Teorijsko i eksperimentalno istraživanje ponašanja veze armiranobetonskog i čeličnog elementa preko armaturnih spojnica

Savremenu primenu spregnutih konstrukcija od armiranobetonskih i čeličnih elemenata prate intenzivna istraţivanja njihovih meĎusobnih veza. Istovremeno, nova tehnološka rešenja, vezana za pojednostavljenje oplate i povećanje brzine betoniranja, donose sve širu upotrebu armaturnih mehaničkih spojnica, pre svega za nastavljanje armature, ali i kao jedan od načina za vezu armiranobetonskih i čeličnih elemenata. Osnovni cilj istraţivanja u okviru ove teze je da se ispita mogućnost i način primene konektora formiranih od mehaničke spojnice sa armaturnim ankerom, ugraĎenih u armiranobetonski element, i čeličnog zavrtanja, za prenos sila smicanja u okviru spoja čeličnog i armiranobetonskog elementa u spregnutoj konstrukciji. Posebno se kod ovakvih spojeva ističu problemi lokalnog naprezanja betona u zoni spoja, kao i problemi vezani za prenos sila smicanja, odnosno sila upravnih na pravac mehaničkih spojnica. Nakon izvršenog detaljnog istraţivanja savremene naučnoistraţivačke i stručne literature u oblasti smičućih veza u spregnutim konstrukcijama, u okviru ove teze su izvršena eksperimentalna, numerička i teorijska istraţivanja granične nosivosti i ponašanja smičućih konektora sa mehaničkom spojnicom i armaturnim ankerom. Eksperimentalna ispitivanja su sprovedena na 18 uzoraka, rasporeĎenih u 5 serija. Numerička nelinearna analiza u programu ABAQUS sprovedena je na 28 numeričkih modela u konačnim elementima, prethodno kalibrisanih prema rezultatima eksperimentalnih isptivanja. U okviru ovih istraţivanja je pokazano da se smičući konektori sa mehaničkom spojnicom i armaturnim ankerom, sa aspekta nosivosti, mogu koristiti kao elementi smičućih spojeva u spregnutim konstrukcijama, i da se njihovo ponašanje moţe uporediti sa ponašanjem naknadno ugraĎenih ankera i ostalih ankera koji se ne sidre glavom. Na osnovu rezultata istraţivanja je zaključeno da granična nosivost ispitivanog smičućeg konektora po betonu u blizini ivice, moţe biti odredjena korišćenjem izraza za odreĎivanja iste nosivosti za naknadno ugraĎene ankere, opterećene paralelno sa betonom, uz prethodno odreĎivanje efektivne duţine zamenjujućeg konektora sa mehaničkom spojnicom konstantnog poprečnog preseka... Contemporary structures composed from reinforced concrete and steel elements use is followed by intensive research of their interconnection. Simultaneously, new technologies, regarding the simplification of formwork and concreting speed increase, are bringing mechanical couplers into the wider use, firstly as rebar splices, than as a mean of the connection between reinforced concrete and steel elements in composite structures. The main research goal within the theses is to investigate the possibilities and ways of use of the connectors composed from mechanical couplers with rebar anchors, embedded in concrete, and steel bolts, as a mean of shear transfer in composite structures connections. Specific issues related to this type of connections are local concrete pressure in the connector vicinity, as well as the sear flow along the connector axes. After detailed reviewing of the state of the art regarding shear connectors in composite structures, experimental, numerical and theoretical research on the shear connectors composed from mechanical couplers and rebar anchors resistance and behavior were conducted within this theses. The experimental research was conducted on 18 specimens, arranged in 5 series. Nonlinear numerical analyses, using ABAQUS software, was conducted on 28 numerical models in finite elements, after calibration with the experimental research results. The research resulted in conclusion that the shear connectors composed from mechanical couplers and rebar anchors have sufficient capacity to be used as shear connectors in composite structures, and that their behavior is similar to behavior of post installed anchors, as well as other types of connectors anchored without the head. Based in the research results, it can be concluded that the concrete edge breakout capacity of the investigated connectors subjected to the shear load parallel to the edge can be calculated using the formula for post installed anchors, after determining the effective length of the corresponding constant diameter shear connector with mechanical coupler. The original formula for determining of this length, as a function of coupler and rebar anchor diameter, as well as the concrete compression strength, was developed within this thesis...