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Decision making between hybrid and in-situ concrete construction in South AfricaLombard, Adele 12 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: A construction method that proves to be the best today will not necessarily be the best method for
application in 20 years. Therefore, with changing circumstances, engineers have to consider all
the options before selecting a specific method. Options that are weighed in this study are in-situ
concrete construction and hybrid concrete construction.
Hybrid concrete construction is the combination of in-situ and precast concrete in structures, with
the purpose to exploit the advantages of each to its full potential. This construction method gained
popularity in the United States and in Europe due to its distinctive benefits. However, the increase
of its application in some countries (including South Africa) has been slow and possible reasons for
this are investigated in this study. With the intention of improving the South African construction
industry, a model is developed for decision making between hybrid concrete construction and insitu
concrete construction.
The main purpose of a larger research project is to assist project teams in the decision making
between precast concrete and in-situ concrete in building construction projects. This decision
making is not based on decision making models with mathematical output, since the decision of a
construction method is influenced by many variables that may not all be quantifiable.
Consequently, instead of prescribing a decision making method, the relevant information is to be
provided for the decision maker. The aim of this study is to identify the relevant parameters and to
set a framework for further in depth investigation by subsequent theses.
A decision making process in any field normally involves having a list of advantages and
disadvantages of the different options. Therefore this study includes the following managerial
discussion topics: factors that influence hybrid concrete construction, as well as benefits, barriers
and other aspects to consider, structural systems and elements, decision making methods and
important factors that will be the basis of the decision making process.
Traditionally the most important factors for decision making between construction methods were
construction cost and duration, but more recently sustainability is becoming increasingly important.
It is the civil duty of all parties involved in a project to foresee that most of the criteria of
sustainability are met. Sustainability covers all the aspects of economic, social and environmental
impacts. Furthermore quality is identified as an important aspect in the decision making process
for a construction method. The comparison of precast and in-situ concrete construction is
therefore discussed, considering all the abovementioned criteria and investigating possible
quantification methods. This information, together with information from future studies, would then
allow the project team to consider each aspect involved in the decision making process. / AFRIKAANSE OPSOMMING: Die beste konstruksiemetode vandag sal nie noodwendig die beste metode oor 20 jaar wees nie.
Met veranderende omstandighede, moet ingenieurs altyd al die moontlike opsies oorweeg voordat
‘n spesifieke konstruksiemetode gekies word. Opsies wat in hierdie studie bestudeer word, is in-situ betonkonstruksie en hibriede betonkonstruksie. Hibriede betonkonstruksie is die kombinasie van in-situ en voorafvervaardigde beton elmente in strukture, ten einde die voordele van elke metode ten volle te benut. As gevolg van sy voordele,
het hierdie konstruksiemetode al hoe meer gewild geraak in Amerika en Europa. Nietemin is die
toename in die gebruik van hierdie metode in sommige lande (insluitend Suid-Afrika) traag en
moontlike redes hiervoor word in hierdie studie ondersoek. Met die voorneme om die Suid-
Afrikaanse konstruksie-industrie te bevorder, is ‘n model vir besluitneming tussen hibriede
betonkonstruksie en in-situ betonkonstruksie ontwikkel. Die hoofdoel van ‘n groter navorsingsprojek is om projekspanne te help met die besluitneming
tussen voorafvervaardigde en in-situ beton in konstruksieprojekte vir geboue. Hierdie besluitneming is nie gebaseer op besluitnemingsmodelle wat wiskundige resultate lewer nie, want
die keuse van ‘n konstruksiemetode word deur te veel veranderlikes, wat nie altyd kwantifiseerbaar
is nie, beïnvloed. Gevolglik word relevante inligting aan die besluitnemer verskaf, eerder as om ‘n
gekwantifiseerde besluitnemingsmetode voor te skryf. Die doel van hierdie studie is om relevante
aspekte te identifiseer en om ‘n raamwerk te skep vir verdere, in diepte studies van volgende
tesisse. ‘n Besluitnemingsproses in enige veld word gewoonlik gebaseer op ‘n lys van voordele en nadele
van die verskillende opsies. Daarom sluit hierdie studie die volgende bestuursaspekte in: faktore
wat hibriede betonkonstruksie beïnvloed, asook voordele, beperkings en ander aspekte om te
oorweeg, strukturele sisteme en –elemente, besluitnemingsmetodes en belangrike faktore wat die
basis van die besluitnemingsproses sal wees. Tradisioneel was die belangrikste faktore vir besluitneming tussen konstruksiemetodes die koste
en tydsduur daaraan verbonde, maar deesdae word volhoubaarheid al hoe meer belangrik geag.
Dit is die plig van alle persone betrokke by ‘n projek om te sorg dat die projek aan so veel as
moontlik van die kriteria van volhoubaarheid voldoen. Volhoubaarheid sluit al die aspekte van
ekonomiese-, sosiale- en omgewingsimpakte in. Verder is kwaliteit ook geϊdentifiseer as ‘n
belangrike aspek in die besluitnemingsproses van ‘n konstruksiemetode. Die vergelyking van
voorafvervaardigde- en in-situ betonkonstruksie word dus bespreek met die oog op al die
bogenoemde kriteria en, sover moonlik, word die kwantifisering van hierdie aspekte ondersoek. Met hierdie inligting en die inligting van toekomstige studies, kan die projekspan dan elke aspek in
die besluitnemingsproses oorweeg.
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Mechanical properties of fly ash/slag based geopolymer concrete with the addition of macro fibresRyno, Barnard 12 1900 (has links)
Thesis (MEng) -- Stellenbosch University, 2014. / ENGLISH ABSTRACT: Geopolymer concrete is an alternative construction material that has comparable mechanical
properties to that of ordinary Portland cement concrete, consisting of an aluminosilicate and
an alkali solution. Fly ash based geopolymer concrete hardens through a process called
geopolymerisation. This hardening process requires heat activation of temperatures above
ambient. Thus, fly ash based geopolymer concrete will be an inadequate construction material
for in-situ casting, as heat curing will be uneconomical.
The study investigated fly ash/slag based geopolymer concrete. When slag is added to the
matrix, curing at ambient temperatures is possible due to calcium silicate hydrates that form
in conjunction with the geopolymeric gel.
The main goal of the study is to obtain a better understanding of the mechanical properties of
geopolymer concrete, cured at ambient temperatures. A significant number of mix variations
were carried out to investigate the influence that the various parameters, present in the matrix,
have on the compressive strength of fly ash/slag based geopolymer concrete. Promising
results were found, as strengths as high as 72 MPa were obtained. The sodium hydroxide
solution, the slag content and the amount of additional water in the matrix had the biggest
influence on the compressive strength of the fly ash/slag based geopolymer concrete.
The modulus of the elasticity of fly ash/slag based geopolymer concrete did not yield
promising results as the majority of the specimens, regardless of the compressive strength,
yielded a stiffness of less than 20 GPa. This is problematic from a structural point of view as
this will result in large deflections of elements. The sodium hydroxide solution had the most
significant influence on the elastic modulus of the geopolymer concrete. Steel and polypropylene fibres were added to a high- and low strength geopolymer concrete
matrix to investigate the ductility improvement. The limit of proportionality mainly depended
on the compressive strength of the geopolymer concrete, while the amount of fibres increased
the energy absorption of the concrete. A similar strength OPC concrete mix was compared to
the low strength geopolymer concrete and it was found that the OPC concrete specimen
yielded slightly better flexural behaviour. Fibre pull-out tests were also conducted to
investigate the fibre-matrix interface. From the knowledge gained during this study, it can be concluded that the use of fly ash/slag
based geopolymer concrete, as an alternative binder material, is still some time away as there
are many complications that need to be dealt with, especially the low modulus of elasticity.
However, fly ash/slag based geopolymer concrete does have potential if these complications
can be addressed. / AFRIKAANSE OPSOMMING: Geopolimeerbeton is ‘n alternatiewe konstruksiemateriaal wat vergelykbare meganiese eienskappe
met beton waar OPC die binder is, en wat bestaan uit ‘n aluminosilikaat en ‘n alkaliese oplossing.
Vliegas-gebaseerde geopolimeerbeton verhard tydens ‘n proses wat geopolimerisasie genoem word.
Hierdie verhardingsproses benodig hitte-aktivering van temperature hoër as dié van die onmiddellike
omgewing. Gevolglik sal vliegas-gebaseerde geopolimeerbeton ‘n ontoereikende konstruksiemateriaal
vir in situ gietvorming wees, aangesien hitte-nabehandeling onekonomies sal wees.
Die studie het vliegas/slagmentgebaseerde geopolimeerbeton ondersoek. Wanneer slagment by die
bindmiddel gevoeg word, is nabehandeling by omliggende temperature moontlik as gevolg van
kalsiumsilikaathidroksiede wat in verbinding met die geopolimeriese jel vorm.
Die hoofdoel van die studie was om ‘n beter begrip te kry van die meganiese eienskappe van
geopolimeerbeton, wat nabehandeling by omliggende temperature ontvang het. ‘n Aansienlike aantal
meng variasies is uitgevoer om die invloed te ondersoek wat die verskeie parameters, aanwesig in die
bindmiddel, op die druksterkte van die vliegas/slagmentgebaseerde geopolimeerbeton het. Belowende
resultate is verkry en sterktes van tot so hoog as 72 MPa is opgelewer. Daar is gevind dat die
sodiumhidroksiedoplossing, die slagmentinhoud en die hoeveelheid water in die bindmiddel die
grootste invloed op die druksterkte van die vliegas/slagmentgebaseerde geopolimeerbeton gehad het.
Die styfheid van die vliegas/slagmentgebaseerde geopolimeerbeton het nie belowende resultate
opgelewer nie. Die meeste van die monsters, ongeag die druksterkte, het ‘n styfheid van minder as 20
GPa opgelewer. Vanuit ‘n strukturele oogpunt is dit problematies, omdat groot defleksies in elemente
sal voorkom. Die sodiumhidroksiedoplossing het die grootste invloed op die styfheid van die
vliegas/slagmentgebaseerde geopolimeerbeton gehad. Staal en polipropileenvesels is by ‘n hoë en lae sterke geopolimeer beton gevoeg om die buigbaarheid
te ondersoek. Die die maksimum buigbaarheid het hoofsaaklik afgehang van die beton se druksterkte
terwyl die hoeveelheid vesels die beton se energie-opname verhoog het. ‘n OPC beton mengsel van
soortgelyke sterkte is vergelyk met die lae sterkte geopolimeerbeton en daar is gevind dat die OPC
beton ietwat beter buigbaarheid opgelewer het. Veseluittrektoetse is uitgevoer om die veselbindmiddel
se skeidingsvlak te ondersoek.
Daar kan tot die gevolgtrekking gekom word dat, alhoewel belowende resultate verkry is, daar steeds
sommige aspekte is wat ondersoek en verbeter moet word, in besonder die styfheid, voordat
geopolimeerbeton as ‘n alternatiewe bindmiddel kan optree. Volgens die kennis opgedoen tydens hierdie studie, kan dit afgelei word dat die gebruik van
vliegas/slagmentgebaseerde geopolimeerbeton, as 'n alternatiewe bindmiddel, nog 'n geruime tyd weg
is, as gevolg van baie komplikasies wat gehandel moet word, veral die lae elastisiteitsmodulus. Tog
het vliegas/slagmentgebaseerde geopolimeerbeton potensiaal as hierdie komplikasies verbeter kan
word.
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Analysis of curved bridge decks陳國煌, Chan, Kwok-wong. January 1969 (has links)
published_or_final_version / Civil Engineering / Master / Master of Science in Engineering
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464 |
Ultimate strength and deformation of rectangular prestressed concrete beams subjected to combined bending and shear鍾鴻穩, Chung, Hung-wan. January 1963 (has links)
published_or_final_version / Civil Engineering / Master / Master of Science in Engineering
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The effect of composite action on the behaviour of space structuresEl-Sheikh, Ahmed Ibrahim January 1991 (has links)
No description available.
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466 |
Ferrocement structures : constitutive relations, non-linear finite element analysis, and analogy with reinforced concretePrakhya, Ganga Kasi Viswanadha January 1989 (has links)
No description available.
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467 |
Constitutive relations for finite element analysis of tension stiffening in reinforced concreteLam, W-K. F. January 1987 (has links)
No description available.
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468 |
The effect of carboxylated acrylic polymer latices on the hydration kinetics of ordinary Portland cementDennington, Simon P. J. January 1997 (has links)
No description available.
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469 |
Pore pressure in concrete : theory and triaxial testsLi Kim Mui, S. T. January 1987 (has links)
No description available.
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470 |
Water flow into unsaturated concretePeer, Leslie B. B. January 1990 (has links)
No description available.
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