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Thermo-mechanical stability of FRP and FGM plates with geometrical imperfections using layer wise finite element
Get PDFOne of the ultimate limit state important for the safe design of structures is failure due to buckling. The origin of buckling, as the sudden change in shape of structural component, may arise from mechanical as well from thermal loading conditions. Apart from the loading conditions, the geometrical imperfections are another parameter important for the overall structural stability. In wish to fulfil the lack of thermo-mechanical stability solutions based on Layer Wise (LW) plate theories, which will be able to include general form of geometrical imperfection, this study presents the LW finite element for thermo-mechanical stability of geometrically imperfect FRP (Fibre reinforced polymer) and FGM (Functionally Graded Material) plates. The mathematical model, based on Layer wise theory of Reddy, assumes layer wise variation of in plane displacements and constant transverse displacement through the thickness, non-linear strain displacement relations and isotropic/orthotropic material properties. The material properties of FGM plates are assumed to be constant in xy-plane and vary through the thickness by a power law function in terms of the volume fraction of the constituents. The Koiter’s model for initial geometric imperfection is adopted. The principle of virtual displacement (PVD) is utilized to derive Euler-Lagrange differential equation of linearized buckling problem. The weak form is discretized using nine node Lagrangian isoparametric finite element. The original MATLAB computer program is coded for the finite element solution and used to study influence of plate thickness a/h, aspect ratio a/b, power low index, imperfection form and material properties on thermo-mechanical stability of FRP and FGM plates. The results are compared with the one from the literature
Importance of the global sensitivity analysis in development of metamodels for geotechnical back analysis
Get PDFThis paper investigates the use of global sensitivity analysis during the development of
metamodels for back-analysis of geotechnical problems. Variance-based global sensitivity analysis
was combined with Particle swarm optimization algorithm and POD-ERBF metamodel to backcalculate
the hypothetic (synthetic) problem of anchor-supported excavation. PLAXIS 2D FE code
was used for numerical simulations. The results of the back analysis for different sets of model
parameters were compared to emphasize the importance of global sensitivity analysis before
performing the back analysis and the recommendations for the robust modeling of presented
geotechnical problem were given
Klimatske promene i zemljani nasipi
Get PDFKlimatske promene negativno utiču na životnu sredinu, privredu, zdravlje i bezbednost
ljudi. Sa intenziviranjem klimatskih promena tokom 21. veka ugrožena je i geotehnička
infrastruktura. Poznavanjem trenutnih i budućih klimatskih trendova u Evropi i Srbiji i klimatskih
scenarija može se vršiti analiza i kvantifikacija rizika i odrediti uticaj na geotehničku
infrastrukturu. U takvoj analizi, neizvesnost je neizostavan deo, kao i nepouzdanost/varijabilnost
osnovnih ulaznih promenljivih. Analiza interakcije geotehničke infrastrukture sa atmosferom
podrazumeva modeliranje termo-hidro-mehaničkih procesa koji se odvijaju u tlu i koji su povezani
sa klimatskim i vegetacionim uslovima na površini tla. Termo-hidro-mehaničko sprezanje
predstavlja najnapredniji numerički pristup u analizi uticaja klimatskih promena na infrastrukturne
nasipe
Methodology for the formation and development of the database of retaining structures
Get PDFOne of the key problems that occurs in the management of the maintenance of state transport infrastructure facilities is the lack of systematized and updated information on the condition of the elements of infrastructure facilities such as the condition of embankments, bridges, tunnels, retaining structures etc. Systematized information enables rational, efficient maintenance, timely reactions that will reduce the risk of building failures and increase traffic safety. In addition, such an approach contributes to the optimization of the allocation of budget funds for that purpose and the rational use of available technical resources. Management of the maintenance process of retaining structures requires the formation of a unique (central) database that will record all retaining structures that meet the prescribed criteria for recording and systematically monitor their condition over time. This paper presents the methodology for the formation and development of a database of retaining structures, using examples of good practice.Српско друштво за путеве “Via Vita
Two types of the second Hankel determinant for the class U and the general class S
Get PDFIn this paper we determine the upper bounds of the Hankel
determinants of special type H2(3)(f ) and H2(4)(f ) for the general class
of univalent functions and for the class U
Nature based solutions as the sustainable measures for hydrometeorological risk reduction – the Tamnava river case study
Get PDFУ раду се даје кратак приказ холистичког приступа смањењу ризика од поплава помоћу природи блиских решења. Овакав приступ узима у обзир не само смањење ризика као основни циљ мера заштите од поплава, већ и друге циљеве заједнице као што су заштита животне средине, добробит и здравље људи и друштвено-економски развој. На примеру слива реке Тамнаве, а као резултат истраживачког рада у међународном пројекту RECONECT у оквиру H2020 програма ЕУ, приказују се прелиминарни резултати примене овог концепта уз разматрање неколико сценарија могућих мера заштите и користи које оне могу донети у погледу смањења ризика од поплава и унапређења екосистемских услуга на сливу. Приказана методологија укључује новчано вредновање ефеката мера са гледишта смањења ризика (избегнутих штета), као секундарних ефеката од смањења ерозије додатним пошумљавањем. Ово друго вредновање је такође искоришћено за прелиминарну процену свих релевантних екосистемских услуга на сливу, што указује на вредност природног капитала овог слива. Овакве процене су важне за процес доношења одлука о мерама заштите од поплава.This paper presents briefly a holistic approach to reducing flood risks using the nature-based solutions. This approach takes into account not only the reduced risk as the primary goal of flood mitigation, but also involves other goals such as the protection of the environment, human well-being, socio-economic goals etc. The Tamnava River basin is used as a pilot case to demonstrate the methodology of such an approach, resulting from the work within the RECONECT project from the EU Horizon 2020 programme. The paper presents preliminary results for the Tamnava River basin by considering several scenarios for flood mitigation measures and potential benefits from these measures in flood risk reduction and in improved ecosystem services in the basin. The methodology includes monetary valuation of the effects of the proposed flood mitigation measures in terms of the avoided damages, as well as of the secondary benefits from the erosion control by additional afforestation. The latter also provides basis for preliminary valuation of all relevant ecosystem services in the basin, thus indicating the value of the basin’s natural capital. Such an evaluation is important for the decision-making process on possible flood mitigation strategies.Рад је добио Награду за најбољи научни рад са Прве меморијалне научно-стручне конференције ,,Предраг Марић". Конференција је одржана 11.2.2022. године. у просторијама Института за међународну политику и привреду, Македонска 25, у Београду.
Годишњак Факултета безбедности 2022 (Faculty of Security Studies Annual), издавач Факултет безбедности Универзитета у Београду; адреса - Господара Вучића 50, Београд; обим 434 стране, штампани тираж 100 примерака, припрема и штампа ,,Чигоја штампа". Категорија часописа - M52.
UDK 556.166(282)(497.11)
COBISS.SR-ID 112460809
https://aseestant.ceon.rs/index.php/fb_godisnjak/article/view/37341/2267
Projektovanje mostova prema zahtevima životne sredine
Get PDFZaštita životne sredine nesumnjivo postaje primarni zadatak čovečanstva u 21. veku. Razvoj tehnologije i tehnike doneo je mnoge lagodnosti ljudima, ali istovremeno je negativno uticao na njihovu okolinu. U okviru ovoga rada predstavljen je uticaj mostovskih konstrukcija na životnu sredinu. Pregledom literature, utvrđeni su određeni negativni efekti kroz različite faze projekta, od izvođenja do sanacija konstrukcija mostova. Pokazani su rezultati primene koncepta Ocene životnog ciklusa (Life Cycle Assessment - LCA) u projektovanju mostova na određenim primerima. Studijom slučaja je prikazana mogućnost upotrebe integralnih mostova u smanjenju zagađenja životne sredine. U zaključnim razmatranjima, predstavljen je model uvođenja zahteva životne sredine u proces projektovanja i izvođenja
Airborne Laser Scanning to Digital Elevation Model – LAStools approach
Get PDFAirborne Laser Scanning (ALS) is one of the most popular and cost-effective approaches for collecting Digital Elevation Model (DEM) data. This especially applies to large areas, forested areas, areas with dense vegetation and urban environments. The ALS results in a vast amount of data in the form of point clouds. Successful use of such data requires applying semi-automatic and automatic approaches to classify points according to which objects or phenomena it represents. LAStools software package represents a set of highly efficient tools for processing ALS data. Through this study, the functionality of the LAStools software package for DEM generation has
been analyzed. The proposed procedure for generating DEM products from ALS point cloud with LAStools has been determined and presented. The study also focuses on the important parameters of each tool in the proposed DEM procedure, with a special focus on advantages and disadvantages, possibilities and limitations
Stability Calculation of the Plane Steel Frame Structures Using Tangent Modulus Theory
No full textThis paper considers the phenomenon of the instability of steel plane frame structures in the elastic-plastic domain. The numerical analysis uses FEM, where the corresponding stiffness matrices are based upon the trigonometric and hyperbolic interpolation functions of normal forces. The tangent modulus concept is applied when buckling occurs in the plastic range. Thus, the stiffness matrices for nonlinear material behavior are also derived. The procedure for determining effective length factors of compressed columns, which implies a global stability analysis of entire frames, is established too. It means that the proposed approach is based on the assumption that the collapse of the structure occurs when the most loaded columns reach their stability limit. So, the presented procedure enables the calculation of the real critical load of plane frame structures in the elastic-plastic domain and determines the corresponding effective length factors