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Creep and shrinkage prediction models for concrete water retaining structures in South AfricaMucambe, Edson Silva David 12 1900 (has links)
Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Concrete water retaining structures (WRS) in South Africa are under scrutiny due to
the numerous durability problems that they have experienced lately; despite the
efforts by local and national authorities in conserving these structures. At the heart of
these problems are the creep and shrinkage phenomena. While shrinkage is the
reduction of concrete volume with time, creep is defined as the time-dependent
increase of concrete strain under constant or controlled stress. Both phenomena are
affected by conditions to which WRS are exposed hence their accurate prediction is
required.
Numerical models have been developed to calculate the extent to which concrete
creeps or shrinks over time. The objective of this thesis is to identify which of these
models is better equipped to be used in South African WRS design. This is achieved
through a systematic method that involves an investigation into the contents of these
models and a statistical comparison of model calculations to WRS representative
data.
In partnership with reputable universities, a pioneer experimental creep and
shrinkage data base is created in this project from which the WRS related data is
selected. While investigating the contents of the numerical models, their applicability
to South African WRS is identified and the integrity of model contents is assessed.
Indeed, a few irregularities are found in the process and are presented in this thesis.
The model calculations are statistically compared to data in the form of individual
experiments as well as in the form of groups of experiments with similar concretes to
find the ideal prediction model for different types of concretes as well.
Also pioneered in this project is a weighted criteria and point system in which the
findings of the model content assessment and statistical evaluations are
incorporated. It is based on this system that conclusions are drawn and the most
suitable prediction model for WRS design in South Africa is selected.
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The occurrence and extent of collapse settlement in residual granite in the Stellenbosch areaGildenhuys, Nanine 12 1900 (has links)
Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Large areas of the earth’s surface are covered by soils that are susceptible to large
decreases in bulk volume when they become saturated. These soils are termed
collapsing soils and are very common in parts of the USA, Asia, South America and
Southern Africa. This study is concerned with the occurrence of these collapsible soils
in the residual granites of the Stellenbosch area. The study was undertaken as
relatively little is known about the collapse phenomenon in the problematic weathered
granites of the Western Cape. The majority of research thus far has been carried out
on the deep residual soils formed on basement-granite in the Transvaal areas, whereas
little attention has been paid to the Cape granites.
The aim of the study was achieved through the experimental work which included
double oedometer testing, indicator analyses and shear strength testing. Double
oedometer tests were performed to quantify the potential collapse settlement of the
soils from the demarcated study area. To provide a better understanding of the
collapse behaviour of the soils, indicator analysis, which included Atterberg limits
and particle size distributions, were performed. Direct shear tests were further carried
out on saturated and natural moisture content specimens to establish the effect of
collapsibility on shear strength and whether substantial additional settlement of the
saturated soils would occur during shear.
It was found that collapsible soils are prevalent in the demarcated study area as the
majority of soils showed a potential collapse settlement of 1% or more. Collapse
exceeding 5% were calculated in a few instances proving some soils to be highly
collapsible. The double oedometer and indicator analysis results were used in an
attempt to obtain a relationship between collapse settlement and a combination of
easily determined properties such as dry density (void ratio), moisture content and
grading, but no meaningful conclusions have emerged. The shear strength tests
indicated that a clear correlation does not exist between collapsibility and shear
strength. It was further established that a relationship between collapse settlement
determined during the double oedometer testing and the volume change during shear strength testing cannot be assumed. It can thus be concluded that soils can be very
unpredictable and further research on the collapse phenomenon is indicated. / AFRIKAANSE OPSOMMING: Groot dele van die aarde se oppervlakte is bedek deur grondtipes wat geneig is tot ‘n
afname in volume as dit deurweek word. Hierdie gronde word swigversakkende
gronde genoem en dit word algemeen teëgekom in dele van die VSA, Asië, Suid-Amerika en
Suider-Afrika. In hierdie studie word die voorkoms van swigversakkende
gronde in die residuele graniet in die Stellenbosch area ondersoek. Die studie is
onderneem aangesien relatief min i.v.m. die swigversakking-verskynsel in die
problematiese verweerde graniet van die Weskaap bekend is. Die meeste van die
navorsing sover is onderneem op die diep residuele gronde wat gevorm is op die
Argaïese graniet in die Transvaal gebied, en betreklik min aandag is geskenk aan die
Kaapse graniet.
Tydens die studie is eksperimente wat dubbele oedometer toetse, indikator analises,
en skuifsterkte toetse insluit, uitgevoer. Dubbele oedometer toetse is uitgevoer om die
potensiële swigversakking van die grond in die afgebakende studiegebied te
kwantifiseer. In ‘n poging om die swigversakking-verskynsel van die grond beter te
verstaan, is indikator analises wat Atterberg grense en partikel grootte verspreiding
insluit, uitgevoer. Direkte skuiftoetse is ook uitgevoer op deurweekte grondmonsters
en op monsters wat natuurlike vog bevat, om sodoende die effek van swigversakking
op skuifsterkte vas te stel en om uit te vind of aansienlike addisionele sakking van die
deurweekte gronde tydens skuif plaasvind.
Daar is gevind dat swigversakkende gronde die oorheersende grondtipe in die
afgebakende studiegebied is waar meeste van die gronde ‘n potensiële swigversakking
van meer as 1% toon. ‘n Swigversakking van meer as 5% is in ‘n paar gevalle
bereken, wat bewys dat sommige grondtipes hoogs versakkend is. Die resultate van
die dubbele oedometer en indikator analises is gebruik in ‘n poging om te bewys dat
daar ‘n verhouding bestaan tussen swigversakking en ‘n kombinasie van kenmerke
wat maklik vasgestel kan word soos droë digdheid (ruimte verhouding), voginhoud en
gradering, maar daar kon nie tot ‘n sinvolle slotsom gekom word nie. Die skuifsterkte
toetse toon dat daar nie ‘n duidelike korrelasie bestaan tussen swigversakking en
skuifsterkte nie. Daar is verder vasgestel dat dit nie moontlik is om te aanvaar dat daar ‘n verhouding bestaan tussen swigversakking soos vasgestel tydens die dubbele
oedometer toetsing, en die verandering in volume tydens skuifsterkte toetsing nie.
Daar is dus tot die slotsom gekom dat grond baie onvoorspelbaar kan wees en dat
verdere navorsing na die swigversakking-verskynsel nodig is.
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Downstream changes in river morphology as a result of dam developmentsBeck, Julia S. (Julia Samantha) 12 1900 (has links)
Thesis (MEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: A dam can have a significant impact on the downstream river morphology by altering
both the flow regime and the sediment load. The effect of a dam is dependent on
factors such as the storage capacity relative to the mean annual runoff (MAR), the
operation of the reservoir and the sediment yield of the catchment. Changes in the
river morphology include the degradation and coarsening of the riverbed, generally
closer to the dam, and aggradation further downstream where the sediment delivered
by tributaries cannot be carried through because of the reduced sediment transport
capacity of the river. The impact of a dam can stretch over several hundreds of
kilometres.
The main objective of this thesis was to gain a better understanding of the impacts
that dams can have on the downstream river morphology. This was done by
developing equations that can describe the channel geometry, investigating the effect
of the presence of clay and silt on the sediment transport behaviour of sediments, as
well as detailed evaluation of simulations carried out with a one-dimensional
mathematical river model (MIKE 11).
The calibrated regime equations were found to be comparable to other internationally
developed regime equations and to be suitable for natural rivers. It was found,
however, that these regime equations are not applicable to rivers downstream of dams
that have highly unnatural release patterns. Further research is needed in this regard.
By investigating the effect of cohesive sediments on the sediment transport behaviour
of mixed sediments it was found that as little as 7% clay and silt in the bed could
affect their sediment transport characteristics. A methodology was also developed by
which the critical conditions for mass erosion of cohesive sediments can be described
in terms of the applied stream power. Sediment transport equations were calibrated
and verified in terms of the unit input stream power for fine and non-cohesivesediments. The sediment transport equation for fine sediments was implemented in
MIKE 11.
The simulations over a 40 km reach of the Pongola River downstream of
Pongolapoort Dam, have shown that even when a large demand is placed on the
stored water, and most of the smaller floods are therefore absorbed by the dam, the
downstream impact can still be considerable, with as much as 5 m deep erosion in
places. The sediment loads are generally reduced (by as much as 35%), but the
effective catchment area downstream of the dam has been reduced by as much as
90%, indicating that substantial erosion had to have taken place in the river.
Coarsening of the riverbed was also observed during the simulations. / AFRIKAANSE OPSOMMING: 'n Dam kan 'n aansienlike impak he op die riviermorfologie stroomaf daarvan,
deurdat dit beide die vloei en sedimentlading drasties kan verander. Die effek van 'n
dam hang van verskeie faktore af, soos die opgaarkapasiteit in vergelyking met die
gemiddelde jaarlikse afloop (GJA), die bestuur van die dam en die sedimentlewering
van die opvanggebied. Veranderings in die riviermorfologie behels die degradering
van die rivierbed, sowel as die uitspoel van fyn materiaal uit die rivierbed, veral nader
aan die dam. Deponering vind verder stroomaf van die dam plaas, waar die sediment
wat deur die sytakke ingevoer word nie deurgevoer kan word nie, weens die verlaagde
sedimentdravermoe van die rivier. Sodoende kan rivierlope oor honderde kilometers
deur 'n dam bemvloed word.
Die hoofdoel van die tesis was om meer insig te verkry oor die impak wat damme op
die stroomaf riviermorfologie kan he. Derhalwe is vergelykings ontwikkel wat die
riviermorfologie kan beskryf. Die effek van die teenwoordigheid van klei en slik op
die sedimentvervoer-eienskappe is ondersoek, en gedetaileerde ontledings is met 'n
een-dimensionele wiskundige riviermodel (MIKE 11) is gedoen.
Daar is bevind dat die regime-formules goed vergelyk met ander intemasionaalontwikkelde
formules en dat hulle geskik is vir toepassing op natuurlike riviere. Daar
is egter gevind dat die formules nie geskik is vir riviere wat stroomaf Ie van damme
wat hoogs onnatuurlike loslatings het nie. Verdere navorsing is op hierdie gebied
nodig.
Ondersoek na die effek wat klei en slik op die sedimentdravermoe het, het getoon dat
slegs 7% klei en slik in die rivierbed die sedimentvervoer-eienskappe van mengsels
van fyn en growwe materiaal kan bemvloed. 'n Metode is ontwikkel waarmee die
kritiese toestande vir massa-erosie van kohesiewe sediment beskryfkan word in terme
van die aangewende stroomdrywing teen die bed. 'n Sedimentvervoer-vergelyking in
terme van die eenheids-insetstroomdrywing vir fyn en nie-kohesiewe sedimente is gekalibreer en geverifieer. Die nuwe sedimentvervoer-vergelyking vir fyn sedimente
is gebruik in die MIKE 11 simulasies.
Hierdie simulasies oor 'n 40 km loop van die Pongolarivier stroomaf van
Pongolapoort Dam, het getoon dat selfs as daar 'n groot aanvraag op 'n dam se water
geplaas word, en gevolglik meeste van die kleiner vloede deur die dam geabsorbeer
word, die impak van die dam nogs steeds aansienlik kan wees, met soveel as 5 m diep
uitskuring in plekke. Die sedimentladings het gewoonlik verminder (met soveel as
35%), maar die die effektiewe opvanggebiedarea stroomafvan die dam het met meer
as 90% verminder, wat daarop dui dat daar aansienlike erodering in die rivier
plaasgevind het. Die simulasies het ook getoon dat die hoeveelheid fyn materiaal in
die rivierbed verminder het.
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The behaviour of strain-hardening cement composites under biaxial compressionMolapo, Katiso Tokoloho 12 1900 (has links)
Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Reinforced concrete is susceptible to cracking. This makes it less durable than
it would be had it been crack-free. Ingress of harmful substances into reinforced
concrete through cracks – which causes corrosion of steel – is not desirable.
This can be mitigated by the use of fibre reinforced-concretes or mortars
showing strain hardening properties accompanied by improved ductility and
multiple cracking under tensile loading. Such materials are called Strainhardening
cementitious composites (SHCC’s).
At Stellenbosch University, work has been done in previous years on SHCC to
determine its behaviour under various loading conditions. Some of the aspects
of the material that have been studied are the behaviour under uni-axial tensile
loading, uni-axial compression and shear. The behaviour of SHCC under biaxial
stresses was investigated to enable the prediction of the material behaviour
under complex stress conditions.
Square plate specimens of nominal dimensions 100 x 100 x 20 mm were cast
and subjected to biaxial compressive loading at stress path angles of 00, 150,
300 and 450; which were equivalent to vertical/horizontal stress ratios of 0/1,
0.27/1, 0.58/1 and 1/1 respectively, at ages 23 to 33 days. Comparisons were
made between specimens tested using steel platens and those tested using
Vesconite sheets. Those tested using Vesconite yielded lower failure stresses.
Vesconite was used to reduce the retraining effect of the frictional force
between the specimens and the steel platens.
Poisson’s ratios were calculated for specimens tested using steel and those
tested using Vesconite. The values for Vesconite were found to be higher than
for steel. Additionally, the values for the uni-axial case were different from those
obtained for other stress ratios. This could have been due to the assumption
made that plane stress was realised and that Elastic moduli in tension and in compression was the same. The possibility of the existence of a triaxial stress
state could render the calculated Poisson’s ratios incorrect.
Shear slip type failure accompanied by wedging was observed. Vertical to near
diagonal cracks were evident on the front faces of the specimens for the stress
path angles of 00 to 450 respectively. The observed crack patterns showed
closely spaced multiple micro-cracking on the narrow edges of specimens
indicating Strain-hardening behaviour. The stress-strain curves also showed a
slight indication of strain-hardening where tensile strains were measured. / AFRIKAANSE OPSOMMING: Gewapende beton is vatbaar vir krake. Dit maak dit minder duursaam as
wanneer dit kraak-vry is. Instroming van skadelike stowwe in gewapende beton
deur middel van krake - wat korrosie van staal veroorsaak - is nie wenslik nie.
Dit kan verbeter word deur die gebruik van veselversterkte beton of mortel wat
vervormingsverharding eienskappe toon, vergesel deur verbeterde rekbaarheid
en veelvuldige krake onder trekspanning. Sulke materiaal word Strainhardening
cementitious composites (SHCC's) genoem.
Die Universiteit Stellenbosch, het in vorige jare werk gedoen om SHCC se
gedrag te bepaal onder verskillende belastingstoestande. Sommige van die
aspekte van die materiaal wat bestudeer is, is gedrag onder uni-aksiale trek,
uni-aksiale druk en skuif. Die gedrag van SHCC onder biaksiale spannings is
ondersoek om voorspelling van materiaalgedrag onder komplekse
spanningstoestande moontlik te maak.
Vierkantige plaat monsters van nominale dimensies 100 x 100 x 20 mm is
gemaak en aan biaksiale drukkragte onderwerp, met spannningspad hoeke van
00, 150, 300 en 450; wat soortgelyk is aan die horisontale spanning verhoudings
van 0/1, 0.27/1, 0.58/1 en 1/1 onderskeidelik, op ouderdomme 23-33 dae.
Vergelykings is getref tussen monsters getoets met staal plate en diegene
getoets word met Vesconite plate. Die proefstukke getoets met Vesconite het
laer falingsspannings opgelewer. Vesconite is gebruik om die uitwerking van die
wrywingskrag tussen die monsters en die staal plate te verminder.
Poisson se verhouding is bereken vir die staal en Vesconite monsters
afsonderlik. Daar is gevind dat die Vesconite waarde hoër was as die vir staal.
Daarbenewens het die waardes vir die uni-aksiale geval, verskil van dié vir
ander spanningsverhoudings. Dit kan wees as gevolg van die aanname van
vlakspanning en dat die Elastiese moduli in druk en in trek dieselfde is. Die moontlikheid van die bestaan van 'n drie-dimensionele spanningstoestand, kan
beteken dat die berekende Poisson’s verhoudings onakkuraat is.
Skuif-glip tipe faling, vergesel deur vaswigting is waargeneem. Vertikale tot
feitlik diagonale krake is duidelik sigbaar op die voorkant van die monsters vir
spanningspadhoeke van 0-450 onderskeidelik. Die waargeneemde kraak
patrone het nou gespasieerde, veelvuldige mikro-krake op die smal randte van
die monsters, wat dui op vervormingsverharding. Die spanningsvervormings
kurwes het ook effense aanduidings getoon van die vervormingsverharding
waar trekvervorming gemeet is.
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Rheology of polymer modified binders : a comparative study of three binders and three binder/filler systemsBurger, A. F. January 2001 (has links)
Thesis (MEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: The use of polymer modified binders have increased drastically over the past twenty
years. It is generally accepted that current empirical specification tests do not adequately
characterise the improvement in binder properties when bitumen is modified with
polymers.
At the University of Stellenbosch, a programme was initiated to relate binder properties
to asphalt mix performance. This study forms part of that programme.
This study focuses on three binders and is an attempt to characterise binder properties
fundamentally. The binders that were tested are:
• 60/70 penetration grade bitumen
• SBS modified 60/70 bitumen
• Bitumen-Rubber
Two rheometers were used to characterise the binder properties:
• Sliding Plate Rheometer (SPR)
• Dynamic Shear Rheometer (DSR)
The Sliding Plate Rheometer was modified to allow testing at elevated temperatures. The
modification is described in this thesis.
Three types of testing were used to test the binders:
• Creep tests (SPR and DSR)
• Dynamic tests (Strain and Frequency Sweeps - DSR)
• Flow tests (high temperature viscosity tests - DSR) The results of the tests were used to characterise differences between the binders. Shear
susceptibility lines were plotted and viscosities calculated from the creep test results;
Master Curves and Black Diagrams were plotted from frequency sweep results; flow test
results were used to characterise high temperature behaviour.
A further development in the asphalt industry is the move towards the development of
performance based specifications. A programme has been initiated in this regard and this
study forms part of the programme.
As a step towards the development of performance based specifications filler was
included in this study. BinderlFiller systems were subjected to the same test programme
the binders were, to characterise the influence on binder properties of filler addition.
Some of the conclusions that were drawn at the end of the study are:
• Polymer modification improves binder properties related to rutting.
• Filler addition does not affect binder properties negatively.
• Shear rate is very important during production of asphalt mixes and construction
of asphalt layers containing polymer modified binders. / AFRIKAANSE OPSOMMING: Die gebruik van polimeer gemodifiseerde bitumen het drasties toegeneem oor die
afgelope twintig jaar. Dit word algemeen aanvaar dat die huidige empiriese spesifikasie
toetse nie die verbetering in bindmiddeleienskappe van polimeer modifisering
aanvaarbaar karakteriseer nie.
'n Program is geïnisieer by die Universiteit van Stellenbosch om 'n verband te vind
tussen bindmiddeleienskappe en asfaltmengseleienskappe. Hierdie studie vorm deel van
die program.
Hierdie werk fokus op drie bindmiddels en is 'n poging om die bindmiddeleienskappe
fundamenteel te karakteriseer. Die bindmiddels wat gebruik is in hierdie werk, is:
• 60/70 penetrasiegraad bitumen
• SBS gemodifiseerde 60/70 bittimen
• Bitumen-Rubber
Twee reometers is gebruik om bindmiddeleienskappe te karakteriseer:
• Glyplaat Reometer (SPR)
• Dinamiese SkuifReometer (DSR)
Die glyplaat reometer is aangepas om toetse by hoër temperature te doen en die
aanpassing wat gemaak is word in die tesis beskryf.
Drie tipes toetse is uitgevoer om die bindmiddels mee te toets:
• Kruiptoetse (SPR en DSR)
• Dinamiese toetse (DSR)
• Vloei toetse (DSR) Die resultate van die toetse is gebruik om die verksille tussen die bindmiddels te
kwalifiseer. Verskillende grafieke en figure is getrek van die resultate om die onderskeie
bindmiddels te karakteriseer.
Die beweging weg van empmese spesifikasies na werkverrigting gebaseerde
spesifikasies in die asfalt industrie is 'n verder nuwe ontwikkeling. 'n Program is
geïnisïeer ten opsigte hiervan en hierdie werk vorm deel van die program.
As 'n stap in die ontwikkeling van die werkverrigting gebaseerde spesifikasies is 'n
vuIler ingesluit in die toetsprogram. Bindmiddel/vuIler stelsels is onderwerp aan dieselfde
toetse waaraan die bindmiddels onderwerp is om die invloed van die vuIler op die
bindmiddels te karakteriseer.
Sommige van die gevolgtrekkings waartoe gekom is aan die einde van die tesis, is:
• Polimeer modifisering verbeter bindmiddeleienskappe met betrekking tot
wielsporing.
• Die toevoeging van vuIler affekteer nie die bindmiddeleienskappe negatiefnie.
• Die vervormingstempo is van groot belang wanneer asfaltmengsels gemeng en lae
gebou word van mengsels wat polimeer gemodifiseerde bitumen bevat.
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The application of Doppler velocity meters in the measurement of open channel dischargesGunther, U. K. (Uwe Karsten) 12 1900 (has links)
Thesis (MEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: This report deals with the use of Doppler meters to measure flow velocities
and hence discharges in streams. The Doppler meter measures the shift in
frequency of an acoustic wave, which it emits and then becomes reflected by
a moving particle. The reading is converted into a velocity by dividing the
shifted frequency by a calibration constant. The particles that reflect the
signal need to follow the flow sufficiently closely so that their velocity may
be assumed equal to the flow velocity.
A previous study on the use of the Doppler meter at a Crump weir (Du Toit
and Venter, 1999) indicated that velocities measured with a Doppler meter
showed a distinct relationship with recorded water levels. However, the wide
scatter of the observed frequencies in this study, necessitated further tests on
the use of the Doppler meter at measuring structures as well as calibration
tests on the instrument in the hydraulic laboratory of the University of
Stellenbosch.
The mam objective of this investigation was to establish the relationship
between measured Doppler velocities at a Crump weir and the approach
velocities in the stream. The instrument was to be tested in both modular and
non-modular flow ranges. In addition, the instrument had to be calibrated in
the hydraulic laboratory under varying flow conditions, such as very low
flow velocities and different sediment concentrations. The placement of the
probe at different depths of the flow was also investigated to comment on
the accuracy of the Doppler readings at these depths. The results of these
tests should serve as guidelines for any additional tests required for use of
this instrument in open channel discharge measurements.
The Doppler meter used for this study was supplied and manufactured in
Stellenbosch by Flotron, and is being marketed as DFM-P-067. It was
calibrated in the laboratory in a channel with limited width and hence non-two-dimensional flow conditions. Conclusions were drawn on the calibration
constant that was established. The calibration of the instrument requires the
division of the cross-sectional flow area into a number of sub-divisions over
which the flow was integrated. The calibration constant of 1460 established
in this study differs by approximately 6 percent from the theoretical constant
value of 1375.
The sensitivity of the Doppler meter to different sediment concentrations
was also investigated. For the instrument to read a shifted frequency, it is
essential that suspended particles that follow the water movement
sufficiently closely are present in the stream. It was observed that readings
of the instrument in "sediment-free" water differed only by 3.6% from the
readings taken in water containing sediments. The instrument was thus not
very sensitive to different sediment concentrations. It was also found that
the angle at which the probe was placed in the water had no effect on the
accuracy of the observed Doppler velocity. It was furthermore found that the
Doppler meter worked reliably at all depths, including levels very close to
the channel floor and levels just below the water surface. One drawback of
the apparatus was the minimum velocity that it can measure accurately. This
minimum velocity of 0.046 mis does not compare well with that for other
commercially available Doppler meters. The Argonaut-Acoustic Doppler
meter for example can measure velocities as low as O.OOOlm/s, meaning that
the DFM-P-067 measures a minimum velocity 460 times swifter than the
minimum velocity of the Argonaut-Acoustic Doppler meter.
After the Doppler meter had been calibrated, it was tested at a Crump weir
in the laboratory to determine the relationship between the Doppler
velocities, measured at the weir's crest, and the velocities in the approach
channel. These tests were performed for both modular and non-modular flow
conditions. The report concludes that, within the flow range in which the instrument was
tested, there is a linear relationship between the two velocities mentioned. It
is likely that the results obtained in the modular flow range can be used to
extrapolate for high flows, especially for submergence ratios less than 0.93.
The wide scatter of results obtained in the previous study was due to the
readings not being averaged. The Doppler meter does not measure a point
velocity but an average velocity within the acoustic field that it emits. This
acoustic field is very small and depends on the geometry of the probe.
Finally it is recommended that the linear relationship in the non-modular
flow range be investigated further in a larger model, where the submergence
ratio can be better controlled. The Doppler meter should in future also be
calibrated in a wide channel in which two-dimensional flow conditions are
approached and these results should be compared to the results obtained in
this study. Every instrument is expected to have its own calibration constant,
and depending on its application, it can either be calibrated at a weir or in
the laboratory. The calibration of the instrument at a Crump weir should
allow for a wider range of flows, and also very low flow velocities.
At the end of this report guidelines were drawn up that are based on the
results and conclusions obtained in this investigation. They may serve as an
aid for measurements that could be carried out with this instrument in open
channels. / AFRIKAANSE OPSOMMING: Hierdie verslag handeloor die gebruik van die Doppler-meter om
vloeisnelhede en derhalwe die vloeitempos in riviere te meet. Die Doppler
meter word gebruik om die verandering in die frekwensie van 'n akoustiese
golf wat deur bewegende deeltjies in die water gereflekteer word te meet.
Die lesing word dan omgeskakel in 'n snelheid deur die gewysigde
frekwensie deur 'n kalibrasie konstante te deel. Die bewegende deeltjies wat
die sein reflekteer, volg die vloei genoegsaam sodat aanvaar kan word dat
hulle snelhede gelyk aan die vloeisnelheid is.
'n Vorige studie in die gebruik van die Doppler meter by 'n Crump meetwal
het baie belowende resultate getoon deurdat daar gevind is dat die gemete
Doppler snelheid 'n duidelike verwantskap toon met veranderings in gemete
water vlakke. As gevolg van die wye band in die waargenome frekwensies in
die studie is aanbeveel dat verdere toetse op die gebruik van die Doppler
meter by meetstasies gedoen moet word. Die instrument moet ook in die
laboratorium gekalibreer word.
Die hoofdoel van hierdie ondersoek was om die verwantskap tussen die
gemete Doppler snelhede by 'n Crump meetwal en die aankomssnelhede in
die stroom te bepaal. Dit moes gedoen word in beide die modulêre en niemodulêre
vloeibestekke. Behalwe vir die kalibrasie van die instrument in die
laboratorium moes die betroubaarheid daarvan onder verskillende vloei
toestande ook getoets word, soos byvoorbeeld by lae vloei snelhede en by
verskillende sediment konsentrasies. Die instrument is ook op verskillende
vlakke binne die vloei getoets om te bepaal of daar op hierdie vlakke
betroubare lesings verwag kon word. Resultate verkry, kan dan dien as
riglyne vir enige verdere toetse wat nog op die instrument in oop kanale
uitgevoer moet word. Die Doppler meter wat vir die ondersoek gebruik is, word in Stellenbosch
vervaardig deur Flotron en word onder die naam DFM-P-067 bemark. Dit
is in die laboratorium in 'n kanaal met 'n beperkte breedte getoets en IS
daarom in nie-twee dimensionele vloei gekalibreer. Gevolgtrekkings IS
gebaseer op die kalibrasie konstante verkry uit die toetse. Die kalibrasie van
die instrument vereis dat die deursnee area van die vloei in verskeie
segmente onderverdeel moes word. Die kalibrasie konstante van 1460 bepaal
in hierdie studie verskilongeveer 6% van die teoretiese waarde van 1375 vir
die konstante.
Die Doppler meter se sensitiwiteit vir verskillende sediment konsentrasies is
ook ondersoek. Dit is noodsaaklik dat daar gesuspendeerde deeltjies
teenwoordig in die water is en dat die deeltjies saam met die water beweeg
om te verseker dat die instrument die gewysigde frekwensie kan registreer.
Daar is egter gevind dat die lesings van die instrument in sediment-vrye
water slegs met 3,6% verskil van lesings wat in water met sediment geneem
is. Dit lei tot die gevolgtrekking dat die instrument nie baie sensitief vir
veranderlike sediment konsentrasies in die water is nie. Daar is ook gevind
dat die hoek waarteen die sender in die water geplaas word nie die
akkuraatheid van die Doppler snelhede beinvloed nie. Verder is gevind dat
die Doppler meter bevredigende resultate lewer, ongeag op watter diepte
lesings geneem word. Tydens toetse is waarnemings baie nabyaan die
kanaal bodem asook nabyaan die water se oppervlak gedoen. 'n
Tekortkoming van hierdie instrument is die minimum snelheid wat dit
akkuraat kan meet. Daar is gevind dat die Doppler meter se muurnum
snelheid lesing van 0.046 mis nie goed vergelyk met dié van ander meters
wat kommersieël beskikbaar is nie. Die Argonaut-Acoustic Doppler meter
kan byvoorbeeld vloeisnelhede so laag as 0.0001 mis meet wat beteken dat
die DFM-P-067 se minimum betroubare vloeisnelheid 460 keer vinniger is as
die Argonaut-Acoustic Doppler meter se minimum betroubare vloeisnelheid. Nadat die Doppler meter gekalibreer is, is dit by 'n Crump meetwal in die
laboratorium getoets om die verhouding tussen die Doppler snelhede gemeet
by die oorloopkruin en die snelhede wat in die aanloopkanaal gemeet is, te
bepaal. Hierdie toetse is uitgevoer op beide modulêre en nie-modulêre vloei
toestande.
Daar is gevind dat daar binne die vloeibestek waarin die toetse plaasgevind
het 'n liniêere verband tussen die twee bogenoemde snelhede bestaan. Dit is
hoogs waarskynlik dat die resultate wat in die modulêre vloeibestek gevind
is gebruik kan word om vir hoë vloeie te ekstrapoleer, veral vir grade van
versuiping laer as 0.93. Die vorige studie se uiteenlopende resultate kan
toegeskryf word aan lesings waarvan die gemiddelde lesing vir 'n spesifieke
vloeitoestand nie bepaal is nie. Die Doppler meter meet nie 'n bepaalde
punt-snelheid nie, maar 'n gemiddelde snelheid binne die akoestiese veld
wat dit uitstraal. Hierdie akoestiese veld is baie klein en afhanklik van die
geometrie van die sender.
Ten slotte word aanbeveel dat die lineêre verband in die nie-modulêre
vloeibestek in 'n groter model, waar die graad van versuiping makliker
beheerbaar is, verder ondersoek moet word. Die Doppler meter moet ook in
'n breë kanaal waarin twee dimensionale vloei voorkom, gekalibreer word.
Resultate so verkry moet vergelyk word met die wat in hierdie studie behaal
is. Elke instrument behoort sy eie kalibrasie konstante te hê en afhangende
van waar dit gebruik word, kan dit of by 'n meetwal of in die laboratorium
gekalibreer word. Die kalibrasie van die instrument by 'n Crump meetwal
behoort 'n wyer reeks vloeie toe te laat met ook baie lae snelhede.
Die verslag word afgesluit met riglyne gebaseer op die resultate en
gevolgtrekkings wat uit die ondersoek voortgespruit het. Hierdie riglyne en
gevolgtrekkings kan dan dien as 'n hulpmiddel vir metings wat met hierdie
instrument in oop kanale uitgevoer word.
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An overview of municipal information systems of Drakenstein municipality with reference to the Actionit open decision support frameworkDe Kock, Jacobus M. (Jacobus Michiel) 12 1900 (has links)
Thesis (MScEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Actionl'I' is a project undertaken by a consortium consisting of CSIR, Simeka
Management Consulting, University of Pretoria and the University of Stellenbosch for
the Innovation Fund of the Department of Arts, Culture, Science and Technology in
South Africa. Their objective is to create a basic specification for seletected information
exchange that is compatible with all levels of government.
The comparison between existing information systems at municipal level and ActionIT
specifications will be investigated for the purpose of exposing shortcomings on both
sides. Appropriate features of existing information systems will be identified for the
purpose of enhancing the ActionIT specifications.
The ActionIT project is presently in its user requirement and conceptual model
definition phase, and this thesis aims to assist in providing information that may be
helpful infuture developments.
The study undertaken in this thesis requires the application of analytical theory and a
working knowledge of information systems and databases in order to:
1. Research existing information systems and relevant engineering data at local
municipal authorities. Also important will be the gathering of information
regarding systems currently in use, and the format in which information is stored
and utilised at municipalities.
2. Do an adequate analysis of the contents of recorded information. This
information will establish background knowledge on the operations of local
authorities and a clearer understanding of information systems.
3. Evaluate to what degree existing information systems comply with ActionIT
specifications. This will be the main focus of this thesis.
Thus the focus of this thesis is to record (provide an overview oj) activities in a
municipal environment and the interaction with the environment on information system
level where standards provided by ActionIT as an Open Decision Support Framework
can be of value. / AFRIKAANSE OPSOMMING: ActionIT is in projek wat deur ActionIT konsortium bestaande uit die WNNR, Simeka
Management Consulting, Universiteit van Pretoria en die Universiteit van Stellenbosch,
onderneem is vir die Innovasie Vonds van die departement van Kuns, Kultuur,
Wetenskap en Tegnologie van Suid-Afrika. Hul mikpunt is om in spesifikasie vir
informasie sisteme te onwikkel, wat met alle vlakke van regering kan skakel.
Die vergelyking tussen die bestaande informasie sisteme op munisipale vlak en ActionIT
spesifikasies salondersoek word vir die doelom tekortkominge aan beide kante uit te
wys. Vir die verbetering van ActionIT spesifikasies moet aanvaarbare eienskappe van
bestaande informasie sisteme geindentifiseer word.
Die ActionIT projek is tans in die gebruikers vereiste en konseptueIe model definisie
fase, en die tesis is gemik daarop om 'n bydrae te lewer tot die bevordering van
informasie wat mag help in toekomstige ontwikkeling.
Die werk onderneem in die tesis vereis in teoretiese kennis van informasie sisteme en
databasise om:
1. in Ondersoek in die bestaande informasie sisteem en relefante ingenieurs data
van in plaaslike munisipaliteit te doen. Die insameling van informasie oor die
huidige sisteme in gebruik, die formaat waarin die informasie gestoor en
gebruik word is ook belangrik.
2. in Analise van die inhoud van die waargenome informasie te doen. Die
informasie sal agtergrond kennis gee oor die werking van plaaslike munisipale
owerheid en in beter insig in informasie sisteme gee.
3. in Evaluasie van die verband tussen die bestaande informasie sisteme en
ActionIT spesifikasies te doen. Dit is die hoof fokus punt van die tesis.
Dus die doel van die tesis is om in oorsig te gee oor die aktiviteite in in munisipale
omgewing en die interaksie met die omgewing op informasie sisteem vlak. Waar
standaarde wat deur ActionIT voorgeskryf word as in "Open Decision Support
Framework" van belang kan wees.
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Steps as hydraulic roughness elements in segmentally lined tunnelsBester, J. W. January 2002 (has links)
Thesis (MEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Segmentally lined tunnels are increasingly being built to transfer water from one water
scheme to another. The segments that line such tunnels are often in the form of pre-cast
concrete sections, which are placed around the perimeter of the tunnel.
As these tunnels are very expensive to construct, it is imperative that their hydraulic
capacities can be calculated accurately. Even a slight variation in the design diameter has a
significant effect on the cost of the tunnel.
Due to the construction method involved, alternative segments are not always properly
aligned. This creates roughness elements in the tunnel commonly known as steps. These
steps occur randomly and vary in size. Since the steps lead to increased roughness and thus
decrease the hydraulic capacity of the tunnel, it is essential that this effect be allowed for in
the design of the tunnel.
A hydraulic model was used to determine the contribution of steps to the hydraulic
roughness, according to step size and frequency of steps. / AFRIKAANSE OPSOMMING: Tonnels word al hoe meer gebou om water tussen waterskemas te vervoer. Die voering
van sulke tunnels word dikwels saamgestel uit voorafvervaardigde beton panele wat
geplaas word om 'n huls langs die omtrek van die tonnel te vorm.
Aangesien hierdie tonnels geweldig duur is om te bou, is dit uiters noodsaaklik dat die
hidrouliese kapasiteit van 'n tonnel akkuraat bereken kan word. 'n Klein variasie in die
diameter van die tonnel het 'n betekenisvolle effek op die koste daarvan.
Die konstruksiemetode van sulke tonnels veroorsaak dat opeenvolgende panele nie altyd
presies oplyn nie. Sulke afwykings in die belyning van die tonnelpanele veroorsaak klein
trappies, wat bydra tot die ruheid in die tonne I en sodoende die kapasiteit daarvan laat
afneem. Die afwykings varieer in grootte en kom in geen spesifieke patroon voor nie.
'n Modelstudie is uitgevoer om die bydrae wat die afwykings in the belyning van die
opeenvolgende ringe tot die hidrouliese weerstand maak, te bepaal.
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Assessing management processes of labour based construction worksNyando, Cleaverson K.C. 12 1900 (has links)
Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Labour based technology has extensively been utilized in delivery of poverty alleviation
programmes. Most of the projects implemented have been of construction in nature. In many
cases, labour based works have been characterized with poor performance of not having projects
completed within budget, in time and of good quality. Furthermore labour based works projects
have been ad hoc in nature, lack spatial focus with no link to national development and sparingly
involves engineering skills in its make shift administrative arrangements. Research has shown
that most construction problems have been management process related and not product related.
This research was initiated as a response to these challenges and represents an attempt to deliver
sustainable improved performance of labour based works projects. The research identifies seven
phases with various deliverables through the assessment and analysis of management processes
of labour based works using the Process Protocol. The Process Protocol based phases consider
the whole life cycle of a construction project whilst integrating the process elements under a
common framework. To achieve a successful project and process execution, the findings indicate
three operational levels of the participants of the activity zone. Several risk factors which need to
receive special attention during planning and implementation of labour based works projects
have been identified. The practical experiences in responding to, monitoring and controlling of
the risk factors are also provided.
The analysis of the key sequential phases and documentation of management of labour based
works was based on a literature review of conference papers, reports, available project
documents and limited interviews with officials involved in public works programmes. Best
practices in management of labour based works have been used to follow and synthesise the
Process Protocol approach to the management processes of labour based works. / AFRIKAANSE OPSOMMING: Arbeid-baseerde tegnologie word algemeen gebruik in programme wat ontwerp is om armoede
te verlig. Die meeste van die programme wat geïmplementeer is, het te make met konstruksie.
In baie gevalle is hierdie arbeid-baseerde projekte gekenmerk deur swak prestasie en die projekte
is nie betyds voltooi nie, daar is nie gehou by die begroting nie, of die gehalte van die werk was
swak. Verder is hierdie projekte ad hoc van aard, is daar ’n gebrek aan ruimtelike fokus, is dit
nie gekoppel aan nasionale ontwikkeling nie en word daar te min gebruik gemaak van
ingenieursvernuf en is die administrasie gebrekkig. Navorsing het bewys dat die meeste
konstruksie probleme te wyte is aan bestuurs-prosesses en dat dit nie produk-verwant is nie.
Hierdie navorsing is gedoen as gevolg van hierdie probleme en is ’n poging om volhoubare
verbeterde prestasie te lewer in arbeid-baseerde projekte. Tydens die navorsing is sewe fases
geïdentifiseer d.m.v. die ontleding van bestuursprosesse. Die Proses Protokol is gebruik. Hierdie
Proses Protokol gebaseerde fases behels die hele lewens-siklus van ’n konstruksie projek en
integreer al die proses komponente in ’n enkel raamwerk. Die bevindinge toon dat daar drie
operasionele vlakke van deelnemers in die aktiwiteit sone nodig is om die sukses van ’n projek te
verseker. Daar is verskillenmde risiko faktore wat tydens die beplanning en implementering van
projekte spesiale aandag moet geniet . Praktiese wenke betreffende die monitor van, reageer op
en beheer van risiko faktore word ook verskaf.
Die ontleding van sleutel fases en die dokumentasie van die bestuur van arbeid gebaseerde
projekte is gebaseer op ’n literatuur oorsig van konferensie verslae, beskikbare projek dokumente
en beperkte onderhoude met amptenare wat betrokke was in openbare programme. Daar is
gebruik gemaak van beste praktyke in bestuur van arbeid gebaseerde projekte in die sintese van
bestuurprosesse vir arbeid gebaseerde projekte.
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Imposed loads for inaccessible roofs of light industrial steel buildingsDe Villiers, Pieter Jacobus 04 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2003. / Some digitised pages may appear illegible due to the condition of the original hard copy. / ENGLISH ABSTRACT: A critical evaluation of provisions for imposed loads in the South African Loading
Code for design of structures, SABS 0160-1989 (SABS), by comparison with other
codes was performed earlier. The evaluation revealed the SABS loading code to be
generally non-conservative in its provisions for imposed loads for a range of general
and specialist occupancy classes. The SABS provision for imposed loads for
inaccessible roofs was found to be substantially non-conservative in comparison with
the other codes. An investigation into the imposed load for inaccessible roofs is
subsequently performed in order to establish a scientific rationale through which the
codified design values may be measured effectively. Due to the lack of information
and the large uncertainties involved in the imposed roof load, stochastic treatment of
the loads is implemented. This is in line with the stochastic modelling of loads as
implemented in general.
The approach applied is to select a type of building that can be regarded as a generic
example of buildings to which these loads apply, and to discretisize the load into the
various sub-mechanisms that translate into the imposed roof load. The probabilistic
models for the load mechanisms are then quantified, either through physical load
surveys, or through conducting an expert survey for those variables which are not
observable. The use of expert opinion as a resource for information is not readily
accessible in terms of yielding scientifically defendable results. Therefore, the expert
survey is performed as a calibrated experiment whereby weights were calculated for
the individual experts' opinions and their opinions combined accordingly.
The probabilistic models for the load mechanisms are then translated into load effects
by taking into account the physical process resulting in the load effects. By applying
these mechanisms in such a way as to maximise the said load effects, equivalent
uniformly distributed loads (EUDL's) were calculated for each mechanism. The
probabilistic models obtained in terms of the EUDL's pose an easily accessible
format through which existing load models and codified provisions can be evaluated.
These load models are then utilised to evaluate the SABS provisions in terms of the
level of reliability catered for by SABS ultimate limit-state design criteria. It is
concluded that the SABS conservatively provides for maintenance loads on the roof,
while the reliability for construction loads is non-conservative for large tributary areas
and highly non-conservative for small areas. The load models so obtained can
further be applied for structural reliability assessment. / AFRIKAANSE OPSOMMING: "n Kritiese evaluasie van die voorskrifte vir opgelegde belastings in die Suid-
Afrikaanse Selastingskode vir die ontwerp van strukture, SASS 0160-1989 (SASS)
deur 'n vergelyking met ander kodes is vroeër uitgevoer. Die evaluasie het getoon
dat die SASS in die algemeen onkonserwatief is in sy voorsiening vir opgelegde
belastings oor 'n bereik van algemene en spesialis okkupasie tipes. Die SASS
voorskrif vir opgelegde belastings vir ontoeganklike dakke is hoogs onkonserwatief in
vergelyking met die ander kodes. 'n Ondersoek na die opgelegde belasting vir
ontoeganklike dakke word gevolglik uitgevoer met die doelom 'n wetenskaplike
rasionaal daar te stel waardeur die gekodifiseerde voorskrifte effektief gemeet kan
word. As gevolg van die gebrek aan inligting en groot onsekerhede betrokke by die
opgelegde dakbelasting word stogastiese modellering geimplimenteer.
Die aanslag wat gevolg is, is om 'n tipe gebou te selekteer wat beskou kan word as
verteenwoordigend van die geboue waarvoor hierdie belastings van toepassing is, en
om die belasting te diskretiseer in die verskeie lasmeganismes wat die opgelegde
dakbelasting voortbring. Die waarskynlikheidsmodelle vir die lasmeganismes word
dan gekwantifiseer, óf deur fisiese opnames, óf deur die uitvoering van 'n ekspertopname
vir daardie veranderlikes wat nie waarneembaar is nie. Die gebruik van
ekspert opinie as "n bron van inligting is nie maklik toeganklik in terme daarvan om
wetenskaplik verdedigbare resultate te lewer nie. Daarom is die ekspert-opname
uitgevoer soos 'n gekalibreerde eksperiment waardeur relatiewe gewigte bereken
word vir die individuele eksperts en hulopinies daarvolgens gekombineer word.
Die waarskynlikheidsmodelle vir die lasmeganismes word dan omgeskakel in laseffekte
deur in agneming van die fisiese proses wat die las-effek voortbring. Deur die
lasmeganismes op só 'n manier toe te pas dat die betrokke las-effekte gemaksimeer
word, word ekwivalent uniforme belastings (EUS's) bepaal. Die waarskynlikheidsmodelle
in terme van EUS's bied "n maklik toeganklike formaat waardeur bestaande
lasmodelle en gekodifiseerde voorskrifte evalueer kan word. Die lasmodelle word
gevolglik gebruik om die SASS voorskrifte te evalueer in terme van die vlak van
betroubaarheid wat gehandhaaf word deur SASS limiet-staat ontwerp kriteria. Dit is
bepaal dat die SASS konserwatief voorsiening maak vir onderhoudslaste op die dak,
maar onkonserwatief tot hoogs-onkonserwatief is vir konstruksie laste. Die bepaalde
lasmodelle kan verder toegepas word in strukturele betroubaarheids analise.
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