TRAGFÄHIGKEITSERHÖHUNG VON VERBUNDTRÄGERN MIT TEILWEISER VERKLEIDUNG DES STAHLPROFILS MIT BETON

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

POUZDANOST LIJEPLJENIH LAMELIRANIH NOSAČA NA SAVIJANJE

This paper presents probabilistic reliability analyses of glulam beams by using level I semiprobabilistic procedure according to Eurocode standards and level II first-order reliability method. The analyses were performed for normal design situations on two groups of girders: roof and ceiling girders. The girders were first dimensioned for the ultimate limit state of bending according to Eurocode 5, after which the limit state equations were set with stochastic values of basic variables. A sensitivity analysis showed that the effect of strength variation is not significant when the coefficient of strength variation is approximately 15%: the recommended value from previous literature. The reliability indices obtained in this study are compared with the corresponding standard values for structural categories RC2 and RC3 according to Eurocode 0.U radu je prikazana analiza pouzdanosti lameliranih drvenih nosača na razini I., primjenom semiprobabilističkog postupka danog u Eurokodu i razini II., primjenom metode pouzdanosti prvog reda – FORM metoda. Analiza je provedena za normalnu proračunsku situaciju na dvjema različitim skupinama nosača: krovnim i stropnim nosačima. Nosači su najprije dimenzionirani prema graničnom stanju nosivosti na savijanje u skladu s Eurokodom 5, nakon čega su postavljene jednadžbe graničnog stanja sa stohastičkim vrijednostima osnovnih varijabli. Analizom osjetljivosti je pokazano da utjecaj varijacije čvrstoće na savijanje nije značajan ako se koeficijent varijacije čvrstoće na savijanje uzme oko 15 %, kolika je preporučena vrijednost iz literature. Rješenjem jednadžbi dobiveni su indeksi pouzdanosti koji su uspoređeni s normiranima za razred konstrukcije RC2 i RC3, prema Eurokodu 0

NUMMERISCHE SIMULATION DER EINWIRKUNG EINER EXPLOSION AUF ÜBERFÜHRUNGEN

Nadvožnjak nije moguće učiniti, projektiranjem i/ili izvedbom, apsolutno sigurnim na djelovanje eksplozije jer se ni sama količina eksploziva koja bi se detonirala ispod mosta u nekakvom napadu ne može odrediti s prihvatljivom vjerojatnošću. U radu je analizirano djelovanje tri količine eksploziva detonirane ispod rasponske konstrukcije nadvožnjaka. Promatrano je djelujuće opterećenje, ponašanje i oštećenje rasponskog sklopa nadvožnjaka. Zaključeno je kako sve tri količine eksploziva znatno oštećuju uobičajeni nadvožnjak te uzrokuju rušenje. Nelinearna numerička analiza nadvožnjaka provedena je koristeći hidrokod softver Ansys Autodyn.Overpasses can not be made absolutely safe to explosive action, regardless of interventions made during their design and/or realisation. This is due to the fact that the very quantity of explosive to be activated under the bridge during an attack can not be defined with an acceptable level of probability. Three quantities of explosives activated under the overpass structure are analysed. The load, behaviour, and damage to overpass superstructure are considered. It is stated in conclusion that all three quantities of explosive afflict considerable damage to usual overpasses, and cause their collapse. The nonlinear numerical analysis of the overpass was conducted using the Ansys Autodyn hydrocode software.In Übereinstimmung damit wurde die Wirkung von drei Sprengstoffmengen analysiert, die unter der Konstruktion der Überführung detonierten. Beobachtet wurden die einwirkende Belastung, das Verhalten und die Beschädigung am Überbau der Überführung. Es wurde festgestellt, dass alle drei Sprengstoffmengen eine normale Überführung erheblich beschädigen sowie den Einsturz verursachen. Die nicht lineare nummerische Analyse der Überführung wurde durch Anwendung der hidrokod Software Ansys Autodyn durchgeführt

Increase in bearing capacity of composite griders by partial steel-section encasement

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

Increase in bearing capacity of composite griders by partial steel-section encasement

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

UDAR MOTORNOG VOZILA U STUP MOSTA

As speed limits and traffic on city roads continue to increase, collisions between road vehicles and bridge columns are becoming more common. Current regulations analyze collision with one major simplification: replacing dynamic action with the equivalent static force. In the present paper, we develop a numerical model of a typical Croatian overpass and loaded it with an equivalent static load according to the EN1991-7 and ASSHTO LRFD provisions, analyzing the differences in overpass behavior between them. We compared this to a simplified dynamic analysis, which assumed the impact forces to be impulse loads. Protection measures can be installed around bridge columns that reduce the probability of vehicle collision and open possibilities for reducing collision forces.Udar vozila u stup mosta više nije rijetkost, ponajviše zbog sve veće opterećenosti prometnica i povećanja dopuštenih brzina vozila. Problem udara obrađen je u propisima uz znatno pojednostavljenje, dinamičko djelovanje zamijenjeno je ekvivalentnim djelovanjem statičke sile. Izrađen je numerički model tipičnog mosta na hrvatskim cestama na koji je primijenjena sila udara prema EN1991-7 i ASSHTO LRFD propisima kako bi se pokazala razlika između preporučenih djelovanja. Izvedena je dodatna usporedba s pojednostavljenim dinamičkim proračunom, gdje je sila udara pretpostavljena kao impulsno opterećenje. Oko stupova mostova mogu biti postavljene zaštitne mjere koje umanjuju vjerojatnost pojave udara i omogućavaju smanjenje veličina sila korištenih u proračunu

Utjecaj vertikalne komponente potresa na AB nosače velikog raspona

Most of the previous studies in the field of earthquake engineering have neglected the effects of vertical ground motion and are usually guided by horizontal motion. The EN1998 proposes action analysis of the vertical acceleration for certain types of elements and their length and their distance from the active fault. In this paper simply supported beams with various spans, 10, 15 and 20 m, are calculated for the action of real earthquakes with different intensities. Two typical cross sections were chosen: "T" cross section and rectangular cross section. The linear and nonlinear material models were used, and all the models were calculated using rigid and elastic supports. Through the combinations of these different spans, cross sections, material models and types of the supports, the influence and importance of the vertical component of the ground motion is estimated. Based on the results obtained it was concluded that there is a need for the application of vertical acceleration in the seismic analysis of these elements.Dosadašnja su ispitivanja učinaka potresa zanemarivala vertikalno gibanje tla te se uglavnom usmjeravala prema horizontalnoj komponenti. EN1998 daje preporuku analize djelovanja vertikalnog ubrzanja za određene vrste elemenata i njihovih duljina te njihove udaljenosti od aktivnog rasjeda. U radu se analiziraju jednostavno oslonjeni nosači različitih raspona, 10, 15, 20 m te pravokutnog i "T" poprečnog presjeka. Primijenjena su dva tipa oslanjanja, kruti i elastični ležaj te dva tipa modela materijala, linearni i nelinearni. Nosači su podvrgnuti djelovanju četiri realna potresa različitog intenziteta. Na ovaj se način pratila promjena u momentima savijanja nosača u polovici raspona kako bi se vidio doprinos vertikalnog ubrzanja. Na temelju dobivenih rezultata zaključeno je kako za analizirane nosače ipak postoji potreba primjene vertikalne akceleracije prilikom seizmičke analize

DIE ÄLTESTE GRÖSSERE VERBUNDBRÜCKE DER WELT

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

GLULAM BEAMS WITH HOLES

This paper provides a systematic review of research on glued laminated timber beams with circular and rectangular openings. Experiments on girders with unreinforced openings varied several parameters, including the girder span and shape, opening position and shape, and the relationship between the stress state near the opening and the ratio of opening size to girder size. We compare experimental results with recommendations given by DIN 1052:2004-08, DIN EN 1995-1-1/NA: 2010, prEN 1995-1-1: Final Draft, analytical expressions, and other relevant standards, as well as with the results of numerical models using the finite element method. Because of its myriad complexities and uncertainties, this area remains open for further research and for implementation of that research into practical design guidelines and rules

The world\u27s oldest major bridge with a composite deck structure

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\u27s 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