Dynamic Design of Systems with Semi-rigid Connections Based on Experimental Investigation of the Full Scale Structure

Semi-rigid connections in the construction permit mutual rotation of the nodes. Since such connections are quite common in constructions, especially in the precast ones, it is of interest to determine their dynamic characteristics that is the subject of this proposed paper. During our investigation full scale experiments have been carried out and experimentally determined dynamic characteristics have been compared with those obtained by use of the computational model. The real dynamic characteristics are determined and resonant frequencies of the basic modes in the horizontal and vertical directions, the forms of vibrations at these frequencies, as well as the corresponding coefficient of viscous damping. Testing has been done on the frame structure without facade walls. For the typical precast system "Minoma 1" with span of 12m, "Minoma 2" with span of 20m, and "Minoma 3" with span of 27m, dynamic characteristics: have been determined experimentally by use of forced harmonic excitation, free oscillations and ambient vibration. Experimentally and theoretically obtained values are in a relatively good agreement that is a good starting point for mathematical modeling

Sinteza i antihipoksično djelovanje alifatskih i arilalifatskih amida kofein-8-tioglikolne kiseline

The synthesis of some aliphatic and arylaliphatic amides of caffeine-8-thioglycolic acid was studied. The structures of synthesized compounds were proved by microanalyses, IR- and 1H NMR data. Values of acute p.o. and i.p. toxicity in mice show lower toxicity compared to caffeine. Declines in spontaneous locomotor activity support the idea of depressive CNS activity of the compounds. Two compounds exhibited brain antihypoxic activity (5a and 5b against haemic and circulatory hypoxia, respectively).U radu je opisana sinteza alifatskih i arilalifatskih amida kofein-8-tioglikolne kiseline i njihova karakterizacija elementarnom analizom, IR- i 1H NMR spektroskopijom. Testiranja na miševima pokazuju da su sintetizirani spojevi primijenjeni p.o. i i.p. manje toksični od kofeina. Smanjenje lokomotoričke aktivnosti podupire ideju o njihovom depresivnom djelovanju na SŽS. Spojevi 5a i 5b djeluju antihipoksički u uvjetima krvne i cirkulacijske hipoksije u mozgu

Flexural behavior of continuous beams made of self-compacting concrete (Scc)—experimental and numerical analysis

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. Self-compacting concrete (SCC) is a type of concrete that is placed in the formwork under its own weight. Although there are many studies showing the behavior of SCC beams, most relate to the behavior of simple supported beams. Unlike those, this is a study of continuous beams made of SCC aimed to analyze their flexural performance as well as to confirm the possibility of using nonlinear finite element analysis (FEA) in the design of such structural elements. An experimental study of three two-span continuous beams of a total length of 3400 mm, with the span between supports of 1600 mm, with 150/200 mm cross section made of SCC exposed to short-term loading, was carried out. The parameter that varied is the percentage of tensile reinforcement, with values of 0.65, 0.86 and 0.94 being selected. As all analyzed beams have shown a satisfactory load-bearing capacity and stiffness, the research confirmed the possibility of using SCC in continuous beams in civil engineering practice. Using Abaqus/Standard software, a nonlinear numerical model is proposed, which is validated and verified against experimental research, as there is only a 5% difference in the numerically calculated ultimate load compared to the experimentally measured values

Experimental analysis of continuous beams made of self‐compacting concrete (Scc) strengthened with fiber reinforced polymer (frp) materials

Strengthening of concrete structures is applied as a solution for various deterioration problems in civil engineering practice. This also refers to the structures made of self‐compacting concrete (SCC), which is increasingly in use, but there is a lack of research in this field. This paper presents an experimental analysis of flexural behavior of reinforced concrete (RC) continuous beams made of SCC, strengthened with fiber reinforced polymer (FRP) materials (glass (GFRP) and carbon (CFRP) bars, CFRP laminates), by the use of near surface mounted (NSM) and externally bonded (EB) methods. Six two‐span continuous beams of a total length of 3200 mm, with the span between supports of 1500 mm and 120/200 mm cross section, were subjected to short‐term load and tested. The displacements of beams and the strains in concrete, steel reinforcement, FRP bars and tapes were recorded until failure under a monotonically increasing load. The ultimate load capacities of the strengthened beams were enhanced by 22% to 82% compared to the unstrengthened control beam. The ductility of beams strengthened with GFRP bars was satisfactory, while the ductility of beams strengthened with CFRP bars and tapes was very small, so the failure modes of these beams were brittle