Thesis (MScEng)-- Stellenbosch University, 2013. / ENGLISH ABSTRACT: Concrete is used in most of the modern day infrastructure. It is a building material for which there
exist various design codes and guidelines for its use and construction. It is strong in compression, but
lacks tensile strength in its fresh and hardened states and, when unreinforced, fails in a brittle manner.
The structural use of synthetic fibres in concrete is investigated in this study to determine its effect on
enhancing the mechanical properties of concrete. Slabs on grade are used as the application for which
the concrete is tested. The material behaviour is investigated in parallel with two floor design theories.
These are the Westegaard theory and the Yield-Line theory. The Westegaard theory uses elastic
theory to calculate floor thicknesses while the Yield-Line theory includes plastic behaviour.
Conceptual designs are performed with the two theories and material parameters are determined from
flexural tests conducted on synthetic fibre reinforced concrete (SynFRC) specimens. Large scale slab
tests are performed to verify design values from the two theories.
Higher loads till first-crack were measured during tests with concrete slabs reinforced with
polypropylene fibres than for unreinforced concrete. It is found that the use of synthetic fibres in
concrete increases the post-crack ductility of the material. The Westegaard theory is conservative in
its design approach by over-estimating design thicknesses. This was concluded as unreinforced slabs
reached higher failure loads than predicted by this theory. The Yield-Line theory predicts design
thicknesses more accurately while still accounting for the requirements set by the ultimate- and
serviceability limit states. By using SynFRC in combination with the Yield-Line theory as design
method, thinner floor slabs can be obtained than with the Westegaard theory. / AFRIKAANSE OPSOMMING: Beton word gebruik as boumateriaal in meeste hedendaagse infrastruktuur. Daar bestaan verskeie
ontwerp kodes en riglyne vir die gebruik en oprig van beton strukture. Alhoewel beton sterk in
kompressie is, het beton ‘n swak treksterkte in beide die vars- en harde fases en faal dit in ‘n bros
manier indien onbewapen.
Die gebruik van sintetiese vesels in beton word in hierdie projek ondersoek om die invloed daarvan
op die eienskappe van die meganiesegedrag van beton te bepaal. Grond geondersteunde vloere word
as toepassing gebruik. Parallel met die materiaalgedrag wat ondersoek word, word twee ontwerpsteorieë
ook ondersoek. Dit is die teorie van Westegaard en die Swig-Lyn teorie. Die teorie van
Westegaard gebruik elastiese teorie in ontwerpsberekeninge terwyl die Swig-Lyn teorie ‘n plastiese
analise gebruik.
‘n Konseptuele vloerontwerp is gedoen deur beide die ontwerpsmetodes te gebruik.
Materiaalparameters is bepaal deur buig-toetse uit te voer op sintetiesevesel-bewapende beton.
Grootskaalse betonblaaie is gegiet en getoets om die akkuraatheid van die twee metodes te verifieer.
Die betonblaaie wat bewapen was met polipropileen vesels het groter laste gedra tot by faling as die
blaaie wat nie bewapen was nie. Die vesels verbeter die gedrag van beton in die plastiese gebied van
materiaalgedrag deurdat laste ondersteun word nadat die beton alreeds gekraak het. Die Westegaard
teorie kan as konserwatief beskou word deurdat dit vloerdiktes oorskat. Hierdie stelling is gegrond op
eksperimentele data wat bewys dat onbewapende betonblaaie groter laste kan dra as wat voorspel
word deur die Westegaard teorie. Die Swig-Lyn teorie voorspel ontwerpsdiktes meer akkuraat terwyl
daar steeds aan die vereistes van swigting en diensbaarheid voldoen word. Deur gebruik te maak van
sintetiese vesels en die Swig-Lyn teorie kan dunner betonblaaie ontwerp word as met die Westegaard
teorie.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/85877 |
| Date | 12 1900 |
| Creators | Bothma, Jacques |
| Contributors | Boshoff, W. P., Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | xiii, 103 p. : ill. |
| Rights | Stellenbosch University |
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