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Influence of Monolith Length on Temperature Field of Concrete Gravity Dams
Get PDFThis paper examines the influence of monolith length on the temperature field of concrete gravity dams built using the block method. The developed 3D model is capable of conducting a thermal analysis of a 95.0 m high concrete gravity dam built using the block method, where each newly cast block represents a new analysis phase. The calculation accounts for the period of construction, the filling of the reservoir, and the service for a total duration of about 5 years. The thermal properties of the material, the influence of cement hydration heat, the temperature of the surrounding rock mass, the temperature of the fresh concrete mixture, and the corresponding boundary conditions defining a heat transfer were taken into account. The height and width of the blocks, as well as the sequence of concreting, were considered invariable, while the length of the blocks (dimension in the direction of the dam’s axis equal to the monolith length) varied, with values of 10.0, 12.5, 15.0, and 20.0 m. The obtained calculation results for the control nodes showed that the maximum reduction in the monolith length (from 20.0 m to 10.0 m) caused a decrease in the maximum temperature values of the concrete (from 1.6 to 3.4 °C, depending on the control node). Also, the results showed that, by reducing the length of the monolith, there was a delay in the moment at which the maximum temperature values of the concrete appeared in the selected control node. The delay in reaching the maximum, in relation to the 10.0 m long monolith, was from 7 days (for points on the crest dam) to 49 days (for points in the central zone of the monolith) for the other considered monolith lengths. The above indicates the importance of concrete temperature control for longer monoliths, especially during construction in extreme air temperatures. The main contribution of the conducted analysis is the development of insight into temperature field changes depending on monolith length, which can help engineers during the design and construction of new, as well as the maintenance of existing, dams
Non-interacting masonry infills as a solution for improving the seismic behavior of infilled RC frames: Experimental results
No full textMasonry infills serve as a prevalent solution for both interior and exterior partitions within reinforced concrete (RC) frame structures. However, recent earthquake events (especially earthquake series in Turkey, February 2023) have revealed significant, uncontrolled damage to masonry infills, primarily attributed to their interaction with RC frames. This high seismic vulnerability poses substantial economic losses and a considerable threat to human safety. Recognizing the imperative need for enhanced seismic performance, this paper explores an innovative approach aimed at mitigating damage to RC structures with masonry infills. The proposed solution centers on the principle of decoupling (non-interacting) masonry infills from the surrounding RC elements. This decoupling is achieved by inserting recycled rubber strips between the masonry infills and the RC frame. The implemented decoupling system effectively delays the activation of ma-sonry infills under in-plane seismic loads and offers crucial support during out-of-plane seismic events. In order to investigate the effectiveness of the decoupling system, quasi-static cyclic tests were performed on full scale specimens. The paper presents a comprehensive examination of experimental results, drawing comparisons between traditionally infilled RC frames and those employing the novel decoupling system. The study takes into consideration infills with and without openings. The findings demonstrate a markedly enhanced seismic performance of masonry infills with the innovative decoupling system
Decarbonisation of the construction sector: is net zero by 2050 feasible?
No full textAccording to the world’s leading authority in climate changes IPCC, in order to prevent the
serious damage to climate and well-being of all species on the planet, it is necessary to limit the
global average temperature rise to 1.5°C by 2100. For that goal to be accomplished, carbon
neutrality (net CO2 emissions equal to zero) is required globally by 2050. In this paper,
decarbonisation technologies that are currently under development in energy and construction
sector are critically assessed from the holistic point of view, including environmental, economic
and social aspects. Carbon capture and storage (utilisation), green hydrogen and green hydrogenbased fuels, and sustainable bioenergy are critical to achieve net zero emissions; deep and very rapid progress is however needed by 2030. The prognosis is heavily dependent on political and economic interests and wealth/power distribution currently prevailing in the world
Earlier onset of the spring in Serbia (1950-2020)
No full textThe strongest temperature increase in Europe has been mainly recorded in spring and/or summer season over recent decades, in particular over its southern areas. Northern parts of Europe are showing positive trends in temperature over the cold season. Territory of Serbia, with its transitional position, in between Mediterranean and continental climate influences shows a significant positive trend of temperature during the summer season. while spring season does not reveal any significant trends. However, despite the absence of any significant trends in the spring season, changes in timing of the warm-spell, which is considered as an indicator of spring onset, might suggest climate seasonal shifts as a result of global warming. In our study, we calculate trends in timing of the warm-spell in Serbia over last decades (1950-2020) using observational, and gridded records. We also examine spatial patterns of trends in timing of the warm spell in Serbia. Finally, we answer what are the large- scale atmospheric causes underpinning such changes. Earlier start of the spring season can cause earlier snowmelt, which can further trigger shifts in timing of the maximum streamflow. Apart from the given hydrological response, temperature-driven changes in the climate seasonal cycle can have considerable impacts for the growing season as well as timing of the phenological changes. The fact that agricultural land comprises 70% of the total territory of Serbia, highlights the importance of warm-spell timing shifts considered in our study
Sistem za nepristrasnu analizu kašnjenja baziran na tehnikama veštačke inteligencije
No full textKašnjenja su uobičajena pojava na građevinskim projektima širom sveta. Identifikacija uzroka kašnjenja je prvi i najznačajniji korak u procesu eliminisanja ili umanjenja kašnjenja na budućim građevinskim projektima. Cilj ovog istraživanja jeste predlog sistema za nepristrasnu detekciju uzroka kašnjenja na građevinskim projektima na bazi tehnika veštačke inteligencije. Postojeća istraživanja su bazirana su ekspertskom mišljenju koje je obojeno subjektivizmom, pristrasnošću i bez iskorišćenog potencijala tekstualne dokumentacije sa projekta. Post-projekte analize su koristan izvor informacija o kašnjenjima, međutim, kompleksnost koordinacije projektnog tima završenog projekta doprinosi negativnom trendu izrade ovih dokumenata. Kroz istraživanje su predstavljeni ključni elementi sistema za detekciju uzroka kašnjenja baziranog na Transformer jezičkim modelima - DREAM (Delay Root causes Extraction and Analysis Model). Predloženi DREAM kombinuje stručno znanje, Transformer jezičke modele i zapisnike sa nedeljnih sastanaka (MoM) kao značajan korpus nestrukturirane tekstualne dokumentacije. Rezultati predloženog sistema treba da omoguće ekspertima da razumeju prirodu uzroka kašnjenja kako bi se pokrenuo proces inteligentnog donošenja odluka na budućim projektim
The professionals’ perspective on the causes of delay in the Serbian road infrastructure projects
No full textConstruction projects are very complex in terms of scope, duration, and a large number of stakeholders. Therefore, the time overrun of construction projects is one of the most significant indicators of project success. Detecting the causes of delay on ongoing or completed projects is the initial step to eliminating or mitigating time overruns on future projects. The main goal of this research is to bridge the void in the literature related to the causes of delay in road infrastructure projects in Serbia. To achieve this aim, empirical research was conducted to identify the significant causes of delay from contractors’ and owners’ perspectives. The unique questionnaire consisted of 53 causes of delay grouped into eight major groups: design, procurement, resources, owner, contractor, consultant, project, and external. The data collected are ranked using the Severity Index (SI). The most significant causes of delay from the contractors’ perspective are related to Design documentation. Additionally, the top-ranking causes of delay from the owners’ perspective refer to contractors’ issues and lack of resources. The common causes of delay identified by both parties are "Problems with property-legal relations," "Lack of details and specifications in the design documentation," and "Non-compliance of the project with the environmental conditions." The low result of the Spearman rank correlation (0,204) showed different attitudes on what causes delays in road infrastructure projects in Serbia. Implicitly, such a result indicates poor communication between the participants in projects. These findings can provide an understanding of the nature of time overruns and discover the root causes of delay. All of the aims above are to mitigate or eliminate delays in future projects
On the application of kernel-based independence tests to variable selection problems
No full textKernel-based generalizations of distance covariance are explored and are applied to variable screening procedures. The flexibility of this association measure allows for the inclusion of models with spherical and hyperspherical data, which are common in various applied research fields such as meteorology, geology, biology, and more. The robustness and adaptability of the proposed method are demonstrated through extensive empirical studies. Overall, the findings suggest that kernel-based distance covariance is a powerful tool for variable selection in high-dimensional datasets
Geometric characteristics of the portals of the katholika in the Studenica, Sopoćani and Dečani monasteries in medieval Serbia
No full textThis paper analyzes the geometric characteristics of the church portals in the Serbian medieval monasteries of Studenica (12 c), Sopoćani (13 c), and Dečani (14 c). The comparative analysis of the portals, regarding their compositions of structural elements (jambs, colonettes, lesenes, and archivolts) and dimensional articulation of ground floor plans and archivolts, is based on the precise digital data collected by terrestrial laser scanning and on the reliable literature and the drawings prepared by architectural conservators. The paper shows that medieval architects applied harmonious proportioning in the design, characteristic of the Romanesque portals along the Adriatic coast. The proposed parametric interpretation of geometric characteristics of analyzed medieval church portals has the potential for use in Heritage building information modeling (HBIM), which is needed to reconstruct and preserve these or other cultural heritage monuments.Rad je prezentovan na konferenciji, ali nije publikovan, sa namerom da se proširi i publikuje u časopisu Wo
Uticaj sredine na trajnost čelične konstrukcije – Studija slučaja stubova reklamnih medija
Get PDFThe steel structures of canopies, public garage columns, street lighting, power lines and other street furniture are constantly exposed to weather effects in their service life. The steel structure of street furniture is often exposed to the effects of de-icing salts from the roads. The paper analyses the effects of the urban environment on the durability of steel structures. The macroscopic visual inspection included 181 steel billboard poles on the territory of the City of Belgrade. The analysis of the surface treatment, the condition of the structure and its location provided conclusions regarding the durability of steel structures in urban environments. The environmental corrosivity on the territory of the City of Belgrade has been analysed. The analysis included the bearing steel structure of poles and the joint between the steel structure and foundations.Čeličnu konstrukciju nadstrešnica, stubova javnih garaža, ulične rasvete, dalekovoda i drugog urbanog mobilijara karakteriše stalna izloženost atmosferskim uticajima tokom životnog veka. Čelična konstrukcija urbanog mobilijara je neretko izložena i uticaju soli za održavanje saobraćajnica. U radu je analiziran uticaj gradske sredine na trajnost čelične konstrukcije. Stručnim vizuelno-makroskopskim pregledom obuhvaćen je 181 stub čelične konstrukcije za nošenje reklamnih medija na teritoriji grada Beograda. Analizirajući vrstu antikorozione zaštite, stanje konstrukcije i lokaciju konstrukcije izvedeni su zaključci o trajnosti čelične konstrukcije u urbanoj sredini. Analiziran je i stepen korozivnosti sredine na teritoriji grada Beograda. Analiza je obuhvatila noseću čeličnu konstrukciju stubova i detalj veze čelične konstrukcije i temelja
Laser scanning at the location of Devils' Town for the purpose of detecting the degree of erosion of earth pillars
Get PDFThe detection of erosion was carried out on a characteristic rocky pillar, with the localization and quantification of differences between two surfaces. For this purpose, based on the defined area and spatial configuration of the scanning object, scanner positions, arrangement of control points, and appropriate spatial scanning resolution were planned. The spatial resolution of the point cloud is 1 cm, with a standard deviation of individual points up to 3 mm. Based on the collected data, registration of adjacent scenes was performed using typical scanner signals and the surface matching method. Georeferencing of the second epoch was carried out using the surface matching method. Locations where erosion of the rocky mass occurred were detected, amounting to 0.036 m³ (36 dm³)