1. Model uncertainty in a parametric fire curve approach : a stochastic correction factor for the compartment fire load densityFlorian Put, Andrea Lucherini, Bart Merci, Ruben Van Coile, 2024, izvirni znanstveni članek Povzetek: A commonly used approach to represent the thermal load in a compartment fire is the Eurocode Parametric Fire Curve (EPFC), which specifies gas temperatures (or rather adiabatic surface temperatures). Recognizing the significant deviations between real fires and the EPFC framework, the concept of model uncertainty is explored. This study does not aim to assess or improve the EPFC, but introduces a model uncertainty, allowing for reliability-based structural fire engineering (SFE). It presents a stochastic correction factor for the fire load density, based on the maximum temperature in steel sections. The focus is on the fire load density, but in general other parameters can be jointly taken into account as well. This correction factor considers protected and un- protected sections, incorporating variations in section factor and protection thickness. The findings reveal that the fire load density within the EPFC framework can be modified to better represent the severity of fire ex- periments. This approach ensures physical consistency of the obtained compartment gas temperatures, as opposed to alternative approaches for addressing the EPFC model uncertainty. While promising results are evident in this proof of concept, exploration for other types of structural elements and evaluation for structural systems is necessary before integration into design practices.
Ključne besede: structural fire engineering, compartment fires, fire load density, steel structures, reliability, probability of failure
Objavljeno v DiRROS: 17.04.2024; Ogledov: 73; Prenosov: 24
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2. Lessons learned from the monitoring of retaining structures, built in demanding geotechnical conditions in SloveniaPavel Žvanut, Janko Logar, 2019, objavljeni znanstveni prispevek na konferenci Povzetek: A typical retaining structure built with large-diameter bored piles in soft clastic rock, and sup-ported by pre-stressed permanent ground anchors, is discussed. Step-by-step back analyses were performed. A simplified geological structure was first used in the analyses, together with a simple Mohr-Coulomb model. The results were compared with more complex analyses using a Hardening Soil model and a more detailed geological structure. Much better results were obtained with the use of the HS model, which is more suitable for the modelling of rock of such a type, but even with the use of the MC model the final results were quite good, making the use of the observational method attractive for engineers.
Ključne besede: geotechnics, gretaining structures, bored piles, numerical modelling, finite element method, observational method
Objavljeno v DiRROS: 27.03.2024; Ogledov: 119; Prenosov: 58
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3. The cut method on hypergraphs for the Wiener indexSandi Klavžar, Gašper Domen Romih, 2023, izvirni znanstveni članek Povzetek: The cut method has been proved to be extremely useful in chemical graph theory. In this paper the cut method is extended to hypergraphs. More precisely, the method is developed for the Wiener index of $k$-uniform partial cube-hypergraphs. The method is applied to cube-hypergraphs and hypertrees. Extensions of the method to hypergraphs arising in chemistry which are not necessary $k$-uniform and/or not necessary linear are also developed.
Ključne besede: hypergraphs, Wiener index, cut method, partial cube-hypergraphs, hypertrees, phenylene, Clar structures
Objavljeno v DiRROS: 15.03.2024; Ogledov: 122; Prenosov: 58
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4. Reviewing the modeling aspects and practices of shallow geothermal energy systemsPaul Christodoulides, Ana Vieira, Stanislav Lenart, João Maranha, Gregor Vidmar, Rumen Popov, Aleksandar Georgiev, Lazaros Aresti, Georgios Florides, 2020, pregledni znanstveni članek Povzetek: Shallow geothermal energy systems (SGES) may take different forms and have recently taken considerable attention due to energy geo-structures (EGS) resulting from the integration of heat exchange elements in geotechnical structures. Still, there is a lack of systematic design guidelines of SGES. Hence, in order to contribute towards that direction, the current study aims at reviewing the available SGES modeling options along with their various aspects and practices. This is done by first presenting the main analytical and numerical models and methods related to the thermal behavior of SGES. Then, the most important supplementary factors affecting such modeling are discussed. These include: (i) the boundary conditions, in the form of temperature variation or heat flow, that majorly affect the predicted thermal behavior of SGES; (ii) the spatial dimensions that may be crucial when relaxing the infinite length assumption for short heat exchangers such as energy piles (EP); (iii) the determination of SGES parameters that may need employing specific techniques to overcome practical difficulties; (iv) a short-term vs. long-term analysis depending on the thermal storage characteristics of GHE of different sizes; (v) the influence of groundwater that can have a moderating effect on fluid temperatures in both heating and cooling modes. Subsequently, thermo-mechanical interactions modeling issues are addressed that may be crucial in EGS that exhibit a dual functioning of heat exchangers and structural elements. Finally, a quite lengthy overview of the main software tools related to thermal and thermo-hydro-mechanical analysis of SGES that may be useful for practical applications is given. A unified software package incorporating all related features of all SGES may be a future aim.
Ključne besede: shalow geothermal energy systems, energy geo-structures, thermal analysis, thermo-hydro-mechanical, modelling, software tools
Objavljeno v DiRROS: 05.03.2024; Ogledov: 163; Prenosov: 67
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5. 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, izvirni znanstveni članek Povzetek: 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.
Ključne besede: bridge, steel, UHPFRC, structures
Objavljeno v DiRROS: 21.12.2023; Ogledov: 211; Prenosov: 82
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6. Corrosion monitoring of steel structure coating degradationBojan Zajec, Mirjam Bajt Leban, Tadeja Kosec, Viljem Kuhar, Andraž Legat, Stanislav Lenart, Karmen Fifer Bizjak, Gavin Kenneth, 2018, izvirni znanstveni članek Povzetek: An important aspect regarding the sustainability of steel structures is to ensure the structure is protected from corrosion. A number of surface coatings are availablethat play an important role in protecting these structures. An important part of the management of these structures is reliable and regular inspection along with methods forearly detection of corrosion processes. In this paper, a development and application of sensors for monitoring the steel coating degradation and corrosion damage to steelsubstrate are presented. An encapsulated corrosion kit with integrated EIS sensors and ER probes was developed. To test its efficiency, steel probes were coated withselected coatings in the laboratory and their performance was assessed under various aggressive atmospheres, including; salt, industrial and humid atmosphere.
Ključne besede: coatings, corrosion, electrochemical impedance spectroscopy, electrical resistance probes, railways, steel structures
Objavljeno v DiRROS: 13.12.2023; Ogledov: 192; Prenosov: 100
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7. Self-assembled structures composed of single polypeptide comprising at least three coiled-coil forming elements : patentRoman Jerala, Ota Fekonja, Jelka Pohar, Helena Gradišar, Mojca Benčina, Iva Hafner Bratkovič, Robert Bremšak, Špela Miklavič, Urška Jelerčič, Anja Lukan, Tibor Doles, Sabina Božič Abram, Marko Verce, Nika Debeljak, Jožica Friedrich, 2014, patent Ključne besede: self assembled structures, polipeptide chain, nenostructures
Objavljeno v DiRROS: 13.05.2015; Ogledov: 6203; Prenosov: 917
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