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Deflection Calculation for Beam-type Structures from Measured Strain Data
Get PDFBehavior of structures under various load types is determined by their deformation characteristics, global deformation characteristics - deflections and rotations, and local deformation characteristics - strains / stresses in structure base material. If we know global and local deformation characteristics of a structure, then it is possible to determine the structure behavior under acting loads, on the whole structure or at some part of that structure. The main objective of this research is to verify calculation algorithm for obtaining vertical displacements - the deflection of the structure, based on the known strain values in the structure base material, under acting load. The verification of the calculation algorithm is performed by comparing the numerical and experimental results
Prediction model based on artificial neural network for pyrophyllite mechano-chemical activation as an integral step in production of cement binders
No full textThe optimal outputs of pyrophyllite mechano-chemical activation in an ultra-centrifugal mill performing under different technological conditions were determined by analytical modeling and verified via Artificial Neural Network in order to be employed in the production of cement-based binders. Cluster Analysis and Principal Component Analysis were utilized in assessment of the effect of activation process parameters on the activated pyrophyllite quality. Artificial Neural Network which performed with high prediction accuracy, i.e. 0.914 during the training period, was sufficient for precise prediction of activated pyrophyllite quality in a wide range of processing parameters. The probability of utilization of observed activation products was estimated through interrelation of technological parameters (mesh size sieve, activation period, specific energy consumption) and acquired characteristics of pyrophyllite (grain diameter, specific surface area). The optimal products singled out from each activation sequence were used as mineral additives in the mix-designs of four cement binders (cement replacement portion was 30%). Influence of activated pyrophyllite additions on the cement chemistry, mineral phase compositions and microstructures of the cement binders were monitored by instrumental techniques (DTA/TGA, XRD, SEM). Activated pyrophyllite showed characteristics of pozzolana as it slightly accelerated early stages of hydration, decreased cement hydration energy and increased the quantity of cement mineral alite at later hydration stages. Micron-sized crystalline foila characteristic for mechanically activated pyrophyllite formed micro-reinforcement within cement binder microstructure
Linear thermal expansion of the building stone from plutonic massifs of the Vardar zone of Serbia
Get PDFToplotna svojstva građevinskog kamena koji se koristi za oblaganje vertikalnih i horizontalnih površina građevinskih objekata, naročito u eksterijeru, imaju veliki značaj za stabilnost i vek trajanja, ali i estetska svojstva obloženih površina. Linearno toplotno širenje elemenata od prirodnog kamena određuje se laboratorijskim ispitivanjima, kako bi se pri ugradnji ovih elemenata obezbedio odgovarajući prostor za dilataciju i kontrakciju materijala. Na vertikalnim i horizontalnim površinama obloženim elementima od prirodnog kamena, na kojima nije predviđen ovaj prostor, pri povišenju ambijentalne temperature, nastaju naponi koji uzrokuju deformacije i narušavanje integriteta elemenata i površina. U literaturi se relativno retko nailazi na podatke o linearnom toplotnom širenju prirodnog kamena, naročito za kamen poreklom iz nalazišta u Srbiji, pa je shodno tome cilj ovog rada da doprinese poznavanju toplotnih svojstava za domaće vrste kamena. Ispitivanje linearnog toplotnog širenja kamena poreklom iz osam plutonitskih kompleksa Eksterne vardarske zone Srbije pokazalo je da su njihove vrednosti vrlo male, delovi milimetra, i niže u poređenju sa vrednostima toplotnog širenja genetski srodnih vrsta stena iz Kine, Brazila i istočne Srbije. Zapaženo je jasno grupisanje vrednosti toplotnog širenja kamena prema genetskim grupama kojima pripadaju plutoni iz kojih kamen potiče. Mineraloški sastav, krupnoća zrna i prisustvo metaličnih minerala u uzorcima nisu pokazali značajan uticaj na vrednosti toplotnog širenja, ali nehomogenost sklopa utiče na povišenje ovih vrednosti.Thermal properties of the building stone used for cladding and flooring, especially in exteriors, are significant for durability and lifespan of buildings' surfaces covered with it, but also their aesthetic properties in the sense of integrity. Linear thermal expansion of natural stone units is determined in laboratory examinations, aiming to provide the value of yield between the units as free space for their dilatation and contraction upon temperature oscillations. Where this space is not provided, diurnal changes, especially temperature increase, create stone expansion and tension which can lead to deformations of stone units and mar units' and covered surfaces' integrity and aesthetics. Data on linear thermal expansion values of natural stone, especially from Serbia, are very rare in the literature, so our aim is to contribute to this type of knowledge. Examination of thermal dilatation of stone originating from eight plutonic massifs in External Vardar zone of Serbia has shown that the values are very small, parts of millimetres, and lower than those of the similar rock types originating from China, Brazil and Eastern Serbia. A clear grouping of the values of thermal expansion of the stone according to the genetic groups to which the plutons belong to can be observed. Mineral composition, grain size and presence of metallic minerals in samples have shown no clear influence on thermal dilatation values, but fabric inhomogeneity appears to cause the increase of these values
Optimizacija kompozitne mešavine domaćih prirodnih ilitsko-kaolinitskih glina za primenu u proizvodnji keramičkih pločica
No full textImpact of CO2 Emissions on Low Volume Road Maintenance Policy: Case Study of Serbia
Get PDFAbout 20% of the Serbian national road network has sections with low volume traffic. These sections are maintained in relatively poor condition since the maintenance budget is typically allocated to the road sections with most traffic. This paper aims to define the appropriate maintenance policy for keeping these sections in "optimal" condition. The traditional approach has been to consider as optimal the condition leading to the minimum sum of road agency costs and road user costs. However, currently there is an emphasis on including environmental cost (greenhouse gas emissions, in particular) into pavement management systems. This extends the concept of optimum by defining it as the maintenance policy leading to the minimum sum of (a) road agency costs, (b) road user costs, and (c) the cost to society of CO2 emissions. Three potential influencing factors are further analyzed: traffic loading, pavement structural number, and the initial condition of the road section. The World Bank's Road Network Evaluation Tools (RONET) model was used to analyze the Serbian low volume road network and develop the optimal maintenance policy. The results show that the cost of CO2 emissions plays an important role in calculating the optimal policy, but unlike the high volume parts of the road network, in the case of low volume roads, a substantial part of total emissions is related to the production and placement of new pavement layers, rather than from vehicle emissions.This is the peer-reviewed version of the article: Ćirilović-Stanković, J., Mladenović, G.,& Queiroz, C.. (2019). Impact of CO2 Emissions on Low Volume Road Maintenance Policy: Case Study of Serbia. in Transportation Research Record
Sage Publications Inc, Thousand Oaks., 2673(12), 747-755
Repair of cracks detected in cast components of vertical Kaplan turbine rotor hub
Get PDFDuring the revitalization of the hydroelectric generating station A4 at the hydro power plant 'Djerdap 1', all of its parts are subjected to non-destructive testing. Cracks are detected in cast part of generator rotor hub, in the flange area toward the turbine shaft. Cracks were 10-500 mm long (determined by magnetic particle tests) and 60-100 mm deep (ultrasonic tests). The generator rotor hub is made of cast steel 25L, in accordance with the standard 977-75. The welding/surface welding repair technology in the detected crack zones of the cast part of generator rotor hub includes a large number of details, due to the structural solution and generator rotor function in service. It was also necessary to provide the carefully undertaken activities in order to enable safe operation and continuous use of the rotor hub. Failing to notice, underestimation or incorrect perception of important details could cause significant problems in hydroelectric generating station operation. The paper, due to specifics of reparation technology, contains arranged preparatory activities for the procedure apart from the welding/surface welding technology. It is of importance to mention a huge amount of money savings, The manufacture of a new generator rotor would cost over 4 million EUR (generator mass is over 300 tonnes), not taking into account the time needed for its making (6-12 months), which is directly related to the amount of energy a hydroelectric generating station can produce during that period. This technology of repair welding is also applicable for other components and structures of the turbine and the hydromechanical equipment subjected to various causes of damage during exploitation
Buckling resistance of stainless steel angle column
Get PDFA numerical study of compressive capacities of stainless steel angle columns is presented in the paper in order to assess the design procedures presented in Eurocode 3. The study focuses on pin-ended hot-rolled equal angle columns made of austenitic stainless steel grade EN 1.4301. The study shows that the implementation of buckling curve b, used for the design of carbon steel hot-rolled angles, gives higher and unsafe buckling resistance of equivalent stainless steel angles in low and intermediate slenderness domains in comparison with numerical results
Integrated LCA and LCCA network level pavement maintenance model
No full textPavement management systems tend to lead to sound decision making regarding the optimal maintenance strategy which is, in most cases, based on the achievement of minimal total society costs which are defined as the sum of user cost and road agency cost. In the last several years, in addition to the user cost related to the costs of gasoline or diesel fuel, motor oil, spare parts, pneumatics, costs related to travel time and accidents, costs related to environmental impacts have been also considered as significant contributors to overall costs. The objective of this paper is to present a model that integrates Life Cycle Assessment (LCA) and Life Cycle Cost Analysis (LCCA), on a network level. The model has been applied on the national road network of Serbia. The results show how this integrated approach leads to more sound decision making compared with current state of practice
