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Stojic D.,Sveuciliste u Nisu | Nestorovic T.,Sveuciliste Ruhr u Bochumu Fakultet | Markovic N.,Sveuciliste u Nisu | Cvetkovic R.,Sveuciliste u Nisu | Stojic N.,Institute za Ceste
Gradjevinar | Year: 2016

The implementation of active monitoring systems to diagnose damage to reinforced concrete structures using piezoelectric smart aggregates, and based on wave propagation, ranks among the world's most advanced research activities. Original models, with parametric analysis of the damage index variation problem, depending on the size, position and orientation of cracks, are presented in the paper. Numerical modelling of wave propagation in reinforced concrete is conducted using the explicit finite element method, which is highly effective for this purpose.

Acic M.,University of Zagreb | Vlaiic L.M.,University of Zagreb | Kostic D.,Sveuciliste u Nisu
Gradjevinar | Year: 2013

The stability of prestressed cable trusses subjected to static and dynamic loads is analysed in the paper. The stiffness of the elastic cable truss system was varied by changing the prestressing force. Modelling results for different levels of tension show that, in terms of satisfying dynamic resistance conditions, a much greater tensile force is required for cable grids with diagonal members, compared to those with vertical rods. The conclusions derived constitute recommendations for the use of calculation methods, as well as for the determination of prestressing forces under which stability criteria are fulfilled.

Spasojevic-Surdilovic M.,Sveuciliste u Nisu | Spasojevic A.,University of Applied Sciences and Arts Western Switzerland | Stojic D.,Sveuciliste u Nisu
Gradjevinar | Year: 2014

Analytical expressions for determining the required tensioning force in strands, and the corresponding deformation of cables during the multi-cycle tensioning process, are derived in the paper based on the proposed mathematical model of a bridge stay cable. Monostrand jacks are used in this procedure and, at that, strands are tensioned in each cycle by individual application of force of the same intensity. The number of cycles depends on geometrical and mechanical properties of the cable, on the final tensioning force intensity, and on the moveability of the cable support points. The efficiency of the proposed analytical procedure is illustrated by a numerical example.

The column punching through the slab is most often related to floor structures, and less often to foundation slabs under columns. Calculation models for these two problems are often not separated. The deficit of experimental results for column footings results in the use of floor slab models. A review of the theoretical and experimental research references, including Codes/Regulations for punching calculation of column footings, is presented in the paper. The experimental research program and its implementation is described. The results obtained are compared with calculation results based on various regulations. Recommendations and directions for future research are outlined.

The testing of bearing capacity under static and fatigue loading is mandatory in case of prestressed concrete sleepers for switches and crossings. The authors present the static testing required according to EN13230-4:2009, and the optional dynamic testing of sleepers for switches and crossings, which is conducted at the customer's request only. The criterion for positive evaluation in accordance with the standard is met based on static test results. The determinants from EN13230-2:2009, with deviations in the number of load cycles, are applied during dynamic testing.

Krasic S.,Sveuciliste u Nisu | Pejic P.,Sveuciliste u Nisu | Mitkovic P.,Sveuciliste u Nisu
Gradjevinar | Year: 2013

Other than being highly significant for the comfort of people, an optimum use of daylight in buildings also contributes to a more rational use of heating and air-conditioning systems. Energy-efficient buildings containing passive and active systems for the use of solar energy would not be possible without sunlight The issue of significance and control of lighting in existing buildings during design and construction of new ones on neighbouring plots is increasingly considered on an international scale. Laws and regulations on the use of daylight currently applied in Europe and the USA, are compared in the paper.

Grdic Z.,Sveuciliste u Nisu | Toplicic-Curcic G.,Sveuciliste u Nisu | Mitkovic P.,Sveuciliste u Nisu
Gradjevinar | Year: 2014

Results obtained by testing hydro-abrasive resistance and mechanical properties of concrete with rubber granules are presented in the paper. Fine river aggregate is replaced with 10, 20, and 30 percent of recycled granulated rubber (with respect to the total volume). Research results demonstrate that replacement of fine river aggregate by granulated rubber increases hydro-abrasive resistance of concrete by up to 10 percent. The replacement of fine river aggregate by rubber increases the energy dissipation capacity and ductility.

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