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oa Civil Engineer in South Africa - Die dinamiese gedrag van 'n spoorbaanmodel onder stadigwiegende vertikale laste : technical paper

 

Abstract

'n Verwronge tiende-skaal laboratorium-model is van 'n spoorbaanstruktuur gebou ten einde 'n lineere twee-dimensionele analitiese model wat gebaseer is op die Abaqus eindige element pakket, uit te toets. Die struktuur word belas deur 'n bewegende dubbel-asvoertuig met 'n geveerde massa wat in die vertikale vlak sonder enige wip kan ossileer. Die fondament bestaan uit 'n ballaslaag en 'n ondergrond met beperkte diepte. Alle fondamentlae is van polimere en is as homogeen en isotropies beskou.


Die primere doel van die lineere model was om vir eers 'n basiese begrip van die gedrag van so 'n struktuur te verkry alvorens meer gesofistikeerde modelle aangepak word.
Daar is gevind dat vlakvervormingselemente met diktes wat met diepte toeneem en wat diefondamentlae indie analitiese model voorstel, die werklike gedrag van die fisiese model redelik bevredigend naboots. Die elastisiteitsmoduli van die materiale in die fondamentlae kan egter nie sonder meer deur konvensionele eenassige toetse bepaal word nie, maar dit moet geskied onder toeslande en randvoorwaardes soortgelyk aan die van die fisiese struktuur.
Vervormings in die fondament as gevolg van lae-frekwensie dinamiese laste kan vir alle praktiese doeleindes deur 'n kwasi-statiese ontleding bepaal word, met ander woorde 'n statiese hantering van die dinamiese probleem.
Die maalbeweging wat 'n dwarsleer uitvoer as 'n voertuig daaroor beweeg, word duidelik deur die dinamiese analitiese model gedemonstreer.

A distorted one-tenth scale laboratory model of a railway track structure was built in order to verity a linear two-dimensional analytical model based on the Abaqus finite element code. The structure was loaded with a moving double-axled vehicle with a sprung mass oscillating in the vertical plane without any pitching. The foundation consisted of a ballast layer and supporting base, all made of polymers that were assumed to be homogenous and isotropic.


The primary purpose of the linear model was to obtain a basic understanding of the behaviour of such a structure prior to establishing more sophisticated models.
Plane strain elements with thicknesses increasing with depth and presenting the foundation structure simulated the behaviour of the physical model reasonably well, provided the moduli of elasticity were not determined by conventional uni-axial tests, but under general and boundary conditions similar to those of the physical structure.
Strains in the foundation due to low-frequency dynamic loads can for all practical purposes be determined by a quasi-static analysis, ie a statical treatment of the dynamic problem.
The milling action of a sleeper as a vehicle passes over it is clearly demonstrated by the dynamic analytical model.

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/content/civeng1/32/2/EJC25095
1990-02-01
2016-12-05
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