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Утицај Електрофилтерског Пепела на Чврстоћу Cамоуграђујућег Бетона при Притиску
Get PDFИндустрија цемента сматра се једним од значајнијих узрочника емисије СО2. У циљу изналажења рјешења овој проблематици у раду се предлаже замјена 17,5% потребне количине цемента за производњу самоуграђујућег бетона минералним додацима. Експерименталним истраживањем на четири врсте самоуграђујућих бетона варирана је врста минералног додатка – бетон без минералних додатака, кречњачко брашно, електрофилтерски пепео и комбинација кречњачког брашна и електрофилтерског пепела. У том смислу наглашава се да је електрофилтерски пепео примијењен оригинално, какав је као нуспроизвод настао у термоелектрани, тј. није извршено његово просијавање или додатна обрада прије употребе. Резултати истраживања показују да примјена минералних додатака нема утицај на чврстоћу бетона при старости од 2 дана, али утиче на смањење чврстоће бетона при притиску за старости веће од 2 дана. При томе, значајнији утицај има електрофилтерски пепео. Ипак, тај утицај је у функцији времена опадајућег карактера, са тенденцијом да бетони са минералним додацима достигну чврстоће бетона без минералних додатака у старостима већим од 28 дана
Solidified wastewater treatment sludge as a prospective supplementary cementitious material for processing pervious concrete pavements
Get PDFReversible hydro power plants under the conditions of increasing the share of power plants with high variability of availability
Get PDFUvođenje u elektroenergetske sisteme (EES) velikih snaga intermitentnih, naglo promenljivih izvora energije, solarnih i vetroelektrana, bez odgovarajućih energetskih, ali i ekoloških analiza, stvara sve veće probleme u tim sistemima. Bez dubljih analiza se zatvaraju elektrane sa visokom pouzdanošću proizvodnje (velike TE i NE), da bi se zamenili sa navodno obnovljivim izvorima energije, koji su vrlo nepouzdani sa gledišta obezbeđivanja stabilnosti rada EES. U radu se kritički razmatraju posledice izgradnje solarnih elektrana i vetroelektrana. U nizu država to postaje ozbiljan problem, koji će se sve više zaoštravati. Mogućnosti da se problemi reše skladištenjem energije u baterijama su vrlo ograničenog dometa. Veoma često se pri planiranju solarnih i verto elektrana ne vodi računa o činjenici da se sa takvim uređajima, čija izrada zahteva potrošnju velikih količina primarne enerije, a koji se nakon nekog ograničenog vremena moraju potpuno zameniti, dovodi u pitanje atribut obnovljivosti tih intermitentnih izvora enerije. U takvim okolnostima naglo raste potreba za uvođenjem u sisteme reverzibilnih hidroelektrana (RHE) i pumpno akumulacionih postrojenja (PAP), koji su neophodni da prime na sebe zadatke bilansiranja energije u sistemu i obezbeđivanje njegove stabilnosti u novim uslovima.Increasing power of intermittent power plants (solar and wind), which have sudden and variable changes in availability, are being introduced into electric power systems without appropriate necessary energy and environmental analyses. It creates more and more problems for these systems. Without in-depth analysis, power plants with high production reliability (large thermal power plants and nuclear power plants) are being closed, in order to replace them with supposedly renewable energy sources, which are very unreliable from the point of view of ensuring the stability of the operation of the EES. The article critically examines those processes of spontaneous construction of solar power plants and wind power plants. In a number of countries, this is becoming a serious problem, which will become more and more acute. Optimism that it will be solved by energy storage in batteries is very limited. Important facts are not taken into account: (a) the production of batteries for energy storage requires the consumption of large amounts of primary energy, (b) the batteries must be completely replaced after some limited time. This often calls into question the renewable attribute of these intermittent energy sources, and significantly increases the cost of the energy thus obtained. In such circumstances, the need for the introduction of reversible hydropower plants (RHPP) and pumped storage plants (PSP) into the systems is rapidly growing, which are necessary to take on the task of balancing energy in the system and ensuring its stability in new conditions
The importance of Daylight Savings Time for energy savings in Belgrade latitude and climate
Get PDFThe idea of Daylight Saving Time (DST) was introduced before electrification era in order to prolong diurnal use of daylight during summer. DST has been imposed in European legislation since year 2000, but the legislation left open a back door for its suspension if the overall effect did not show positive results. During past decade it has been debated very often about effects of DST. Although many studies have concluded that DST has positive effect on energy savings in buildings in middle latitudes, there are still arguments that DST is causing loses in other areas of economy.
Many literature surveys have concluded that positive effect of DST on energy consumption in buildings is very small and highly dependable on latitude. This paper investigates how the application of DST in Belgrade climate and latitude influences the change of energy demand in highly glazed office spaces. Office buildings are used for work mainly during daytime, so it might be assumed that the influence of clock shift during summer period has high potential for change in utilisation of environmental energy resources
Application of unstructured text based features in prediction of real estate prices: A comparative study
Get PDFThis study demonstrates the potential of application of unstructured textual data for predicting
real estate prices and compares different protocols for extracting features from textual data.
Performance of the different models for price prediction was evaluated on data set of real estate
listings, which included numerical and categorical features, as well as text descriptions. The
experiments showed that adding features extracted from both the translated description text, as
well as noun chunks from it, resulted in the highest R2 score of 0.768, representing an
improvement over the R2 score of 0.71 for the baseline model without text-based features. The
findings from this study indicate how the performance of real estate price prediction models can
be improved by utilizing text-based features, in turn benefiting property market stakeholders in
making informed decisions and evaluating competitive pricing strategies
Numerical characterization of innovative demountable beam-column connections using long bolts
No full textCircular design strategies such as adaptivity, detachability, and reusability represent
new challenges and increased demands on the future-proof buildings sector. To contribute to
the circularity and sustainability of the steel construction sector, an innovative solution of beamcolumn
moment-resisting joints with long bolts and short steel elements (links) is proposed,
enabling an extension in the service length of existing steel members. This paper assesses the
influencing connection parameters (e.g. bolt preload, bolt length and diameter, end plate thickness,
etc.) on the moment (flexural) resistance, stiffness, rotation, ductility, and failure modes
of base configurations of these joints
Geotechnical aspects of construction of stressed ribbon bridge in Užice old town
Get PDFU radu su prikazani rezultati geotehničkih istraživanja za potrebe izgradnje visećeg pešačkog mosta preko klisure reke Đetinje u Užicu. Predviđeno je da most, sistema prednapregnute trake, omogući prelaz pešacima sa desne dolinske strane na stranu Starog grada, koja je opasana strmom liticom (cca. 40 m visine). Za potrebe formiranja geotehničkog modela i strukturnog sklopa krečnjačke stenske mase korišćen je postupak fotogrametrijskog snimanja dronom. Predviđeno je da se zatežuća sila (od oko 30 MN), koju most prenosi na obalni stub, prihvati i prenese na stensku masu sistemom prednapregnutih ankera. U tom pogledu izvršena su ispitivanja nosivosti dva sidra, koja su ugrađena u subhorizontalne bušotine. Rezultati numeričkih analiza i uspešan test nosivosti sidara pokazuju da je stenska masa u stanju da izdrži sile zatezanja od mostovske konstrukcije. Pomeranja obalnog stuba su nekoliko mm u slučaju pretpostavke o kontinualnoj stenskoj masi. Kada se eksplicitno u analizu uvedu pukotine pomeranja su oko 6 cm. Ovi rezultati se morju verifikovati kroz odgovarajući monitoring tokom izgradnje mosta.This study shows the results of geotechnical investigations performed for the construction of pedestrian suspension bridge, crossing the Đetinja river in the town of Užice. The prestressed ribbon type bridge should connect the right bank of the river with the the vertical cliff (approx. 40 m high) where the Old town is located. Geotechnical model of the limestone rock mass and joint network model are formed by utilization of drone photogrammetry. The tensile force (approx. 30 MN) induced on the bridge pillar should be accepted and transfered to the rock mass by the system of prestressed anchors. Two investigation test were performed on anchors installed in sub-horizontal boreholes. Successful anchor load test and numerical analysis showed that the rock mass is capable of sustaining tensile force induced by the bridge structure. Displacements of the bridge abutment are approx. several mm for an assumption of isotropic rock mass behaviour. If joints are applied explicitly the displacements are in the order of 6 cm. These findings have to be confirmed by monitoring during the construction stage
Classification of residential building stock in Serbia
Get PDFDeveloping a classification system (taxonomy) for buildings is a critical step for seismic risk assessment studies. Such a system can be used to characterize a building portfolio within urban/rural settlements or building stock for the entire country. Serbia is located in a region characterized by a moderate seismic hazard. In the last century, 10 earthquakes of magnitude 5.0 and higher occurred in Serbia, the strongest (M 6.0) in 1922. The strongest earthquake in the 21st century (Mw 5.5), with an epicenter close to Kraljevo, occurred in November 2010 and caused significant damage to residential buildings. In 2019, members of the Serbian Association for Earthquake Engineering (SUZI-SAEE) contributed to the SERA project and its goal to develop a seismic risk model for Europe. A taxonomy of residential buildings in Serbia was developed based on previous national and regional building stock studies. The proposed taxonomy includes the Lateral Load-Resisting System (LLRS) (e.g., wall, frame, dual wall-frame system) and material of the LLRS (e.g., masonry, concrete, wood) as the main attributes. The type of floor diaphragm (rigid or flexible) has been specified only for masonry typologies with unreinforced masonry walls, while building height and date of construction have been implicitly considered. According to the proposed taxonomy, there are 9 residential building typologies in Serbia; out of those, 5 typologies are related to masonry structures, 3 are related to RC structures, and one is related to wood structures. This paper describes the proposed taxonomy and outlines the characteristic features of different building typologies and their relevance for estimating seismic vulnerability and risk. A comparison of the proposed taxonomy for Serbia and published taxonomies for Croatia is also presented
Preisach model for inner hysteresis loops of cyclicly loaded mild steel elements
Get PDFIn this paper, the new type of Preisach model, that describes the inner hysteresis looops of structural mild steel under cyclic loading, is developed. It is the multilinear mechanical model, that describes closed hysteresis loops typical for structural steel. The analytical model and appropriate Preisach triangle, suitable for engineering practice, were defined. This model was verified by comparison with the experimental results. The experiment has been carried out on structural steel S275 specimens, cyclicly loaded