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The Effect of Polypropylene Fibers on the Mechanical and Physical Properties of Foam Concrete
No full textFoam concrete (FC) is a lightweight material
composed of cement, water, and a foaming agent. Including the
foaming agent significantly reduces the density of the concrete,
making it lighter than conventional mixes. However, due to the
absence of coarse aggregates, foam concrete generally exhibits
lower mechanical properties than other lightweight concrete
types. This study explores the potential of enhancing the
mechanical properties of foam concrete by incorporating
polypropylene fibers into the mixture. The research focuses on
evaluating the influence of these fibers on key performance
characteristics, aiming to improve the structural integrity of
foam concrete, and, therefore aiding the mechanical properties.
For this investigation, two types of cement were utilized: Type II
cement with moderate heat of hydration, and Type IV pozzolanic
cement. The findings of this study provide valuable insights into
optimizing foam concrete for broader applications in
construction, based on flexural, compressive strength and
abrasion tests. Keywords Foam concrete, Polypropylene fibers,
Type II cement, Type IV (Pozzolanic) cemen
A novel experimental approach for estimating the impact of surface roughness on structural response
No full textA new experimental rig was devised to study the influence of surface roughness on the structural response of
specially designed test samples shaped as semicircular arcs. The rig was designed to provide consistent testing
conditions for samples with different levels of roughness. Special attention is paid to defining the roughness and
global geometry of semicircular arcs formed from 0.8 mm thick stainless steel SS1.4301 sheets. Experimental
samples are divided into three groups with respect to their arithmetic mean roughness values of 12 nm, 35 nm,
and 670 nm. The obtained results show that the displacement and strain of arcs depend on the roughness of the
contact surfaces. A significant instability in the response of polished arcs is observed
Flood discharge evaluation at the Bezdan gauging station
No full textU ovom radu se za procenu protoka koriste metode Ekersa i razmene količine kretanja koje su do sada detaljno testirane na osnovu rezultata laboratorijskih ogleda u kanalima sa poprečnim presekom jednostavne geometrije (dvogubo pravougaono ili trapezno korito) ili na deonicama vodotoka sa uređenim koritom (dvogubo trapezno korito). Prema saznanjima autora, ove metode još uvek nisu u značajnijem obimu proverene u prirodnim koritima. Hidrološka stanica Bezdan na reci Dunav ima zadovoljavajući fond merenja protoka u domenu velikih voda i pruža mogućnost za
poređenje i validaciju dve metode. Na ovoj hidrološkoj stanici mereni su protoci tokom tri poplavna talasa: u julu 2009. godine (dva merenja), junu 2010. (jedno merenje) i junu 2013. (četiri merenja). Svi izmereni protoci veći su od 6000 m3/s. Merenja je obavio RHMZ Srbije pomoću ADCP uređaja. Pošto ovaj uređaj tokom merenja snima dubine, moguće je rekonstruisati deo poprečnog preseka
pod vodom u onom njegovom delu u kojem je čamac sa opremom mogao da obavi merenja (u plitkim zonama merenje je nepouzdano, a postoji i opasnost od oštećenja opreme). Delovi poprečnog preseka izvan osnovnog korita rekonstruisani su na osnovu satelitskih snimaka za poznate položaje mernih preseka. Na osnovu ovako određene geometrije korita za veliku vodu i zabeleženih vodostaja, izračunati su protoci primenom ove dve metode i upoređeni su sa merenjima iz 2013. godine. Imajući u vidu česte morfološke promene korita, izabrana je jedna godina i to ona sa najvećim brojem merenja.This paper evaluates river discharge using the Ackers method and the momentum exchange method, both of which have been extensively tested in laboratory channels with simple cross-sectional geometries (compound rectangular or trapezoidal) and in regulated reaches with
engineered trapezoidal beds. To the authors’ knowledge, these methods have not yet been widely validated in natural river environments. The Bezdan gauging station on the Danube River offers a robust dataset of highwater discharge measurements, making it an ideal site for comparison and validation. Measurements were conducted during three major flood events: July 2009 (two
surveys), June 2010 (one survey), and June 2013 (four surveys). All recorded discharges exceeded 6000 m³/s. The Serbian Hydrometeorological Service (RHMZ) carried out the measurements using an Acoustic Doppler Current Profiler (ADCP). Because the ADCP simultaneously records depth, it allows partial reconstruction of the underwater cross-section in zones accesto the survey vessel, while shallow areas where measurements are unreliable and equipment risk is high, were supplemented using satellite imagery tied to known survey locations. Based on this reconstructed geometry and observed water levels, discharges were calculated
with both methods and compared against the 2013 measurements. To account for frequent morph-ological changes of the riverbed, the year with the most extensive measurements was selected, providing a robust basis for evaluating the applicability of these methods under natural high-water conditions.Рад је резултат истраживања студената мастер студија на изборном предмету Заштита од поплава
Hybrid system for risk quantification and management on road infrastructure projects
No full textThis doctoral dissertation deals with the development of a hybrid model for risk management on road
infrastructure projects, aiming to accurately predict risk occurrences, their impact on Increasing
Contract Price (ICP) and Extension of Time (EoT), as well as to evaluate the impact of preventive
measures on reducing these overruns. The research is based on the identification of risks and key
project parameters, development of complexity coefficients as aggregated indicators of
environmental, technical, and contractual characteristics, definition of optimal preventive measures
to minimize adverse consequences for all risks, application of fuzzy logic and machine learning for
predicting risk impacts, as well as multi-criteria decision-making methods for evaluating and
prioritizing preventive measures.
The qualitative part of the methodological framework includes a systemic analysis of implemented
infrastructure projects in the Republic of Serbia, creation of a quantified list of risks and their impacts
on EoT and ICP, as well as a structured definition of preventive measures. The quantitative part of
the methodological framework involves applying the TSK method and machine learning methods to
input values of three complexity coefficients for predicting overruns and identifying the most
influential risks, as well as for evaluating the impact of preventive measures on reducing overruns.
The obtained results indicate that the hybrid model achieves satisfactory accuracy in predicting ICP
and EoT, as well as in evaluating the application of preventive measures on the most influential risks.
The proposed approach contributes to the reduction of unplanned overruns and represents a
significant advancement in risk management. The scientific validation of the model developed within
this doctoral dissertation has been carried out through five papers published in international journals
indexed in the SCI list, confirming its originality and scientific foundation
Digital support in the construction industry: the role of large language models in risk management
No full textGrađevinska industrija često beleži prekoračenja troškova i rokova izgradnje. Uzroci poremećaja uključuju fragmentisane procese upravljanja rizicima i zamoran manuelni pregled velike količine nestrukturirane dokumentacije. DREAM model, nastao 2022. godine, je pokazao da kombinacija mašinskog učenja i ekspertskog znanja može sistematičnije otkriti osnovne uzroke kašnjenja u odnosu na manuelne analize. Međutim, svaki novi kontekst je zahtevao opsežno treniranje i bio je podložan ekspertskoj pristrasnosti. Najnoviji iskoraci u velikim jezičkim modelima, posebno GPT-4, omogućavaju zero-shot ili few-shot prilagodljivost velikim količinama nestrukturiranog teksta, uklanjajući potrebu za specifičnim obeležavanjem podataka. Ovaj rad ispituje mogućnost da li GPT-4 model, upotrebljen u zero-shot režimu, precizno klasifikuje uzroke kašnjenja (CoD) iz stvarnih zapisnika sa sastanaka bez dodatnog treniranja. Implementiran je protokol za kreiranje upita sa iterativnim proverama samokonzistentnosti radi maksimalne pouzdanosti. Eksperimentalni rezultati, uključujući analizu matrice konfuzije, pokazuju da ChatGPT-4 nadmašuje DREAM, smanjujući jaz u performansama uz značajno manje rada na obeležavanju podataka. Kvantifikacijom ušteda na anotaciji i karakterisanjem preostalih pristrasnosti, pokazujemo da veliki jezički modeli (LLM) omogućavaju skalabilnu i efikasnu primenu veštačke inteligencije u upravljanju rizicima u građevinarstv
Flexible joints for seismic-resilient design of masonry-infilled RC frames
No full textMasonry infills are among the most seismically vulnerable components in reinforced concrete frame structures. One promising mitigation strategy involves the use of rubber joints, which has shown potential in prior studies. However, further experimental and numerical investigations are needed to fully understand their effectiveness under realistic seismic conditions and to support evidence-based design. To address this, the EU-funded H2020 project FLExible JOInts for seismic-resilient design of masonry-infilled RC frames (FLEJOI) was conducted within the Engineering Research Infrastructures for European Synergies (ERIES) project. Two identical RC frame prototypes with brick infills and different rubber joint systems were constructed and tested at the Institute of Earthquake Engineering and Engineering Seismology – IZIIS in North Macedonia. The first system reduced panel stiffness and increased damping, while the second completely decoupled the infill from the frame. Both were subjected to extensive shaking table testing. This paper presents the resulting dataset, comprising detailed measurements from sensors monitoring the RC frames, infills, and joints – serving as a valuable benchmark for model validation and future research
Uncertainty analysis of CLT floor vibrations due to inherent variability in structural properties
No full textBy neglecting the natural variability of structural parameters and walking loading, design guidelines featuring deterministic approach to calculating pedestrian-induced vibrations of long-span floors do not provide a rational prediction of the actual vibration response. Considering uncertainties of input parameters and assessing the probability of exceeding vibration limits lead to a more informative and reliable evaluation of floor vibration performance. This study presents an uncertainty analysis of modal properties and pedestrian-induced acceleration response of a multi-panel CLT floor, taking into account variability in timber material properties, inter-panel connections and damping ratio. A sensitivity analysis revealed that timber density, longitudinal elasticity modulus and shear modulus had the greatest impact on the natural frequencies and modal masses. In contrast, variability in the inter-panel connections had only a minor influence. The uncertainty analysis of the vibration response was carried out using Monte Carlo simulation, where the timber material properties and a damping level were uncertain. The pedestrian loading was modelled deterministically, accoriding to a popular design guideline for floor vibrations. Two sets of vibration responses were simulated numerically: (i) with a fixed walking frequency across all simulations, and (ii) with variable walking frequency adjusted to induce a resonance in each simulation. The resonant response also was calculated following the guideline for comparison. The first dataset showed that the guideline’s response had a very low probability of occurrence. On the other hand, it compares reasonably well with the second dataset, indicating that the guideline provides rational vibration levels only for a likely occurrence of resonance
Mycenaean roads in the Peloponnese, Greece: Least-cost path modelling using R and Movecost
No full textThis study evaluates multiple methodologies and their variants for Least Cost Path (LCP) modelling, applied in combination with different Digital Elevation Models (DEMs), to explore the broader applicability of the Movecost package, using the Mycenaean Road networks of the Peloponnese (Greece) as case studies. Using a geographic information system (GIS) and the R programming environment, this paper employs the Movecost package for the R statistical package to simulate ancient routes based on existing road segments. By integrating a variety of functions and parameters, this study evaluates their effectiveness across different DEMs, including both Shuttle Radar Topography Mission DEM (SRTM-DEM) and Copernicus DEM (COP-DEM) at 30 m spatial resolution. The study also examines how varying these parameters can lead to different modelling outcomes, underscoring the necessity of calibrating least-cost analysis to specific regional contexts. The road segments around Nichoria (Messenia), Ayios Ioannis Kazarma (Argolis), and in the Berbati Valley (Argolis), provide a historical canvas against which these methodological innovations are tested with the ultimate aim of exploring the capabilities of the Movecost package and how different combinations of DEM, function, parameter, and path points can effectively model the route through the existing road remains, highlighting the variability and context-specific nature of LCP modelling. The results suggest that the 'Wheeled-vehicle critical cost function' (WCS) was effective in modelling the roads through the extant remains based on start and endpoints suggested by previous research and posited by this paper. These results further suggest that Mycenaean roads likely served as key infrastructure links between major centres and ports or harbours, underscoring their role in facilitating regional trade and communication. However, this outcome represents one of several possible results, as the appropriateness of functions and the parameters tested depend on the specific landscape and archaeological context. This underscores the importance of careful parameter selection, providing insights into the economic and social landscapes of Mycenaean Greece, while also highlighting the potential of integrating spatial data with robust computational tools to enhance our understanding of ancient infrastructure
Digitalni geomorfološki katastar Đavolje Varoši
No full textЛокалитет Ђавоља варош представља специфичан геоморфолошки феномен
на југу Србије, који се састоји од преко 200 пирамидалних или стубастих облика, насталих
селективном ерозијом меког вулканокластичног материјала. У оквиру пројекта
„DEMONITOR“ Фонда за науку Републике Србије, извршено је фотограметријско
снимање локалитета у циљу добијања дигиталног геоморфолошког катастра Ђавоље
вароши са најновијим стањем ерозионих облика, који ће послужити као основа за даље
праћење динамике процеса и прогнозирања његовог развоја у будућности. Припадајући
облак тачака, задовољавајућег нивоа детаљности, са просторном резолуцијом од 2 cm,
коришћен је за директно бројање и мерење облика. Укупно је евидентирано 209 облика,
од којих је 158 појединачних, 36 рачвастих, а 15 композитних (састављених од 3 или више
облика). Просечна висина облика износи 4,1 m, а ширина у средини 1,3 m. Највећа
измерена висина облика је 15,1 m, а ширина 4,15 m. Од укупно 209 облика, 92 има
андезитску капу на врху, а 117 је нема. Ранија истраживања имају сличне резултате, али
је ово први јавно доступни интерактивни катастар у којем се могу наћи основне
информације о сваком облику. У плану је да се катастар у току али и по завршетку
пројекта ажурира на годишњем нивоу како би био употребљен за праћење промена и
потенцијално за израду и допуну туристичких водича и брошура
Optimization of observation time in Precise Point Positioning by combining error models
No full textThis study addresses the optimization of observation duration within the Precise
Point Positioning (PPP) technique, focusing on determining the minimal observation
time required to achieve stable and accurate coordinate solutions while accounting for
various error sources, such as precise ephemerides and satellite clock files. The
numerical analysis was conducted using the Bernese GNSS Software, applying different
processing scenarios that included four types of ephemerides (CODE, IGS, IGR, and
IGU) and clock files with sampling intervals of 5 and 30 seconds. Observations were
collected from three permanent GNSS stations over a multi-year period (2017–2019) and
all results were expressed within the IGS14 reference frame. The processed data were
organized into three datasets, enabling a comprehensive evaluation of the influence of
ephemeris quality, seasonal stability and temporal dynamics of coordinate convergence.
The results demonstrate a clear convergence trend dependent on both the quality of
ephemerides and the length of the observation session, while the inclusion of high-rate
clock products (5-second intervals) should further improve positioning precision under
certain conditions. These findings provide valuable insights into the optimization of
observation strategies in scientific and technical GNSS applications, allowing for more
efficient planning of observation durations without compromising the accuracy of
positioning results. The study thus contributes to the rationalization of data acquisition
processes in geodetic and geophysical surveys, where efficient resource utilization is
often critical