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Prediction of the pile behaviour under dynamic loading using embedded strain sensor technology
Andrej Štrukelj, Mirko Pšunder, Helena Vrecl-Kojc, Ludvik Trauner, 2009, izvirni znanstveni članek

Opis: A standard dynamic loading test of the pile was performed on the highway section Slivnica - Hajdina near Maribor, Slovenia. Parallel to standard testing procedures the new monitoring technology based on specially developed strain sensors installed inside the pile body along the pile axis was introduced. On the basis of the measured results the normal strains along the pile axis were measured. Taking into consideration the elastic modulus of the concrete the normal stresses in the axial direction of the pile were also calculated and afterwards the shear stresses along the pile shaft have been estimated as well as the normal stresses below the pile toe. The estimation was made by considering a constant value for the pile diameter. The measured results were also compared with the computer simulation of the pile and the soil behaviour during all the successive test phases. The strain measurements inside the pile body during the standard dynamic loading test in present case did not have the purpose of developing an alternative method of pile loading tests. The presented monitoring technology proved itself as a very accurate and consistent. It gave in the first place the possibility of a closer look at the strains and stresses of the most unapproachable parts of different types of concrete structure elements especially piles and other types of deep foundations.
Ključne besede: piles, deep foundations, dynamic loading test, strain measurement technologies, elasto-plastic modelling, finite-element method
Objavljeno v DKUM: 06.06.2018; Ogledov: 998; Prenosov: 74
.pdf Celotno besedilo (780,04 KB)
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Analyses of the suspended-load sedimentation process and its dynamics in reservoirs with high daily oscillations
Helena Vrecl-Kojc, Bojana Dolinar, Roman Klasinc, Ludvik Trauner, 2008, izvirni znanstveni članek

Opis: The river water pumped into reservoirs with high daily oscillations, e.g. at pumping hydroelectric power plants, contains different amounts of suspended load depending on the time period and the riverćs discharge. This paper presents an analysis of the suspended-load sedimentation process that is based on the interaction between the sedimentation, i.e., the settling, velocity and the motion of the water. The settling velocity of spherical particles in the presence of a buoyancy force is a function of the particle size. Laboratory investigations of the suspended material from the river-watersamples have determined the ratio between the particle size and the concentration of suspended material with respect to the river discharge, the ratio between the concentration of suspended material in the water and the discharge, and the relationship between the concentration of suspended material and the discharge of water, which is for the first time expressed as an exponential function. The motion of the water in the reservoirs with high daily oscillations is solved by the three-dimensional modeling of the liquid streams. The evaluation of the results is presented for the case of the planned Kozjak pumping hydroelectric power plant on the River Drava.
Ključne besede: suspended load, water motion, sedimentation, sedimentation transport, pumped hydroelectric power plant, reservoir
Objavljeno v DKUM: 05.06.2018; Ogledov: 1632; Prenosov: 59
.pdf Celotno besedilo (348,17 KB)
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Analysis of concentration and sedimentation of suspended load in the reservoirs
Helena Vrecl-Kojc, Bojana Dolinar, Roman Klasinc, Ludvik Trauner, 2008, izvirni znanstveni članek

Opis: This paper deals with the sedimentation of suspended load in the reservoirs. As an example the reservoir of the hydroelectric power plant Boštanj on the Sava River is shown. The objective of the described studies was to determine the quantity and type of deposited material in the reservoir during the selected time period. For this purpose, the mineral and chemical composition, and the concentration and the particle size of the suspended load at the intake of the water into the reservoir and at its outflow were examined. In order to determine the concentration of the suspended load, 24 water samples from the area of the intake and outflow from the reservoir were taken. At the same time the discharge of the Sava River was measured. Solid particles were removed from the water with the help of sedimentation and in the final stage of water evaporation. The results of the studies showed that the concentration of the suspended material was changing in relation to the location and the flow rate of the water. This ratio can be described with an exponential function. In suspended load composition carbonates, muscovite/illite and quartz dominate; however, chlorite was also found, as well as small quantities of plagioclase and organic detritus. With regard to the size of the particles the examined samples are classified as silt. It was determined that the concentration of the suspended load, at the same flow rate of water, at the intake into the reservoir is larger than at the outflow. The difference is represented by the material that was sedimented in the reservoir due to the decreased speed of the water as a result of the river's impoundment. A comparison of the composition of the samples from both collection sites showed that at the outflow site of the water from the reservoir there is a somewhat smaller share of carbonate grains and heavy minerals than at the intake site, and a higher content of organic detritus and clay particles can also be observed. Considering the actual discharge of water in the period between July 2006 and July 2007 and the examined ratio between the flow rate of the water and the quantity of suspended and deposited material, the total quantity of sedimented material in this period was estimated.
Ključne besede: suspended load, sedimentation, sediment transport, water storage reservoir
Objavljeno v DKUM: 05.06.2018; Ogledov: 1680; Prenosov: 68
.pdf Celotno besedilo (348,17 KB)
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Determination of passive earth pressure using three-dimensional failure mechanism
Helena Vrecl-Kojc, Stanislav Škrabl, 2007, izvirni znanstveni članek

Opis: This paper presents a modified three-dimensional (3D) failure mechanism for determining the 3D passive earth pressure coefficient using the upper bound theorem within the framework of the limit analysis theory. The translational kinematically admissible failure mechanism generalized with a depth of h = 1.0 is considered in the analysis. The mechanism geometry presents a volume of rigid blocks composed of the central body and two lateral rigid bodies, which are connected by a common velocity field. The front surface of the central body interacts with the retaining wall, while the upper surface can be loaded by surcharge loading. The lateral body segments represent four- and three-sided polygons in the cross section of the central body; therefore, they define the polygonal failure surface of the central part. At the outer side, each segment of the lateral body is bounded by infinitesimally spaced rigid half-cones that describe the envelope of a family of half-cones. The numerical results of 3D passive earth pressure limit values are presented by non-dimensional coefficients of passive earth pressure influenced by the soil weight Kpg and a coefficient of passive earth pressure influenced by the surcharge Kpq. This research was intended to improve the lowest values obtained until now using the limit analysis theory. The results are presentedin a graphical form depending on the geometrical parameters and soil properties. A brief description of two world-recognized failure mechanisms based on the limit analysis approach, and the comparison of three failure mechanism results are also presented.
Ključne besede: soil mechanics, passive earth pressure, upper bound theorem, optimization, three-dimensional failure mechanism
Objavljeno v DKUM: 18.05.2018; Ogledov: 937; Prenosov: 54
.pdf Celotno besedilo (504,97 KB)
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The anchored pile wall optimization using NLP approach
Helena Vrecl-Kojc, 2005, izvirni znanstveni članek

Opis: The type of a retaining structure as well as the structure configuration mainly depends on geological conditions. If geological, urban and other data allow an alternative, the costs should also be considered as an important factor. In geotechnical practise, pile walls are especially used in excavations, in the erection of traffic facilities and in the sanitation of landslides. This paper is aimed at presenting economical differences between cantilever and anchoring pile walls and the impact of different parameters on costs. The optimization method, which uses mathematical programming, gives an optimal solution to geometry, self-manufacturing costs, and other characteristics of the structure in a uniform optimization process. This paper presents the optimization process using the nonlinear programming (NLP) approach for the anchored pile wall. The application presented only serves to confirm the effectiveness of the proposed optimization method. Therefore, the retaining structure is situated in homogeneous non-cohesive soil at three different soil friction angles of 35°, 30° and 25°. The generalized analytical method, the USA method, which was first introduced by Bowles [3], isused in the application. The analysis of the results shows the impact of parameters, the main controlling factors, configuration geometry and savings. The optimal results allowed from 18 up to 47 per cent savings compared to the cantilever pile wall depending on ground and structure input data and the excavation depth.
Ključne besede: civil engineering, optimum design, retaining structures, USA analytical method, nonlinear programming
Objavljeno v DKUM: 16.05.2018; Ogledov: 968; Prenosov: 59
.pdf Celotno besedilo (216,45 KB)
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Jernej Dolinšek, 2011, diplomsko delo

Opis: Diplomsko delo predstavlja splošen opis voziščne konstrukcije, sledi dimenzioniranje voziščne konstrukcije z uporabo tehničnih specifikacij za javne ceste ter izračun napetostno deformacijskega stanja v nevezani nosilni plasti. Izračun napetosti in deformacij izvedemo po metodi končnih elementov z uporabo geotehničnega programa Plaxis. Dobljene rezultate analiziramo in jih primerjamo z izmerjenimi rezultati na terenu. V drugem delu diplomske naloge so na praktičnem primeru uporabe murskih prodov prikazani rezultati laboratorijskih preiskav različnih mešanic murskega proda in s pomočjo matematičnih metod izračunane napetosti in deformacije. Rezultati pokažejo, da se z uporabo drobljenih prodov trajne deformacije v nevezani nosilni plasti bistveno zmanjšajo.
Ključne besede: voziščna konstrukcija, nevezana nosilna plast, prometna obremenitev, program Plaxis, dinamična obremenitev, tehnične specifikacije, trajne deformacije, napetostno stanje, metoda končnih elementov
Objavljeno v DKUM: 20.04.2011; Ogledov: 3332; Prenosov: 597
.pdf Celotno besedilo (3,51 MB)

Ivo Firbas, 2010, diplomsko delo

Opis: Diplomsko delo obravnava problematiko varovanja globokih gradbenih jam v mestnem središču, kjer se v neposredni bližini nahajajo visoki objekti. Narejena je tudi primerjava med 3D modelom izračunanem v programu Plaxis in projektom PZI ( projekt za izvedbo)po katerem je bilo varovanje izvedeno. Ker pa so stroški pomemben razlog pri odločitvi investitorja, katero možnost bo izbral, bo diplomsko delo obravnavalo problem izbire ugodnejše variante izmed izbranima možnostma na konkretnem primeru. Diplomsko delo se sestoji iz treh delov. V prvem delu diplomskega dela je podan splošni opis varovanja in problematike na območju globokih gradbenih jam v središču mesta Maribor in opisom zahtev in pravil za projektiranje le-teh. V drugem delu diplomskega dela so prikazani rezultati izračuna računalniškega 3D modela varovanja gradbene jame hotelsko poslovnega objekta Hotel City III, izračunanega s Plaxisom. Tretji del diplomskega dela pa je stroškovna in tehniška primerjava varovanja gradbene jame med samo izvedbo in prvotnim projektom.
Ključne besede: gradbeništvo, gradbene konstrukcije, zaščita globoke gradbene jame, geotehnično poročilo, benotto piloti, jet-grouting piloti, mikro piloti, 3D model, program Plaxis, geomehanska analiza, popis del, predračun, stroški, ekonomska analiza.
Objavljeno v DKUM: 21.12.2010; Ogledov: 3711; Prenosov: 524
.pdf Celotno besedilo (6,61 MB)

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