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Sustainable design of circular reinforced concrete column sections via multi-objective optimization
Primož Jelušič, Tomaž Žula, 2023, original scientific article

Abstract: An optimization model for reinforced concrete circular columns based on the Eurocodes is presented. With the developed optimization model, which takes into account the exact distribution of the steel reinforcement, which is not the case when designing with conventional column design charts, an optimal design for the reinforced concrete cross section is determined. The optimization model uses discrete variables, which makes the results more suitable for actual construction practice and fully exploits the structural capacity of the structure. A parametric study of the applied axial load and bending moment was performed for material cost and CO2 emissions. The results based on a single objective function show that the optimal design of the reinforced concrete column cross section obtained for the material cost objective function contains a larger cross-sectional area of concrete and a smaller area of steel compared with the optimization results when CO2 emissions are determined as the objective function. However, the optimal solution in the case where the material cost was assigned as the objective function has much more reserve in axial load capacity than in the optimal design where CO2 was chosen as the objective function. In addition, the multi-objective optimization was performed to find a set of solutions that provide the best trade-offs between the material cost and CO2 emission objectives.
Keywords: reinforced concrete columns, circular cross section, costs, CO2 emissions, multi-objective optimization, genetic algorithm
Published in DKUM: 15.04.2024; Views: 210; Downloads: 200
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Nonlinear semi-numeric and finite element analysis of three-point bending tests of notched polymer fiber-reinforced concrete prisms
Žiga Unuk, Milan Kuhta, 2024, original scientific article

Abstract: A nonlinear semi-numeric and finite element analysis of three-point bending tests of notched polymer fiber-reinforced concrete prisms was performed. The computational and experimental results were compared in terms of the load-displacement behavior. The vertical midspan displacement and the crack mouth opening displacement results were considered. The nonlinear semi-numeric computational procedure involved the moment-curvature relation, calculated by considering the constitutive material law from the fib Model Code for Concrete Structures 2010, and considered a plastic hinge mechanism to simulate the cracked region behavior. Two sets of tensile mechanical properties were considered for the constitutive material law: back-calculated (by an inverse analysis) tensile strength properties from the experimental results, and tensile strength properties calculated by simplified expressions from the fib Model Code for Concrete Structures 2010. Other mechanical properties were determined by additional compressive tests and standard relations for the dependency of various mechanical properties on the concrete compressive strength. The nonlinear finite element analysis incorporated the Menetrey-Willam material model to simulate the fiber-reinforced concrete behavior. The nonlinear semi-numeric analysis load-displacement results based on the back-calculated tensile strength properties relatively accurately matched with the experimental results, whereas the nonlinear semi-numeric analysis load-displacement results based on tensile strength properties calculated by simplified expressions from the fib Model Code for Concrete Structures 2010 and the nonlinear finite element analysis load-displacement results showed certain shortcomings.
Keywords: polymer fiber-reinforced concrete, moment-curvature relation, nonlinear plastic hinge, load-displacement relation, crack width, nonlinear analysis, finite element analysis, Menetrey-Willam material model, three-point bending test, compressive test
Published in DKUM: 19.02.2024; Views: 253; Downloads: 14
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Innovative structural systems for timber buildings : A comprehensive review of contemporary solutions
Miroslav Premrov, Vesna Žegarac Leskovar, 2023, review article

Abstract: The remarkable development of timber construction technologies in recent decades has led to an increase in the number of timber buildings worldwide, including multi-storey buildings. The design of timber buildings, especially those of greater height, is relatively demanding and, even in the context of architectural expression, has certain constraints due to the specific structural and physical properties of this material. Thus, it is important for designers to have an overview of existing timber structural systems and their specificities to be able to make the right design decisions during the design process. Unfortunately, there is a lack of scientific literature that systematically addresses the essential features of contemporary timber structural systems. Within the aims of this paper to provide the systematic review of contemporary structural systems, both the scientific and professional literature are comprehensively reviewed. This paper presents a systematic classification and description of the following structural systems of timber buildings: all-timber and hybrid timber structural systems with an additional description of constituent structural elements, while examples of completed multi-storey timber buildings are also given for each structural system. The findings provide a broader view of the knowledge of contemporary solutions of timber structural systems and their application, thus representing a novelty in the field of timber construction review.
Keywords: timber structural systems, hybrid timber structural system, timber-concrete composite, timber-steel composite, timber-timber composite, timber structural elements, timber buildings, multi-storey timber buildings
Published in DKUM: 09.02.2024; Views: 218; Downloads: 25
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A fundamental study of the performance of X-section cast-in-place concrete single piles
Yu Wang, Yaru Lv, Dongdong Zhang, Jieying Zhou, 2016, original scientific article

Abstract: X-section cast-in-place concrete (XCC) piles are used because they have a higher bearing capacity than circularsection cast-in-place concrete (CCC) piles of the same cross-sectional area. Although the bearing capacity of XCC piles has been studied, the performance of XCC single piles, especially for the stress-transfer mechanism dependent on the geometrical effects, is still not fully understood. This paper reports two comparative field static load tests on an XCC and a CCC single pile of the same cross-sectional area. In addition, corresponding threedimensional numerical back-analyses are performed to provide a fundamental understanding. The measured and computed results reveal that the XCC single pile has an approximately 25% higher ultimate bearing capacity than the CCC single pile. This is because the XCC single pile has an approximately 20% larger total side resistance, which is caused by a 60% larger pile perimeter and a slightly smaller unit side resistance. Lateral soil arching effects are developed, causing a non-uniform effective normal stress and a shear stress across the circumference of the XCC single pile. It is suggested that XCC single piles have a higher efficiency in terms of material saving compared with CCC single piles.
Keywords: X-section cast-in-place concrete pile, field static load test, three-dimensional numerical back-analysis, stresstransfer mechanism, side resistance, soil arching
Published in DKUM: 15.06.2018; Views: 1385; Downloads: 173
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New Architecture of The Berane Airport
Ivan Pićurić, 2018, master's thesis

Abstract: This Master's Thesis explores the concept of the New Berane Airport that will serve as a turning point for improving the winter tourism offer of Montenegro and the region, thereby attracting a greater number of tourists to the country. The new facility must follow the guidelines of modern architecture, modern design, and the surrounding mountain landscapes, which represents an additional challenge in terms of construction and design. The main aim is to create an efficient structure, a new regional aviation centre, with well-designed transport links that will meet the needs of a large number of passengers and visitors from the region and the rest of the world. The visual aspects of the structure must be in line with the dominant type of architecture in the municipality of Berane, which is why the use of local materials and traditional elements has been foreseen. The new urban plan will follow the existing plan, although its capacity and content will be expanded in accordance with the former plans for the airport. In the planning phase, appropriate use of airport and traffic manuals is essential.
Keywords: airport, architecture, concrete, shell roof, glass facade, tourism, transport, parametric design, regional centre, Berane
Published in DKUM: 15.06.2018; Views: 1315; Downloads: 366
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Methods for control of seepage in RCC dams with wathertight and drainage measures
Yueming Zhu, Stephan Semprich, Erich Bauer, Cuiping Yuan, Dongmei Sun, 2006, original scientific article

Abstract: The technologies for construction of roller-compacted concrete (RCC) dams have been considerably developed during recent years in China. At the time being, they have been successfully applied to the constructions of even extreme-high gravity dams and medium to high arch dams. There are a few of hundreds of RCC dams (RCCD) under design and/or construction in China. One of the main concerned technical problems according to the construction is about the understanding of the property of seepage in RCCDs and the relevant theory and methods for the control of the seepage. In order to overcome the problem, the senior author has been engaged in a wide study on the property and methods for control of seepage in RCCDs for more than 10 years. The property of seepage, measures for watertightness and drainage, optimal design and construction schemes for control of seepage in the dams have been essentially understood either in theory and practice. The results have been applied for the construction and the backanalysis of several dams. The paper describes the research findings in detail with respect to the theoretical fundament and their application for a high RCC gravity dam.
Keywords: gravity dam, Roller-compacted concrete, RCC, seepage, anisotropic permeability, drainage
Published in DKUM: 17.05.2018; Views: 1215; Downloads: 52
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Potential reduction of concrete deterioration through controlled DEF in hydrated concrete
Samo Lubej, Milan Radosavljević, 2013, original scientific article

Abstract: Delayed ettringite formation (DEF) is a chemical reaction with proven damaging effects on hydrated concrete. Ettringite crystals can cause cracks and their widening due to pressure on cracked walls caused by the positive volume difference in the reaction. Concrete may show improvements in strength at early ages but further growth of cracks causes widening and spreading through the concrete structure. In this study, finely dispersed crystallization nuclei achieved by adding air-entraining agent (AEA) and short vibration of specimens is presented as the main prerequisite for reducing DEF-induced deterioration of hydrated concrete. The study presents the method and mechanism for obtaining the required nucleation. Controlling long-term DEF by providing AEA-induced crystallisation nuclei, prevented excessive and rapid initial strength improvements, and resulted in a slight increase of compressive strength of fine grained concrete with only marginally lower density.
Keywords: delayed ettringite formation, aerated concrete, strength improvement
Published in DKUM: 10.07.2015; Views: 1422; Downloads: 31
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Influence of delayed ettringite formation on the mechanical properties of aerated concrete
Samo Lubej, Andrej Ivanič, Rebeka Rudolf, Ivan Anžel, 2012, original scientific article

Abstract: Delayed ettringite formation (DEF) is a chemical reaction with proven damaging effects on the mechanical properties of a hydrated concrete. Ettringite crystals can cause cracks and their widening due to the pressure on the crack walls caused by a positive volume difference in the reaction. Concrete may show improvements in strength at early stages, but a further growth of the cracks causes widening and spreading of these cracks through the concrete structure. In a hydrated concrete, crystals of ettringite can also cause a disintegration of the concrete. In this paper we investigate the potential to utilise a positive volume difference in DEF in order to improve the mechanical properties of a hydrated fine-grained concrete. Finely dispersed crystallization nuclei, achieved by adding an air-entraining agent (AEA) and a short vibration of specimens, is presented as the main prerequisite for such improvements. The control of the expansion and mechanical properties were performed on the concrete samples with and without AEA by inducing DEF. For a microstructure examination of the fine-grained concrete an optical microscope and a scanning electron microscope were used. We found that controlled DEF, which is guaranteed by adding AEA and with the formation of the uniformly dispersed air bubbles, which are the crystallization sites for ettringite crystals, improves the mechanical properties. The specimens with induced DEF were measured and found to have a 6% increase in the compressive strength.
Keywords: ettringite, concrete, aerated concrete, microstructure, mechanical properties
Published in DKUM: 10.07.2015; Views: 1336; Downloads: 107
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Tadeja Leskovar, 2014, master's thesis

Abstract: This Master’s thesis topic are Enterprise Resource Planning (ERP) solutions in general with emphasis on systems appropriate for small and medium sized enterprises and industry specific solutions. The chosen industry and case study of the present thesis are manufacturing and construction; specifically the industry of ready-mixed concrete manufacturing. An ERP is a company-wide system that replaces many previously scattered and standalone systems of individual departments and offices. After the (successful) implementation it integrates all functions into a single, automated system that runs on a single database. This thesis strives to present different stages of ERP acquiring, from decision-making, through implementation and use. Because the empirical part contains a presentation of an actual business and their requirements, we focus in the particular conditions and issues related to the size and industry of the given company, Beton – Betonski izdelki Kuhar Dušan, s.p throughout the thesis. Additionally, part of the thesis is also presentation and potential beneficial role of one of the leading organizations in the area of project management – Project Management Institute. The outcome of our research is realization that ERP solutions are a crucial aspect of modern companies if they wish to be competitive on the market, have the ability to grow, and continuously maintain the existing pool of costumers. However, before the right ERP solution can be selected, a careful decision-making needs to be undertaken and implementation has to be thoroughly planned. There are many tools and guides that can be used with such demanding project. Project Management Institute, which will be presented in this work, offers many advices on the topic in question.
Keywords: ERP solutions, SMEs, ready-mixed concrete, Project Management Institute
Published in DKUM: 13.10.2014; Views: 2010; Downloads: 196
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Utilization of bottom ash from the incineration of separated wastes as a cement substitute
Filip Kokalj, Niko Samec, Bernardka Jurič, 2005, original scientific article

Abstract: Waste incineration is still an essential technology in the concept of integrated waste management. Most of the combustion residues are incinerator bottom ash. It has been discovered that incinerator bottom ash from the incineration of separated waste in the primary chamber of the modular two-stage incinerator mainly consists of metal oxides, especially SiO2 and CaO, in proportions that are quite similar to those in cement and so the feasibility of its application as a substitute for cement in concrete was investigated. It was found that after 28 days, the flexural and compressive strengths of the binder using bottom ash were practically comparable with those of a pure cement mixture. The results show that it is reasonable to use a binder containing incinerator bottom ash for applications in which an early-stage lower strength of concrete element is acceptable.
Keywords: waste management, solid municipal waste, separated wastes incineration, bottom ash, cement, concrete
Published in DKUM: 01.06.2012; Views: 2229; Downloads: 134
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