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1.
OJAČITEV NEVEZANIH NOSILNIH SLOJEV VOZIŠČNIH KONSTRUKCIJ S PROSTORSKO MREŽNO STRUKTURO TRAKOV
Samo-Peter Medved, 2016, doktorska disertacija

Opis: Voziščne konstrukcije so najpomembnejši element vsake prometnice in tisti del, od katerega je najbolj odvisna varnost, in nivo uporabe prometnice. Prav tako je element, ki pomeni bistven investicijski element pri vsaki gradnji prometnice in element, v katerega se največkrat posega, vzdržuje, obnavlja … Čeprav se zdi, da gre za enostavno konstrukcijo, tako po izboru materialov, tehnologiji gradnje kot matematičnemu modelu za analizo konstrukcije, pa v praksi vse do danes nismo uspeli učinkovito rešiti probleme trajnih deformacij voziščnih konstrukcij. Kljub razvoju materialov v zadnjem obdobju, vsaj kar se tiče vezanih nosilnih plasti, pa problemi voziščnih konstrukcij ostajajo enaki, malo je inovativnih rešitev in modelov. Nevezane nosilne plasti imajo izrazito slabost, da niso sposobne prevzeti nateznih napetosti v horizontalni ravnini. Zaradi tega prihaja do plastičnih deformacij, ki se posledično prenašajo na površino vozišča v obliki razpok in kolesnic. Kljub preoblikovanju naravnega kamnitega materiala in dodajanjem veziv, se še posebej pri preobremenitvah ali poslabšanih hidrogeoloških pogojih naravnih temeljnih tal, ne moremo izogniti vertikalnim deformacijam vozišča, ki so posledica prekomernih horizontalnih napetosti v nevezanih plasteh voziščne konstrukcije. Reševanje z uporabo ojačitvenih mrež (geomrež) v horizontalnem nivoju nevezanih nosilnih plasti, ne da želenih rezultatov, saj prihaja do strižnih deformacij med nivoji ojačitev. V zadnjih letih pa vse do danes, je ideja doživela velik razvoj v smeri 3D struktur vertikalno nameščenih trakov - geocelic. Vezane deformabilne obrabno-nosilne plasti v kombinaciji z geocelicami ojačenimi nevezanimi nosilnimi plastmi zemljin predstavljajo učinkovit inovativen sistem voziščne konstrukcije, ki s svojo sestavo zagotavlja trajno elastičnost, fleksibilnost in zadostno nosilnost same konstrukcije. Eksperimentalna analiza je pokazala bistveno izboljšanje nosilnosti in zmanjšanje deformacij z uporabe mrežne strukture vertikalnih trakov geocelic. Uporabljen material za takšno strukturo, pa je lahko v celoti uporabljen iz recikliranih sintetičnih materialov, kar je z uporabo lokalnih gradbenih materialov lahko tudi pomemben prispevek ekološki gradnji, manjši porabi energije in zmanjšanju emisij v okolje.
Ključne besede: voziščne konstrukcije, geocelice, geosintetiki, nevezani nosilni sloji, fleksibilne voziščne konstrukcije, ojačitev, mrežna struktura, trakovi, prodi
Objavljeno: 18.07.2016; Ogledov: 667; Prenosov: 71
.pdf Celotno besedilo (10,95 MB)

2.
DOLOČITEV BREZDIMENZIJSKEGA FAKTORJA ZA DIMENZIONIRANJE ARMIRANE VOZIŠČNE KONSTRUKCIJE PO TSC
Mitja Picej, 2016, magistrsko delo

Opis: Magistrsko delo predstavlja določitev brezdimenzijskih faktorjev armiranja voziščnih konstrukcij z geomrežo s pomočjo dveh ločenih metod za dimenzioniranje asfaltiranih in neasfaltiranih voziščnih konstrukcij, ojačanih z geomrežo. Predstavljena je metoda dimenzioniranja voziščnih konstrukcij po TSC in način, kako bi lahko pripadajoč brezdimenzijski faktor armiranja vključili v postopek dimenzioniranja po TSC. Opisani so postopki za pridobitev ključnih parametrov, ki so potrebni pri dimenzioniranju voziščnih konstrukcij.
Ključne besede: gradbeništvo, voziščna konstrukcija, dimenzioniranje, brezdimenzijski faktor, armiranje, geomreža, nevezana nosilna plast, metode, TSC
Objavljeno: 12.10.2016; Ogledov: 505; Prenosov: 79
.pdf Celotno besedilo (2,86 MB)

3.
Piezoelektrične voziščne konstrukcije
Matija Ploh, 2018, magistrsko delo

Opis: V magistrskem delu so prikazani postopki dimenzioniranja voziščne konstrukcije z uporabo tehničnih specifikacij za ceste in pridobitev vseh parametrov za dimenzioniranje. Opisane so tudi tri posebne vrste energijskih cest, ki ustvarjajo električno energijo: termoelektrične, solarne in piezoelektrične. Pri termoelektrični voziščni konstrukciji se spremeni dimenzioniranje, pri solarni voziščni konstrukciji se spremenijo vozne lastnosti in dimenzioniranje, medtem ko pri piezoelektričnih voziščnih konstrukcijah tako dimenzioniranje kot vozne lastnosti ostanejo enake. V nadaljevanju je predstavljena analiza uporabe piezoelektrične voziščne konstrukcije. Ta se izvede z uporabo piezoelektričnega materiala, vgrajenega v obrabni sloj voziščne konstrukcije. Piezoelektrični material se pri obremenitvi vozila deformira in s tem ustvarja električno energijo. Analiza je opravljena z uporabo dveh metod – kolesne sledi in uteži. Predstavljeni so rezultati meritev in analize z oceno upravičenosti, na podlagi česar je ugotovljeno, da pridobljena energija ni dovolj velika, ker so stroški gradnje previsoki, zatorej se naložba po desetih letih ne povrne.
Ključne besede: dimenzioniranje, voziščne konstrukcije, laboratorijska analiza, piezoelektrični učinek, piezoelektrika
Objavljeno: 28.03.2018; Ogledov: 181; Prenosov: 31
.pdf Celotno besedilo (3,83 MB)

4.
Cyclic liquefaction potential of lacustrine carbonate from Julian Alps
Bojan Žlender, Stanislav Lenart, izvirni znanstveni članek

Opis: This paper presents the liquefaction studies of lacustrine carbonate silt from the Julian Alp landslide Stože. Geological conditions of the region and geomechanical characteristics of the ground were investigated. The research project was performed with the intention to determine the effects of cyclic loading on lacustrine carbonate silt. Investigation with 77 cyclic triaxial tests was performed on universal triaxial apparatus Wykeham Farrance UP 100 TR, in the Laboratory of soil mechanics, Faculty of Civil Engineering, University of Maribor. The essential equipment comprises cylindrical triaxial apparatus with a cell, a press with appurtenant electro-mechanic equipment, measuring equipment, and computer hardware and software equipment. Specimens with dimensions of height = 140 mm and diameter = 70 mm were saturated, then subjected to the arbitrary initial isotropic stress state and consolidated with vertical and radial draining, and then loaded with distortional loading of chosen dynamical axial force (frequency f = 1 Hz). A set of tests with a spectrum of different stress states and cyclic loading were performed. This research showed that lacustrine carbonate silt is a highly sensitive material.The resistance to liquefaction was somewhat higher than that of typical clean sand, but a perceivable excess pore pressure generation, which causes the decrease of strength parameters, was noticed. Test results of cyclic triaxial tests indicate dynamic characteristics of lacustrine carbonate silt and wide applicability of the test method.
Ključne besede: civil engineering, geomechanics, soil investigations, lacustrine carbonate silt, cyclic triaxial tests, liquefaction potential, shear modulus, damping ratio, cyclic stress ratio, pore pressure ratio
Objavljeno: 15.05.2018; Ogledov: 132; Prenosov: 6
.pdf Celotno besedilo (1,53 MB)

5.
The response of saturated soils to a dynamic load
Stanislav Lenart, 2008, izvirni znanstveni članek

Opis: This paper presents the two most significant types of deformation behavior fordynamically loaded, saturated soil. Flow liquefaction and cyclic mobility deserve special attention because of the large deformations that accompany these two phenomena. The submergence of a railway-line embankment due to the newly built Sava-river accumulation reservoir in Boštanj and the large landslide that occurred in the Stože area in the Julian Alps are case histories in Slovenia where flow liquefaction and cyclic mobility were analyzed. The dynamic loading caused by railway traffic and possible seismic activity were taken into account. Material from these two sites, silty sand and lacustrine carbonate silt, were used in extensive laboratory research, with the objective to define a procedure for excess pore-water pressure-generation modeling in dynamically loaded saturated soil. It has been found recently that the change of the pore-water pressure is related to the dissipated energy density calculated from the hysteresis loops caused by dynamic loading. Based on the experimental results an empirical equation defining the generation of pore pressure during dynamic loading has been proposed. The equation is divided into two parts: the first part describing the residual pore-water pressure generation, and the second part describing the increment and decrement of pore-water pressure within the load cycle, the so-called temporary pore-water pressure change. The proper effective stresses and thus the stress path of the dynamically loaded soil can be defined by using the proposed energy-based numerical model. The proposed pore-pressure model can also be used in deformation-behavior modeling. It was observed from the experimental results that after a few cycles of dynamic loading the saturated soil starts to exhibit a very low stiffness at the beginning of a load cycle, after which it begins to strengthen. The strain developed during this softening phase represents the main share of the total strain. The occurrence and duration of this phase are related to the energy dissipated during the cyclic loading as well, and the relation between the dissipated energy, the excess pore pressure and the short-term flow during cyclic mobility, give us an opportunity for a simple response modeling of the dynamically loaded saturated soils.
Ključne besede: flow liquefaction, cyclic mobility, excess pore pressure, dissipated energy
Objavljeno: 05.06.2018; Ogledov: 39; Prenosov: 5
.pdf Celotno besedilo (370,70 KB)

6.
Soil liquefaction in the Tone river basin during the 2011 earthquake off the Pacific coast of Tohoku
Stanislav Lenart, Junichi Koseki, Yukika Miyashita, 2012, izvirni znanstveni članek

Opis: A brief report about the liquefaction damage in the Tone river basin, caused by the 2011 earthquake off the Pacific coast of Tohoku, is presented. It includes sand boiling, damage to river dikes, the settlement and tilt of superstructures, the uplift of light underground structures and lateral spreading. A history of land reclamation along the Tone river is briefly presented to understand why extensive liquefaction took place predominantly inreclaimed land. The recorded ground motions near the river were analyzed andcompared to near-source ground motions. The effects of the site location and the ground conditions during the peak ground acceleration are discussed.
Ključne besede: 2011 earthquake off the Pacific coast of Tohoku, liquefaction, case history
Objavljeno: 13.06.2018; Ogledov: 82; Prenosov: 5
.pdf Celotno besedilo (1,65 MB)

7.
Modeling of a geocell-reinforced pavement
Samo Peter Medved, Bojan Žlender, Stanislav Lenart, Primož Jelušič, 2016, izvirni znanstveni članek

Opis: This article details how the serviceability of a flexural pavement structure is improved by incorporating the Cellular Confinement System (geocells). For this purpose, two different pavement structures, with and without embedded geocells, were manufactured in a laboratory and an accelerated traffic type of loading was applied. The vertical and horizontal cyclic loads were applied simultaneously to simulate the effect of principal stress rotation. A comparative study between the conventional flexible pavement and the geocell-reinforced flexible pavement is presented. Additionally, numerical models of the laboratory tests were built and the results were compared. The simulation of the experimental tests using the Traffic Load Simulator (TLS) are carried out using the FEM and advanced models that describe the permanent strain behavior of the unbound granular material. The development of permanent deformation within the pavement structure, with and without the geocells, is also presented through the numerical model, which was verified by the experimental results.
Ključne besede: flexible pavement, reinforcement, geocell, traffic load simulator, permanent deformation, numerical modeling
Objavljeno: 18.06.2018; Ogledov: 28; Prenosov: 5
.pdf Celotno besedilo (1,39 MB)

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