11. Getting more out of existing structuresMartín-Sanz Henar, Konstantinos Tatsis, Domagoj Damjanovic, Irina Stipanović, Aljoša Šajna, Ivan Duvnjak, Uroš Bohinc, Eugen Brühwiler, Eleni Chatzi, 2019, original scientific article Abstract: Ultra-high-performance fiber-reinforced cement-based composite (UHPFRC) has been increasingly adopted for rehabilitation projects over the past two decades, proving itself as a reliable, cost-efficient and sustainable alternative against conventional methods. High compressive strength, low permeability and high ductility are some of the characteristics that render UHPFRC an excellent material for repairing existing aged infrastructure. UHPFRC is most commonly applied as a surface layer for strengthening and rehabilitating concrete structures such as bridge decks or building slabs. However, its implementation with steel structures has so far been limited. In this work, the UHPFRC strengthening of a steel bridge is investigated both in simulation as well as in the laboratory, by exploiting a real-world case study: the Buna Bridge. This Croatian riveted steel bridge, constructed in 1893, repaired in 1953, and decommissioned since 2010, was removed from its original location and transported to laboratory facilities for testing prior to and after rehabilitation via addition of UHPFRC slab. The testing campaign includes static and dynamic experiments featuring state-of-the-art monitoring systems such as embedded fiber optics, acoustic emission sensors and digital image correlation. The information obtained prior to rehabilitation serves for characterization of the actual condition of the structure and allows the design of the rehabilitation solution. The UHPFRC slab thickness was optimized to deliver optimal fatigue and ultimate capacity improvement at reasonable cost. Once the design was implemented, a second round of experiments was conducted in order to confirm the validity of the solution, with particular attention allocated to the interface between the steel substrate and the UHPFRC overlay, as the connection between both materials may result in a weak contact point. A detailed fatigue analysis, based on updated FEM models prior to and after strengthening, combined with the results of a reliability analysis prove the benefits of adoption of such a solution via the significant extension of the structural lifespan.
Keywords: bridge, steel, UHPFRC, structures
Published in DiRROS: 21.12.2023; Views: 207; Downloads: 80
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12. Polypropylene blends with m-EPR copolymers : mechanical and rheological propertiesIztok Švab, Anđela Pustak, Matjaž Denac, Andrijana Sever Škapin, Mirela Leskovac, Vojko Musil, Ivan Šmit, 2018, original scientific article Abstract: The effects of two metallocene ethylene-propylene-based elastomers (m-EPR1 and m-EPR2) differing in molecular mass and viscosity on mechanical, rheological and interfacial properties were compared. The m-EPR elastomers were added to iPP in 2.5, 5, 10, 15, and 20 vol.%. Torque values, elongation at break and impact strength measured of the iPP/m-EPR1 blends were higher than the iPP/m-EPR2 blends due to higher molten viscosity of m-EPR1 than m-EPR2 copolymer. Slight differences in Young moduli as well as in tensile strength at yield and at break might indicate that tensile properties of iPP/m-EPR blends were not significantly affected by difference in viscosity or molecular mass, miscibility and spherulite size. Optimization diagrams indicated the metallocene m-EPR copolymers are efficient impact modifiers for polypropylene and showed good balancing of mechanical properties in iPP/m-EPR blends.
Keywords: isotactic polypropylene, metallocene ethylene-propylene-based elastomers, blend, mechanical properties, adhesion parameters
Published in DiRROS: 13.12.2023; Views: 205; Downloads: 99
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13. Preiskave lesenih okvirnih stenskih panelov s cementno-ivernimi obložnimi ploščamiMeta Kržan, Tomaž Pazlar, Ivan Grašič, Boštjan Ber, 2020, original scientific article Abstract: V članku so predstavljeni rezultati eksperimentalnih preiskav študije obnašanja lesenih okvirnih stenskih panelov s cementno-ivernimi obložnimi ploščami pri horizontalnih obremenitvah. Posebnost predstavljene preiskave je uporaba cementno-ivernih plošč pri proizvodnji okvirnih stenskih panelov, saj njihovo obnašanje še ni dobro raziskano. Preiskave so bile izvedene v dveh fazah. Ker je za strižno obnašanje panela bistveno pritrjevanje obložnih plošč na leseni okvir, so se na manjših vzorcih najprej določile nosilnosti zvez s kovinskimi paličastimi sponkami ter analiziral vpliv debelin plošč in razmika med sponkami. Nadalje so bile zasnovane in izvedene monotone in ciklične strižne preiskave različnih izvedb stenskih panelov. Preskušani so bili trije osnovni tipi panelov, med drugim tudi panel z različnima debelinama obložnih plošč. Rezultati preiskave kažejo ugoden duktilen odziv sten pri strižnih obremenitvah ter potrjujejo, da nosilnost sten zaradi različnih debelin obložnih plošč ni dodatno zmanjšana, kot to pri izračunu nosilnosti predvideva SIST EN 1995-1-1. Ključne besede: leseni okvirni stenski paneli, cementno-iverna plošča, strižni preskus, nosilnost sponke v eni strižni ravnini.
Keywords: leseni okvirni stenski paneli, cementno-iverna plošča, ciklični strižni preskus, nosilnost sponke v eni strižni ravnini
Published in DiRROS: 04.12.2023; Views: 219; Downloads: 90
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20. O vplivu onesnaženega zraka na pritalno vegetacijo v gozduIvan Smole, 1990, not set Keywords: gozdovi, pritalna vegetacija, floristična sestava, onesnaženost zraka, emisije, imisija, onesnaženost tal, spremembe vegetacije
Published in DiRROS: 28.08.2023; Views: 342; Downloads: 98
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