1. Development of Methodology for Estimation of Energy-Efficient Building Renovation Using Application of MINLP-Optimized Timber–Glass Upgrade ModulesMaja Lešnik Nedelko, Stojan Kravanja, Miroslav Premrov, Vesna Žegarac Leskovar, 2025, izvirni znanstveni članek Opis: Vertical addition to already-existing structures is an approach to energy-efficient building renovation. It presents an opportunity for the densification of built-up areas and the construction of new usable spaces. While many studies have dealt with the subject of renovating buildings with a focus on energy efficiency, far fewer studies have specifically examined the potential of vertically extending existing buildings, an approach which could be introduced in new sustainable building policies. The objective of this study is to redevelop optimal timber–glass upgrade modules, considering the ideal proportions of glazing for all cardinal directions, by using discrete Mixed-Integer Non-Linear Programming optimization. The novelty of the suggested method resides in the synchronous optimization of the upgrade modules’ daylighting and energy-efficiency performance, resulting in the creation of optimization methods that can determine the optimal glazing proportions for all cardinal directions and incorporate rational design and window measurement. The impact of the developed Mixed-Integer Non-Linear Programming-optimized upgrade modules is compared to previously designed optimized upgrade modules. Finally, a methodology for estimating the energy efficiency of building renovations incorporating vertical additions using the timber–glass upgrade modules was developed, supporting the quick assessment of the reduction in hybrid buildings’ energy consumption for heating and cooling according to boundary conditions, presuming that they undergo the suggested renovations. The findings are applicable (not exclusively) to Slovenia’s residential building stock, which makes up around 20% of the country’s current housing stock and was mainly constructed between 1946 and 1970. This offers a substantial opportunity to improve the overall sustainability and energy efficiency of the country’s housing stock. The proposed approach offers a holistic solution to drive sustainable development in the built environment by incorporating all three pillars of sustainability (environmental, social, and economic).
Ključne besede: energy efficient building renovation, energy efficiency, building vertical addition, timber–glass upgrade modules, mixed-integer non-linear programming, MINLP, optimization, visual comfort, energy sustainability
Objavljeno v DKUM: 16.01.2025; Ogledov: 0; Prenosov: 1
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2. REVITALIZACIJA STAVBNEGA OTOKA NA STUDENCIH V MARIBORUAna Židanik, Uroš LobnikOpis: Naloga je predlog revitalizacije propadlega območja v evropskem mestu na primeru industrijske cone Studenci v Mariboru. Želja je tvoriti kvalitetno okolje za delovanje človeka, mu omogočiti prijetno bivanje in delo, oblikovati veliko površin za rekreacijo in miselno stimulacijo, skrajšati vsakodnevne poti, upoštevati naravo in okolje ter izhodišča za trajnostni razvoj.
Osnove pri oblikovanju projekta so: širjenje goste pozidave centra mesta proti periferiji, vnos centralnih dejavnosti zaradi decentralizacije, mestotvorno oblikovanje, ki se ujame z obstoječo mestno strukturo, ohramba zaznanih kvalitet in njihova nadgradnja ter integracija v zasnovo. Glavne vnesene funkcije so: manjkajoča fakulteta v Mariboru, študentski dom, stanovanjska naselja, restavracije.
Objavljeno v DKUM: 13.01.2025; Ogledov: 0; Prenosov: 7
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3. Computational modeling of natural convection in nanofluid-saturated porous media: an investigation into heat transfer phenomena : Janja Kramer Stajnko ... [et al.]Janja Kramer Stajnko, Jure Ravnik, Renata Jecl, Matjaž P. Nekrep, 2024, izvirni znanstveni članek Opis: A numerical study was carried out to analyze the phenomenon of natural convection in a porous medium saturated with nanofluid. In the study, the boundary element method was used for computational modeling. The fluid flow through a porous matrix is described using the Darcy– Brinkman–Forchheimer momentum equation. In addition, a mathematical model for nanofluids was used, which follows a single-phase approach and assumes that the nanoparticles within a fluid can be treated as an independent fluid with effective properties. A combination of single- and sub-domain boundary element methods was used to solve the relevant set of partial differential equations. The method was originally developed for pure flow scenarios, but also proves to be effective in the context of fluid flow through porous media. The results are calculated for the case of two- and three-dimensional square cavities. In addition to various values of dimensionless control parameters, including the porous Rayleigh number (Rap), Darcy number (Da), porosity (ϕ) and nanoparticle volume fractions (φ), the effects of the inclination angle of the cavity on the overall heat transfer (expressed by the Nusselt number (Nu)) and fluid flow characteristics were investigated. The results indicate a pronounced dependence of the overall heat transfer on the introduction of nanoparticles and inclination angle. The heat transfer in a two-dimensional cavity is increased for higher values of Darcy number in the conduction flow regime, while it is suppressed for lower values of Darcy number in the Darcy flow regime. In the case of a three-dimensional cavity, increasing the volume fraction of nanoparticles leads to a decrease in heat transfer, and furthermore, increasing the inclination angle of the cavity considerably weakens the buoyancy flow
Ključne besede: porous media, nanofluids, natural convection, boundary element method
Objavljeno v DKUM: 10.01.2025; Ogledov: 0; Prenosov: 4
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4. Assessment of in-plane timber floor stiffness as structural diaphragms: a numerical approach to lateral load responseJelena Vilotijević, Miroslav Premrov, 2024, izvirni znanstveni članek Opis: The behaviour of horizontal floor diaphragms plays a crucial role in ensuring the overall response of a building during earthquakes, as the stiffness of these diaphragms determines whether the structure will act as an integrated system. If the diaphragms do not exhibit sufficient stiffness, differences in the redistribution of forces on wall elements arise, increasing the risk of significant deformations and even local damage, which is commonly observed in earthquake-affected areas. Additionally, flexible diaphragms heighten the risk of torsional effects. Due to these factors, more attention should be given to the response of buildings with flexible diaphragms. Eurocode standard specifies general requirements under which diaphragms should be considered rigid within their plane, depending on the maximum diaphragm moment. However, specific guidelines regarding the geometric and material properties of elements that significantly impact seismic behaviour are not included in the existing European standards. This served as a basis for conducting a numerical study analysing the in-plane behaviour of floor elements made from different materials. This study, limited to a simple box-shaped structure with masonry walls, symmetrical in both orthogonal directions, evaluated and thoroughly analysed the deformations for different types of diaphragms, including prefabricated wooden frame-panel floors, CLT panels, and reinforced concrete slabs. Special emphasis was placed on wooden structural elements due to the increased demand for timber construction, as the behaviour of these elements needs to be properly studied, especially in seismic regions. The study results were obtained through FEM analysis using the SCIA Engineer software, version 22. The modelling of elements was carried out considering the orthotropy of brick wall and wooden ceiling elements, as well as simulating the appropriate shear stiffness of the connecting means.
Ključne besede: horizontal diaphragms, floor flexibility, lateral load resisting system, timber frame-panel floor, cross-laminated timber, concrete slab, seismic design
Objavljeno v DKUM: 10.01.2025; Ogledov: 0; Prenosov: 6
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5. Analysing flexural response in RC beams: a closed-form solution designer perspective from detailed to simplified modellingDenis Imamović, Matjaž Skrinar, 2024, izvirni znanstveni članek Opis: This paper presents a detailed analytical approach for the bending analysis of reinforced concrete beams, integrating both structural mechanics principles and Eurocode 2 provisions. The general analytical expressions derived for the curvature were applied for the transverse displacement analysis of a simply supported reinforced concrete beam under four-point loading, focusing on key limit states: the initiation of cracking, the yielding of tensile reinforcement and the compressive failure of concrete. The displacement’s results were validated through experimental testing, showing a high degree of accuracy in the elastic and crack propagation phases. Deviations in the yielding phase were attributed to the conservative material assumptions within the Eurocode 2 framework, though the analytical model remained reliable overall. To streamline the computational process for more complex structures, a simplified model utilising a non-linear rotational spring was further developed. This model effectively captures the influence of cracking with significantly reduced computational effort, making it suitable for serviceability limit state analyses in complex loading scenarios, such as seismic impacts. The results demonstrate that combining detailed analytical methods with this simplified model provides an efficient and practical solution for the analysis of reinforced concrete beams, balancing precision with computational efficiency.
Ključne besede: reinforced concrete structures, non-linear behaviour, transverse displacement, moment–curvature diagram, rotational spring model
Objavljeno v DKUM: 10.01.2025; Ogledov: 0; Prenosov: 4
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6. Flipped learning approach in different academic courses in civil engineering, traffic and transportation engineering and architectureSabina Mulej, 2024, izvirni znanstveni članek Opis: Flipped classroom approach is the educational method which was lately encouraged and supported by the University of Maribor and therefore implemented in certain courses at the Faculty of Civil Engineering, Transportation Engineering and Architecture. As in any other novelty, only practical usage can show its real value. The teachers of discussed courses introduced flipped learning after they had experienced online teaching and returned to face-to-face lectures. The combination of both allows them to use already prepared online study materials and interact with students in the lecture room. Flipped learning encourages students to be involved in active learning activities, they can study at their own pace at any time that is suitable for them, through Moodle and MS Teams they always have access to literature and instructions. However, they should be mature, disciplined, and motivated for the individual work. Even though mastering learning management system and be available for students in the lecture room results in more obligations for teachers, face-to-face lectures prove higher engagement of students and easier educational process for all.
Ključne besede: flipped learning, Moodle, MS Teams, online lectures, face-to-face lectures, active learning activities
Objavljeno v DKUM: 23.12.2024; Ogledov: 0; Prenosov: 2
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7. Priročnik za delo s programom PIPEOPT-SR za optimiranje visokotlačnih jeklenih cevovodov z ojačitvamiStojan Kravanja, Tomaž Žula, 2024, priročnik Opis: Pričujoči priročnik obravnava delo s programom – optimizacijskim modelom - za optimiranje visokotlačnih jeklenih cevovodov z ojačitvami, kakršni se vgrajujejo v izvrtan tunel v hribino. Cevovod je dimenzioniran kot samonosilna jeklena cilindrična lupina s krožnimi ojačitvami brez sodelovanja hribine in okoliškega betona. Cevovod je lahko obremenjen z notranjim ali zunanjim tlakom. Optimizacija cevovoda se izvede z nelinearnim programiranjem, NLP. V ta namen je bil modeliran optimizacijski program PIPEOPT-SR, verzija 1,0. Optimizacijski model vsebuje skalarje (vhodne podatke), spremenljivke in namensko funkcijo mase jeklene konstrukcije, ki je podvržena sistemu pogojnih (ne)enačb iz statične analize in dimenzioniranja cevovoda v skladu s C.E.C.T. priporočili. Na koncu priročnika je predstavljen primer optimizacije visokotlačnega cevovoda z ojačitvami črpalne hidroelektrarne Kozjak, locirane v bližini Maribora.
Ključne besede: program, optimizacijski model, optimizacija, nelinearno programiranje, visokotlačni jekleni cevovod z ojačitvami
Objavljeno v DKUM: 19.12.2024; Ogledov: 0; Prenosov: 7
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8. Cost effectiveness of chip seal and hot mix asphalt pavementsBojan Žlender, Cahit Gürer, Rok Varga, Primož Jelušič, 2024, izvirni znanstveni članek Opis: Chip seal pavements, consisting of one or more layers of asphalt binder and fine aggregate, can be mechanically characterized as a surface treatment that enhances evenness and trafficability. This paper examines the geotechnical aspects of chip seal applicability compared to traditional hot mix asphalt pavements. An analytical model was employed to design unpaved roads and determine the required thickness of unbound layers. Eight optimization models were developed for hot mix asphalt pavements and four for chip seal pavements, aimed at achieving optimal designs for various input parameters. These outcomes were used to conduct a multi-parametric analysis, incorporating an optimization loop for each combination of design variables. The results indicate that, under low traffic conditions, a chip seal pavement structure can be up to 40% less expensive than an optimal hot mix asphalt pavement structure, particularly when the subgrade has low bearing capacity and is exposed to unfavorable climatic conditions. However, at medium traffic loads, with good subgrade bearing capacity and favorable climate, the chip seal pavement structure incurs costs that are 25% higher than those of the hot asphalt pavement structure. In addition, chip seal pavements should always be designed with integrated geosynthetic reinforcement to minimize construction costs, and chip seal is not as sensitive to frost as hot mix asphalt.
Ključne besede: chip seal, hot mix asphalt, pavement design, cost optimization
Objavljeno v DKUM: 10.12.2024; Ogledov: 0; Prenosov: 5
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9. Optimization of embedded retaining walls under the effects of groundwater seepage using a reliability-based and partial factor design approachRok Varga, Bojan Žlender, Primož Jelušič, 2024, izvirni znanstveni članek Opis: In this paper, a comparative analysis of the effects of groundwater, seepage and hydraulic heave on the optimal design of embedded retaining walls is carried out. The optimization model for an optimal retaining wall (ORW) minimizes the total length of the retaining wall considering design constraints. The model is extended to include the probability of failure as an additional constraint. This overcomes the limitations of the partial safety factor approach, which does not fully account for uncertainties in the soil. In contrast, the reliability-based design (RBD) approach integrates these uncertainties and enables an assessment of the impact of seepage and hydraulic heave on the reliability of the structure. A real-coded genetic algorithm was used to determine optimal designs for both optimization methods. The results of the case study show that the addition of seepage (groundwater flow) to the hydrostatic conditions has a modest effect on the embedment depth. The design based on partial safety factors, which takes seepage into account, leads to a slight increase in the embedment depth of 0.94% compared to a retaining wall design that only takes the hydrostatic conditions of the groundwater into account. When designing on the basis of probability failure, the percentage increase in embedment depth due to seepage is between 2.19% and 6.41%, depending on the target probability of failure. Furthermore, the hydraulic heave failure mechanism did not increase the required embedment depth of the retaining wall, which means that the failure mechanism of rotation near the base was decisive for the design.
Ključne besede: embedded retaining wall, reliability-based design, partial safety factor design, optimization, genetic algorithm
Objavljeno v DKUM: 10.12.2024; Ogledov: 0; Prenosov: 4
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10. Sustainable retaining wall solution as a mitigation strategy on steep slopes in soft rock massPrimož Jelušič, Goran Vlastelica, Bojan Žlender, 2024, izvirni znanstveni članek Opis: Steep slopes in soft rock are characterized by their susceptibility to instability (rockfall,
rockslide) due to weathering and erosion of the slope surface. This article deals with the problem of
adapting to the increasing height of the scree slope. The construction of a retaining wall in a scree
slope in front of a slope of soft rock with a steep face, where a very rapid weathering and erosion
process of weathered material takes place, and the simultaneous deposition of material in front of
the steep slope is a common solution. Changes in the geometry of the slope and the front scree are
taken into account, and at the same time, sufficient safety against rockfall must be ensured. The
analysis is shown on a specific example of a steep flysch slope near Split, Dalmatia. The retaining
wall solutions are compared in terms of function, cost and sustainability. The construction of a single
colossal, reinforced concrete retaining wall shows that this solution is not feasible due to the high
construction costs and CO2 emissions of the retaining wall. A model was therefore developed to
determine the height of the retaining walls for different construction time intervals and distances
from the original rock face. The critical failure modes were investigated for various retaining wall
solutions with regard to the highest degree of utilization of the resistance, which also allows the
cost-optimized solutions to be determined. By building two or more successive retaining walls at
suitable intervals and at an appropriate distance from the original rock face, construction costs and
CO2 emissions can be significantly reduced.
Ključne besede: retaining wall, erosion, rockfall, steep slope, flysch, sustainable design, cost optimization
Objavljeno v DKUM: 09.12.2024; Ogledov: 0; Prenosov: 3
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