Transverse Stiffeners Research Articles

Compression zone with partial stiffeners in beam-to-column steel connections

The compression zone in beam-to-column connection can generally imply the use of transverse stiffeners. This paper presents the results of experimental tests to evaluate the strength of steel panels with various transverse stiffener configurations under concentrated load. These results are used to validate the developed finite element models. Twelve panels made of either hot rolled I-sections or welded I-sections have been tested. Different transverse stiffeners are studied including single sided, double sided and partial stiffeners. The main observed results are the maximum strength and the failure mode. The results of the experimental tests are compared with those given by the finite element model using shell elements. The comparison makes it possible to calibrate the nonlinear model considering the elastic-plastic behavior of materials and large displacements. Furthermore, the results are compared with existing analytical formulas for unstiffened and fully stiffened panels to evaluate their accuracy.

Vibration analysis of functionally graded stiffened shallow shells under thermo-mechanical loading

This paper presents a mathematical model to analyse free vibration characteristics of eccentrically stiffened functionally graded shallow shells taking into account the thermo-mechanical loads. The functionally graded shallow shells are simply-supported at all edges and are reinforced by transversal and longitudinal stiffeners on the internal or external surface. The formulation is based on the first-order shear deformation theory with the smeared stiffeners technique for the overall behavior of shells. The equations of motion for eccentrically-stiffened functionally graded shallow shells are obtained using the Galerkin method. The spherical, cylindrical, hyperbolic-paraboloidal shells and plate are modeled and analyzed as special cases by setting components of curvature. Results of the dynamic analysis show that if the number of stiffeners is increased natural frequencies also increases for all the shells but after 10 stiffeners increment is no significant. It is also found that the tendencies of the plate and hyperbolic-paraboloidal shells are similar to each other with the increase in the number of stiffeners and volume fraction index. The effect of volume fraction index is more discernible for spherical shell and least for hyperbolic-paraboloidal.

Buckling strength of steel tube for lifting telescopic wind steel tower

A telescopic pole for wind energy production with low environmental impact and its lifting system for a 60–250 kW turbine and a height of 30 m have been designed and manufactured. The tower, was raised and lowered by automation or by remote control, that allows one to differentiate the presence of the generator within the landscape over time. The jacking systems acting on the legs had a combination of holes (on the legs) and pegs actuated by hydraulic pistons. The aim of the paper was the experimental and the analytical verification of the stability condition of the steel piston as a lifting system of the prototype. An experimental investigation was carried out on small-scale specimens to examine the influence of lateral restraints constituted by external steel tubes and transverse devices to increase the buckling load and to ensure a stability condition during the elevation operation of the telescopic steel pole. Finally, the experimental results were numerically validated. The original contribution of the paper to research was the design of lifting system of telescopic wind tower though a steel piston with transverse stiffeners.

An original framework for triply-coupled bending-torsion dynamics of beams

Triply-coupled bending-torsion in beams with asymmetric cross section is an interesting yet challenging problem in dynamics. In this study, a comprehensive framework is introduced to obtain the response in frequency and time domains under arbitrary loads, considering warping effects. First, a Laplace Transform approach provides the dynamic Green’s functions of the beam, which can be used to obtain the frequency response to arbitrary loads by applying simple integration rules of the theory of generalized functions. Next, on deriving suitable orthogonality conditions for the undamped coupled bending-torsion modes, modal impulse and modal frequency response functions are obtained for any load. The solutions are derived under the assumption of proportional damping; they are exact and easy to implement. Finally, the proposed framework is formulated for beams with in-span transversal stiffeners, external supports and is generalized to non-proportional damping including the presence of in-span external dampers.

Constrained finite element method for thin-walled members with transverse stiffeners and end-plates

In this paper, a new version of the constrained finite element method is reported. The constrained finite method is essentially a shell finite element method, developed for the modal analysis of thin-walled members, where mechanical constraints can be applied to enforce the analyzed member to deform according to specific (e.g., global, distortional, or local) modes. This paper generalizes the method by extending its applicability to members with transverse plates such as end-plates and transverse stiffeners. In the paper, the basic formulae of the extended method are summarized, both for constrained analysis and modal identification. In order to validate the method and demonstrate its capabilities, several numerical examples are presented: the numerical results are evaluated and the results are compared to analytical solutions where available.

Finite Element Analysis on Shear Strength of a Castellated Beam with Hexagonal Web Opening

A beam (flexural member) with several regular openings with different shapes is called a castellated beam. The castellated beams are well accepted in the industry, multi-story buildings, and power plants due to their increased depth of the section along with the web results in increased strength and stiffness. Though numerous simulation and experimental analyses have been made on the castellated beam, with intermediate transverse stiffener, bearing stiffener and torsion stiffener are used to increase a load-bearing capacity of the beam, but the study on the understanding of diagonal stiffener in the opening is very meager. The objective of the research is to investigate the linear behavior – ISMB150 and IC225 castellated beam of hexagonal openings with and without diagonal stiffeners and the effect of fillet radius at the corner of the openings is studied. Using finite element analysis software,Hyper works, with OptiStruct as a solver, under simply supported beam construction with four-point loading conditions was analyzed by developing an efficient 3D model for the analysis. Due to the openings in the section, the sharp corner of the opening is subjected to Vierendeel failure by the formation of plastic hinges at the corners, which makes critical hence by providing diagonal stiffener in the direction of diagonal tension and diagonal compression for the smooth flow of shear forces. The results show an improvement in load-bearing capacity of 1.51 times in the castellated beam than the parent section ISMB150. The stiffener provided further enhances the same to 1.45 times compared to the ISMB150 section. The linear results show lesser stress concentrations at the web opening corners, thus reducing the prominence of failure at the corners.

Flange-induced buckling of plate girders of high strength steel

Design practice shows that the simple web slenderness limit given in EN 1993-1-5 to prevent flange-induced buckling does not usually govern the web design other than for very slenderness class 4 plate girder webs in steel grades S235 to S355. However, the same formula applied to plate girders designed in S690 or S700 high strength steel (HSS) gives much lower slenderness limits that can govern web design and restrains the possibilities for reducing their thickness to profit from the high steel resistance. This paper reviews the background of the simplified web slenderness limit currently used. The results obtained with this formula are compared with numerical results from full non-linear analysis of steel and steel-concrete composite girders that present different buckling modes of the web. The case of hybrid plate girders adopting HSS only on the flanges and the possible benefits of transverse stiffeners are also investigated.

Large deflection and post-buckling of thin-walled structures by finite elements with node-dependent kinematics

In the framework of finite elements (FEs) applications, this paper proposes the use of the node-dependent kinematics (NDK) concept to the large deflection and post-buckling analysis of thin-walled metallic one-dimensional (1D) structures. Thin-walled structures could easily exhibit local phenomena which would require refinement of the kinematics in parts of them. This fact is particularly true whenever these thin structures undergo large deflection and post-buckling. FEs with kinematics uniform in each node could prove inappropriate or computationally expensive to solve these locally dependent deformations. The concept of NDK allows kinematics to be independent in each element node; therefore, the theory of structures changes continuously over the structural domain. NDK has been successfully applied to solve linear problems by the authors in previous works. It is herein extended to analyze in a computationally efficient manner nonlinear problems of beam-like structures. The unified 1D FE model in the framework of the Carrera Unified Formulation (CUF) is referred to. CUF allows introducing, at the node level, any theory/kinematics for the evaluation of the cross-sectional deformations of the thin-walled beam. A total Lagrangian formulation along with full Green–Lagrange strains and 2nd Piola Kirchhoff stresses are used. The resulting geometrical nonlinear equations are solved with the Newton–Raphson linearization and the arc-length type constraint. Thin-walled metallic structures are analyzed, with symmetric and asymmetric C-sections, subjected to transverse and compression loadings. Results show how FE models with NDK behave as well as their convenience with respect to the classical FE analysis with the same kinematics for the whole nodes. In particular, zones which undergo remarkable deformations demand high-order theories of structures, whereas a lower-order theory can be employed if no local phenomena occur: this is easily accomplished by NDK analysis. Remarkable advantages are shown in the analysis of thin-walled structures with transverse stiffeners.

Lifecycle cost assessment of high strength carbon and stainless steel girder bridges

This paper addresses the lifecycle cost assessment of a steel girder bridge considering the material costs and maintenance activities along the bridge's lifecycle. A reference highway bridge case study is chosen. It was initially designed using carbon steel S355. Two more steel grades are included in the comparison: high strength carbon steel S460 and duplex stainless steel EN 1.4162. For each design option, fatigue appears to be the driving design criterion for the following critical welded details: transversal stiffeners, cope holes and full penetration butt welds in the flanges. In addition to ultimate limit state verifications, specific attention is therefore given to fatigue through the use of different verification methods: the well-known nominal stress method and the hot spot stress method. It is concluded that the net present value of the lifecycle cost of the stainless steel option is attractive compared to painted the carbon steel options.

Influence of patch load length on resistance of I-girders. Part-II: Numerical research

The research deals with structural response and ultimate strength of patch-loaded steel I-girders without longitudinal stiffeners and with largely spaced transverse stiffeners. Part-I of the research, i.e. experimental research is presented in the companion paper. Numerical analysis of load length influence on the ultimate strength of the girder is presented in the current paper.Based on conclusions from the experimental research geometrically and materially nonlinear finite element models of experimentally tested girders were developed. Special attention is paid in modelling the contact between load block and loaded flange and in modelling the approximate geometrical imperfections of the web that best fit the experimentally measured imperfections. Detailed validation of numerical models is done by comparison of numerical and experimental results. Following data are compared: ultimate loads, deflections of loaded flange, vertical strains at measuring points on the web and lateral web deformations. Good agreement between numerical and experimental results is achieved.Quantification of load length influence on ultimate strength as a main objective of the research is made through parametric numerical analysis. Numerical base containing 143 runs is created in which the load length and web thickness are varied. Other geometrical characteristics and material properties of girders, as well as initial geometrical imperfections of the web, are kept constant which could not be provided in the experimental study. By regression analysis of the results of parametric study a simple correction factor for load length is proposed. Accuracy of the proposed expression is proved through statistical analysis over concerned numerical base.

Influence of patch load length on resistance of I-girders. Part-I: Experimental research

Problem of behaviour and ultimate strength of the centrically patch-loaded steel I-girders without longitudinal stiffeners and with largely spaced transverse stiffeners is analysed. The research is focused on two parameters - load length and initial geometrical imperfections of a girder web. This paper presents the experimental research, while the companion paper includes a numerical analysis of the problem.The experimental campaign is described in detail. Results, comments and conclusions from seven tests are presented. The observed increase of the ultimate strength with the load length increase is not quantified due to the scatter of results which is typical for all previous experimental studies in this field. The scatter of results is a consequence of the intricate initial geometrical imperfections of the web which were measured on the most of the specimens. Following conclusions from the experimental research are used in the companion paper to develop reliable numerical models of the experimentally tested girders. It is necessary to model in detail the contact between load block and loaded flange, to account for the variation of contact pressure during the load application. The initial geometrical imperfections of the web in the load introduction zone have more significant influence on the development of lateral web deformation and thereof the ultimate strength, compared to the web imperfections adjacent to the unloaded flange.Finally, based on the performed experimental research, the companion paper presents a detailed parametric numerical analysis of the problem and proposes a correction factor for the load length.

Elastic riveted perforated plate with foreign inclusions

The paper focuses on the problem of the elasticity theory for an infinite isotropic elastic plate weakened by circular perforation. The perforated holes are filled with inclusions made of elastic material and sealed along the edges. Transverse stiffening ribs made of another elastic material are riveted to the panel symmetrically to the surface. The elastic perforated plate is subjected to uniform tensile stress (tension at infinity). The action of riveted reinforcing strengthening ribs is modeled by unknown concentrated forces applied to anchor points.

Robustness of the HFMI techniques and the effect of weld quality on the fatigue life improvement of welded joints

Robustness of HFMI treatment in different weld qualities according to ISO 5817 was studied, and fatigue testing of the treated samples was carried out in order to investigate the effect of the weld quality prior treatment. The results show that HFMI-treated welds with weld quality level D shows fatigue life improvements that fall within the IIW recommendations for HFMI. No significant influence from the HFMI operator or HFMI equipment on the fatigue life was found. However, the scatter in fatigue testing results varied with HFMI operator and indicated that different HFMI operators could produce consistent treatment results. A considerable effect on fatigue life from HFMI tool radius was found, where the 2-mm tool radius showed considerably greater fatigue life compared with the 1.5-mm tool radius. According to IIW (Marquis and Barsoum 2016), for steel grade SY = 700 MPa, the fatigue strength recommendation is FAT 160 (m = 5) for transverse stiffener–welded joints with as-welded quality B according to ISO 5817 (ISO/TC 44/SC 10 2011), prior to treatment. It can be observed in the current study that fatigue-tested HFMI-treated welded joints, welded with weld quality D, are in good agreement with the IIW recommendations.

Computational Model of Rib-Reinforced Plate

The article provides a methodology for constructing a calculation model that allows determining displacements in rectangular plates, reinforced by transverse and longitudinal stiffeners. The calculation model is based on the solution of the Sophie Germain’s equation by the Bubnov-Galerkin methods and successive approximations with the representation of the reactive action of the ribs on the plate in the form of a concentrated forces system. Based on the described computational model, the results of the corresponding algorithm implementation and estimation of its convergence are presented. The need to develop a calculation model is explained by the fact that the main cause of cracks in the asphalt concrete coatings of metal bridges with an orthotropic plate is the wheel load. It reaches its maximum values for short periods of time and does not allow the stresses arising in asphalt concrete to relax. At this stage of the development of the calculation model a single-layer plate is considered supported by longitudinal stiffeners. However, since the bridge bed is a multilayer structure, further development of the design model of the multilayer slab reinforced by longitudinal and transverse stiffeners will be necessary. It will help in the joint work of metal flooring and pavement. In addition, it is necessary to take into account the temperature stress factor.

Flexural Behaviour of Delta Hollow Flange Steel Beam with and without stiffeners

In recent years of construction, steel has been considered as the most commonly used construction materials. Cold Formed steel has many structural benefits like high strength, greater stiffness, high ductility with excellent structural properties and fire resistance. The Cold formed steels are usually used in day by day in residential, commercial and industrial buildings around world. It also reduce the cross section of an element. Steel structure are faster in construction. The main aim of this paper is to study new steel beam. Rather than normal I-shaped beam, it is innovated to form Triangular Hollow Flange Beam (THFB) with slender web using required welded connection to improve the flexural capacity. THFB is also called as Delta Hollow Flange Beam (DHFB). Hollow Tubular Flange Beam provide more strength, stiffness, and stability than a flat plate flange with the same amount of steel. Flanges resist the applied moment, whereas web plates resist the induced shearing force. To improve the flexural resistance the use of the stiffeners also plays an important role, hence the flexural behavior of DHFB with the addition of transverse stiffeners has been investigated in this research work. Initially the section for the research has been chosen, Ultimate load has been calculated manually, Weld used for the sections are designed and they were analyzed through the Finite Element software called ‘ANSYS’. Later, five different specimen which includes specimen with and without stiffeners has been tested experimentally. The flexural test was carried out, along with that other properties like Ductility properties also calculated. From both analytical and experimental study DHFB shows positive results. They were highly used in various application which includes purlins, girts, portal frames and steel frame structures. Steel structure are faster in construction.

Residual stress relaxation in HFMI-treated fillet welds after single overload peaks

The induction of near-surface compressive residual stress is an important factor for fatigue life improvement of HFMI-treated welded joints. However, the relaxation of these beneficial residual stresses under single overload peaks under variable amplitude and service loads may significantly reduce fatigue life improvement. For this reason, several recommendations exist to limit the maximum applied load stress for this kind of post-treated welded joints. In this work, the effect of single tension and compression overloads on the relaxation behavior of HFMI-induced residual stresses was studied experimentally by means of X-ray and neutron diffraction techniques complemented by numerical simulation at transverse stiffeners made of mild S355J2 steel and high strength S960QL steel. Loads were applied close to the real yield strength of the base material. Significantly different relaxation behavior was observed for S355J2 and S960QL steel. Furthermore, high compression loads lead to full residual stress relaxation at the weld toe of S960QL and moderate relaxation for S355J2. High tension loads lead only to slight relaxation.

Flexural behaviour of horizontally curved I-girders with round concrete-filled tubular flange

The flexural behaviour of the simply supported individual curved round concrete-filled tubular flange girders (CRCFTFGs) and the corresponding curved I-girder (CIG) under concentrated load at mid-span is investigated experimentally and analytically. Two CRCFTFG specimens and one CIG specimen are considered in this study. One of the CRCFTFG specimens is designed with a pair of transverse stiffeners at mid-span. The other one has uniformly arranged seven pairs of transverse stiffeners along the girder span. These specimens are denoted as CRCFTFG-1 and CRCFTFG-2, respectively. A special rolling track device is designed to ensure that the load is in the vertical direction during the test. In the experiment, the failure mechanism of three specimens and the development of strain and displacement with the vertical load at certain critical positions are measured and analysed in detail. Experimental results show that increasing the number of transverse stiffeners can effectively avoid web distortion and enhance the load carrying capacity of CRCFTFGs. CRCFTFGs have much larger load carrying capacity and smaller lateral displacement and cross-sectional rotation than CIG. The finite element (FE) analysis is used in the numerical analysis to model the test specimens. The comparison outcome between the FE models and the experimental results indicated that they are in reasonably good agreement. A parametric study is conducted based on the validated FE models to investigate the influence of initial geometric imperfections, web distortion, the ratio of span to curvature radius (L/R) and the infilled concrete on the load carrying capacity of CRCFTFGs.

Fatigue behaviour of composite sandwich beams strengthened with GFRP stiffeners

This paper investigated the fatigue behaviour of composite sandwich beams, which consisted of glass fibre reinforced plastic (GFRP) skins and a foam core, strengthened with transverse or longitudinal GFRP stiffeners. A total of 42 specimens were prepared using vacuum-assisted resin transfer molding technology. The effects of GFRP stiffeners (transverse or longitudinal) on failure mode, bending deflection behaviour and fatigue life of specimens were investigated. Experimental results revealed that for beams with transverse stiffeners, the failure initiated from core shear and interface debonding between stiffeners and foam core; while for beams with longitudinal stiffeners, the failure was due to GFRP skins compression failure or longitudinal GFRP stiffeners buckling or fracture failure. Moreover, the bending strengths and failure fatigue cycle numbers of beams with longitudinal GFRP stiffeners were all larger than those of common beams or beams with transverse GFRP stiffeners. Lastly, a fatigue damage model was developed to predict the failure cycle number under different loading levels. The validity of the proposed model has been verified to estimate the fatigue behaviour of sandwich beams strengthened with GFRP stiffeners.

Mechanics of Shear Resistance in Steel Plate Girder: Critical Review

AbstractThis paper highlights the challenges before researchers who are working to understand the postbuckling mechanics of a stiffened web panel, design of transverse stiffener, mechanics of end p...

Torsional Buckling of Thin-Walled Columns with Transverse Stiffeners: Analytical Studies

In this paper the pure torsional buckling of thin-walled column members is investigated, with a special focus on the effect of transverse plate elements, such as end-plates or transverse stiffeners. The linear buckling problem is aimed to solve analytically, therefore the necessary (differential) equations are first established. For some simple problems, namely doubly-symmetric I-sections with pinned-pinned or clamped-clamped supports and with rectangular stiffeners or end-plates, closed formulae are derived to calculate the critical force. It is shown that the transverse elements have two effects: the direct effect is due to the deformation of the transverse elements, while the indirect effect is that the transverse elements modify the longitudinal distribution of the member’s displacements. It is also shown how the stiffener-to-member connection influences the results. The analytical solutions are discussed by several numerical examples: the results from the derived formulae are compared to results from shell finite element buckling analyses.