121. Condition assessment of roadway bridges: from performance parameters to performance goalsMaria P. Limongelli, Eleni Chatzi, Andrej Anžlin, 2018, original scientific article Abstract: Deterioration of bridges due to ageing and higher demands, induced by increased traffic load, require the development of effective maintenance policies and intervention strategies. Such concern should be aimed at ensuring the required levels of safety, while optimally managing the limited economic resources. This approach requires a transversal advance; from the element level, through the system level, all the way to the network level. At the same time intervention prioritisation based on the importance of the system (bridge) inside the network (e.g. highway), or of the single structural element inside the bridge is dependent. The first step in bridge condition assessment is the verification of safety and reliability requirements that is carried out using the traditional prescriptive (deterministic) approach or the current performance-based (probabilistic) approach. A critical issue for efficient management of infrastructures lies in the available knowledge on condition and performance of bridge asset. This information is obtained using a collection of significant Performance Parameters at one or more of the three levels (element, system, and network). Traditional techniques for estimation of Performance Parameters rely on already established visual inspection. However, a more reliable description of the system performance is obtained through Non-Destructive Testing and Structural Health Monitoring. Condition assessment essentially pertains to the check of compliance with Performance Goals and requires the definition and computation of Performance Indicators. They are calculated directly from Performance Parameters or from physical models calibrated using the Performance Parameters collected on the structure. Paper overviews the steps to bridge condition assessment regarding safety and reliability.
Keywords: bridge, reliability, safety, condition assessment, performance goals, performance parameters
Published in DiRROS: 29.11.2023; Views: 226; Downloads: 117
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122. Cost-benefit analysis of fire protection in buildings : application of a present net value approachThomas Gernay, Shuna Ni, David Unobe, Andrea Lucherini, Ranjit Kumar Chaudhary, Ruben Van Coile, 2023, original scientific article Abstract: In fire safety engineering, cost–benefit analysis provides a systematic method to assess whether the projected benefits from a fire safety measure outweigh its costs. However, there remains a wide discrepancy between methods used in the field for cost–benefit analysis, as well as a lack of quantitative data on the costs and economic impact of fire protection in buildings. In a recent research project, a reference methodology was proposed based on Present Net Value evaluation and on a combination of specialized construction database, fire statistics, and numerical modeling for estimation of the cost components. This paper presents the application of the methodology to four case studies. The case studies allow describing the methodology, the collection of data, fire statistics, and loss estimation, as well as illustrating how the methodology can support decision-making when multiple alternatives are compared. Under the assumptions adopted for the single-family house and the residential timber building case studies, it is found that for every 1\$, invested in sprinklers, \$1.06 is saved. This benefit–cost ratio increases with increasing valuation of indirect losses and statistical value of life. Sensitivity analyses are provided to explore the robustness of the investment recommendations. The results of evaluations, adapted from the presented case studies with project-specific inputs, can support decision making for policy makers, insurance companies, and individual building owners.
Keywords: fire safety, cost-benefit analysis, fire protection, fire statistics, sprinklers, compartmentation
Published in DiRROS: 29.11.2023; Views: 275; Downloads: 40
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123. In situ consideration of resistance of bridge girder according to EC2 with AEMAna Brunčič, Andrej Štrukelj, Maja Kreslin, Andrej Anžlin, Aljoša Šajna, 2023, published scientific conference contribution Abstract: The paper presents a case study of a considerably cracked and degraded bridge in Slovenia: with the implementation of in-situ measurements under bending and shear and the use of a non-destructive acoustic emission technique. Despite the existing crack system, the latter was able to detect microstructural changes. These were characterised by low values of average frequency (AF), as well as lower values of the rise time-amplitude ratio (RA), and energy. A correlation between shear capacity and acoustic activity was observed. This promises to expand the use of AE in the process of assessing of the load-bearing capacity of existing concrete structures.
Keywords: shear resistance, shear crack, crack width, acoustic emission (AE) parameters, bridge girder, stiffness, elasticity, damage evaluation
Published in DiRROS: 28.11.2023; Views: 226; Downloads: 119
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124. Pilot production of façade panels : variability of mix designMajda Pavlin, Barbara Horvat, Vilma Ducman, 2023, published scientific conference contribution Abstract: As part of the WOOL2LOOP project, the Slovenian National Building and Civil Engineering Institute (ZAG), in collaboration with Termit d.d. were responsible for the production of façade panels. An initial mix design was developed at ZAG, where alkali-activated façade panels were produced, primarily from stone wool waste, while production took place at Termit. The mix design was changed twice during the pilot production, before a final product with suitable durability was developed. A compressive strength of up to 60 MPa and bending strength of approximately 20 MPa was achieved. The mechanical properties, however, varied, due to the unevenly milled batches of the milled mineral wool. Milling on a larger scale is very challenging, and it is difficult to obtain consistent quality of the milled material. Once the correct curing process had been found, however, the panels produced showed good performance. Moreover, the results from leaching tests showed that the elevated concentrations of certain elements (Cr, As and Mo) did not exceed the legal limits for non- hazardous waste.
Keywords: waste mineral wool, alkali activated material, façade panels, pilot production, circular economy
Published in DiRROS: 28.11.2023; Views: 292; Downloads: 109
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125. Microwave irradiation of alkali - activated metakaolin slurryBarbara Horvat, Branka Mušič, Majda Pavlin, Vilma Ducman, 2023, published scientific conference contribution Abstract: The building and civil engineering industry generates more than 40% of man-caused carbon emissions, consumes a lot of energy just to produce building materials, generates a large amount of waste through construction and demolition, and consumes a large amount of natural resources. One of the possible solutions is to use alkali-activated materials, which can use waste instead of raw materials and are produced at lower temperatures, with less energy consumption and in less time than traditional building products. All of this lowers the carbon footprint, which could be further reduced by the timely-short implementation of microwave irradiation in the early stages of alkali-activation synthesis. Therefore, metakaolin activated with Na-water glass in a theoretically optimal ratio was irradiated with microwaves of 2.45 GHz at powers of 100 W and 1000 W for 1 min, and compared to non-irradiated reference cured only at room conditions. Samples prepared at higher power, i.e., 1000 W, solidified completely and foamed. TG-DTA was performed on all samples in the early stages of curing, mechanical strengths were measured on 3 and 28-day- old samples, and leaching tests on aged samples.
Keywords: metakaolin, alkali activated material, alkali activated foams, microwave irradiation
Published in DiRROS: 28.11.2023; Views: 269; Downloads: 111
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126. Toksikološka analiza vsebine vojaških čutar, zakopanih 70 let v kraški jami na Kočevskem, JV SlovenijaJanez Mulec, Sara Skok, Vesna Zalar Serjun, Andrej Mihevc, 2019, original scientific article Abstract: Za odkrivanje ostankov materialnih sledi se na dobro ohranjenih predmetih lahko opravijo forenzične preiskave. V Breznu v Debliških livadah je bilo odkritih večje število predmetov, ki so bili odvrženi v jamo v maju in juniju 1945. Med odkritim materialom so bile tudi vojaške čutare. Nekatere izmed čutar so še vsebovale tekočino, nekatere pa tudi poltrdo, gelasto oborino. Tekočina in oborina iz čutar sta vsebovali kovine, ki so se najverjetneje s časom izlužile iz kovinske posode. Korozija čutar nakazuje prisotnost minerala hematita. Vsebina čutar je nadalje vsebovala nekaj raztopljene organske snovi (celotni organski ogljik – TOC v tekočini 9,22 mg/l, v tekočini ekstrahirane oborine 34,1 mg/l), nekaj mikrobne biomase ter relativno visoke koncentracije nitrata (240 mg/l v tekočini, 55 mg/l v ekstrahirani oborini) in sulfata (18mg/l v tekočini, 836 mg/l v ekstrahirani oborini). Bakterijskih indikatorjev, Escherichia coli in enterokokov, ki bi kazali na fekalno kontaminacijo vsebine, v vzorcih nismo zaznali. Raztopina in oborina sta izkazovali podobno stopnjo toksičnosti, okrog 20%inhibicijo bioluminiscence bakterije Vibrio fischeri. Glede na Pravilnik o pitni vodi tekočina s sedanjimi kemijskimi lastnostmi ni primerna za uživanje. Rezultati ne kažejo nujno na toksičnost izvornih tekočin iz časa, ko so bile čutare odvržene v jamo, ampak bi se toksičnost lahko razvila postopoma zaradi izluževanja kovin iz posode, zlasti aluminija, in (bio)kemijskih reakcij. Navkljub stabilnim jamskim razmeram, ki so jim bile izpostavljene čutare, ugotovljeni parametri ne podpirajo dolgoročne ohranitve stabilne DNA za morebitne nadaljnje forenzične analize.
Keywords: jame, vojaški material, toksičnost
Published in DiRROS: 23.11.2023; Views: 240; Downloads: 134
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127. Elucidating nucleation stages of transgranular stress corrosion cracking in austenitic stainless steel by in situ electrochemical and optical methodsSarmiento Klapper Helmuth, Bojan Zajec, Andreas Heyn, Andraž Legat, 2019, original scientific article Abstract: The pitting and environmentally assisted cracking resistance of austenitic stainless steels (SS) is challenged in several industrial applications particularly those involving hot chloride-concentrated streams. Directional drilling used in the oil and gas exploration is one of these applications. Indeed, high strength CrMn-SS commonly used in drilling technology have a high tendency to fail by stress corrosion cracking (SCC) preceded by localized corrosion once subjected to highly chloride-concentrated drilling fluids at elevated temperatures. A comprehensive understanding regarding the mechanisms governing the transition from pitting into SCCis not currently available, though. Therefore, mechanistic aspects such as the effect of loading conditions on pit nucleation and repassivation as well as the synergistic effect between pit stabilization and the nucleation of a stress corrosion crack are of great practical significance. To investigate this an electrochemical-, optical- and mechanical- monitored SCC test was conducted on a CrMn-SS in an alkaline brine at elevated temperature. The transition from metastable to stable pitting and subsequently to SCC in this system was documented in-situ for the first time. Results supported H.S. Isaacs postulates regarding the interpretation of electrochemical signals and demonstrated that loading conditions affect pit nucleation and repassivation leading to a higher susceptibility of the material to pitting, which preceded SCC.
Keywords: pitting corrosion, stress corrosion cracking, monitoring, elektrochemical noise, austenitic stainless steel
Published in DiRROS: 23.11.2023; Views: 245; Downloads: 189
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128. Hydrothermal synthesis of rare-earth modified titania : influence on phase composition, optical properties, and photocatalytic activityNejc Rozman, David Maria Tobaldi, Uroš Cvelbar, Harinarayanan Puliyalil, Joao Antonio Labrincha, Andraž Legat, Andrijana Sever Škapin, 2019, original scientific article Abstract: In order to expand the use of titania indoor as well as to increase its overall performance, narrowing the band gap is one of the possibilities to achieve this. Modifying with rare earths (REs) has been relatively unexplored, especially the modification of rutile with rare earth cations. The aim of this study was to find the influence of the modification of TiO2 with rare earths on its structural, optical, morphological, and photocatalytic properties. Titania was synthesized using TiOSO4 as the source of titanium via hydrothermal synthesis procedure at low temperature (200 °C) and modified with selected rare earth elements, namely, Ce, La, and Gd. Structural properties of samples were determined by X-ray powder diffraction (XRD), and the phase ratio was calculated using the Rietveld method. Optical properties were analyzed by ultraviolet and visible light (UV-Vis) spectroscopy. Field emission scanning electron microscope (FE-SEM) was used to determine the morphological properties of samples and to estimate the size of primary crystals. X-ray photoelectron spectroscopy (XPS) was used to determine the chemical bonding properties of samples. Photocatalytic activity of the prepared photocatalysts as well as the titania available on the market (P25) was measured in three different setups, assessing volatile organic compound (VOC) degradation, NOx abatement, and water purification. It was found out that modification with rare earth elements slows down the transformation of anatase and brookite to rutile. Whereas the unmodified sample was composed of only rutile, La- and Gd-modified samples contained anatase and rutile, and Ce-modified samples consisted of anatase, brookite, and rutile. Modification with rare earth metals has turned out to be detrimental to photocatalytic activity. In all cases, pure TiO2 outperformed the modified samples. Cerium-modified TiO2 was the least active sample, despite having a light absorption tail up to 585 nm wavelength. La- and Gd-modified samples did not show a significant shift in light absorption when compared to the pure TiO2 sample. The reason for the lower activity of modified samples was attributed to a greater Ti3+/Ti4+ ratio and a large amount of hydroxyl oxygen found in pure TiO2. All the modified samples had a smaller Ti3+/Ti4+ ratio and less hydroxyl oxygen
Keywords: TiO2, photocatalytic activity, rare earths, modification, visible light activity
Published in DiRROS: 22.11.2023; Views: 288; Downloads: 147
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129. Particle size manipulation as an influential parameter in the development of mechanical properties in electric arc furnace slag-based AAMKatja Traven, Mark Češnovar, Vilma Ducman, 2019, original scientific article Abstract: Alkali-activated materials (AAM) have gained recognition as a promising alternative to technical ceramic and building materials owing to the lower energy demands for production and the potential to use slag as a precursor. In the present study, five sets of slag-based AAM pastes were prepared with different particle sizes (fractions d < 63, 63 < d < 90, and 90 < d < 125 μm in different mass ratios) under the same curing regime and using a fixed precursor to activator (water) mass ratio. Precursors and the hardened AAM are evaluated using BET, XRD, XRF, SEM, FTIR, reactivity of precursors by leaching, and mercury intrusion porosimetry (MIP). Chemical analysis indicated only marginal differences among the different-sized fractions of input materials, whereas the BET surface area and reactivity among the precursors differed significantly-smaller particles had the largest surface area, and thus, higher reactivity. The mineralogical differences between the precursors and hardened AAM were negligible. The results revealed that compressive strength was significantly influenced by particle size, i.e., a threefold increase in strength when the particle size was halved. Microstructural evaluation using MIP confirmed that the porosity was the lowest in AAM with the smallest particle size. The low porosity and high reactivity of the fine fractions led to the highest compressive strength, confirming that manipulation of particle size can significantly influence the mechanical properties.
Keywords: alkalijsko aktivirani materiali, žlindra iz obločne peči, mehanska aktivacija, mehanske lastnosti, poroznost, alkali-activated materials (AAM), electric arc furnace steel slag, mechanical activation, mechanical properties, porosity
Published in DiRROS: 22.11.2023; Views: 297; Downloads: 145
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130. The role of relative humidity on crystallization of calcium carbonate from calcium acetoacetate precursorAndreja Pondelak, Francesca Rosi, Celeste Maurich, Costanza Miliani, Srečo D. Škapin, Andrijana Sever Škapin, 2019, original scientific article Abstract: Calcium acetoacetate, Ca(OAcAc)2, was exposed 7, 30 and 365 days to different values of relative humidity (33%, 48%, 75% and 96%) at 40 °C in order to study its transformation to CaCO3. The resulting Ca(OAcAc)2 decomposition and the time dependence of the phase transformations were monitored and critically evaluated by Fourier transform infrared spectroscopy, field emission scanning electron microscopy and X-ray powder diffraction. The impact of relative humidity on CaCO3 polymorph formation was thoroughly assessed. In all of the conditions used and for all ageing periods, the formed crystal structure is found to be vaterite. At the lowest relative humidity (33%), the amorphous CaCO3 remains more or less almost untransformed even after one year of exposure. It is proposed that the reason for the stability of amorphous CaCO3 is due to the limited amount of physisorbed water on the surfaces of the particles, which is considered the driving force for its transformation. However, the carbonation process is faster in the case of the highest humidity (96%). The findings are not only important for better solutions in the field of cultural heritage, but also shed new light on the fundamental mechanism of CaCO3 crystallization.
Keywords: calcium acetoacetate, relative humidity, carbonation, amorphous carbonate, vaterite, mechanism
Published in DiRROS: 22.11.2023; Views: 364; Downloads: 159
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