Analiza ponašanja grupe elastičnih moždanika kod spregnutih nosača od čelika i betona

Abstract

Diskontinualni podužni smičući spoj ostvaren grupama moždanika je jednostavno i široko rasprostranjeno rešenje za sprezanje čeličnih nosača i montažnih armiranobetonskih ploča. Ovaj rad analizira mogućnost primene grupa moždanika sa redukovanim rastojanjima između susednih moždanika u grupi. Osnovni cilj rada je da se istraži mogućnost smanjenja rastojanja između susednih moždanika u grupi u odnosu na minimalno propisana rastojanja. Smanjenje rastojanja između moždanika u grupi i dimenzija grupe, omogućava izvođenje manjeg otvora u armiranobetonskoj montažnoj ploči potrebnog za smeštaj moždanika. Prikazano je sopstveno eksperimentalno istraživanje nosivosti grupa moždanika, sprovedeno na Građevinskom fakultetu Univerziteta u Beogradu. Eksperimentalnim istraživanjem analizirana je mogućnost primene grupe moždanika kod spregnutih greda u zgradarstvu. Ispitana je nosivost, deformabilnost i ponašanje, podužnog smičućeg spoja ostvarenog grupama moždanika. Glavni parametri analizirani u radu su: raspored moždanika u grupi, orijentacija grupe moždanika u odnosu na pravac podužne sile smicanja i međusobno rastojanje moždanika. Istraživanjem je obuhvaćeno pet različitih dispozicija grupa od četiri elastična moždanika sa glavom, kod kojih su međusobna rastojanja manja od minimalno propisanih rastojanja u Evrokodu 4. Cilj istraživanja je i da se utvrdi kako smanjenje minimalnih propisanih rastojanja između moždanika utiče na ponašanje, odnosno nosivost, duktilnost i ukupne deformacije podužnog smičućeg spoja. Korišćeni materijali, polazne pretpostavke i postupak ispitivanja su u skladu sa Evrokodom 4. Metodom konačnih elemenata simulirano je eksperimentalno istraživanje a kalibrisan numerički model sa eksperimentom je poslužio za izvođenje zaključaka o ponašanju veze ostvarene grupom moždanika sa glavom. Uočeni su i definisani modeli loma koji se mogu javiti u podužnim smičućim spojevima, formiranim grupama moždanika. Na uočenim modelima loma definisana su granična stanja nosivosti grupe moždanika. iv Pomoću numeričkih modela urađena je i parametarska analiza koja je obuhvatila različite prečnike i grupe moždanika...

Discontinuous shear connection with groups of headed studs is simple and widespread solution for connection between steel beam and precast concrete element. This thesis analyzes the possible applications of headed studs group with reduced distances between adjacent headed studs in the group. The main objective of this study was to investigate the possibility of reducing the spacing between adjacent headed studs in the group compared to the minimum required in Eurocode 4. Reducing the distance between the headed studs in the group and the dimensions of the group, would allow construction of a smaller hole in the reinforced concrete precast plate needed to accommodate the headed studs. The paper presents the results of the experimental research conducted on push-out tests at the Faculty of Civil Engineering at the University of Belgrade. Throughout the experiment there has been analyzed the possibility of using the headed studs group in composite beams for buildings. The capacity, deformability and behavior of shear connection with grouped headed studs was investigated (analyzed). A shape of group arrangement along with its orientation to the applied load and distance between the studs were variables considered. The study includes five different groups of four headed studs, with the distance between headed studs less than the minimum distances required in Eurocode 4. The aim of the research is to determine how the reduce of the minimum required distance between the headed studs affects to the behavior, shear capacity, ductility and total longitudinal shear deformation of the shear connection. The materials, initial assumptions and test set up are in accordance with Eurocode 4. The FEM model is used to simulate the experiment. Calibrated FEM models with push-out tests were used to draw conclusions about the behavior of shear connection with group of headed studs. The fracture models which can occur in longitudinal shear connection with headed studs group were identified and defined in the paper. Ultimate limit state for headed stud group based on the fracture models is defined. Parametric analysis, which included a models with different diameters of headed studs and layout of groups were performed by numerical models. vi Based on the results, the recommendations were derived for determining the shear capacity of the headed studs group, when the distance between studs is less than required by Code. The reduction coefficient was suggested to determine the shear capacity of the headed studs group. Derived recommendations can be applied to shear connections in composite steel-concrete beams applied in buildings...