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Efficency of self-healing chemical additives on the freeze/thaw resistance of concrete
No full textUzroci nastanka pukotina u betonu su različiti, ali bez obzira na njihovo podrijetlo, one uvijek štetno djeluju na trajnost betonskih konstrukcija i znatno utječu na povećavanje troškova njihova održavanja. Ovaj rad razmatra cikluse smrzavanja i odmrzavanja kao jedan od uzroka nastanka pukotina u betonu te pronalazi nove načine za unaprjeđenje otpornosti betona na smrzavanje i odmrzavanje. Rad se sastoji iz osam poglavlja; šest poglavlja koji prikazuju pregled stanja područja, jednog eksperimentalnog poglavlja na razini materijala, jednog eksperimentalnog poglavlja na razini konstrukcija i zaključka. U eksperimentalnom poglavlju na razini materijala pripremljeno je osam betonskih mješavina od čega šest mješavina uz v/c = 0,35; referentna mješavina, mješavina s aerantom, dvije mješavine s kristalnim hidrofilnim dodatkom (1 % i 3 % na masu cementa) i dvije mješavine sa
samostalno pripremljenim mikrokapsulama (jezgra od toluen 2,4-diizocijanata, a opna od parafina) te dvije mješavine s kristalnim hidrofilnim dodatkom (1 % i 3 % na masu cementa) uz v/c = 0,45. Ispitivanje otpornosti betona na cikluse smrzavanja i odmrzavanja provedeno je direktnim (ljuštenje i unutarnje oštećenje s i bez soli, faktor razmaka pora) i indirektnim (promjena dinamičkog modula elastičnosti, omjeri tlačne i vlačne čvrstoće te dubine prodora vode nakon i prije ciklusa smrzavanja i
odmrzavanja) postupcima, a za potrebe interpretacije rezultata određeni su udio pora pojedine veličine živinom porozimetrijom, raspodjela pora i njihova povezanost mikrotomografijom te SEM/EDS analiza na uzorcima tretiranim i netretiranim ciklusima smrzavanja i odmrzavanja, kao i praćenje širine pukotina tijekom procesa samozacjeljivanja na uzorcima tretiranim i netretiranim
ciklusima smrzavanja i odmrzavanja. Kristalni hidrofilni dodaci su pokazali potencijal u poboljšanju otpornosti betona na cikluse smrzavanja i odmrzavanja. Mikrokapsule su se također pokazale korisnim, no manje učinkovitosti nego kristalni hidrofilni dodaci. Na razini konstrukcijskih elemenata izrađene su po dvije armiranobetonske grede od svake od po tri mješavine betona; referentna mješavina, mješavina s 1 % kristalnog hidrofilnog dodatka i mješavina s 1 % mikrokapsula. Po dvije grede su izložene ciklusima smrzavanja i odmrzavanja, a po dvije nisu. Na gredama je praćena promjena dinamičkog modula elastičnosti i upijanje vode prilikom izlaganja ciklusima smrzavanja i odmrzavanja, a nakon toga su grede tretirane i netretirane ciklusima smrzavanja i odmrzavanja opterećivane do sloma, pri čemu im je praćen progib, sekantna krutost, duktilnost i sila pri slomu te su isti stavljeni u omjer. Na temelju rezultata zaključeno je i na razini konstrukcijskih elemenata kako primjena kristalnog hidrofilnog dodatka i mikrokapsula ima potencijala za unaprjeđenje otpornosti armiranobetonskih elemenata na cikluse smrzavanja i odmrzavanja.The causes of cracks in concrete are different, but regardless of their origin, they always have a detrimental effect on the durability of concrete structures and significantly increase their maintenance costs. This paper considers freezing and thawing cycles as one of the causes of cracks in concrete and finds new ways to improve concrete's resistance to freezing and thawing. The paper consists of eight chapters; six chapters showing an overview of the state of the area, one experimental chapter at the level of materials, one experimental chapter at the level of structures and a conclusion. In the
experimental section, eight concrete mixtures were prepared at the material level, six of which were mixtures with v/c = 0.35; a reference mixture, a mixture with aerant, two mixtures with a crystalline hydrophilic additive (1 % and 3 % by mass of cement) and two mixtures with self-prepared microcapsules (core of toluene 2,4-diisocyanate and a shell of paraffin) and two mixtures with a crystalline hydrophilic additive (1 % and 3 % by mass of cement) with v/c = 0.45. Testing of concrete's
resistance to freezing and thawing cycles was carried out by direct (scaling and internal damage with and without salt, pore spacing factor) and indirect procedures (change in dynamic modulus of elasticity, compressive and tensile strength ratios, and depth of water penetration after and before freezing and thawing cycles), and for the purposes of interpreting the results, the proportion of pores of a particular size was determined by mercury porosimetry, the distribution of pores and their connection by microtomography, and SEM/EDS analysis on samples treated and untreated by freezing and thawing cycles, as well as monitoring the width of cracks during the self-healing process on samples treated and untreated with freezing and thawing cycles. Crystalline hydrophilic admixtures have shown potential in improving concrete resistance to freeze-thaw cycles. Microcapsules have also been shown to be useful, but less effective than crystalline hydrophilic
admixtures. At the level of structural elements, two reinforced concrete beams were made from each of the three concrete mixes; reference mixture, mixture with 1 % crystalline hydrophilic additive and mixture with 1 % microcapsules. Two of the beams are exposed to freezing and thawing cycles, and two of them are not. The changes in the dynamic modulus of elasticity and water absorption were monitored on the beams during exposure to freezing and thawing cycles, and after that, the beams treated and untreated by freezing and thawing cycles, were loaded until failure, while their deflection, secant stiffness, ductility and ultimate force were monitored and are shown in ratio. Based on the results, it was concluded at the level of structural elements that the application of crystalline hydrophilic additives and microcapsules has the potential to improve the resistance of reinforced concrete elements to freezing and thawing cycles
Analysis of local head losses in pipes in flow under pressure
No full textTema ovog završnog rada su lokalni gubitci u tlačnim cijevima. Završni rad se sastoji od dva dijela. Prvi dio je teorijski dio u kojem će biti opisana problematika lokalnih gubitaka. Analizirat ćemo fenomen lokalnih gubitaka strujanja u cijevima. Ovaj fenomen predstavlja važan aspekt u hidrodinamici i ključan je za razumijevanje energetskih gubitaka u različitim inženjerskim sustavima.
U drugom dijelu završnog rada će biti prikazan praktičan rad u laboratoriju potkrijepljen slikama iz laboratorija te mjerenjima.The aim of this final paper is local losses in pressure pipes. This bachelor’s thesis consists of two parts. The first part of the paper is the theoretical part in which the issue of local losses will be described. The phenomenon of local flow losses in pipes will be analyzed. This phenomenon represents an important aspect in hydrodynamics and is crucial for understanding energy losses in various engineering systems. In the second part of the paper, the practical work in the laboratory, supported by
pictures from the laboratory and measurements, will be presented.
Design of steel frame with tension brace
No full textU ovom radu prikazan je proračun čelične proizvodne hale koja se nalazi na lokaciji grada Osijeka. Hala ima dimenzije 15 x 25 metara, dok visina hale iznosi 6,0 metara. Proračun uključuje glavne elemente konstrukcije, spojeve dijelova konstrukcije, te spojeve konstrukcije sa tlom. Dimenzioniranje i analiza opterećenja provedeni su u skladu s HRN EN normama.
Za statičku analizu korišten je računalni program Autodesk Robot Structural Analysis Professional 2021. Profil glavnih elemenata konstrukcije je HEA 200 i HEA 240, dok je čelik korišten u konstrukciji kvalitete S235. Proračun konstrukcije izvršen je za granično stanje nosivosti (GNS) i granično stanje uporabljivosti (GSU), što osigurava da konstrukcija zadovoljava sve potrebne sigurnosne i funkcionalne zahtjeve.This paper presents the calculation of a steel production hall located in the city of Osijek. The dimensions of the hall are 15 x 25 meters, with a height of 6.0 meters. The main structural elements, connections between the structural parts, and connections of the structure to the ground are calculated in the paper. The design and load analysis were conducted according to HRN EN standards. The structural analysis was performed using the Autodesk Robot Structural Analysis Professional 2021 software. The profiles of the main structural elements are HEA 200 and HEA 240, and the steel used is of grade S235. The
structural calculation was performed for the ultimate limit state (ULS) and serviceability limit state (SLS)
Architectural - urban design of Gacka business zone
No full textPredmetni zadatak završnog rada je urbanističko-arhitektonsko rješenje poslovne zone Gacka koja se nalazi koja se nalazi u južnom dijelu grada Osijeka. Zbog blizine frekventnih prometnih osi i same lokacije unutar grada, obuhvat predstavlja važnu vizuru ulaska u grad. Koncept urbanističkog rješenja proizlazi iz više čimbenika, ali oni osnovni su tipologija okolne izgradnje i promet. Koncept je, dakle, odgovor na kontekst. Postavljanjem dijagonalnih pravaca, obuhvat je podijeljen na četiri kvadranta od kojih se svaki referira na okolnu izgradnju stvarajući tako različite ambijente. Dijagonale su osigurale protočnost na parceli. Urbanističkim dijelom zadatka su definirani položaji, odnosno markice zgrada poslovne i ugostiteljske namjene. Zgrade poslovne namjene povezane su čeličnom strukturom koja prati koncepciju pravilnog rastera, a svojim oblikovanjem poziva korisnika na zadržavanje. Struktura natkriva prostor trga koji je okrenut ka budućoj stambenoj izgradnji i tako postaje središte šireg obuhvata. Projektna zgrada nalazi se na istočnom dijelu parcele i svojim oblikovanjem se referira na okolnu stambenu izgradnju. Zgrada se sastoji od tri volumena međusobno povezana mostovima. Koncept zgrade se nadovezuje na koncept urbanizma. Svojim oblikovanjem, zgrada se referira na okolne oblike. Koncept prostorne organizacije proizlazi iz proučavanja odnosa geometrijskih likova unutar zadanih okvira pri čemu su glavna inspiracija djela ruskog suprematista Kazimira Maljeviča. Igrom punog i praznog, pozitiva i negativa, stvoreni su prostori različitih karakteristika i ambijenata.The topic of the final paper is to portray an urban architectural solution for a business zone Gacka which is situated in southern Osijek. Due to proximity of frequent traffic axes and the location itself, scope is one on the first views while entering the town. The concept of this urban solution derives from many factors but mainly from the typology of surrounding buildings and traffic. The concept, therefore, responds to context. Diagonal lines divide the scope into four squares each referring to the surrounding architecture, creating that way various ambients. Furthermore, diagonals enabled parcel high fluidity. Part of the task that engages with urban solutions defines the position, namely business and hospitality buildings stamps. Business buildings are linked using steel structures that follow the conception of a square grid and its design arouses customers' decision to stay on. The structure covers the part of a square that faces future housing buildings becoming that way the center of a broader scope. The project building is located in the eastern part of the parcel and its composition refers to neighboring housing buildings. The building consists of three volumes interrelated with bridges. The concept of the building follows up the urban concept. Moreover, the configuration of the building refers to surrounding shapes. The concept of spatial organization arises as the result of studying the relations of plane figures within defined frames and the main inspiration were the creations of a Russian suprematist Kaziir Maljevič. Interweaving full and empty, positive and negative, areas of various characteristics and atmospheres were created
Architecture and urban design of Retfala south business zone
No full textKoncept poslovne zgrade nastao je iz želje za odbacivanjem konvencionalnih pravokutnih i oštrih oblika zadanih idejnim rješenjem urbanizma. Upisivanjem krivulje unutar zadanih dimenzija dobiva se građevina koja svojom organskom formom stvara mjesto u kojem se potiče kreativnost i ublažava stres eliminacijom oštrih rubova. Ovom gestom postižu se povoljniji i kreativniji uvjeti za rad. S namjerom da se maksimizira količina prirodnog osvjetljenja u interijeru i da se uvedu smirujući ambijenti, formiraju se dvije vertikale; svjetlarnik - pod kojim su raspoređeni otvoreni prostori kroz galerije i atrij koji objedinjuje ostale radne prostore.The concept for the office building developed from the desire to reject the conventional rectangular and sharpedged forms given by the conceptual solution for urbanism. By inscribing a curve within the given dimensions, a building is obtained that, with its organic form, creates a place where creativity is encouraged and stress is alleviated by eliminating sharp edges. With this gesture, more favorable and creative working conditions are achieved. With the intention to maximize the amount of natural light in the interior and to introduce calming ambiences, two verticals are formed; skylight - under which open spaces are arranged through the galleries and an atrium that unites the rest of the work spaces
Measurements of material consumption and comparison with standard norms
No full textU uvodu je ukazano na potrebu planiranja materijala i vremena rada radnika i probleme do kojih pri tome dolazi u građevinskoj praksi. Građevinskim normativima definiran je potreban rad radnika s obzirom na njihovu kvalifikaciju, potreban rad stroja te utrošak materijala za jednu mjernu jedinicu proizvoda. S obzirom na zastarjelost i nedostatke javno dostupnih normativa potrebno je provoditi interno normiranje, odnosno stvaranje odgovarajućih baza podataka izvođača o trošenju materijala i vremena za radove koje uobičajeno obavlja, uzimajući u obzir resurse s kojima raspolaže. Od metoda koje se primjenjuju za interno normiranje ovdje je s 55 promatranja (mjerenja tijekom 55 dana) 5 vrsta radova na 5 gradilišta građevinskih projekata metodom tehničke evidencije, odnosno dokumentacije s gradilišta uz osobna zapažanja, utvrđen utrošak materijala. Dobiveni rezultati su uspoređeni s podacima iz dostupnih općih (javnih) normativa iz SFRJ, iskazano je prosječno odstupanje evidentiranog utroška materijala od normativa, te su analizirani razlozi tih odstupanja
Calculation of inner forces for a three-hinged frame canopy and projections of displacements
No full textZadatak za završni rad iz kolegija Mehanika 1 se sastoji od dva dijela. U prvom dijelu zadatka o konstrukcijskim sustavima unutarnje sile u n-n presjeku treba izračunati iz crteža na dva načina.Prvi način proračuna unutarnjih sila u presjeku je klasičnim postupkom iz uvjeta ravnoteže gdje je potrebno proračunati momente savijanja, poprečne i uzdužne sile.Drugi način proračuna unutarnjih sila je metodom virtualnog rada.Uz proračun je potrebno nacrtati dijagrame unutarnjih sile te rezultate kontrolirati u nekom od programskih paketa. U drugom dijelu zadatka gdje nam je zadan mehanizam na crtežu uz kut zaokreta tijela 1, potrebno je odrediti kuteve zaokreta tijela 2 i 3 te pomake zadanih pet točaka.Zadatak je potrebno riješiti pomoću planova pomaka te rezultate kontrolirati računski.The assignment for the final paper from the course Mechanics 1 consist of two parts. In the first parto f the task on structural systems, the internal forces in the n-n section should be calculated from the drawing in two ways.The first way of calculating the internal forces in the cross section is by the classical procedure from balance conditions where it is necessary to calculate
bending moments,transverse and longitudal forces.Another way of calculating internal forces is the method of virtual work.In addition to the calculation, it is necessary to draw internal force diagrams and check the results in one of the software packages. In the second part of the task, where we are given the mechanism in the drawing along the turning angle of the body 1, it is necessary to determine the turning angles of bodies 2 and 3 and displacements of the given five points.It is necessary to solve the task using displacement plans and control the results computationally
Comparison of Seismic and Structural Parameters of Settlements in the East Anatolian Fault Zone in Light of the 6 February Kahramanmaraş Earthquakes
No full textOn 6 February 2023, two very large destructive earthquakes occurred in the East Anatolian Fault Zone (EAFZ), one of Türkiye’s primary tectonic members. The fact that these earthquakes occurred on the same day and in the same region increased the extent of the destruction. Within the scope of this study, twenty different settlements affected by earthquakes and located directly on the EAFZ were taken into consideration. Significant destruction and structural failure at different levels were induced in reinforced concrete (RC) structures, the dominant urban building stock in these regions. To determine whether the earthquake hazard is adequately represented, the PGA values predicted in the last two earthquake hazard maps used in Türkiye for these settlements were compared with the measured PGAs from actual earthquakes. Subsequently, the damage to reinforced concrete structures in these settlements was evaluated within the scope of construction and earthquake engineering. In the final part of the study, static pushover analyses were performed on a selected example of a reinforced concrete building model, and target displacement values for different performance levels were determined separately for each earthquake. For the 20 different settlements considered, the displacements were also derived based on the values predicted in the last two earthquake hazard maps, and comparisons were made. While the target displacements were exceeded in some settlements, there was no exceedance in the other settlements. The realistic presentation of earthquake hazards will enable the mentioned displacements predicted for different performance levels of structures to be determined in a much more realistic manner. As a result, the performance grades predicted for the structures will be estimated more accurately
Road building using wood ash
No full textThis paper describes the specifics of constructing a test section of an internal road where wood ash was used to improve the bearing capacity of the subgrade and to construct the base layer of the pavement structure. Laboratory testing and field control testing were conducted during the construction. The results showed that the increase in the bearing capacity of the subgrade by applying stabilization with wood ash ranges from 155 to 235 % compared to the natural clay subgrade. Due to the binding properties of wood ash, the bearing capacity of the subgrade continues to increase even after construction, with an observed increase of 31 to 39 % in bearing capacity within 14 days of construction. The base layer made of wood ash of different fractions achieved compressive modulus Ms = 60 to 80 MN/m², thus meeting the bearing capacity criteria. The experiences from the test section confirm the potential of wood ash for use in improving subgrade bearing capacity and in the construction of the base layer of pavement structures. This could encourage more rational and economical design and construction of pavement structures, especially in areas with large amounts of waste ash from wood biomass, such as the region of Slavonia
Architecture and Urban Design of Gacka Business Zone
No full textPoslovna zona Gacka nalazi se u južnom dijelu grada. Novoplanirana zgrada nalazi se između zelene površine na istoku i poslovne zone, hotela i trga na sjeverozapadu. Ideja zgrade proizašla je upravo iz želje za uvlačenjem zelenila kako u urbanističko rješenje tako i u poslovnu zgradu.The Gacka business zone is located in the southern part of the city. The newly planned building is located between the green area in the east and the business zone, the hotel and the square in the northwest. The idea of the building arose precisely from the desire to draw greenery into both the urban solution and the office building