Numerical Simulation of Dynamic Interaction between Fluid and Construction : Doctoral Thesis

U radu je prikazan numerički model simulacije međudjelovanja armirano-betonske konstrukcije i tekućine za 3D (prostorne) probleme pod statičkim i dinamičkim opterećenjem. Konstrukcija je modelirana degeneriranim elementima ljuske, a tekućina prostornim „brick“ elementima. Za opis ponašanja tekućine korišteni su linearni i nelinearni model. Nelinearnim modelom tekućine simulirana je pojava kavitacije. Za opis ponašanja betona korišten je specijalni model materijala kojim se može simulirati tečenje betona u tlaku te otvaranje i zatvaranje pukotina u vlaku. Valjanost modela i razvijenog softwarea testirana je na nekoliko numeričkih primjera.A numerical model of dynamic interaction between fluid and reinforced concrete structure in 3D space is presented in this work. Degenerated shell elements for construction and 3D brick elements for fluid are used. Linear and nonlinear material model are used for a description of the fluid behaviour. Nonlinear model can be used for simulated phenomena of cavitation. Special model, which can describe concrete yielding in compression and crack opening and closing in tension, is used for simulation of the concrete behaviour. The efficiency of model and developed software are tested on several numerical examples

Numerical model for determining fire behaviour of structures

U radu je prikazan numerički model i razvijeni računalni program za predviđanje ponašanja konstrukcija uslijed djelovanja požara. Nelinearni numerički postupak provodi se u zadanim vremenskim inkrementima, pri čemu se u svakom inkrementu proračunava razdioba temperature, u ovisnosti o njoj korigiraju karakteristike materijala i krutost elementa te rješava statički problem. Na jednostavnom primjeru čeličnog grednog nosača prikazana je efikasnost i točnost razvijenog modela i računalnog programa.A numerical model and computer program for predicting behaviour of structures subjected to fire action are presented in the paper. The nonlinear numerical procedure is conducted in pre-defined time increments. At that, the distribution of temperature is calculated in each increment and, depending on this calculation, material properties and stiffness of the element are corrected, and the static problem is resolved. The efficiency and accuracy of the model and computer program are presented on an example of a simply supported beam

Modelling flexural stiffness in concrete frames

Prvo je raspravljena problematika utvrđivanja stvarne krutosti greda i stupova betonskih okvira. Potom su opisani neki njihovi najčešće korišteni modeli krutosti na savijanje. Zatim je analiziran utjecaj odabranih modela krutosti greda i stupova na raspodjelu momenata savijanja u stvarnom okviru. Na kraju su navedeni zaključci za odabir adekvatnih modela krutosti elemenata okvira pri proračunu mjerodavnih unutarnjih sila, u cilju postizanja podjednake sigurnosti greda i stupova.The issue of determining actual stiffness of beams and columns of concrete frames is discussed in the initial part of the paper. This is followed by description of some of the most frequently used flexural stiffness models. Then the influence of selected beam and column stiffness models on the distribution of bending moments in a real-life frame is analyzed. Conclusions for the selection of adequate frame- element stiffness models for analysis of relevant internal forces, aimed at achieving similar level of safety for beams and columns, are given in the final part of the paper

Experimental tests of some composite steel-concrete, wood-concrete and concrete-concrete elements

The paper presents the results of experimental tests of some composite steel-concrete, wood-concrete and concrete-concrete elements. Deflections at midspan under monotonically increasing static load were measured. The influence of different composite making means on the results was researched. The emphasis was given to efficiency of different composites with Omnia-slabs that are commonly used in practice

USPOREDBA KONSTRUKCIJSKIH RJEŠENJA KROVNE KONSTRUKCIJE DVORANE U STOBREČU

U radu je prikazana usporedba dvaju konstrukcijskih rješenja krova školske sportske dvorane u Stobreču pokraj Splita. Školsku dvoranu se planira nadograditi pokraj postojeće škole, za što je izrađen projekt koji je sada u postupku ishođenja građevinske dozvole. Prema zahtjevima investitora, nad školskom dvoranom se planira izvesti školsko igralište. Na vječno pitanje: „Što je optimalno: beton ili čelik?“, pokušali smo dati odgovor kroz ovaj diplomski rad. Napravljena su dva rješenja za rasponsku konstrukciju krova: prednapeti nosač i standardna čelična rešetka koji su opterećeni istim opterećenjem, proračunati i dimenzionirani prema trenutačno važećim propisima

Static and dynamic analysis of concrete shells - shell element and models

Opisan je model i odgovarajući softver za statičku i dinamičku analizu betonskih ploča i ljusaka. Model simulira materijalnu i geometrijsku nelinearnost. Pokazano je da je moguće uključiti dominantne nelinearne efekte armiranog betona (betona i armature). U ovom radu koji čini prvi dio jedne cjeline, opisan je usvojeni element ljuske, modeli materijala za beton i armaturu, te model geometrije. U drugom radu koji slijedi bit će prikazana numerička analiza, ilustrirana primjerima.The model and the corresponding software for the static and dynamic analysis of concrete plates and shells is described. The model simulates the material and geometrical nonlinearity. It is demonstrated that dominant nonlinear effects of the reinforced concrete (concrete and reinforcing bars) can be taken into account. This paper, which is the first portion of a more extensive analysis, describes the adopted shell element, material models for concrete and reinforcing bars, and the geometry model. In the second paper, which is to follow shortly, the authors will describe numerical analysis illustrated with appropriate examples

Wooden footbridge in Trogir

Prikazano je rješenje pješačkog drvenog mosta preko kanala Foša u Trogiru kojim ga se nastojalo uklopiti u ambijent grada. Montažno-demontažnu rasponsku konstrukciju mosta tvore dva dvozglobna drvena luka raspona 25 m. Lukovi su povezani poprečnim gredama, iznad kojih je izvedena dvoslojna križna daščana podloga. Svi su dijelovi rasponskog sklopa izvedeni iz masivne hrastovine. Spojna sredstva su vijci i moždanici. Ispod mosta moguć je prolaz plovila visine do 4,5 m.The solution used for the wooden footbridge across the Foša Canal in Trogir, specifically aimed at blending this structure with its urban surroundings, is presented. The mountable-dismountable superstructure of this bridge is formed of two double-hinged wooden arches, 25 m in span. The arches are linked with cross beams, above which a two layered cross-boarded surface was realized. All superstructure segments are made of massive oak-wood. Bolts and stud connectors were used as connecting elements. Vessels up to 4.5 m in height can pass under the bridge

Numerical procedure in the static and dynamic analysis of concrete shells

Rad je nastavak i čini cjelinu s radom [44] u kojem su opisani elementi ljuske za analizu i modeli za numerički postupak. Detaljnije je prikazan praktični postupak za provedbu proračuna. Opisan je posebno izrađeni proračunski program DALJ namijenjen nelinearnoj analizi armiranobetonskih ploča i ljusaka. Prikazan je način proračuna na dvama primjerima – na paraboličnoj cilindričnoj ljuski promjenjive debljine i na armiranobetonskim tornjevima za hlađenje u nuklearnim elektranama.The paper is a continuation of, and forms a whole with, the paper [44] in which shell elements for analysis and models for numerical procedure, are described. A practical procedure for calculation is presented in more detail. A special computer program DALJ for nonlinear analysis of reinforced-concrete palets and shells is also described. The calculation method is illustrated with two examples – using a parabolic cylindrical shell of variable thickness and reinforced-concrete fefrigeration towers in nuclear power plants

Influence of ties on compressive strength of concrete piers

Prikazani su rezultati eksperimentalnih ispitivanja utjecaja spona na tlačnu nosivost i deformabilnost centrično opterećenih betonskih stupova kvadratnoga poprečnog presjeka. Istražen je utjecaj čvrstoće betona te razmaka i ploštine spona na graničnu nosivost i deformabilnost stupova. Rezultati pokazuju da se granična nosivost i granično skraćenje ispitivanih stupova povećava s povećanjem količine poprečne armature, pri čemu je primaran utjecaj razmaka spona, a ne njihova debljinu.The experimental testing of the effect of ties on the compressive strength and deformability of centrically loaded concrete piers of rectangular cross-section is presented. The authors present the way in which the ultimate bearing capacity and deformability of piers are influenced by concrete strength, and by the spacing and area of ties. The results show that the ultimate bearing capacity and the ultimate shortening of tested piers increases with the increase in the quantity of transverse reinforcement. At that, the tie spacing, rather than its thickness, is of primary significance

Static and dynamic analysis of concrete shells - shell element and models

Opisan je model i odgovarajući softver za statičku i dinamičku analizu betonskih ploča i ljusaka. Model simulira materijalnu i geometrijsku nelinearnost. Pokazano je da je moguće uključiti dominantne nelinearne efekte armiranog betona (betona i armature). U ovom radu koji čini prvi dio jedne cjeline, opisan je usvojeni element ljuske, modeli materijala za beton i armaturu, te model geometrije. U drugom radu koji slijedi bit će prikazana numerička analiza, ilustrirana primjerima.The model and the corresponding software for the static and dynamic analysis of concrete plates and shells is described. The model simulates the material and geometrical nonlinearity. It is demonstrated that dominant nonlinear effects of the reinforced concrete (concrete and reinforcing bars) can be taken into account. This paper, which is the first portion of a more extensive analysis, describes the adopted shell element, material models for concrete and reinforcing bars, and the geometry model. In the second paper, which is to follow shortly, the authors will describe numerical analysis illustrated with appropriate examples