Ústav kovových a dřevěných konstrukcí

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Welded beam-to-column steel joints: Assessment of European design rules
(Elsevier, 2024-03-30) Conde, Jorge; Freire, Fernando; Ljubinković, Filip; Vild, Martin; da Silva, Luís Simes
Properly validated high-quality Finite Element (FE) models with experimental tests permit an accurate description of the load-deformation path and stress state of steel joints and are nowadays accepted as “experimental results”. Changes to the design of welded joints in Eurocode 3 are currently proposed that affect the resistance and stiffness of the components associated with the column web panel. This paper presents an assessment of the design formulations included in the current Eurocode 3, part 1–8, and its forthcoming update in terms of stiffness and moment resistance, compared against a large parametric study of strong-axis beam-column welded joints for open sections carried out using validated sophisticated FE models. The results show that both the old and new Eurocode formulations provide a large scatter and no big differences between both methods. Additionally, the presence of axial force in the column shows a clear increase in the ratio between design resistance vs numerical resistance that, particularly in the case of transversally stiffened joints, may be unconservative.
Strengthening under Load: Numerical Study of Flexural Buckling of Columns
(Elsevier, 2017-06-03) Vild, Martin; Bajer, Miroslav
The paper refers to the strengthening of doubly symmetric columns under load by welded plates. A validated numerical study containing more than 500 models was performed to question the currently used design procedures. These procedures are not unified but vary greatly in different countries. The overly conservative design approach used in the Czech Republic contrasts with the approach completely neglecting the effect of preload commonly used in the USA. The effect of various parameters on the flexural buckling resistance of columns strengthened under load was investigated. The selected parameters were the thickness of the strengthening flange, the column length, the initial bow imperfection, the preload magnitude and the direction of the axis which is pinned while the other axis is fixed. Several conclusions were reached from provided results and a simple analytical method is proposed. The load under which the column is strengthened weakens the column but only slightly.
Advanced analysis of members with gusset plate joints
(Taylor & Francis, 2021-06-16) Vild, Martin; Chalupa, Vojtěch; Šabatka, Lubomír; Wald, František
The compressive resistance of truss members connected by gusset plates is estimated by taking the buckling length of the member equal to the member length. Usually, no check is provided for the gusset plate, although several design methods were proposed in the past. The paper presents an advanced member analysis, a design-oriented finite element method of a member including its joints. Geometrically and materially nonlinear analysis with imperfections is used to determine the load resistance of the joint-member-joint subsystem. Component-based Finite Element Method is used for joints; i.e. bolts and welds are modeled by nonlinear springs with properties based on design codes. The advanced analysis is demonstrated on two cases. The buckling length of angles, vastly used for masts, may be assumed smaller than the theoretical length if the boundary conditions determined by bolted gusset plates provide sufficient stiffness. The experiments and detailed numerical analysis performed at the Graz University of Technology are used for validation of the advanced analysis. The buckling resistance of gusset plates may govern the compressive resistance of the bracing. The experiments performed at the Czech Technical University in Prague (Vesecký), together with analytical design methods, are used for validation of buckling resistance of bolted eccentric gusset plate joints of circular hollow section braces. The results depend on the chosen shape and amplitude of initial imperfections. Using recommended procedures, the proposed method provides results very close to the experiments.
Some aspects of designing and numerical modelling of glass railing exposed to impact load
(VSB – Technical University of Ostrava, 2022-01-19) Pešek, Ondřej; Melcher, Jindřich
In recent architecture glass is widely used structural material of facades, walls, roof, stairs and other applications. Glass as a material is popular for its transparency, but it need to be carefully analysed for its fracture behaviour. This paper deals with some aspects of numerical modelling and designing of all-glass railings acting as cantilever element fixed at the bottom edge and with a handrail on the top edge. In the frame of study, number of different glass railings models were analysed to find out the best way how to simulate glass railing imposed to the impact load. The impact load is in most cases decisive load case acting on that type of structure. Variable parameters entering the analysis are the aspect ratio of glass railing pane, impact intensity, impact member hardness and finite element meshing. Finite element analysis of 250 models was performed in ANSYS Workbench.
Study of Behaviour of Beams and Panels Based on Influence of Rigidity
(Elsevier, 2012-09-26) Pešek, Ondřej; Melcher, Jindřich
The aim of this paper is the elaboration of a study on the real behaviour of beams and thin panels considering the effect of large deflection. The classic plate theory was developed for panels whose deflections are lower than their depth. This is so-called a simple deflection theory. At thin panels of steel or structural glass the deflections are higher than their depth. Therefore, we have to apply the large deflection theory. Membrane effects influence the behaviour of thin panels. Typical rigid beams can be analyzed by a classic elastic theory. The results of large deflection theory give more accurate image of behaviour of non-rigid structures. Therefore, it is necessary to realize non linear calculations. The numerical models are realized using ANSYS software based on finite element method. Numerical models were realised using space and planar finite elements. They were analyzed by linear and nonlinear computation. The resulting computations were compared. Results using large deflection theory may provide more favourable base for designing of structural element and they correspond to actual beam and plate behaviour.

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