15 research outputs found
Reduction in wind force in relation to corner design of bridge piers
The effects of wind on beam bridges can be significantly reduced with careful design of deck, roadway and wind barriers, as well as with appropriate design of piers. In this paper, the influence of corner design of rectangular cross-sectional piers to total wind force on piers is investigated. The total wind force changes, due to a different corner design of rectangular cross section of piers in free standing phase, are analyzed for piers of different heights, different environments and different wind velocities. The correlation between changes in total wind force and changes in geometric properties of a pier is also shown. By rounding the corners of a pier square cross section, the total wind force on pier in free standing phase can be drastically reduced in comparison to the total wind force on sharp corner pier with a small reduction in a load bearing properties of the pier. Changes in the bridge pier environment, as well as changes in pier height and wind velocity have negligible influence on changes in reduction of total wind force due to rounding the pier corners
Interaction diagrams for reinforced concrete circular cross-section
U radu je opisan postupak izrade dijagrama interakcije za armiranobetonske kružne popreÄne presjeke prema normi HRN EN 1992-1-1. UvoÄenjem novih razreda ÄvrstoÄe betona s neÅ”to drugaÄijim parametrima proraÄunskog dijagrama naprezanje-relativna deformacija dolazi do potrebe izrade novih dijagrama interakcije. Proveden je postupak proraÄuna temeljem kojeg su izraÄeni dijagrami interakcije za kružni popreÄni presjek za sve razrede betona. Primjenom dobivenih dijagrama interakcije pojednostavljuje se postupak dimenzioniranja armiranobetonskih kružnih popreÄnih presjeka.The procedure for creating interaction diagrams for reinforced-concrete circular crosssections, based on HRN EN 1992-1-1, is described in the paper. Due to introduction of new concrete strength classes, with somewhat different parameters for the stressrelative strain diagram, it has become necessary to develop new interaction diagrams. The computation procedure based on which circular cross section interaction diagrams were made for all concrete classes, was conducted. The use of these interaction diagrams will simplify dimensioning of reinforced-concrete circular cross-sections
Novo graÄevinsko tehniÄko zakonodavstvo u Hrvatskoj
U radu je dan osvrt na osnovne zakone i podzakonske akte koji reguliraju podruÄje graditeljstva, a osiguravaju ujednaÄavanje hrvatskog s europskim tehniÄkim zakonodavstvom u podruÄju graditeljstva. TakoÄer je uspostavljena veza izmeÄu pojedinih zakona i podzakonskih akata. U radu je posebno obraÄeno podruÄje tehniÄkih propisa i hrvatskih normi za graÄevne proizvode, projektiranje, graÄenje i održavanje graÄevina koji su izraÄeni u skladu s novim graÄevinskim tehniÄkim zakonodavstvom koje se temelji na ispunjavanju bitnih zahtjeva za graÄevinu i Direktivi o graÄevnim proizvodima. ObjaÅ”njena je razlika izmeÄu obvezne i neobvezne primjene hrvatskih normi na koje upuÄuju tehniÄki propisi. Na kraju rada je dan sažeti tabliÄni prikaz važeÄih tehniÄkih propisa iz podruÄja graditeljstva sa pripadnim podruÄjem primjene i izuzecima na koje se ne odnosi ili ne primjenjuje pojedini tehniÄki propis i broj hrvatskih normi na koje izravno upuÄuju važeÄi tehniÄki propisi
ODREÄIVANJE DINAMIÄKOG KOEFICIJENTA NA MOSTOVIMA
U radu je, sa svrhom odreÄivanja globalnog dinamiÄkog koeficijenta mosta, koriÅ”ten programski paket DARK kojim se može provesti dinamiÄki proraÄun ravninskih Å”tapnih konstrukcija pod djelovanjem pokretnog optereÄenja. Programom DARK mogu se, uz osnovne dinamiÄke karakteristike, izraÄunati dinamiÄki progibi, brzine i ubrzanja konstrukcije izložene djelovanju optereÄenja koje se kreÄe konstrukcijom. Primjena programa za odreÄivanje globalnog dinamiÄkog koeficijenta prikazana je na modelu mosta Drave u Osijeku. Uporabom navedenog programa odreÄeni su dinamiÄki progibi mosta zbog prometovanja razliÄitih kamiona razliÄitim brzinama po mostu i usporeÄeni sa statiÄkim progibima od istih optereÄenja, tj. odreÄeni su dinamiÄki koeficijenti. Ovako odreÄeni dinamiÄki koeficijenti usporeÄeni su s normama i pravilnicima predviÄenim koeficijentima
ODREÄIVANJE PRORAÄUNSKE Å IRINE T-PRESJEKA POPREÄNOG NOSAÄA REBRASTOG GREDNOG MOSTA
U ovom radu analizira se i vrjednuje proraÄunska Å”irina T-presjeka popreÄnog nosaÄa podvožnjaka Vrata 1 na temelju proraÄuna i rezultata pokusnog optereÄenja. Rebrasti gredni mostovi najÄeÅ”Äe se proraÄunavaju kao Å”tapni roÅ”tiljni sustavi. Uzdužni i popreÄni nosaÄi se, zajedno sa sudjelujuÄim dijelom kolniÄke ploÄe, promatraju kao T-presjeci. Njihova krutost ovisi o proraÄunskoj (sudjelujuÄoj) Å”irini T-presjeka koja ovisi o viÅ”e Äimbenika, meÄu ostalim i o optereÄenju koje na mostu može biti razliÄito po intenzitetu i položaju. U ovom radu se odreÄuju proraÄunske Å”irine T-presjeka popreÄnog nosaÄa u polju roÅ”tiljne rasponske konstrukcije pomoÄu numeriÄkih proraÄuna po metodi konaÄnih elemenata za razliÄite položaje pokusnog optereÄenja. Na taj naÄin odreÄene proraÄunske Å”irine rabe se za proraÄun progiba na jednostavnim roÅ”tiljnim modelima. ProraÄunani progibi usporeÄuju se s odgovarajuÄim progibima podvožnjaka izmjerenima pri pokusnom optereÄenju i progibima proraÄunanima na jednostavnom roÅ”tiljnom modelu u kojemu je uporabljena proraÄunska Å”irina T- presjeka popreÄnog nosaÄa u polju prema normi HRN ENV 1992-1-1
Shear resistance of reinforced concrete beams in dependence on concrete strength in compressive struts
U aktualnoj europskoj normi EN 1992-1-1 za dimenzioniranje armiranobetonskih greda na popreÄne sile predviÄa se uporaba reÅ”etkastog modela sa slobodnim odabirom nagiba betonskih tlaÄnih ispunskih Å”tapova u Å”irokim granicama, to jest od 21,8Ā° do 45Ā° prema osi grede. MeÄutim, postoje istraživanja i prijedlozi koji upuÄuju na oprez kod odabira donje granice nagiba ispunskih tlaÄnih Å”tapova s obzirom na umanjenje tlaÄne ÄvrstoÄe raspucanog betona u hrptu armiranobetonskih elemenata izloženih popreÄnim silama. U radu je dan pregled teorijskih postavki i metoda proraÄuna armiranobetonskih elemenata na popreÄne sile. Provedena je parametarska analiza nosivosti na popreÄne sile pri drobljenju tlaÄnih Å”tapova kao funkcije njihovog nagiba. Pri tom su koriÅ”tena su tri razliÄita pristupa za ograniÄenje naprezanja u tlaÄnim Å”tapovima. Na temelju provedene analize i usporedbe rezultata u radu je dan prijedlog za odreÄivanje nosivosti armiranobetonskih greda na popreÄne sile po kriteriju ÄvrstoÄe betona ispunskih tlaÄnih Å”tapova reÅ”etkastog modela.In the current European Code EN 1992-1-1 a truss model with variable inclination angle of concrete compressive struts with a quite wide range of inclination angle, from 21,8Ā° to 45Ā°, is intended for use for shear design of reinforced concrete beams. However, some researches and recommendations indicate special attention when choosing the lower bound of inclination angle of the concrete compressive struts, due to the reduced compressive strength of cracked concrete. This work reviews theoretical background and shear design methods of reinforced concrete beams. Relation of the shear resistance to crushing of the compressive struts as a function of their inclination angle has been investigated through a parametric study, where three different approaches have been used in order to limit stresses in the compressive struts. Based on the comparison of results from the analysis a recommendation for shear resistance calculation of reinforced concrete beams in dependence on concrete strength in compressive struts of the truss model is given
Testing semi-prefabricated floors made of prestressed brick elements
Prikazani su postupci i rezultati ispitivanja polumontažnih stropova od prednapetih opeÄnih gredica. Ispitivana je nosivost stropova i progibi pod dugotrajnim djelovanjem. Prikazan je postupak za odreÄivanje stanja naprezanja u gredicama od prednapinjanja i opisan je proraÄunski model i postupci za proraÄun progiba. Na temelju usporedbe izmjerenih veliÄina i onih dobivenih proraÄunom dvjema metodama odabire se metoda s rezultatima koji se bolje slažu s izmjerenim vrijednostima.Test procedures and results for semi-prefabricated floors made of prestressed brick elements are presented. The load bearing capacity of floors and deflection values following long term load, are tested. The procedure for determining the state of stress of these elements due to prestressing is presented, and the calculation model and procedures used in deflection calculation are described. Measured values are compared with those obtained by calculation based on two methods, and the method whose results correspond to a greater extent to measured values is then selected
Seismic insulation of buildings with elastomeric bearings
Prikazane su teorijske podloge za seizmiÄki proraÄun protupotresno izoliranih zgrada. Protupotresna izolacija s pomoÄu elastomernih ležajeva prikazana je na trokatnoj zgradi. Tako se mogu bitno smanjiti seizmiÄke sile u konstrukcijskim i nekonstrukcijskim elementima. Opisan je proraÄun konstrukcija otpornih na djelovanje potresa u Hrvatskoj i uporaba elastomernih ležajeva u protupotresnoj izolaciji graÄevina. U radu je prikazana približna metoda proraÄuna uÄinka protupotresne izolacije.Theoretical support data for seismic analysis of buildings insulated against earthquake action are presented. The seismic insulation with elastomeric bearings is presented on an example of a three-story building. This insulation enables significant reduction of seismic forces in structural and non-structural elements. The analysis of structures resistant to earthquake action in our country, and the use of elastomeric bearings in seismic insulation of structures, is described. An approximate method for calculating efficiency of seismic insulation is presented in the paper
Experimental and Numerical Study of Mild Steel Behaviour under Cyclic Loading with Variable Strain Ranges
To simulate the effect of variable strains on steel grades S275 and S355, an experimental displacement control test of plate specimens was performed. Specimens were tested under monotonic and cyclic loading according to the standard loading protocol of SAC 2000. During experimental testing, strain values were measured with an extensometer at the tapered part of the specimen. Strains obtained by the experimental tests are disproportional to the applied displacements at the ends of the specimens. This phenomenon occurs due to the imperfections of the specimen, hardening of the material, and the buckling behaviour that appears in real structures due to the high deformation experienced during earthquakes. Due to the relative simplicity and wide applicability of the Chaboche hardening model of steel, the calibration of hardening parameters based on experimental test results was conducted. For the first time, calibration of steel hardening parameters was performed following the Chaboche procedure to define the cyclic behaviour with variable strain ranges. The accuracy of the hardening model with variable strain ranges, which were simulated using ABAQUS software, was verified using the experimental results
Experimental stress-strain diagram of corroded reinforcing-steel bars
Smanjenje mehaniÄkih svojstva korodirane armature u odnosu na nekorodirani Äelik za armiranje bitno utjeÄe na preostalu nosivost i uporabljivost armiranobetonskih konstrukcija. Temeljem provedenog vlastitog eksperimentalnog rada predlažu se izrazi za odreÄivanje mehaniÄkih svojstva korodirane armature u ovisnosti o stanju korodiranosti armature i proraÄunski dijagram naprezanje-deformacija korodirane armature za proraÄun preostale nosivosti armiranobetonskih konstrukcija.When compared to the non-corroded reinforcing steel, the corroded bars and deterioration of their mechanical properties, exert a considerable impact on the residual bearing capacity and serviceability of reinforced-concrete structures. Original expressions are proposed for defining mechanical properties of corroded reinforcement, as related to the level of corrosion. An experimental stress-strain diagram of corroded reinforcing-steel bars, useful in the analysis of residual bearing capacity of reinforced concrete structures, is also proposed