long-span laminated glass (LG) beams is investigated through full-scale model test and numerical simulation. In the test program, the LG beams consisting of up to four glass plies and spanning 5000[Formula: see text]mm are constructed and tested. The load-displacement curves and development of strain in glass plies are recorded, based on which the deformation and stress state of buckled LG beams are analyzed, and the strength checking criterion is provided. The test results are also used to determine the shape and amplitude of initial imperfection through statistical analysis and to validate a numerical model based on the finite element method (FEM). Parametric analysis based on the FEM model is then conducted to investigate influential factors on the LTB resistance of LG beams, among which the influence of shape and amplitude of initial imperfection is emphasized. For the LTB design of LG beams, the applicability of existing formula to determine the critical buckling moment through effective stiffnesses is evaluated for multi-layered LG beams with the test and numerical results. Finally, the design buckling curves adopting the Ayrton–Perry formula (APF) are proposed and validated for LG beams categorized with glass type and load duration.

Experimental and numerical investigation of lateral torsional buckling behavior and capacity of welded Q460 beams

Compared to normal strength steel (NSS), high strength steel (HSS) has many advantages, such as high yield strength, high tensile strength, and high structural reliability. Recently, HSS beams have gradually been employed in practical engineering. In this investigation, eight tests and parametric analysis were carried out to study the lateral torsional buckling (LTB) behavior and capacity of welded Q460 beams. An effective loading system that released the lateral constraint of the loading point was developed. Totally eight tests of welded beams with lateral restraints at two end supports were conducted under a mid-span concentrated force. Among these eight welded beams, one Q235 beam was tested to compare with seven Q460 beams. The flange width-to-thickness ratio changed from 4.6 to 9.6, the web height-to-thickness ratio changed from 28.75 to 47.50, and the beam span was varied from 3 m to 5 m. In addition, a series of parametric analyses considering initial geometric imperfections were performed to evaluate and investigate the effects of key parameters on the LTB behavior of welded Q460 beams. The experimental and numerical results were compared with the LTB curves from Chinese design codes GB50017-2017 and GB50017-201X, Australian code AS4100, and Eurocode 3. The GB50017-201X, AS4100, and Eurocode 3 for general sections underestimate their LTB capacity. The current GB50017-2017 and Eurocode 3 for rolled and equivalent welded sections are unsafe for evaluating the LTB capacity of HSS beams. Modified design equations that are more appropriate for predicting the LTB capacity of welded Q460 beams are presented.

Lateral instability of steel beams in fire: Behaviour, numerical modelling and design

The lateral torsional buckling behaviour and design of steel beams in fire are investigated in this paper. Finite element models able to replicate the lateral-torsional buckling (LTB) response of steel beams at elevated temperatures are developed and validated. The validated finite element models are used to carry out extensive parametric studies to explore the LTB behaviour of steel beams in fire, considering various cross-section shapes, member slendernesses, steel grades, elevated temperature levels and different fabrication processes. A design equation for the LTB assessment of steel beams at elevated temperatures is developed on the basis of the results from the extensive parametric studies. The high accuracy, safety and reliability of the proposed design approach are illustrated, which is also compared against the beam design rules existing in the European structural steel fire design standard EN 1993-1-2. The design proposals made in this paper are compatible with the new LTB assessment equations that are due to be incorporated into the next version of the European room temperature structural steel design standard EN 1993-1-1 and lead to more accurate ultimate strength predictions relative to the beam buckling design equations existing in EN 1993-1-2.

Experimental Study on the Lateral Torsional Buckling Behaviour of the Triangular Web Profile Steel Section

A triangular web profile (TriWP) section is a structural steel section that is made of two flanges connected to a web plate of triangular profile. Only certain research works have been carried out to study the characteristic, behaviour and the advantages offered by this section compared to the normal flat web (I-beam). An area that is not given full attention is the capability of this section to resist the lateral torsional buckling moment capacity compared to that of the normal flat web. The objectives of this thesis are to study the lateral torsional buckling behaviour of Triangular Web Profile (TriWP) steel section and compare to that of the flat web by experimental and to find the value of Mb, moment buckling resistance for TriWP. The scope of study covered the experimental work and theoretical investigation of triangular web profile steel section subjected to lateral torsional buckling moment resistance. The effect of the shape of the triangular web profile beam compared to that of the flat web beam was also be studied. For the buckling moment resistance, several factors were taken into account such as buckling parameter, torsional index, warping constant and torsional constant. All these factors are related to the second moment of area with respect to minor axis. The lateral torsional buckling test includes 8 specimens (4 flat webs and 4 TriWP). Each specimen was tested in two different sizes which is 200x100x6x3 and 180x75x5x3. Findings from the lateral torsional buckling tests were compared to the manual calculation using BS 5950: Part 1:2000. The lateral torsional buckling test shows that the moment buckling resistance of the triangular web profile steel beam section is better than that of the flat web in smaller size while in bigger size flat web beam has better moment resistance than that of triangular web profile steel beam. The section properties such as width (B), depth (D), thickness of flange (tf) and thickness of web (tw) affect the buckling moment resistance, Mb of the steel section

Analytical study on controlled lateral thermal buckling of antisymmetric mode for subsea pipelines triggered by sleepers

Subsea pipelines exposed to high temperature and high pressure (HTHP) conditions is susceptible to lateral buckling. In order to control lateral buckling, engineered buckle initiators, such as sleepers, are introduced to initiate planned lateral buckles along the pipeline at specific locations in order to ensure that the stress in each lateral buckle remains acceptable. In this study, taking the interaction of adjacent buckles into account, analytical solutions of antisymmetric lateral buckling mode triggered by sleepers are derived. With the proposed formulations, the method to obtain the accurate locations of lateral displacement amplitude and maxima of bending stress is presented and discussed. And a detailed comparison between symmetric and antisymmetric mode of lateral buckling triggered by single sleeper is presented. Moreover, the influence of the sleeper spacing on controlled lateral buckling behaviour with the consideration of axial interaction between adjacent buckles is conducted. Finally, a detailed analysis about the influence of the sleeper height, lateral frictional coefficient and submerged weight of the pipeline on the controlled post-buckling behaviour is presented. Our results show that, for smaller sleeper friction or smaller sleeper height, the symmetric mode is more likely to happen, while the antisymmetric mode is prone to occur for larger sleeper friction and larger sleeper height. One effective method to reduce displacement amplitude and maximum stress is to decrease the sleeper spacing. The minimum critical temperature difference decreases with increasing sleeper height and increases with increasing lateral friction coefficient or submerged weight of the pipeline. And an alternative way to reduce the maximum stress is to reduce the lateral friction coefficient or submerged weight of the pipeline even though the displacement amplitude increases.

Investigations on the lateral impact behaviour of combined geometry tubular structures and its effect of cap fillet radius

Thin-walled tubular elements with square, conical and polygonal sections have been effectually employed as impact energy dissipating structures in modern automotive vehicles for their less weight, stable deformation and outstanding energy dissipating ability. In the current research article, finite element simulation on the lateral buckling behavior and influence of crashworthiness performance indicators on the variation of cap fillet radius were executed. Finite element models were developed with ABAQUS/CAE® code to predict the buckling behavior of the proposed tubes under lateral impact force. The lateral impact crushing behavior of the proposed combined geometry tubes was compared with the traditional simple geometry tubes and the outcomes revealed that combined geometry tubes deformed progressively and absorbed better impact energy than the traditional cylindrical tubes. The maximum energy absorption capacity that could be attained is with a circular tube with 30 mm fillet radius.

The simplified method of the equivalent compression flange

AbstractExtended version of the Tomáš Vraný SDSS Award 2019The method of the equivalent compression flange simplifies the verification of lateral torsional buckling of steel beams to flexural buckling of an equivalent part of the cross‐section that is in compression. The current simplified method is based on outdated normative rules and the design results may be both, uneconomic and non‐conservative. To remedy these shortcomings, the simplified method is modified based on the basic structural behaviour of steel beams taking into account the effects of material, cross‐sectional geometry and residual stresses. This paper presents a comprehensive experimental study on the lateral torsional buckling behaviour and residual stresses of welded doubly‐ and mono‐symmetric I‐shaped steel beams. Moreover, an improved simplified method of the equivalent compression flange is proposed for design purposes.

Inelastic Ultimate Load Analysis of Steel Frames Considering Lateral Torsional Buckling Under Distributed Loads

Contemporary structural design approaches necessitates ways to determine realistic behavior of structures. For this purpose, inelastic ultimate load analysis methods are used widely since strength and stability of whole structure can be represented. In this study, a numerical method is proposed for determining inelastic ultimate load capacity of steel frames considering lateral torsional buckling behavior under distributed loads. In the analyses, inelastic material behavior, second-order effects and residual stresses of the structural frame system and its members are taken into account. Additionally, lateral torsional buckling behavior is considered in the analysis using finite difference method and it is used for determining the structural load carrying capacity of steel frames. Consequently, the problem associated with flexural capacity decreases due to lateral torsional buckling is precisely considered in the load increment steps of inelastic ultimate load analysis. In order to validate the proposed method, numerical examples from the literature are calculated considering the proposed method, AISC 360-16 design specification equations and approaches from the literature. Results of the numerical examples show that lateral torsional buckling is a key issue in determining structural load carrying capacity. Thus, proposed analysis method is shown to be an efficient and consistent tool for inelastic ultimate load analysis.

Limit Analysis of Thin-Wall Metal Frames Taking into Account their Foundations Rigidity

In this paper, the mathematical model of shakedown optimization problem of limit analysis for the thin-wall metal frames under variable quasi-static loads is presented. Authors assume the elastic-plastic flexural buckling in one plane without lateral torsional buckling behavior of members on conditions of the ideal elastic-plastic behaviour of the frames materials. According to Eurocodes requirements, the features of these frames taking into account rigidity of their foundations are described. There is problem with definition equivalent uniform moment factors for frames under variable quasi-static loads, because moment diagram is not constant. Classification of joints by stiffness was analyzed. The cases when the conditions of rigidity are not satisfied were described. The variants of solving tasks for thin-wall metal frames have been developed, for which there is a discrepancy between the classification by stiffness of the column base and the initial design model. It’s demonstrated on the principle scheme of the iteration process. With the help of numerical example, the problems which deal with classification of joints by stiffness on the final step of the optimal design of the thin-wall metal frames were performed.

Lateral distortional buckling of rivet fastened rectangular hollow flange channel beams

Cold-formed steel hollow flange beams have been commonly used as flexural members in buildings due to their structural efficiency. The rivet fastened Rectangular Hollow Flange Channel Beam (RHFCB) is a new type of cold-formed steel section, characterized by two torsionally rigid hollow flanges connected to a web element. The RHFCB takes advantage of an intermittent fastening method using self-pierce riveting. Buckling analyses have shown that the moment capacity of short-span RHFCB is governed by local buckling while intermediate span RHFCB is governed by the unique lateral distortional buckling. An experimental investigation of RHFCB flexural members was carried out based on a quarter point loading method to investigate their lateral distortional buckling behaviour and moment capacities. It considered the effects of intermittent rivet spacing on the member moment capacity of RHFCBs. The results from the experiments were compared with the member moment capacities predicted using the Australian cold-formed steel structures standard. Following the experimental study, finite element models of tested RHFCBs were developed to simulate the experiments. The developed finite element models were validated by comparison of ultimate moment capacities, applied moment versus deflection curves and failure modes. This paper presents the details of the experimental investigation, the development of finite element models of RHFCBs subject to lateral distortional buckling effects, and the results.

Analytical study of distributed buoyancy sections to control lateral thermal buckling of subsea pipelines

Unburied subsea pipelines operating under high temperature and high pressure (HT/HP) conditions tend to relieve their axial compressive force by forming lateral buckles in an uncontrolled manner. In order to control lateral buckling, a distributed buoyancy section is often employed. In this study, analytical solutions are deduced for lateral buckling of unburied subsea pipelines with a distributed buoyancy section. An energy analysis is employed to investigate the stability of the buckled pipeline. The influence of the length and weight of the distributed buoyancy section on pipeline buckled configurations, typical lateral buckling behaviour and the minimum critical temperature difference is illustrated and analysed. The results are shown to be in good agreement with experimental data in the literature. The effect of imperfections is also discussed and an error analysis is conducted for one of the main assumptions of the proposed analytical method. The results show that increasing the length or decreasing the weight of the distributed buoyancy section can both be used to decrease the minimum critical temperature difference. The maximum compressive stress will decrease with decreasing weight of the distributed buoyancy section. However, the influence of the length of the distributed buoyancy section on the maximum compressive stress is complicated.

FINITE ELEMENT ANALYSIS ON LATERAL TORSIONAL BUCKLING BEHAVIOUR OF I-BEAM WITH WEB OPENING

Lateral torsional buckling may occur in an unrestrained beam. A beam is considered to be unrestrained when its compression flange is free to laterally rotate and laterally displace. In this paper, the finite element analysis is used to investigate the lateral torsional buckling behavior of I-beam with and without web opening. The analysis considers a wide range of practical distances between two openings as well as, various shapes and sizes of web opening. Analysis results show that the size of web opening has slightly effect on the buckling moment resistance. Furthermore, five shapes and three sizes of opening with 1.1m section length were used to find the optimum size and shapes of opening. It was concluded that, the optimum size is 0.5D due to the high values of the buckling moment compared with 0.6D and 0.7D. Meanwhile, model 2 is classified as the optimum model because the value of buckling moment is higher than model 1. It was noted that C-hexagon has the highest buckling moment compared to other web opening shapes. Besides that, the differences in buckling moment values decrease when the opening becomes larger in size such as square opening. However, I-beam without web opening has the highest buckling moments resistance compared to C-hexagon.

Analytical study of lateral thermal buckling for subsea pipelines with sleeper

Unburied subsea pipelines operating under high-temperature and high-pressure conditions tend to relieve their axial compressive force by forming lateral buckles. Uncontrolled lateral buckling may lead to pipeline failure. In order to control lateral buckling, a sleeper is often employed as a buckle-initiation technique. In this study, analytical solutions of lateral buckling for unburied subsea pipelines with sleeper are derived. An energy analysis is employed to investigate the stability of the buckled pipeline. The influence of sleeper height and sleeper friction on pipeline buckled configurations and typical lateral buckling behaviour is illustrated and analysed. The results are shown to be in very good agreement with experimental data in the literature. We also discuss the effect of imperfections and conduct an error analysis of one of the main assumptions of the proposed analytical method. Our results show that increasing the height of the sleeper or decreasing the friction between pipeline and sleeper can all be used to decrease the minimum critical temperature difference. However, only the sleeper height is effective in substantially reducing the maximum compressive stress.

Numerical study on lateral buckling of pipelines with imperfection and sleeper

Lateral buckling is an important issue in unburied high-temperature and high-pressure (HT/HP) subsea pipelines systems. The imperfection–sleeper method is one of the most well-known methods used to control lateral buckling of HT/HP pipelines. Pipelines–sleeper–seabed numerical models are established and verified to analyze the buckling behavior of pipelines using the imperfection–sleeper method. The influence of six main factors on lateral buckling behavior is investigated in details based on the numerical results. Equations of buckling displacement (buckling displacement is defined by the final displacement of the middle point of the pipelines), critical buckling force, and buckling stress (Mises stress) are proposed using the gene expression programming technique. These equations show good accuracy and can be used to assist in the design of sleepers and assess the compressive and stress levels of pipelines.