Flange Sections Research Articles

Modular Building Design: Post‐Brexit Housing

ABSTRACTThe use of modular building systems (MBSs) in the construction sector is increasing. MBSs enhance structural performance of buildings, quality control, and construction speed than traditional methods at a lower cost. Additional benefits can be associated with resource efficiency at both the production and construction phases, which may increase MBSs' attractiveness and popularity in the short‐ and long‐term future. In the UK, the government is planning to solve Britain's housing crisis by constructing more than 100,000 modular homes in an effort to meet its target to provide a million new homes by 2020. At the same time, the construction sector is facing post‐Brexit skills shortages, while it is undergoing a technological revolution. One outcome of the latter has been the production of cold‐formed steel (CFS) hollow flange sections, which can be optimised using genetic algorithm and finite element analyses in order to improve the load‐carrying capacity of modular buildings. These optimised CFS beams, employed in MBSs, can light gauge the frame building constructions. This paper presents a review of MBSs and the application of CFS hollow flange steel sections in construction. It then summarises some of the key outputs of numerical studies on the structural behaviour of hollow flange beams to justify its applicability in MBS.

Web compression buckling capacity prediction for unstiffened I-sections with opposite patch loading

Two web compression buckling capacity prediction methods are introduced for unstiffened steel I-sections subject to opposite patch loading applied to the flanges. The methods are generally posed as a function of loaded width to web depth ratio, and are applicable for opposite patch loading applied at the interior of a wide flange section or at the end of it, where the web has a free edge. The proposed methods include three parts: 1) an expression for predicting the squash load, 2) an expression for predicting the elastic buckling load, and 3) a resistance function. The squash load is calculated using an empirically derived effective width concept based on observations at the ultimate load from an extensive experimental database and validated numerical simulations. Web slenderness is defined as the square root of the ratio of the web squash load to the web critical elastic buckling load. The critical elastic buckling load is defined consistently with that obtained with a plate buckling energy solution for patch loading on infinitely long strips and considers the shortened web buckling half-wavelength resulting from flange rotational restraint provided to the web. The methods are validated with existing experimental data and shell finite element collapse simulations, and are shown to be more accurate and more widely applicable than current American Institute for Steel Construction (AISC) Specification provisions.

Part I: The Analytical Model Predicting Post-Yield Behavior of Concrete-Encased Steel Beams Considering Various Confinement Effects by Transverse Reinforcements and Steels.

The purpose of the work was to propose analytical model considering double confinements (provided by both transverse reinforcements and a wide flange steel section), which was verified by the nonlinear finite element analysis considering concrete-damaged plasticity. The scope of the effort and the procedures to achieve the aim of this study included the identification of the concrete confinements provided by both transverse reinforcements and a wide flange steel section based on the elasto-plastic model in tension for both rebar/steel sections and elasto-buckling for rebars in compression. The influence of rebar buckling in the compression zone on flexural moment strength was also investigated with and without considering confining effects offered by steel sections. The analytical approach predicted a post-yield behavior of composite beams based on the confining effect offered by both the shear reinforcement and wide steel flange sections. However, for beams without axial loads, the compressive zones with high and partial confinements for concrete sections at the yield and maximum load limit state were limited when compressive buckling failure was not considered, preventing the confining factors from significantly influencing the flexural load resisting capacity. An accurate flexural capacity of composite beams can be obtained when rebar was modeled with buckling in the compression zone.

An assessment of the lateral-torsional buckling and post-buckling behaviour of steel I-section beams using a geometrically exact beam finite element

The goal of this paper is twofold. The first goal is to show that geometrically exact beam finite elements can be successfully employed to determine, accurately, the behaviour of steel I-section beams undergoing large displacements and finite rotations. For this purpose, a two-node geometrically exact beam element is presented and validated, which can handle arbitrary initial configurations (e.g. curved configurations), plasticity, geometric imperfections and residual stresses. The second goal is to employ the proposed element to assess the behaviour of I-section beams undergoing lateral-torsional buckling. In particular, the element is used to determine (i) elastic non-linear bifurcation loads (i.e., bifurcation loads accounting for pre-buckling deflections), (ii) large displacement elastic post-buckling paths including geometric imperfection effects and (iii) large displacement elastoplastic equilibrium paths accounting for geometric imperfections and residual stresses. Three support/loading cases are examined, namely: (i) simply supported beams under uniform moment, (ii) simply supported beams subjected to a mid-span vertical force and (iii) cantilevers subjected to a free end vertical force. Besides I-sections with standard height-to-width ratios, wider flange sections are also considered and it is demonstrated that, for the latter, the post-buckling behaviour is quite different from that of standard sections and an increase in the load carrying capacity is observed, which is not predicted by the current Eurocode 3 [1] provisions. Based on the results obtained, a set of relevant conclusions are drawn.

Flexural Behavior of Beams Fabricated Using Light Gauge Steel with Rectangular or Triangular Hollow Flanges

Although the hot-rolled steel members have been considered as the most common and widely used steel profiles, but light gauge steel (LGS) use in structures is widely increasing recently. The structural attitude of this light gauge is characterized by different buckling modes as local, distortional, and torsional buckling. Light gauge steel sections are being produced in many forms. One of these forms is the hollow flanged beam sections which proved its effectiveness but their behavior still not fully understood. In this paper, the moment behavior of LGS beams is verified using the finite element analysis. A numerical study was applied to figure out the parameters affecting the behavior of the LGS beams in case of using hollow flanges, either rectangular or triangular, with and without vertical stiffening under flexural loading. All beams were simply supported and subjected to two-point loadings configuration. The ultimate load capacity and failure mode of all beams were determined. Three different design codes were utilized to validate the results.

Investigating the inelastic cyclic behaviour of large-size steel wide-flange section braces

Wide flange (WF) section members represent an attractive alternative to tubular braces to resist seismic excitations in braced frames. In the current study, an average true stress-true strain curve is proposed and used to model six large-scale WF brace members in combination with a refined fracture model. The effects of various material and geometric parameters are investigated. Increasing or reducing either or both the strength and the thickness of gusset plates by 10% or 20% has negligible effect on the hysteresis behaviour under reverse cyclic loading and the fracture of the large-scale WF brace members analysed.

Profile of cold-formed steel for compression member design a basic combination performance

Experiment previously showed several findings that the strength of cold-formed steel cross-section are not the same, where web strength and flange strength do not give the same response when receiving the axial load. This occurs not only because of a shift in the center point of the force due to deformation of the cross section, but also due to different strengths in cross-section, especially on the web section and flange section. To find out more details of this case, the experiment carried out the tensile test for mechanics property and compression test with an axial load to find which parts are weaknesses, then used as a reference in combining the profile. The compression test results showed significant increase in compression capability between single profile with double profile back to back (Dbb) or double profile flange to flange (Dff) with ratio 1: 2.24 and 1: 2.44 respectively. There is a non-linear increase in the value of Aeff and Ieff when becomes combine profiles (double, quadruple, hexatruple), so this can be the basis for increasing the combine profile capacity to be able to withstand larger loads. This experiment can show a basic performance of CFS, where are weak section parts of a profile can be used as a reference to put combine profile to increase compression capacity. With a numerical analysis approach compared to the experimental results, the combination of Cold-formed steel profile is established as a column for the low-rise building structure.

Numerical Analysis of the Ultimate Bearing Capacity of Thin-walled Rectangular-section Columns Using 18Mn2CrMoBA High Strength Steel in Bending and Axial Compression

The ultimate bearing capacity of thin-walled rectangular-section columns (which is welded by channel section steel plate) using 18Mn2CrMoBA high strength steel in bending and axial compression was studied by finite element method. The influence of slenderness ratio, flange width-thickness ratio and section side ratio on the ultimate bearing capacity of member was studied. The calculation method for ultimate bearing capacity of member was proposed on the basis of previous study (which can be found reference document) and many numerical calculation results. Results show that the moment-compression interactive curve changes downward concave from upward bulge with the increasing of slenderness ratio, the ultimate bearing capacity was reduced with the flange width-to-thickness ratio and section side ratio increased, the effects of these parameters were interactive. The proposed calculation formula is in good agreement with the finite element numerical results.

Minimum reinforcement revisited

Minimum reinforcement has a significant impact on the economy and sustainability of concrete structures. Current code formulations do not always address all practical cases, in particular the amount of minimum reinforcement required in thick members, for which codes generally over‐estimate the necessary values. Also, some codes have formulations which are only applicable to limited conditions, or, as is the case of Eurocode 2, have a general formulation, which, however, is not easy to understand, is not complete, and still over‐estimates the necessary reinforcement. In the light of the revision of Eurocode 2, this paper proposes a general formulation for general cross sections formed by a combination of rectangles (rectangular, flanged, or box sections) subjected to both bending and axial force based on mechanical principles and provides a reduction in minimum reinforcement for thick members by allowing the formation of larger interior cracks while providing adequate control of surface cracks.

Section moment capacity tests of hollow flange steel plate girders

Hollow flange steel plate girder (HFSPG) is a new hollow flange I-section made using cold-formed rectangular hollow sections (RHS) as flanges and a steel plate as web. Due to the increased torsional rigidity and unique geometry, it can provide enhanced flexural capacities and thus are effective flexural members in long span applications. The production of proposed HFSPGs contains welding currently available RHS sections to a web plate, which allows engineers to form girders by varying dimensions, thicknesses and grades to suit their design requirements. As the first step of this study, the section moment capacities of fully laterally restrained HFSPGs were investigated. Despite earlier researches on the flexural capacities of hollow flange sections, HFSPGs have not been tested previously. Therefore, twelve section moment capacity tests were conducted to study the flexural performance and capacities of HFSPGs. The ratios of ultimate moment capacity per unit area of tested beams were compared with conventionally used hot-rolled I-sections with similar cross-sectional area, which proved the structural efficiency of HFSPGs over commonly used hot-rolled I-sections. The ultimate capacities of tested HFSPGs were then compared with capacity predictions provided by the Australian, American and European design standards (both hot-rolled and cold-formed). It was found that the current design standards under-estimate the section moment capacities of HFSPGs in general and the level of under-estimation varied depending on the section slenderness. Suitable recommendations are made regarding the appropriate use of these design standards for HFSPGs. This paper presents the details of this research and its findings.

Experimental Test of Welded Wide Flange Fuses

Metallic dampers are one of the most prevalent structural components that are used to dissipate earthquake energy. A novel metallic damper, named Welded Wide Flange Fuse (WWFF), is proposed in this paper. WWFF utilizes commonly available welded wide flange sections to dissipate the earthquake energy through shear yielding of the web in the longitudinal direction, which makes the WWFF easy to be fabricated and efficient in providing high elastic stiffness and stable energy dissipation capacity. In this paper, a detailed experimental study was conducted to examine the influence on the design parameters (such as aspect ratios and slenderness ratios) on the component response (such as yielding force and elastic stiffness). The result shows that the WWFF has stable energy dissipation capacity which can be used as an efficient and robust metallic damper.

Effects of the shear lag on longitudinal strain and flexural stiffness of flanged RC structural walls

The shear lag effect is a commonly reported observation in tests on flanged reinforced concrete (RC) structural walls. This effect is conventionally ignored but more evidence has shown that calculation and analyses ignoring this effect could significantly overestimate flexure strength and stiffness. Existing research indicates that well distributed diagonal cracks exist in the flange of the flanged RC walls with the shear lag effect and the effect should be calculated based on shear stiffness of the cracked concrete. A truss model was proposed but the model can only consider the effect at the bottom sections of cantilever flanged walls loaded at the top which therefore precludes its application in the design of flanged RC structural walls. This paper presents an improved truss analogy for calculating the shear lag effect for flanged section at any height of RC walls with any lateral load distributions. Predictions of the proposed method are compared with available experimental data and finite element (FE) results. The method is then applied to improve the fibre beam-column element models to generate a new prediction model which was found to predict to be able to accurately predict the flexure stiffness of RC walls.

A Simplified Approach for Fire Resistance Design of High Strength Q460 Steel Beams Subjected to Non-uniform Temperature Distribution

Presented in this paper is an analytical investigation on fire resistance of high strength Q460 steel beam subjected to non-uniform temperature distribution. Based on the critical bending moment associated with overall flexural stability and results obtained from the previous experimental investigation on the mechanical properties of Q460 steel at elevated temperature, an equivalent stiffness method is established to evaluate the fire resistance of the beam with the consideration of the influence of temperature gradient across the section of the beam. Lateral torsional buckling resistance, critical temperature and overall stability coefficient are obtained for flexure of high strength Q460 steel beams at elevated temperature. A 3-D nonlinear finite element model, which is capable of accounting for temperature gradient and predicting critical bending moment of Q460 steel beam at elevated temperature, is developed. Results from the finite element simulations are compared with the results determined by the proposed equivalent stiffness method and there is a good agreement between the results of the two methods with the maximum difference of 6%. Using the equivalent stiffness method, parametric studies were carried out to investigate effects of steel grade and temperature distribution pattern on fire resistance of high strength Q460 steel beams. Accordingly, a simplified design approach was proposed to predict the critical temperature and overall stability coefficient of Q460 steel beams subjected to non-uniform temperature distribution. The simplified approach is applicable to high strength Q460 steel beams with cross section dimensions ranging from 175 mm to 350 mm and 250 mm to 500 mm for flange width and section height, respectively.

Shear lag effect in tension flange of RC walls with flanged sections

A new method for considering the shear lag effect in the flange of reinforced concrete (RC) walls with flanged sections is proposed. The method is developed based on the truss analogy for the cracked flange segment in tension. Comparisons with the experimental data reveal that the proposed method can predict the influence of the shear lag effect in the tested RC structural walls with flanged sections with greater accuracy as compared to the conventional method of effective flange width. Furthermore, parametric studies were performed based on nonlinear finite element models for further investigation of the shear lag effect and accuracy of the proposed method. The parametric studies show that the influences of the height and the length of the wall and the distribution of longitudinal reinforcement were reasonably captured by the proposed method when the maximum tensile strain in the flange was close to the yielding strain of the longitudinal reinforcing bars.

Compression tests of built-up cold-formed steel hollow flange sections

Cold-formed steel hollow flange sections are structurally efficient compared to the conventional open channel sections. They can be of different forms including hollow flange I- and channel sections, which are generally fabricated by first cold-forming a single sheet to form the desired shape and then connecting their flange and web elements by continuous welding. Instead of welding, intermittently screw/rivet fastened or spot welded connection can also be used. A detailed investigation is currently under way on the structural performance characteristics of such intermittently screw/rivet fastened steel hollow flange sections. This paper presents the details of an experimental study performed to investigate the behaviour of built-up cold-formed steel hollow flange sections in compression, where more than 45 stub columns were tested. Both hollow flange I- and channel sections built-up using either single steel sheet or three steel elements were tested. Tests also included built-up hollow flange channel sections with stiffened web elements. Test results including the failure loads, load versus axial deformation plots and failure characteristics are presented in this paper. Test failure loads are compared with the predictions based on both effective width and direct strength methods to verify their adequacy in predicting the section compression capacity of built-up hollow flange sections. This paper has shown that although hollow flange I-sections made of three elements with a 100mm fastener spacing can perform similar to continuously welded sections, hollow flange channel sections undergo premature failures even with a 50mm fastener spacing, and the reasons are discussed.

New Variational Solutions for the Rolling of Flanged Sections in Universal Roll Passes

The variational principle of minimum total power and modern computational means are used to describe the deformation of metal in and to determine the power/force conditions for rolling rails and I-beams in universal beam passes. The results are engineering formulas for designing roll passes and calculating process parameters.

Effects of axial-shear-flexure interaction in static and dynamic responses of steel beams

This paper proposes analytical model for axial-shear-flexure interaction, with inelastic shear stress and strain distributions, for 2D beam elements with AISC flanged and hollow box cross-sections. The shear stress and shear strain distributions within the beam section, for an applied shear force, are developed considering both elastic and inelastic ranges. Standard shear stress distribution is adopted for the elastic range. The distribution of the plastic component of the shear stress is assumed to have a quadratic variation. The shear stress and strain distributions are verified adequately with the finite element software ABAQUS/CAE with 3D brick elements. Further, incremental axial load (P), bending moment (M), and shear force (V) are applied to the section, along the various direction vectors in the PVM space, up until the section attained a certain level of plasticization according to the von-Mises material model, to generate the (P, V, M) points. Using these (P, V, M) data points, a quadratic PVM surface equation is proposed by combining an elliptical and a planar surface with a smoothening function. The PVM interaction is then integrated with an existing force based beam formulation with full geometric nonlinearity. Force-displacement responses obtained with the PVM interaction for 2D beams agreed well with the ABAQUS models simulated with 3D inelastic brick elements. Static responses with P-M interaction predicted higher yield force and lower displacement demand, for lower span to depth ratios and heavier flanged sections. Dynamic responses with the PVM interaction predicted higher displacement demand than that with the P-M interaction.

Computational Analysis Supporting the Design of a New Beamline for the Mines Neutron Radiography Facility

The Colorado School of Mines installed a neutron radiography system at the United States Geological Survey TRIGA reactor in 2012. An upgraded beamline could dramatically improve the imaging capabilities of this system. This project performed computational analyses to support the design of a new beamline, with the major goals of minimizing beam divergence and maximizing beam intensity. The new beamline will consist of a square aluminum tube with an 11.43cm (4.5 in) inner side length and 0.635cm (0.25 in) thick walls. It is the same length as the original beam tube (8.53 m) and is composed of 1.22 m (4 ft) and 1.52 m (5ft) flanged sections which bolt together. The bottom 1.22 m of the beamline is a cylindrical aluminum pre-collimator which is 0.635cm (0.25 in) thick, with an inner diameter of 5.08cm (2 in). Based on Monte Carlo model results, when a pre-collimator is present, the use of a neutron absorbing liner on the inside surface of the beam tube has almost no effect on the angular distribution of the neutron current at the collimator exit. The use of a pre-collimator may result in a non-uniform flux profile at the image plane; however, as long as the collimator is at least three times longer than the pre-collimator, the flux distortion is acceptably low.

通しダイアフラム形式の柱梁溶接接合部を設けた鋼梁の耐火性能

Verification on both load-bearing and plastic deformation capacity for a steel beam-column welded connection at elevated temperature is of importance to secure fire safety of steel building structures. At the fire resistant design, it is required that the beam-column welded connection does not fracture before the adjacent heated steel beam exhibits stable plastic collapse mechanism. The AIJ design recommendation (Architectural Institute of Japan, 2017) cannot, however, offer a fire resistant verification method for the beam-column welded connection, because the fire resistance has not been verified experimentally. Main purpose of this study is to clarify both load-bearing and deformation capacity for steel beams including the beam-column welded connections at high temperature, by conducting their experiments under a condition on constant temperature and gradually increasing load. The beam-column welded connection with through diagrams is arranged in the center of beam specimen. The boundary condition is simple support and a shear force is applied through the medium of the column above the beam-column welded connection. In the welded connection, scallop working for a web plate in the wide flange section is not used. This kind non-scallop working is widely used for the actual beam-column welded connections to avoid brittle fracture at the structural design in Japan. The base metal and weld material are JIS SN490B and JIS YGW11, respectively. Stiffener plates to avoid local buckling of the flange plate in the beam are arranged near the beam-column welded connection, because the large tensile force is acted to the welded connection. The number of specimens is five and an experimental parameter is specimen temperature, which is given by ambient temperature, 600, 700, 800 and 900 °C. The specimen temperature was gradually risen by an electric furnace, and the shear force was applied after the temperature reached to the test temperature and kept constant it. Bending moment and rotation angle of the specimen are estimated respectively, and the shear force loading continued until the rotation angle exceeded 0.2. From minute investigations on the experimental results, the following knowledge was obtained. All specimens exhibited the beam bending collapse mode and the welded connections did not fracture. They possessed the larger bending strength than the full plastic moment at each temperature. The shear force applied at the high temperature experiments approximately kept constant with the specimen plastic deflection increase. From specimen observation after those experiments, the weld metal itself in the beam-column connection besides the beam largely deformed, however, ductile cracks in the weld metal and heat affected zone were not observed. It is expected that the beam-column welded connection with the high seismic performance by the non-scallop working also possesses the high load-bearing and deformation capacity at the fire. Furthermore, in-plane numerical analyses using a beam element were conducted, and it was clarified that both numerical and experimental specimen behaviors approximately agreed.

Finite element modelling of composite castellated beam

Nowadays, castellated beam becomes popular in building structural as beam members. This is due to several advantages of castellated beam such as increased depth without any additional mass, passing the underfloor service ducts without changing of story elevation. However, the presence of holes can develop various local effects such as local buckling, lateral torsional buckling caused by compression force at the flange section of the steel beam. Many studies have investigated the failure mechanism of castellated beam and one technique which can prevent the beam fall into local failure is the use of reinforced concrete slab as lateral support on castellated beam, so called composite castellated beam. Besides of preventing the local failure of castellated beam, the concrete slab can increase the plasticity moment of the composite castellated beam section which can deliver into increasing the ultimate load of the beam. The aim of this numerical studies of composite castellated beam on certain loading condition (monotonic quasi-static loading). ABAQUS was used for finite element modelling purpose and compared with the experimental test for checking the reliability of the model. The result shows that the ultimate load of the composite castellated beam reached 6.24 times than the ultimate load of the solid I beam and 1.2 times compared the composite beam.