László Dunai

Behaviour of steel-to-concrete connections under combined axial force and cyclic bending

Abstract Experimental study is completed on the behaviour of end-plate-type steel-to-concrete mixed connections under combined compressive normal force and cyclic bending. The main focus of the research in on the rotational stiffness of the mixed connection and its cyclic deterioration. The initial elastic stiffness is analyzed under different values of constant compressive axial forces. Interpretation and definition of rotational stiffness are introduced. The compressive axial force significantly increases the rotational stiffness, depending on the structural solution. Characteristics of the ultimate behaviour are determined under increasing cyclic bending moment and constant axial force. The tested mixed connections are classified according to strength and rigidity using the moment-rotation envelope curves. The cyclic characteristics of the moment-rotation response of the joints are analyzed. Early deterioration of the rotational stiffness is observed.

Fracture mechanics based fatigue analysis of steel bridge decks by two-level cracked models

Abstract An alternative fatigue assessment is introduced for orthotropic highway bridge decks, based on fracture mechanics. Crack growth simulation is carried out by the numerical integration of the Paris formula, using K factors obtained from two-level cracked models of the bridge deck. Prior to the simulation, unit wheels are applied to the 3D-shell model of the deck, and the translations of characteristic points are transferred to the 2D plane strain or plane stress finite element sub-models of fatigue-sensitive areas. The K factor is computed by numerical extrapolation, introducing cracks in the sub-models. Fixed values of input parameters (initial- and critical crack length, crack growth rate data, and the error of K factor computation) are used for single simulations as well as parametric studies for sensitivity analysis. Reliability assessment is performed by repeated crack growth analysis, using histograms to generate input parameters by Monte-Carlo simulation at the start of each “virtual experiment”.

Behaviour of bolted composite joints: experimental study

Abstract In this paper, an experimental program on bolted end-plate type column-base joints is reported. Composite base columns are investigated under cyclic loading to study and characterise the typical cyclic behaviour modes of these types of joints. Details of the specimens, test results and the evaluated experimental data of the tests are presented. The tests also had a scope of investigating the influence of several parameters (the application of different bolt grades, the thickness of the end-plate, the type of the column and the influence of the reinforcement). The cyclic behaviour of the joints is studied by the moment–rotation relationships, where cyclic curves are used to evaluate the cyclic parameters of each specimen. On the basis of the evaluation of the measured data and the calculation of the cyclic characteristics, the typical cyclic behaviour modes of the studied connection type are determined and presented.

Behaviour of bolted end-plate portal frame joints

Abstract Experimental and analytical research on rafter-to-column joints of portal frames built up from cold-formed sections is presented. The haunched rafter was connected to the column by bolted end-plate connection. Two full-scale frame corners were tested, applying cantilever testing mode. Effects of different structural arrangements on the connection moment-rotation performance were investigated. The ultimate behaviour of the joints was determined. On the basis of the experimental results the connections were classified according to the international proposals. An analytical method was introduced for the prediction of the strength and stiffness of the connection. A combination of a finite element model and a mechanical model was used in two steps: the finite element model for the analysis of the T-stub element of the connection (local behaviour); and the mechanical model for the analysis of the moment-rotation relationship (global behaviour). Results of comprehensive studies are reported.

Experimental Studies on Deep Trapezoidal Sheeting with Perforated Webs

AbstractIn this paper, the behavior of deep trapezoidal sheeting with perforated webs is studied. The analyzed panel has longitudinal stiffeners both in the webs and flanges, which improves the load-bearing capacity but makes the behavior more complicated. The considered panel is produced with and without web perforations. When web perforation is applied, it is located in the middle part of the web. The primary aim of web perforation is to enhance noise resistance, but it also has an influence on the static behavior. Because reliable design rules for web-perforated trapezoidal sheeting panels are not available, an experimental program is undertaken: panels with and without web perforations are tested in parallel. The test setup and specimens are designed to provide information on all the behavior modes. On the basis of the test results, it is possible to define the degrading effect of web perforation on the rigidity, bending, and shear resistances and on the resistance to direct transverse forces close to...

Cyclic Buckling Analysis of Steel Plate Elements

The main aim of the current research is to develop an efficient classification system for cross-section of structural members under cyclic loading. This classification system has to take into consideration the complex cyclic stability phenomena of the different elements of the profile in a simpler way, similarly to the cross-section classification method in Eurocode 3 under monotonic loading. As the first step of the research this paper focuses on the hysteretic behaviour of in-plane loaded, simply supported steel plate elements. A finite element model is developed and verified to analyse the cyclic buckling behaviour. An extended numerical study is performed considering the influencing parameters of the phenomenon. The hysteretic plate buckling behaviours are evaluated and discussed.

Experiments of Corroded Angle-Section Compressive Members with Bolted Connections

Current study intends to analyse the behaviour of the corroded angle-section members under eccentric compression. The arrangement and volume of the corrosion are various on the elements. Two different end supports are applied in the tests and the effect of them on the behaviour and on the resistance are studied. The applied supports are bolted connections to a gusset plate and under that an edge support is applied to the loading frame. The tendencies of the resistance reduction are determined in term of the different types of support and pattern/volume of corrosion.

STABILITY BEHAVIOR AND DESIGN OF NONCONVENTIONAL COLD-FORMED STEEL STRUCTURES — RESEARCH REVIEW

In the paper, the methodology and main results of two research projects on nonconventional cold-formed thin-walled steel structures are presented. Laboratory tests, standard-based calculations, numerical models, and the connection of these to design method development are summarized. The implementation of the methodology is presented on two areas in detail: CompressionC-section members and a truss made of C-section members. The studied CompressionC-section members are of various cross-sectional arrangement and end- and lateral-supporting conditions. They consist of single or double asymmetric C-section members; in the latter case, either a back-to-back arrangement is applied or two sections are stuck in each other, forming a box-like closed section. The applied load is in each case compression with different eccentricities. Test arrangement, program, and results are presented; measured load-bearing capacities are compared to resistances calculated according to Eurocode 3, Part 1–3 where applicable, design rules for the cases not covered by the code are proposed. Trusses made of C-sections from the same product line are analyzed in the light of full-scale laboratory tests. EC3-based design formulae are derived for the failure modes obtained in the tests either by modifying existing application rules or by deriving new ones from these. Advanced numerical models of both structures are presented with focus on modeling imperfections, bolted connections, and joint rigidities.

Rehabilitation of historical bridges over the Danube in Budapest

ABSTRACT This article gives an overview on the rehabilitation of historical Danube bridges, which are located in the UNESCO World Heritage part of Budapest: Széchenyi chain bridge, Margaret bridge, Liberty bridge, and Elizabeth bridge. The bridges are briefly introduced and then their rehabilitations are presented. The special aspects of the design of reconstruction are shown. Site measurements and advanced studies, which supported the rehabilitation in the design and construction phase, are discussed in the case of the two recently reconstructed bridges and for one planned case, while, in the case of the Elizabeth bridge, the old and the new structures are introduced.

On the Stiffening the Shear Panels of Beam-to-Column Joints

In case of steel beam-to-column joints the bending resistance is significantly influenced by the shear strength of the web panel. The compression side resistance of the joint is limited by the web panel in shear component and in case of special geometries it can give a relatively strong limitation for the bending resistance of the whole joint. In typical frames the increase of the web thickness at the corner area is not an optimal solution from the fabrication point of view, this is why other reinforcement methods, such as application of stiffeners can result in more economical solutions. This paper has a focus on the effectiveness of the different shear panel reinforcement methods by the application of stiffeners.