An improved analytical model based on rheological-dynamical analogy (RDA) is briefly explained and used for the analysis of concrete cylinders under compression. The approach involves standard mechanical properties such as compressive strength, elastic modulus, concrete density and Poisson's ratio for the prediction of both the ascending and the descending branch of the stress-strain curve. Our own experimental data for arbitrarily selected high strength concrete with high deformability was analyzed. Further, the validity of the RDA model is checked against tests of other authors for one normal concrete and for six recycled aggregate concrete mixtures. To demonstrate the capabilities of the improved model, using analytically established stress-strain relations for analyzed samples, the moment-curvature relations and ductility of reinforced concrete beams in bending were numerically examined. The analysis showed that the ductile behavior of beams made of concrete with recycled aggregate can be achieved by limiting the reinforcement ratio to 0.01 if the recycled concrete aggregate is used and to 0.02 for recycled brick aggregate.
The Paris law equation can be used only for describing the growth of long cracks. The region of application is defined between threshold energy release rate and fracture energy. The short crack growth occurs under the threshold energy release rate value. Many authors are modified the Paris law for its application on this region. The growth of short cracks of concrete is more complicated than for metals and it is not enough researched. In this paper a novel method for describing a short cracks of concrete is proposed using rheological-dynamical analogy (RDA). This method presents the modification of previously determined RDA method for long crack propagation, where stress range in the crack tip is increased using Kitagawa and Takahashi diagram. Cyclic tensile under three-point bending tests on notched beams are considered. The test results for the verification of RDA method are taken from literature.
This paper presents repair design for bridge over the Resnica River in Koceljeva municipality (Serbia). As part of repair strategy, visual inspection of damages and condition diagnostics of structural elements were conducted. In addition, the bridge was tested with trial static loads. Structural system of the existing bridge is constructed as a double overhanging slab with inner span of app. 4,5 m and cantilevers of approx. 1,0 m each. Main span is supported by transverse beams with variable cross-section which are constructed on top of the abutments. As part of repair design, the bridge was widened on each side with 1.0 m wide footways. Since the original structural design documents are missing, control calculations were conducted with Tower Radimpex Software (according to national codes). This analysis was followed by more sophisticated numerical modelling and analysis according to Eurocode with Abaqus Software.
UVODIzgradnja geotehničkih objekata na terenima nepogodnim za građenje uslovljena je primenom tehnoloških postupaka za poboljšanje tih terena. Jedan od tih postupaka je injektiranje stenskih masa. Injektiranje ima za svrhu da se ubrizgavanjem raznih injekcionih smesa u stensku masu poveća otpornost i smanji vodopropusnost, a u izvesnim slučajevima da obezbedi neposrednu vezu između objekta i stenske mase. Injektiranja se mogu se podeliti u četiri grupe [1]: -kontaktno injektiranje-ispuna šupljina na kontaktu betona i stenske mase -vezno injektiranje-povezivanje u konstruktivnu celinu obloge i stenske mase -konsolidaciono injektiranje-poboljšanje mehaničkih karakteristika stena -naponsko injektiranje 1 Prof. dr Dragan Lukić, dipl.inž. građ., Univerzitet u Novom Sadu, Građevinski fakultet Subotica, Kozaračka
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