Darko Dujmović

Composite structures according to Eurocode 4 : worked examples

The use of composite structures in construction is increasing. The optimized combination of the two materials concrete and steel produces particularly cost-efficient structures. This book presents a large number of numerical examples with detailed explanations of the provisions of Eurocode 4. It deals with the most common structural components in building construction: beams, columns and slabs. Furthermore, comprehensive chapters provide insight into the topics of creep and shrinkage, as well as fatigue. This book enables the reader to efficiently perform analyses of composite structures. It is a valuable reference book for professionals as well as an outstanding means for students to become familiar with the Eurocode 4.

Review of Fatigue Assessment Methods for Welded Steel Structures

Due to high stress concentrations, welded joints represent the most common locations of fatigue crack initiation in steel structures that are prone to fatigue. Welding affects material properties by the process of heating, cooling, and combining basic and additional material. Since welding is the primary process of joining elements in steel structures, it is obvious that fatigue assessment during the design and maintenance process becomes inevitable. There are many fatigue assessment methods of welded joints, but their precision remains questionable. This paper represents a review of the most common fatigue assessment methods used for welded steel joints. As a result of this review, areas that require additional research are highlighted.

LINEAR AND NON-LINEAR ANALYSES OF CABLE-STAYED STEEL FRAME SUBJECTED TO SEISMIC ACTIONS

In this study, linear and non-linear dynamic analyses of a cable-stayed steel frame subjected to seismic actions are performed. The analyzed cable-stayed frame is the main supporting structure of a wide-span sports hall. Since the complex dynamic behavior of cable-stayed structures results in significant geometric nonlinearity, a nonlinear time history analysis is conducted. As a reference, an analysis using the European standard approach, the so-called linear modal response spectrum method, is also performed. The analyses are conducted for different seismic actions considering dependence on the response spectrums for various ground types and the corresponding artificially generated accelerograms. Despite fundamental differences between the two analyses, results indicate that the modal response spectrum analysis is surprisingly consistent with the internal forces and bending moment distributions of the nonlinear time history analysis. However, significantly smaller values of bending moments, internal forces, and displacements are obtained with the response spectrum analysis.

Composite columns made of concrete-filled hollow steel sections with embedded steel cores

A review of current surveys related to composite columns made of concrete filled tubes with embedded steel cores, known as Geilinger columns, is presented in the paper. Advantages and scope of application of this innovative composite column type are presented. Calculation of such columns according to the general method given in EN 1994-1-1, which is applied with known geometrical and structural imperfections, is explained. The simplified calculation method suitable for engineering practice is also considered. The aspects of fire resistance design are discussed. The load introduction into composite columns is also presented as well as some shearhead connection details to provide shear and moment transfer between reinforced concrete flat slabs and composite columns.

Fatigue life assessment by using local Hot Spot approach

Prilikom procjene preostaloga životnog vijeka čeličnih detalja izloženih umoru najčešće se zbog jednostavnosti proračuna primjenjuje S-N metoda uz globalni pristup preko nominalnih naprezanja. Ta metoda na strani djelovanja zanemaruje lokalne utjecaje poput koncentracija naprezanja uzrokovanih lokalnom promjenom u geometriji detalja. Ovi se utjecaji indirektno uzimaju na strani otpornosti pomoću eksperimentalno dobivenih S-N krivulja. Ako se radi o geometrijski složenijemu detalju ili je detalj opterećen složenim stanjem naprezanja, primjenjuju se lokalni pristupi kojima se prilikom proračuna uzimaju u obzir lokalni utjecaji. Ovaj rad prikazuje procjenu životnoga vijeka zavarenoga čeličnog detalja dodatne lamele izloženog umoru. Detalj je sastavni dio čelične konstrukcije željezničkoga mosta, a procjena se provodi lokalnim pristupom preko hot spot naprezanja. Naprezanja se određuju mjerenjem deformacija na određenim mjestima u detalju zbog prolaza karakterističnih vlakova. Karakteristični vlakovi sastavni su dio modela opterećenja formiranoga prema podacima Hrvatskih željeznica. Na taj se način proračunava životni vijek zavarenoga detalja zbog umora, a rezultati se uspoređuju sa životnim vijekom istoga detalja dobivenog pristupom preko nominalnih naprezanja.

Combined lattice and Vierendeel girder in long-span steel frame

A lattice girder frame was compared with a combined lattice and Vierendeel girder frame on a singlestory building with a frame span of 62.0 m, column height of 15.0 m, and ridge height of 17.3 m. The lattice girder frame has the advantage of being a cheaper solution when considering steel usage. In contrast, the combined girder frame is a less complex production that has the advantage of cheaper labor costs in relation to the higher material consumption costs. The T-joint in Vierendeel girders, designed in accordance with EN 1993-1-8, was analyzed because of its key importance when designing the overall frame. Guidelines for the preliminary selection of the chord and post member cross sections in the Vierendeel girders based on their geometrical compatibility are given in this paper. This paper also describes a method for selecting the optimal static system for combined girder frames to achieve a more uniform bending moment distribution along the frame girder by adding additional posts.

Primjena hladno oblikovanih šupljih čeličnih profila

Prema EN 1993-1-1 primjena supljih profila dopustena je u izradi celicnih konstrukcija neovisno o tome jesu li profili toplo dogotovljeni prema EN 10210 ili hladno oblikovani prema EN 10219. Kod projektanata cesto postoji dvojba u vezi s primjenom hladno oblikovanih profila uslijed negativnog utjecaja hladnog oblikovanja na njihovo ponasanje. Nedoumicu može izazivati i nedorecenost u normi EN 1993-1-8 koja se odnosi na mogucnost zavarivanja u hladno oblikovanim zonama. Osnovna svrha rada je prikazati smjernice za odabir pravokutnih supljih profila kod projektiranja celicnih konstrukcija, a posebno se obrazlaže opravdanost primjene hladno oblikovanih profila.

Finite Element Modelling of the Flange Cleats

The most important component of the bolted beam to column joints with the flange cleats is the angle cleat in bending (tension zone). Numerical simulation of the angle cleat in bending is complicated problem primary because of its three dimensional (3D) nature. In addition, the non-linear phenomena’s, such are the material and geometrical nonlinearities, friction, sliding, contact, bolt-plate interaction and fracture must be reproduced. Theoretical simulations of the angle cleat F-\(\triangle\) behaviour are conducted on the (Finite Element) FE models of the angle cleats pairs in tension. Four different types of the angle cleats are analysed with the computer package ABAQUS. Calibration of the numerical models is carried out by using the results from conducted original experimental tests of the twelve angle pairs in tension. It was shown that the numerical and experimental F-\(\triangle\) curves are in very good agreement, which means that the described FE models are accurate and reliable.

Assessment of reliable fatigue life of orthotropic steel deck

The fatigue life assessment of orthotropic steel decks of highway bridges still hasn’t been sufficiently investigated. The inspection results of orthotropic steel decks have shown that their working life can be shorter than other members of steel highway bridges due to fatigue. This means that particular details of orthotropic decks can be critical regarding the service life of a bridge. The fatigue life of typical details of orthotropic steel decks for the real load models in Croatia and for the standardized load model of highway bridges in Eurocode has been analysed. The reliability indices have also been calculated for these details and they have been used to determine reliable fatigue life. The paper proposed the introduction of the reliable fatigue life concept which is not explicitly specified in the modern standards for structures. This concept has been offered as well as the guidelines for further probabilistic research on reliable fatigue life.