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Accidental torsional behaviour induced by horizontal loading is difficult to predict, being a complex phenomenon governed by many variables. This problem gains an additional dimension of complexity when nonlinear responses with imperfections need to be considered. Therefore, evaluation and understanding the influence of accidental torsion are fundamental in seismic reliability estimation. This study offers vital insights based on the results of a 1/2.5 scale three-story masonry infilled reinforced concrete frame building’s test on a shaking table. The building was tested under ten consecutive ground motions with increasing ag/g, recorded at Herzeg Novi station during the 1979-M6.9 Montenegro earthquake. The accidental eccentricity, considered a random variable, resulted from unsymmetrical masonry infill wall damage in an otherwise regular building. Its effect, in relation to that of other random (design) variables, was evaluated utilising weight factors and, in addition, assessed through various building code provisions and state-of-the-art research findings. The analysis revealed that the accidental eccentricity, as compared to other random variables considered, could, under certain conditions, reach values higher than those prescribed by the building codes. This unacceptable seismic reliability clearly warns that accidental torsion of masonry-infilled reinforced concrete frames in in-situ conditions must be considered even in regular buildings. Doi: 10.28991/CEJ-2023-09-02-017 Full Text: PDF

Despite numerous research studies conducted in the field of masonry-infilled steel (and concrete) frames, there is still no adequate codified design method. There is, however, a consensus that masonry-infilled frames should be treated as potentially hazardous earthquake context structural solutions. While masonry infill has positive effects on steel frames, which are often neglected in design, adverse effects cannot be overlooked. Over the last decade, several structural solutions aimed to improve the overall structural behavior of these interactive composite systems were proposed and tested in laboratory conditions. It is not rare that these approaches are opposite to each other, which additionally stresses the fact that there is a need for recognition and validation of the key structural directions. Among various proposed design options, the authors are very interested in those which tend to include the beneficial effect of masonry infill, but at the same time preserve desired ductile behavior of steel frames, all by using simpler and easy to apply structural solutions. Some of them are already proposed by the authors, which are discussed in the paper, along with a summary and comparison of contemporary structural solutions in steel masonry-infilled frames, as an important step towards codification.

Continuing development of aluminium alloys highlights the problem of choosing adequate constitutive stress-strain relationships, especially as aluminium has no pronounced yield strength and a significant degree of nonlinearity before reaching the 0.2% proof strength. Thus, for the sake of a more realistic approximation of the stress-strain relation more complex models are required. These complex models are continuous, defined either as a function of stress or strain. Unfortunately, basic mechanical properties available to engineers are often not adequate for material behaviour modelling in nonlinear numerical analysis, which are required for intricate design problems. Moreover, studies regarding suitability of various models are scarce. Since any deviations from experimental stress-strain behaviour consequently introduces errors in simulation results, it is necessary to quantify errors, and to enable a reliable choice among available models, depending on type of modelled phenomena. To gain insight on these problems, own experimental stress- strain data of coupons from alloys EN AW-6082-T6 and EN AW-6060-T66 was utilized. Alloys were selected as being representative of a group of commonly used alloys in structural engineering (T5, T6, and T66), due to their similar shape of the stress-strain curve. Experimental curves were divided into two zones, the dominantly elastic and plastic, and relative errors between six constitutive laws and experimental data by zone and in total behaviour were established. Descriptive and dispersion statistics of determined relative errors allowed for quantitative indicators of suitability, which then allowed for conclusions regarding choice of tested constitutive relationships.

Clay brick waste is usually delivered to the landfill sites for disposal. The utilisation of recycled brick aggregate (RB) in self-compacting concrete (SCC) has the potential to reduce both the environmental impact and financial cost. Due to increasing charges of landfill and scarcity of natural coarse aggregate (NA), recycled brick aggregate (RB) derived from masonry waste is of increasing interest in construction industry. In the presented study, RB is used as full re- placement of natural aggregate (NA) to produce low strength self- compacting concrete (SCC). Nine different SCC mixes were produced. The water to binder ratio and water to powder ratio were kept the same for all concrete mixtures. The impacts of RB on the key fresh properties such as filling ability and passing ability of SCC, and on the properties in his hardened state were investigated. Based on experimental results, conclusions are made about usage of crushed bricks as partial replacement of natural aggregate in SCC for precast concrete blocks which will serve as steel and R/C frame infill. It is well-known fact that common masonry infill significantly affects the structural behaviour of frames. This type of structures is still considered as ‘earthquake risk’ structural systems so our intention is to improve the structural behaviour of these systems by applying an infill which may possess beneficial characteristics from the aspect of frame-infill interaction. This puts a new perspective on the use of crushed clay bricks as SCC aggregate with the additionally benefit of providing a sustainable management of such material.

Bilo da se radi o pregradnim ili nosivim zidovima, zidana ispuna značajno utječe na ponašanje primarne konstrukcije. U ovom se radu najprije razmatraju dvije različite vrste zidnih blokova (tzv. jaki i slabi) često korištenih u Hrvatskoj kao ispune čeličnih okvira. Na osnovu eksperimentalnih rezultata dobivenih ispitivanjem ponašanja tih dviju vrsta blokova predložena je treća vrsta ispune koja predstavlja specifičnu kombinaciju prethodnih dviju, kao mogućnost ostvarivanja kontroliranog ponašanja čeličnih okvira sa zidanom ispunom., Whether used as a curtain/partition wall or a bearing part of the structure, masonry infill significantly affects structural behaviour of the primary structure. Two different types of masonry units (‘strong’ and ‘weak’), often used in Croatia as infill of steel frames, are initially considered in the paper. Based on experimental results obtained by testing behaviour of these two types of masonry units, a third type of infill is proposed, which is a specific combination of the initial two types, and enables realisation of controlled behaviour of masonry-infilled steel frames., Unabhängig davon, ob es sich um Trennwände oder tragende Wände handelt, beeinflusst ausfachendes Mauerwerk das Verhalten des primären Tragwerks bedeutend. In dieser Arbeit werden zunächst zwei verschiedene Typen von Mauerwerksblöcken betrachtet (s. g. starke und schwache), die in Kroatien als Ausfachung verwendet werden. Basierend auf experimentellen Resultaten aus Versuchen an diesen Blöcken, wurde als ihre spezifische Kombination ein dritter Mauerwerkstyp vorgeschlagen, um ein kontrolliertes Verhalten von Stahlrahmen mit Mauerwerksausfachungen vorzuschlagen.

Iako je aluminij već dugo prisutan konstrukcijski materijal, uporaba mu nije u skladu s dobrobitima koje se ostvaruju njegovom primjenom. Sličan je čeliku, no između njih postoje značajne razlike kako u proizvodnji, tako i u fizikalnim i mehaničkim svojstvima. Upravo iz tih razlika proizlaze posebnosti u područjima stabilnosti dijelova poprečnih presjeka i konstrukcijskih elemenata te u područjima zavara. Ta polja još uvijek predstavljaju aktivna područja istraživanja zbog velikog broja legura, obrada i oblika poprečnih presjeka profila., Although aluminium is a structural material that has been present on the market for a long time, its use is not in accordance with the benefits that can be achieved by its application. While it is similar to steel, there are significant differences between these materials, both in manufacturing and in physical and mechanical properties. Due to such differences, these materials exhibit distinct features in the areas of cross sectional and elements stability and welds. These areas are still an active field of research due to a large number of alloys, processing methods, and cross-sectional shapes., Obwohl Aluminium schon lange als Konstruktionsmaterial bekannt ist, wird es nicht den Vorteilen seiner Anwendung entsprechend eingesetzt. Auch wenn das Material mit Stahl verglichen werden kann, bestehen bedeutende Unterschiede, sowohl in der Herstellung, als auch in den physikalischen und mechanischen Eigenschaften. Folglich umfassen die Stabilität der Querschnitte oder Elemente und die Schweißflächen eine Reihe von Besonderheiten, die weiterhin einen aktiven Forschungsbereich darstellen, insbesondere aufgrund der großen Anzahl von Legierungen, Verarbeitungsmethoden und Querschnittsformen.

The behaviour prediction of frame structures with masonry infill exhibited under lateral loading is still relatively complex. Although such composite constructions are frequently applied in buildings, there are no practice oriented models for their design, as it is the case with most other types of building systems. The use of existing approaches can lead to inadequate or overestimated load capacities, as different models are more or less suitable for certain applications and can give diverse results for the same system. This paper presents some of the modelling approaches used in strength prediction of steel frames with masonry infill. Based on experimental results of constitutive parts properties (steel material, masonry elements, mortar), is shown implementation of an equivalent diagonal model prediction using nonlinear and linear strength envelopes. Results gained by this investigation will serve for an experimental investigation on a steel one story – one bay frame with different types of masonry infill.

Okviri sa zidanim ispunom često se primjenjuju u Republici Hrvatskoj kod niskih i srednje visokih građevina. Ipak, ponašanje takvih konstrukcija još uvijek nije moguće obuhvatiti nekim relativno jednostavnim modelom ponašanja niti proračuna, kao što je to slučaj s većinom drugih uobičajenih tipova konstrukcija koje se koriste u praksi. Dapače, u konstrukterskoj se praksi može naći nekoliko, često i potpuno različitih pristupa za proračun okvirnih konstrukcija s zidanim ispunom. Pri tome čelični okviri imaju svoje specifičnosti u odnosu na češće korištene armiranobetonske. U radu se opisuje priprema predviđenog eksperimentalnog ispitivanja nekoliko modela čeličnih jednokatnih okvira s različitim tipovima zidanog ispuna koje će se provesti na Građevinskom fakultetu Osijek. Osnovni cilj načina konstruiranja i ispitivanja modela je pokušaj dobivanja kontroliranog odgovora sustava, posebna za veća (potresna) opterećenja, budući da je iz dosadašnjih spoznaja jasno da je u većini slučajeva vrlo teško predvidjeti točno ponašanje ovog kompozitnog sustava. U prilog tome govori i činjenica da u najnovijoj verziji eurokoda iz područja proračuna konstrukcija na potres (EN 1998-1) još uvijek nema detaljnije kodificirane procedure proračuna ovakvih konstrukcija, iako se naglašava potreba uzimanja u obzir interakcije između okvira i zidanog ispuna.

U radu se opisuju neke aktivnosti Zavoda za materijale i konstrukcije Građevinskog fakulteta Osijek usmjerene na primjenu znanstvenih i ekperimentalnih metoda u građevinskoj praksi. Primjenjena inženjerska znanja vrlo su značajna u postupku obrazovanja građevinskih inženjera, te se u većinu stručnih poslova Zavoda uključuju i studenti koji posjećuju gradilišta, rade seminarske radova iz pojedinih aspekata procesa projektiranja i nadzora i sl. Ilustracija praktične primjene stručnih i eksperimentalnih metoda dana je na primjeru nekoliko karakterističnih izvedenih građevina - zamjena dostrajalih željezničkih nadvožnjaka novima u širem gradskom centru, zamjena čeličnih pješačkih nadhodnika novim, te je opisan i postupak eksperimentalnog ispitivanja građevina zamjenskim opterećenjima.

Rad obrađuje problematiku kompleksnijeg numeričkog modeliranja čeličnog preklopnog spoja s jednim vijkom izloženog vlačnoj sili. Modeliranje je provedeno primjenom metode konačnih elemenata u programskom paketu Ansys, a na temelju vlastitih provedenih eksperimentalnih ispitivanja ponašanja ovakvih spojeva. Spojevi su konstruirani na način da do otkazivanja nosivosti dođe uslijed prekoračenja naprezanja po omotaču rupe vijka, a taj je način otkazivanja duktilan i najčešće popraćen značajnim deformacijama (za razliku od ostalih mogućih načina otkazivanja ovakvog spoja). Kako se takve vrste spojeva često koriste kod vezova (spregova) za stabilizaciju konstrukcije, spomenute moguće značajnije deformacije (koje nekad dosežu i veličinu promjera vijka prije konačnog otkazivanja) spoja bitnije utječu na samu uporabljivost odnosno funkcionalnost konstrukcijskog rješenja te ih je potrebno ograničiti za razinu uporabnih opterećenja. Na nelinearnom, detaljnom numeričkom modelu ovakvog spoja uspoređuju se i analiziraju rezultati eksperimentalnih ispitivanja, ocjenjuje iznos deformacije uslijed prekoračenja pritiska po omotaču rupe te vrši usporedba s kodificiranim pristupom prema eurokod propisima (EN 1993-1-8).

U radu se razmatraju nastanak, značajke, trenutno stanje i potencijali prenamjene zgrade električne centrale, bivše Munjare, u Osijeku. Munjara je jedna od najznačajnijih industrijskih građevina Osijeka iz razdoblja Moderne, zidana zajedno s Remizom 1926. godine, s ciljem osiguravanja električne energije za novi osječki tramvaj. U prvom dijelu članka prikazano je istraživanje ekstenzivne postojeće dokumentacije o Munjari, arhivskih nacrta i fotografija, podataka o natječaju za izgradnju centrale, troškovnika i sl. U drugom dijelu prezentirana je ideja prenamjene Munjare u tehnički muzej Osijeka. Grad nema takvog muzeja koji bi zabilježio njegovu bogatu industrijsku prošlost, a Munjara, koja do danas nije značajnije mijenjala namjenu (trenutno je rezervni pogon Toplane), je zadržala konstrukcije, oblike i dio originalne opreme iz prve polovice 20. stoljeća. U završnom dijelu rada elaborirana je isplativost i izvedivost nove namjene, uz potrebne analize, nacrte, opise i proračune zamjenskih konstrukcija te model financiranja.

Daje se pregled relevantnih parametara u seizmičkom proračunu čeličnih i spregnutih konstrukcija prema EN 1998-1:2004. Ti su propisi još uvijek bazirani na dokazivanju čvrstoće (nosivosti) dok se kontrola deformacija provodi naknadno, iako bi za ovaj slučaj opterećenja obrnuti postupak bio primjereniji. Stoga je, kao prijelazno i kompromisno rješenje u sadašnjoj verziji propisa uveden faktor ponašanja q koji ima centralnu ulogu u povezivanju tradicionalnog načina inženjerskog razmišljanja i korištenja propisa s novim pristupima i saznanjima koja se više ne mogu zanemarivati u proračunu konstrukcija. Inženjer stoga mora voditi računa da se pretpostavljena razina duktilnosti može u realnoj konstrukciji i ostvariti, te je određivanje faktora ponašanja q ali i još nekih relevantnih parametara seizmičkog proračuna čeličnih i spregnutih konstrukcija kao što faktor viška nosivosti materijala (ov), parametar plastične preraspodjele (u/1), faktor viška nosivosti nosača i sl. vrlo važno, budući da oni imaju značajan utjecaj na točnost rezultata proračuna.

Na Građevinskom fakultetu Osijek sustav upravljanja i osiguravanja kvalitete funkcionira sukladno pravilima norme HRN EN ISO 9001:2008 te Europskim standardima i smjernicama za osiguravanje kvalitete u visokom obrazovanju (ESG). U skladu s planiranim aktivnostima opisanima u Priručniku kvalitete te Strategiji razvitka GFOS za razdoblje 2009.-2013. godine redovito se provode unutarnje i vanjske prosudbe sustava kvalitete. U ovom radu su opisani postupci navedenih prosudbi, rezultati istih te njihova primjena u svakodnevnom radu kao i konkretne koristi za sustav osiguravanja i unaprjeđivanja kvalitete visokog obrazovanja.

Drvo je nehomogen, anizotropan građevinski materijal što ga čini teško kontroliranim zbog mogućih raznih devijacija. Najbolji uvid u stvarno ponašanje drvene konstrukcije velikog raspona pri određenom djelovanju moguće je spoznati tzv. hybridnom statikom. Hybridna statika podrazumijeva rješenje statičkih pitanja međusobno dopunjujućih rezultata eksperimentalnog i proračunskog istraživanja odgovora konstrukcije na promatrano djelovanje. Hrvatski Tehnički propisi za drvene konstrukcije zahtijevaju pored proračunskog i pokusno ispitivanje drvenih konstrukcija raspona većeg od 30 m te konzola većeg raspona od 15 m. a koje su definirane kao naročite.

This paper critically presents the codified design of joints in steel truss girders, according to the latest european norms [1, 2] , as contemporary norms in which this issue is included and processed in detail for the first time. Rules in [2] are based on simplified analytical models in combination with experimental research, so the regulations consist of semi-empirical calculation formulae which are valid in limited conditions. Thus, in engineering practice it is required to take care of parameters which affect the global or local behaviour of truss girder such as secondary bending moments, bending moments resulting from eccentric member joints, and joint deformability, so this paper gives distinct attention to these effects. Typical truss girder behaviour modelling modes using finite element method (FEM) are illustratred so to predict their values, and take them in the final estimate if needed. The steel truss girder made of hollow rectangular sections with welded joints is reviewed in detail and numerically exemplified. The accuracies are compared and recommendations are given for the application of each model.

U članku je opisan cestovni most preko Save u Zagrebu (tzv. Savski most), pušten u promet prije sedamdeset godina. To je najstariji veći spregnuti most na svijetu, iako pri projektiranju nije tako proračunan. Zapravo je projektant upotrijebio armiranobetonsku ploču kao vjetrovni spreg, ali je ipak predvidio ugradbu svojevrsnih moždanika. Rezultati provedenog pokusnog opterećivanja potaknuli su dalja laboratorijska istraživanja i smjeliju primjenu spregnutih sklopova u mostogradnji., The road bridge over the Sava River in Zagreb (the so called Sava Bridge), was opened to traffic seventy years ago. It is the world's oldest major bridge with a composite deck structure, although it was not designed with that objective in mind. In fact, the designer intended to use the reinforced-concrete deck slab as a wind bracing only, but he nevertheless installed a sort of shear connectors. The load testing results encouraged additional laboratory testing, as well as a more daring use of composite structures in bridge construction., Le pont routier sur la rivière de Sava à Zagreb (dit le pont de Sava) à été ouvert à la circulation il y a soixante-dix ans. Bien que ce soit le plus ancien pont majeur à tablier composite du monde, il n'a pas été conçu dans cette intention. En fait, le projeteur a voulu utiliser le tablier en béton armé exclusivement comme contreventement, mais a néanmoins installé une sorte de connecteurs. Les résultats de l'essai de portance ont encouragé la réalisation des essais de laboratoire additionnels, ainsi qu'un emploi plus audacieux des constructions composites dans la construction de ponts., В статье описывается дорожный мост в Загребе через реку Саву (Савский мост), пущенный в эксплуатацию семьдесят лет назад. Это старейший в мире более крупный сопряженный мост, хотя при проектировании расчеты были иные. В начале проектировщик намеревался использовать железобетонные плиты для ветровой связи, но все-таки были установлены своеобразные анкерные стержни. Результаты проведенной опытной нагрузки инициировали дальнейшие лабораторные исследования и более смелое применение сопряженных конструкций в мостостроении., Im Artikel beschreibt man die Strassenbrücke über die Sava in Zagreb (sgn. Savski most), dem Verkehr übergeben vor siebzig Jahren. Das ist die älteste grössere Verbundbrücke der Welt, obwohl sie beim Entwurf nicht so berechnet war. Eigentlich wollte der Entwurfsverfasser die Stahlbetonplatte als Windverband benützen, doch hat er immerhin den Einbau eigenartiger Dübel vorgesehen. Die Ergebnisse der durchgeführten Probebelastung veranlassten weitere Laboruntersuchungen und wagemutigere Anwendung von Verbundgefügen im Brückenbau.

U radu je dan prikaz rada na izradi nacionalnih dodataka za primjenu normi EN 1994-1-1, EN 1994-1-2 i EN 1994-2 u Republici Hrvatskoj s glavnim podacima.

U radu su prikazani načini modeliranja spregnutih konstrukcija od čelika i betona u dijelu koji ne pokriva europska norma.

Nove europske norme za proračun čeličnih konstrukcija [1] ne sadrže proračunski tretman saćastih nosača. Stoga inženjeri proračune ovih nosača provode odgovarajućim metodama (npr. MKE). Jedna od specifičnosti proračuna saćastih nosača je i bočno-torzijsko izvijanje, koje se također može javiti kao mogući način otkazivanja nosivosti. U radu je obrađena opća problematika bočnog-torzijskog izvijanja, te aspekt nelinearnog modeliranja saćastih nosača prema preporukama navedenim u [1]. Na numeričkom primjeru ilustrirana je primjena i jedne i druge metode.

W kregach inzynierskich (nie tylko chorwackich) most drogowy przez Sawe w Zagrzebiu (tzw. Savski most) byl znany jako wybitne osiagniecie na polu spawania wyjatkowo grubych blach.

Kritički se komentiraju postupci modeliranja ponašanja dvostranih priključaka prema EN 1993-1-8, te se izlaže mogućnost metode konačnih elemenata kojom se u obzir uzima ponašanje priključaka na način da se standardni štapni model konstrukcije na dijelu priključka oko hrptenog panela stupa nadogradi ravninskim konačnim elementima. Na taj način se u obzir uzima stvarna geometrija priključka, nije potreban iteracijski postupak, a složenost modeliranja se prihvatljivo povećava., Performance modelling procedures for two-sided connections, based on EN 1993-1-8, are critically analyzed. Possibilities offered by the finite element method in the sphere of determining behaviour of connections, and this by adding in-plane finite elements to a standard structural model in the connection zone around the web panel of the pier, are determined. Thus the real geometry of connection is taken into account, the iterative procedure becomes unnecessary, and the modelling complexity is not significantly increased., La modélisation de comportement des connexions à deux faces, selon EN 1993-1-8, est analysée de point de vue critique. Les possibilités offertes par la méthode des éléments finis dans la détermination du comportement des connexions, et cela en introduisant les éléments plans finis dans le modèle standard structurel dans la zone de connexion autour de panneau d'âme de la pile, sont déterminées. De cette manière, la géométrie réelle de la connexion est prise en compte, la procédure itérative devient inutile, el la complexité de modélisation n'augmente pas de manière considérable., Приведены критические комментарии по процедурам моделирования поведения двухсторонних присоединений по EN 1993-1-8, изложена возможность применения метода конечных элементов, который учитывает поведение присоединений таким образом, что стандартная стержневая модель конструкции в области присоединения у хребтовой панели опоры достраивается плоскостными конечными элементами. Это позволяет учесть реальную геометрию присоединения, отпадает необходимость в выполнении итерационной процедуры, а усложнение моделирования является приемлемым., Die Verfahren der Modellierung des Verhaltens zweiseitiger Anschlüsse nach EN 1993-1-8 sind kritisch kommentiert. Ausgelegt ist die Möglichkeit der Methode der endlichen Elemente mi der man das Verhalten der Anschlüsse derweise in Betracht nimmt dass man das Standard-Stabmodell der Konstruktion am Teil des Anschlusses um das Stegpanel des Pfeilers mit ebenen endlichen Elementen anbaut. Auf diese Weise wird die tatsächliche Geometrie des Anschlusses berücksichtigt, ein iteratives Verfahren ist nicht nötig, und die Kompliziertheit des Modellierens ist annehmbar vergrössert.

Prikazana je problematika numeričkog modeliranja čeličnih okvira sa zidanim ispunom pri djelovanju potresa. U novim europskim normama (EN 1998-1) predviđeno je proračunavanje interaktivnog djelovanja kod takvog sastavljenog sustava, ali se ne daju pravila proračuna. Na primjeru su prikazane najčešće primjenjivane mogućnosti modeliranja ponašanja takvih konstrukcija, primjenom metode konačnih elemenata te je upozoreno na potrebu praktičnog pristupa rješavanju ovoga problema., Problems encountered in numerical modelling of masonry-filled steel frames subjected to earthquake action are presented. According to new European standards (EN 1998-1) an interactive action should be calculated for such composite systems, but calculation rules are not provided. A practical example is used to show most frequent possibilities for modelling behaviour of such structures based on the finiteelement method, and the need to use a practical approach to find solution to this problem is emphasized., Des problèmes rencontrés au cours de modelage numérique des cadres d'acier à remplissage en maçonnerie soumis à l'action sismique sont présentés. Selon les normes européennes nouvelles (EN 1998-1) l'action interactive devrait être calculée pour de tels systèmes composites, mais les règles de calcul ne sont pas fournies. Un exemple pratique est utilisé pour montrer les possibilités les plus fréquentes dans le modelage du comportement de telles constructions selon la méthode des éléments finis, et l'accent est mis sur la nécessité d'utiliser l'approche pratique pour trouver solution à de tels problèmes., Dargestellt ist die Problematik des numerischen Modellierens von Stahlrahmen mit Ausfachungsmauerwerk bei Erdbebenwirkung. In den neuen europäischen Normen (EN 1998-1) ist die Berechnung des interaktiven Wirkens bei solchem zusammengesetzten System vorgesehen, aber sind Berechnungsgrundsätze nicht angegeben. Am Beispiel zeigt man die häufigst angewendeten Modellierungsmöglichkeiten für das Verhalten solcher Konstruktionen durch Anwendung der Methode der endlichen Elemente. Es wird auf die Notwendigkeit des praktischen Zutritts zum Lösen dieses Problems hingewiesen.

Behavior of bridges in transversal direction is very difficult to foresee because of the large number of parameters which influences them. Ratio between stiffness of the piers and bridge deck is one of the most important parameters of the bridge response. If the piers are relatively high and slender the response of the bridge is dictated with deck stiffness. Then it is important to determine the exact ratio of the stiffness when the piers do not disturb the response. One method uses wave equation to determine the behavior of structure and another uses finite elements. It is impossible to solve all construction static systems with wave equation but only simple ones and it has a shortfall that it can determine only first few accurate modal shapes. Although less accurate, with the FEM it is possible to determine larger number of modal shapes. In this paper example of continuous bridge will be analyzed using both methods.

The research objective in this paper was determination of the influence of the reduced geometrical characteristics of castellated beams on the value of elastic critical moment of lateral-torsional buckling (Mcr) in relation to the plated beams with the same geometrical dimensions (same height, width and thickness of flange, and web thickness). Elastic critical moment for the lateral-torsional buckling has been calculated according to the expression given in Eurocode 3 (ENV 1993-1-1:1992, Annex F), and applying the finite element method with the linear buckling analysis. Analysis of the simply supported beams with various spans subjected to two types of the loading (uniform and concentrated) is performed.

Contrary to the prenorm ENV 1993-1-1:2002/A2:2008 the final version of the European norm for the design of steel structures EN 1993-1-1:2005 does not afford special attention to castellated beams. Therefore, engineers should determine the resistance of castellated beams by application of the finite element method (§ 6.3.4.). Furthermore, determining the lateral-torsional buckling resistance of castellated beams is more complicated because appropriate buckling curves are not assigned in this norm. The non-linear modelling of castellated beams in bending according to recommendations given in EN 1993-1-1:2005 is shown in this paper. Moreover, while modelling this structural element geometrical and material non-linearity are taken into account. 3D models of beams are used and the design resistance to lateral-torsional buckling is determined by computer programme NISA II/DISPLAY. The cross-section, span and restraint conditions of the castellated beam matched the tested castellated beam in the laboratory.

Saćasti nosači su vrlo racionalno konstrukcijsko rješenje kod nosača većih raspona i dominantnog naprezanja savijanjem u ravnini nosača, a karakterizirani su relativno velikom vitkošću i značajnom prošupljnosti hrpta. U radu su opisana istraživanja stabilnosti saćastih nosača iz aspekta otpornosti na bočno-torzijsko izvijanje, za koje se u novim propisima Eurokod 3 predlaže pojednostavljeni dokaz otpornosti.

Opisana su istraživanja razine povećanja nosivosti spregnutih nosača čelik-beton djelomičnim oblaganjem čeličnog profila betonom u područjima unutarnjih ležajeva. Razmatrani su kontinuirani nosači, a spregnuti su valjani čelični nosači i armiranobetonske monolitne ploče konstantne debljine. Rezultati istraživanja pokazuju da se prikazanim načinom osjetnije povećava nosivost spregnutih nosača, što je izraženije pri većim rasponima i upotrebi HE-A čeličnih profila., The studies of increase in the bearing capacity of steel-concrete composite girders, as obtained by partial steel section encasement with concrete in the zone of internal bearings, are described. Continuous girders are considered, and composite action is applied to rolled steel girders and reinforced-concrete monolithic slabs of constant thickness. The results obtained show that a significant increase in the bearing capacity of composite girders can thus be achieved, and that this increase is even more pronounced in case of greater spans, and when HE-A steel sections are used., Les études de l'augmentation de la capacité portante des poutres acier-béton composites, par bétonnage partiel du profilé en acier dans la zone occupée par les appareils d'appui internes, sont décrites. Les poutres continues sont prises en considération, et l'action composite est maintenue pour le profilé roulé et pour la dalle monolithique en béton armé d'épaisseur constante. Les résultats obtenus montrent qu'une augmentation considérable dans la capacité portante des poutres composites peut ainsi être obtenue, et que cette augmentation est encore plus prononcé dans le cas des portées de grandeur considérable, et aussi quand les profilés métalliques en HE-A sont utilisés., Beschrieben sind Forschungen des Ausmasses der Tragfähigkeitserhöhung von Stahl-Beton- Verbundträgern durch teilweise Verkleidung des Stahlprofils mit Beton im Bereich der Innenlager. Betrachtet sind Durchlaufträger, wobei Walzstahlträger und Stahlbetonmonolithplatten von kostanter Dicke verbunden sind. Die Forschungsergebnisse zeigen dass mit dem dargestellten Verfahren die Tragfähigkeit von Verbundträgern erheblich erhöht wird, was bei grösseren Spannweiten und Anwendung von HE-A Stahlprofilen ausdrucksvoller ist.

Bridges are structures which are very sensitive to the transversal excitation. Some recent events have shown this fact in very drastic fashion (Loma Prieta 1989, Northridge 1994, Kobe 1995.). Dynamic analysis of such structures may be time consumable due to complicated response and large number of the degrees of freedom, but it is necessary step in the preliminary stage of the design process. This paper presents simple method for obtaining eigenvalues, eigenvectors and participation masses of the continuous girder bridge. It is shown that bridges with the same stiffness ratio between piers and the bridge deck have dynamic properties in the direct relationship, assuming that their span ratios are the same. Procedure shown in the paper presents simple method for obtaining these dynamic characteristics, using as input just simple geometry of the cross sections. This is useful in the preliminary stage of the design because all the important dynamic parametars are calculated very fast. By changing stiffness ratio one can customize bridge response and reduce seismic forces acting on the bridge in the transversal direction, according to microseismic location of the bridge.

Opisana su istraživanja razine povećanja nosivosti spregnutih nosača čelik-beton djelomičnim oblaganjem čeličnog profila betonom u područjima unutarnjih ležajeva. Razmatrani su kontinuirani nosači, a spregnuti su valjani čelični nosači i armiranobetonske monolitne ploče konstantne debljine. Rezultati istraživanja pokazuju da se prikazanim načinom osjetnije povećava nosivost spregnutih nosača, što je izraženije pri većim rasponima i upotrebi HE-a čeličnih profila.

The problem of the dynamic response of the highway bridge under the actual traffic load has been analysed. The dynamic influence of the heavy lorry vehicles under usual circumstances does not affect on a bearing load capacity, but continuosly degrades serviceability of the bridge and thus its service life. Increasing number of the lorry vehicles and their weight, as well as more lighter and flexibile bridges, additionally empahasize this fact. Determination of the dynamic response of the bridge resulting from the passage of a heavy vehicles across the bridge is very complicated and depends on many parameters such as dynamic characteristics of the vehicle and the bridge, heavy vehicle geometry and the speed, roughness of the surface profile of the bridge, the natural frequencies of the vehicle and the etc. The classical calculation procedure includes simplified calculation of the dynamic bridge response based on increased static load. This procedure neglects the fact that degradation of the bridge appears not only by the extreme traffic load but continuously by the real heavy vehicles. Moreover, the dynamic interaction between the vehicle and the bridge and stochastic nature of the traffic load also is usually neglected. In this paper we present approach which is based on a stochastic characteristic of the actual traffic flow and numerical calculation of dynamic interaction system heavy vehicle-bridge. Vehicles are modelled as a group of axles (SDOF model) with the dynamic characteristic (stiffness and damping), and the weight is treated as stochastic variable. Dynamic vehicle-bridge model has been defined by the system of coupled partial differential equations.

Two small railway flyovers in the city of Osijek, Croatia, at a short distance between each other, were in such condition that they had to be replaced by a new structure. The railway authorities imposed a choice of a concrete superstructure and to lead the bal-last along the structure. Given the distance between the extreme abutments of about 46 m, a two-span non-continuous prestressed concrete trough bridge was adopted. The railway traffic had to be maintained during construction. Therefore the superstructures were built on scaffolding beside the flyovers and were laterally launched onto the supports after pre-stressing. The superstructures pertaining to individual spans have been built subsequently. The substructure consists of abutments arranged in the form of a space frame, and the middle support is a plain frame. The cross-beams of these frames support bearing pads and the columns of both frames are a direct continuation of bored piles. The construction is underway and is scheduled for completion in spring 2006.

Modelling the road bridge-actuall traffic dynamic interaction

U radu su navedeni rezultati postupaka kalibracije za spregnute nosače kao podloga za izradu dokumenta NAD (National Application Document) potrebnog za primjenu eurokoda u Hrvatskoj. Obuhvaćeni su spregnuti nosači na dva ležaja s monolitnom armiranobetonskom pločom s ili bez trapeznog lima kao izgubljene oplate i s valjkastim moždanicima kao sredstvom sprezanja. Pokazano je da su predložene veličine parcijalnih faktora sigurnosti za otpornost prihvatljive za primjenu u našoj zemlji.

Dinamička interakcija vozila i cestovnog grednog mosta

A short survey of the reliability indices obtained by calibration of different types of composite structures in Croatia is presented. This paper delas with reliability indices of composite beams in buildings, shear connection of composite beams in buildings and composite road bridges using calculation resistance models according to Eurocode 4 – all for ultimate limit state. The Ministry of Science and Technology of Republic of Croatia has founded a project about calibration of composite structures. The results obtained can serve for preparing NAD (National Application Document) in applying Eurocode to the national standard.

The procedure of a safety evaluation of road composite (steel-concrete) bridges with a span of 25 to 45 m is described. The question of safety evaluation is important from the aspect of inspections but also for the conception of designing solutions that are more modern. Research of all essential parameters for bridge evaluations must be initialized in national frameworks, which will enable for a comparison and uniforming on higher levels. Research results obtained for the region of Croatia which are based upon the collecting and working-over of appropriate statistical data were used for the formulation of basic variables of actions and resistances in this paper. Deterministic and probabilistic traffic models were formed. Safety checking was performed using the FORM method for the case of ultimate limit state on the basis of flexural cross-section resistance, as well as the serviceability limit state through a limitation of stresses in structural steel. Safety indices ß were obtained for particular spans of bridges and different conceptions of erection.

This paper deals with a probabilistic method of introduction of new materials during the conception of sandwich panels. The result of application of this method is that all sandwich panels layers have the same safety degree and in this way effective development is enabled for new generations of sandwich panels.

U ovom je radu provedena ocjena sigurnosti spregnutih mostova slobodno oslonjenih na dva ležaja, raspona 25 do 45 metara. Analizirane koncepcije izvedbe mosta obuhvatila je slučaj potpunog i djelomičnog sprezanja. Za ishodišne konstrukcije su usvojeni spregnuti mostovi starosti 40-50 godina, kako bi se dobio uvid u ostvareni stupanj sigurnosti i rezultati istraživanja koristili pri projektiranju i koncipiranju suvremenijih rješenja mostova. Dimenzioniranje mostova je izvršeno prema u spomenutom vremenu važećim tehničkim propisima. Za određivanje dimenzija poprečnog presjeka je korištena elastična analiza, a presjek je koncipiran u skladu s konstrukterskim pravilima iz toga razdoblja. Procjena sigurnosti izvršena je primjenom probabilističkom metodom FORM, za krajnje granično stanje, granično stanje uporabivosti te granično stanje obzirom na umor materijala. Krajnje granično stanje ocijenjeno je na temelju otpornosti poprečnog presjeka na savijanje. Tretman otpornosti poprečnog presjeka vršen je na temelju zahtjeva novih tehničkih propisa, Eurocoda, te je u skladu s njim i izvršeno definiranje odgovarajućih jednadžbi graničnog stanja. Granično stanje uporabivosti obuhvatilo je provjeru ostanka konstrukcije u elastičnom području, odnosno ograničenje vrijednosti naprezanja u čeličnom dijelu spregnutog presjeka. Umornost je ocijenjena za osnovni materijal, te poprečno i uzdužno ukrućenje hrpta. Sva ocjene sigurnosti su izvršene za različite raspone unutar zadanog intervala. Analize su provedene s relativno velikim brojem baznih varijable čiji su statistički parametri birani tako da što bolje predstavaljaju naše uvjete. Izvršeno je modeliranje realnog prometnog opterećenja u našoj zemlji. Za tu svrhu je formiran set reprezentativnih vozila čije su karakteristike dobivene na temelju obrade odgovarajućih statističkih podataka o hrvatskom prometu. Pri tome je formiran deterministički i probabilistički model, što je ovisilo o tretmanu ukupne težine teretnog vozila kao mjerodavnog parametra.

The fatigue analysis of road bridges requires specific traffic data, such as stress-range spectrum and percentage of vehicle types. Eurocode proposes the fatigue load model with using actual traffic data which are suitable for countries of the European community. The fatigue load model is obtained on the basis of statistical data of road traffic in Croatia, which is different from the Eurocode model (EC model). The fatigue load model obtained in Croatia (CRO model) results in a lower stress-range spectrum than the EC model.

U radu se obrađuje problematika istraživanja osjetljivosti čeličnih cestovnih mostova na fenomen umaranja konstrukcijskih elemenata. Za istraživanje ovoga fenomena potrebno je poznavati stvarne karakteristike cestovnog prometa na nekom području a ne granične ili maksimalne na temelju kojih se vrši dimenzioniranje konstrukcijskih elemenata mostova. Stoga je u radu predloženo nekoliko načina kako se može izvršiti procjena ovoga opterećenja prema stvarno prikupljenim statističkim podatcima za nekoliko godina u Republici Hrvatskoj te se ilustrira procedura njihove primjene.