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Performance Evaluation of Asphalt Mixtures Containing Different Proportions of Alternative Materials
Get PDFWith the increasing scarcity and cost of virgin materials for asphalt mixtures, the exploration of alternative components has intensified. Reclaimed asphalt pavement (RAP), crumb rubber (CR), steel slag (SS), and waste engine oil (WEO) have emerged as promising alternatives. Individually, RAP enhances rutting resistance but may compromise cracking tolerance; CR boosts cracking resistance; WEO affects cracking and rutting differently; and SS can influence moisture sensitivity. However, their combined impacts on asphalt performance, specifically on moisture damage, rutting, and cracking resistance, remain underexplored. In this study, 44 mixtures were assessed with varying RAP (0–75%), WEO (0–15%), and CR (0–15%) contents, alongside a constant SS aggregate (0% or 20%). The results indicate that specific combinations of these alternative materials can satisfy all performance thresholds for rutting, cracking, and moisture damage. To pinpoint ranges of optimal material contents for different high-traffic scenarios, prediction models were crafted using techniques like feed-forward neural network (FNN), generalized linear model (GLM), support vector regression (SVM), and Gaussian process regression (GPR). Among these, GPR demonstrated superior efficacy, effectively identifying regions of satisfactory performance
Solidified waste water treated sludge as partial replacement of cement in concete composites
Get PDFIn this research, tests of mortar and porous concrete made with solidified waste water treatment sludge (SWWTS) used in two forms as a partial replacement of cement were carried out. SWWTS mainly consisted out of CaCO3 and Ca(OH)2, having no pozzolanic properties. For this reason, it was used both, as produced, and modified by adding Al2O3 and Mg3Si4O10(OH)2 in certain percentages. One mortar type and two types of porous concrete were tested. For each of the three products two mixtures were prepared: the reference mixture and the mixture made with 30% replacement of cement, while the other components remained the same. Based on the given comparative analysis, conclusions were drawn regarding the structure of porous concrete slabs, which refer to individual analyzed properties, but also to the possibility of applying energy-efficient materials. The obtained results point to the conclusion that the use of SWWTS reduces the values of almost all tested properties of porous concrete (flexural and compressive strength, pull-off strength, abrasion resistance), but also that the modification of SWWTS led to a smaller difference in the results of the samples made with 30% of cement replacement and the reference samples. Although, the use of SWWTS led to the reduction of mechancal properties of concretes, the most important benefit is development of possible way for reuse of this waste material and avoid its disposal in the landfills
Geometrijsko oblikovanje trase kao parametar prostorne uskladjenosti puta sa njegovom okolinom
Get PDFPojam geometrijskog oblikovanja podrazumeva proces skladnog komponovanja projektnih elemenata sa osnovnim ciljem da se ostvari prostorna slika puta koja u vizuelnom smislu ostavlja pozitivan utisak i vozačima uliva osećaj sigurnosti i predvidljivosti. S obzirom da se u vidnom polju vozača istovremeno nalazi više geometrijskih oblika koji zajedno definišu trasu puta u prostoru, neophodno je voditi računa o optičkim svojstvima svakog elementa. Harmonični odnosi se postižu samo kod usklađenih elemenata trase puta kroz sve projekcije puta (situacioni plan, podužni profil i poprečni profil). U radu će biti prikazane osnovne zahtevi i preporuke koji mogu pomoći da se još u početnim fazama projektovanja postignu optimalni odnosi koji značajno doprinose skladnom uklapanju puta u postojeću okolinu
A multi-fidelity wind surface pressure assessment via machine learning: A high-rise building case
Get PDFComputational fluid dynamics (CFD) represents an attractive tool for estimating wind pressures and wind loads on high-rise buildings. The CFD analyses can be conducted either by low-fidelity simulations (RANS) or by high-fidelity ones (LES). The low-fidelity model can efficiently estimate wind pressures over a large range of wind directions, but it generally lacks accuracy. On the other hand, the high-fidelity model generally exhibits satisfactory accuracy, yet, the high computational cost can limit the number of approaching wind angles that can be considered. In order to take advantage of the main benefits of these two CFD approaches, a multi-fidelity machine learning framework is investigated that aims to ensure the simulation accuracy while maintaining the computational efficiency. The study shows that the accurate prediction of distributions of mean and rms pressure over a high-rise building for the entire wind rose can be obtained by utilizing only 3 LES-related wind directions. The artificial neural network is shown to perform best among considered machine learning models. Moreover, hyperparameter optimization significantly improves the model predictions, increasing the ��2 value in the case of rms pressure by 60%. Dominant and ineffective features are determined that provide a route to solve a similar application more effectively
Razvoj specifikacija za bitumen – Kako predvideti ponašanje u fazi eksploatacije
Get PDFOsnovni cilj prilikom razvoja novih metoda ispitivanja bitumena je da se odrede karakteristike veziva koje su vezane za ponašanje asfaltnih slojeva u fazi eksplatacije i za nastanak dominantnih oštećenja na fleksibilnim kolovoznim konstrukcijama: kolotraga, pukotina usled zamora i termičkih pukotina. Ova ispitivanja je neophodno sprovesti pri različitim nivoima starenja, koje treba da simulira eksplatacione uslove za bitumen i asfaltne mešavine tokom njihovog životnog veka.
U radu je prikazan razvoj specifikacija za ispitivanje putnih i polimer modifikovanih bitumena, kao i savremeni postupci za ispitivanje karakteristika bitumena koji se primenjuju u Sjedinjenim Američkim Državama, u kontekstu unapređenja specifikacija Superpave, kao i u Evropi, pre svega imajući u vidu očekivano novo izdanje standarda EN 14023 koji se odnosi na polimer modifikovane bitumene. Posebno su obrađene metode za karakterizaciju veziva na visokim eksplatacionim temperaturama, kao što su metoda MSCR (Multiple Stress Creep Recovery), razvijena u SAD, i Brza metoda za karakterizaciju bitumena BTSV razvijena u Nemačkoj. Na kraju je dat pregled novouvedenih ispitivanja u okviru predloga specifikacija za polimer modifikovane bitumene
Combining machine learning and spatial data processing techniques for allocation of large-scale nature-based solutions
Get PDFThe escalating impacts of climate change trigger the necessity to deal with hydro-meteorological hazards. Nature-based solutions (NBSs) seem to be a suitable response, integrating the hydrology, geomorphology, hydraulic, and ecological dynamics. While there are some methods and tools for suitability mapping of small-scale NBSs, literature concerning the spatial allocation of large-scale NBSs is still lacking. The present work aims to develop new toolboxes and enhance an existing methodology by developing spatial analysis tools within a geographic information system (GIS) environment to allocate large-scale NBSs based on a multi-criteria algorithm. The methodologies combine machine learning spatial data processing techniques and hydrodynamic modelling for allocation of large-scale NBSs. The case studies concern selected areas in the Netherlands, Serbia, and Bolivia, focusing on three large-scale NBS: rainwater harvesting, wetland restoration, and natural riverbank stabilisation. Information available from the EC H2020 RECONECT project as well as other available data for the specific study areas was used. The research highlights the significance of incorporating machine learning, GIS, and remote sensing techniques for the suitable allocation of large-scale NBSs. The findings may offer new insights for decision-makers and other stakeholders involved in future sustainable environmental planning and climate change adaptation
Monitoring vlažnosti zemljišta korišćenjem jeftinih senzora
Get PDFVlažnost zemljišta je jedan od važnijih parametara u modeliranju i analizi podzemnih
voda, poljoprivredi, ekologiji i sl. Monitoring vlažnosti omogućava upravljanje vodnovazdušnim režimom zemljišta čime se obezbjeđuju bolji uslovi za razvoj biljaka i
povećanje prinosa. Određivanje vlažnosti zemljišta laboratorijskim metodama zahtijeva
značajna materijalna sredstva kao i određeno vrijeme. Razvojem tehnologije danas su
dostupni relativno jeftini senzori koji omogućavaju na vrlo efikasan način monitoring
vlažnosti na terenu. U ovom radu istražena je mogućnost korišćenja jeftinih senzora za
mjerenje vlažnosti na uzorku humusa u laboratorijskim uslovima. Urađena je kalibracija
senzora za analizirani uzorak zemljišta korišćenog u eksperimentu na kojem je
sprovedeno mjerenje vlažnosti, a rezultati sprovedenog istraživanja provjereni su
pomoću Hydrus 1D modela
Determination of Mode I fracture properties of European spruce
No full textIn this paper an efficient procedure for obtaining a cohesive law for Mode I timber fracture (crack opening), based on the Double Cantilever Beam (DCB) tests is given. DCB tests were performed on ten European spruce specimens in order to determine the energy release rate vs crack length (R curves). Two crucial parameters - crack length during the experiment and the crack tip opening displacement were obtained using 2D Digital Image Correlation (DIC) technique. In order to determine accurate fracture resistance (R curve), procedure which includes calculating cumulative released energy was employed. The cohesive law for Mode I fracture of wood was obtained by differentiation of the strain energy release rate as a function of the crack tip opening displacement. This cohesive law is further implemented in the successful numerical modelling of failure modes in large-scale end-notched glulam beams which were experimentally tested in four-point bending configuration
