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The characterisation of South African sea stormsMacHutchon, K. R. January 2006 (has links)
Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2006. / This research provides and overview of sea storms around the South African Coast in terms
of weather types, characteristic wave statistics, storm processes and wave energy.
Sea Storm Profiles are unique to the particular storm events causing them, but they can be
associated with Equivalent Wave Energy (EWE) Storm Profiles, which are representative of
them and have a linear, symmetric, “Capital Lambda” ( Λ ), shape. The actual storm profile
and the EWE Profile are equivalent in wave energy, and the benefit of the EWE is that it is
regular and can be can be readily compared with another EWE Storm Profile for analysis,
and for the comparison of impacts.
The ability to compare the impacts of Sea Storms from different areas, on the basis of
characteristic Equivalent Wave Energy (EWE) Storm Profiles within the South African
Coastal Regions, is considered to be advantageous. This will allow Engineers to apply the
knowledge gained in one area to another with a similar EWE Storm Profile, with more
confidence.
There will always be the need for site-specific investigations, data recording, data analysis
and interpretations in Coastal Engineering Work, but one needs to start with an
understanding of the general nature of the coastal region in which one is working. This
research adds to the background “Body of Knowledge” relating to the character of the sea
storms in the Regions around South Africa.
The study is based on a literature survey of atmospheric weather, sea wave theory and wave
climates, as well as the analysis of weather and sea state data at selected recording stations
around the South African Coastline.
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Deflections of reinforced concrete flat slabsEigelaar, Estee M. 03 1900 (has links)
Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH SUMMARY: It is found that the serviceability limit state often governs the design of slender reinforced concrete
members. Slender flexural members often have a percentage tension reinforcement less than 1.0%
and an applied bending moment just above the point of first cracking. For such members, the
available methods to evaluate the serviceability conditions produce inadequate and unrealistic
results. The evaluation of the serviceability of a slender member includes the calculation of the
predicted deflection, either by empirical hand-calculation or analysing a finite element model, and
the verification using the span-to-effective-depth ratio.
The focus of the study is on flat slab structures. It investigates the different deflection prediction
methods and the span-to-effective-depth ratio verifications from various design standards. These
design standards include the ACI 318 (2002), the SABS 0100-1 (2000), the EC2 (2004) and the BS
8110 (1997). The background to the methods, as well as the parameters which influences the
deflection development for lightly reinforced members, are investigated in order to define the
limitations of the methods. As a result of the investigation of the deflection calculation methods, an
Alternative Approach is suggested and included in the comparisons of the various methods.
The deflection prediction methods and the span/effective depth verification procedures are
accurately formulated to predict the serviceability behaviour of beams. Additional approaches had
to be used to apply these methods to a two-dimensional plane such as that of a flat slab structure.
The different deflection prediction methods and the span/effective depth verification methods are
calculated and compared to the recorded data of seven experimental flat slab specimens as
performed by others. A study by Gilbert and Guo (2005) accurately recorded the flexural behaviour
of flat slab specimens under uniformly distributed loads for test periods up to 750 days. The
methods to evaluate the serviceability of a slender member were also applied to slab examples
designed using South African standards.
The study concludes by suggesting a suitable deflection prediction method for different parameter
(limitation) categories with which a slender member can comply to. The typical span/effective depth
ratio trend is also presented as the percentage tension reinforcement for a slender member changes. It is observed that the empirical hand-calculation methods present more reliable results
than those of the finite element models. The empirical hand-calculation methods are accurate
depending on the precision to which the slab was constructed relative to the actual slab design.
The comparison of the deflection methods with South African case studies identified the role played
by construction procedures, material parameters and loading history on slab behaviour. / AFRIKAANSE OPSOMMING: Die diensbaarheidstoestand is in baie gevalle die bepalende faktor vir die ontwerp van slank
gewapende beton elemente bepaal. Slank elemente, soos lig bewapende buigbare beton elemente,
het gewoonlik ‘n persentasie trekbewapening van minder as 1.0% en ‘n aangewende buigmoment
net wat net groter is as die punt waar kraking voorkom. Die metodes beskikbaar om die
diensbaarheid van sulke elemente te evalueer gee onvoldoende en onrealistiese resultate. Die
evaluering van die elemente in die diensbaarheidstoestand sluit in die bepaling van defleksies deur
berekening of die analise van ‘n eindige element model, en die gebruik van die span/effektiewe
diepte metode.
Die fokus van die studie is platbladstrukture. Die doel van die studie is om die verskillende metodes
vir die bereking van defleksie asook die verifikasie volgens span/effektiewe diepte metodes van die
verskillende ontwerp standaarde te ondersoek. Die ontwerp standaarde sluit die ACI 318 (2002),
SABS 0100-1 (2000), EC2 (2004) en die BS 8110 (1997) in. Die agtergrond van hierdie metodes is
ondersoek asook die parameters wat ‘n rol speel, sodat die beperkings van die metodes
geidentifiseer kan word. As ‘n gevolg van die ondersoek na die beperkings van die metodes, is ‘n
Alternatiewe Benadering voorgestel. Die Alternatiewe Benadering is saam met die metodes van die
ontwerpstandaarde gebruik om die verskille tussen die metodes te evalueer.
Die defleksievoorspelling en die span/effektiewe diepte verifikasie metodes is korrek geformuleer
om die diensbaarheid van balke te evalueer. Ander benaderings was nodig om die diensbaarheid van
blad blaaie te toets.
Die onderskeie defleksievoorspelling en span/effektiewe diepte metodes is bereken vir sewe
eksperimentele plat blaaie soos uitgevoer deur ander navorsers. Gilbert and Guo (2005) het ‘n studie
uitgevoer waar die buigingsgedrag van die sewe plat blaaie, met ‘n uniforme verspreide las vir ‘n
toetsperiode van tot 750 dae, akkuraat genoteer is. Die metodes om die diensbaarheid van ‘n slank
element te toets, was ook op Suid-Afrikaanse blad voorbeelde getoets. Dit was gedoen om die Suid-
Afrikaanse ontwerp van ligte bewapende beton elemente te evalueer. Die gevolgetrekkings stel ‘n gepaste defleksie metode vir ‘n slank element vir verskillende beperking
kategorië voor. Dit is ook verduidelik hoe die tipiese span/effektiewe diepte verhouding met die
persentasie trek bewapening vir ‘n slank element verander. Dit is bevind dat die imperiese
handmetodes om defleksies te bereken, meer betroubaar as die eindige element modelle se
resultate is. Die imperiese handberekening metodes is akkuraat relatief tot hoe akkuraat die blad
konstruksie tot die blad ontwerp voltooi is.
‘n Vergelyking van defleksieberekening met Suid-Afrikaanse gevallestudies het die belangrikheid van
konstruksieprosedures, materiallparamteres and belastingsgeskiedenis geïdentifiseer.
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Protrusions on Stepped Spillways to Improve Energy DissipationWright, Henry-John 12 1900 (has links)
Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2006. / Stepped spillways constructed of roller compacted concrete (RCC) is a hydraulic
and cost effective measure to dissipate energy of large water flows over the
spillway of a dam. Stepped spillways, like other spillway types, have its limitations
and a measure to improve the energy dissipation effectiveness is proposed.
Two hydraulic models were constructed at the hydraulics laboratory of the
Department of Water Affairs and Forestry (DWAF) in Pretoria, South Africa. The
scales of the models were 1:20 and 1:30.
The study proposes the use of triangular protrusions applied over the spillway
surface. The protrusions have the same height as the steps, with the width of the
protrusions varying. The triangular protrusions deflect the water sideways resulting
in higher energy losses.
The results indicate that the protrusions reduce scouring at the toe of the dam, thus
increasing the roughness of the steps. It also indicate that aeration occur earlier
than with normal stepped spillways. An optimal spacing, lateral and across the
steps, are proposed. The construction of the protrusions is also discussed, as well
as the cost implications.
It is concluded that the protrusions are effective at a unit discharge up to 35
m3/s.m. This value is however dependent on the configuration of the apron
downstream of the toe of the dam. It is proposed that protrusions be added on the
downstream face of the dam on every second step, with one protrusion and then
no protrusion alternating in the flow path. It is recommended that the protrusions be
cast in situ.
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An investigation of the wave energy resource on the South African Coast, focusing on the spatial distribution of the South West coastJoubert, J. R. 03 1900 (has links)
Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2008. / This thesis is an investigation of the wave power resource on the South African coast,
focusing on the spatial distribution of wave power of the coastal region exposed to the
highest wave power. The study’s main objective is to provide a detailed description of the
spatial distribution of wave power to assist in the selection of locations for deployment of
Wave Energy Converter (WEC) units in this zone. The study methodology employed to
achieve this main objective entails an analysis of measured wave data recorded at wave
recording stations distributed along the South African coast. The analysis provided a
general description of wave power at locations for which wave data exist. From this analysis
it was found that the South West Coast is exposed to the highest wave power, with an
average wave power of approximately 40 kW per meter wave crest. The rest of the South
African coast is exposed to average wave power between approximately 18 kW/m to 23
kW/m.
The wave power characteristics on the South West Coast region (from Cape Point to Elands
Bay) were therefore the focus of this thesis. The study objective was achieved by
transferring deep sea wave data into the nearshore South West Coast study area with the
Simulating WAves Nearshore (SWAN) wave model. The deep sea wave data was obtained
from a 10 year period of available hindcast data. A simplified simulation procedure was
required in order to make the study practically feasible. A sensitivity analysis was carried
out to determine the validity of the simplified simulation procedure and it was found that the
procedure slightly overestimate wave power in the shallower water regions due to the
underestimation of energy dissipation processes. This overestimation was deemed
acceptable for the dominant wave conditions and the simplified model was therefore applied
in the study. An appropriate programming system was developed and used to transfer the
available 10 year deep sea wave data into the selected South West Coast region. From this
exercise spatial distribution of wave power and related statistical parameters were obtained
for the study area. The accuracy of the modelled output was investigated by directly
comparing it to wave data recorded during the overlapping recording period. It was found
that the model slightly overestimates the monthly wave power resource compared to the
measured data with a maximum overestimation of 9%; which is sufficiently accurate for the
purpose of the study.
The results of this investigation can be used for the identification of areas of high wave
power concentration within the study area for the location of WEC units. Further numerical modelling is required for the detailed design of wave farms, especially if potential
sites are located in shallow water (shallower than approximately 50 m). / Centre for Renewable and Sustainable Energy Studies
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Sediment yield prediction based on analytical methods and mathematical modellingMsadala, V. P. 12 1900 (has links)
Thesis (MScEng (Civil Engineering)--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: A study of the state of reservoir sedimentation in South Africa based on reservoir
sediment deposit data, has shown that a considerable number of reservoirs have
serious sedimentation problems. The analysis of the reservoir sediment deposit data
showed that almost 25% of the total number of reservoirs have lost between 10 to
30% of their original storage capacity. The average storage loss due to sedimentation
in South African reservoirs is approximately 0.3% per year while the average annual
storage loss for all the reservoirs in the world is 0.8%.
The aim of this research was to develop sediment yield prediction methods based on
analytical approaches and mathematical modelling. The sediment yield prediction
methods can be used in planning and management of water resources particularly in
reservoir sedimentation control. The catchment erosion and sediment yield modelling
methods can be applied in temporal and spatial analysis of sediment yields which
results are essential for detailed design of water resources, particularly in the
identification of critical erosion areas, sediment sources and formulation of catchment
management strategies.
Current analytical methods for the prediction of sediment yield have been reviewed.
Nine sediment yield regions have been demarcated based on the observed sediment
yields and catchment characteristics. Empirical and probabilistic approaches were
investigated. The probabilistic approach is based on analysis of the observed
sediment yields that were calculated from reservoir sediment deposit, river suspended
sediment sampling data and soil erodibility data. The empirical equations have been
derived from regression analysis of the variables that were envisaged to have a
significant effect on erosion and sediment yields in South Africa. Empirical equations
have been developed and shown to have accurate and reliable predictive capability in
six of the nine regions.
The probabilistic approach has been recommended for the prediction of sediment
yields in the remaining three regions where reliable regression equations could not be
derived. The predictive accuracy of both the probabilistic and empirical approaches was
checked and verified using the discrepancy ratio and graphs of the observed and
calculated data.
While the analytical methods are needed to predict the sediment yield for the whole
catchment, mathematical modelling to predict sediment yields is applied for more
detailed analysis of sediment yield within the catchment. An evaluation of available
catchment sediment yield mathematical modelling systems was carried out. The main
criteria for the choice of a numerical model to be adopted for detailed evaluation was
based on the following considerations: the model’s capabilities, user requirements
and its application. The SHETRAN model (Ewen et al., 2000) was therefore
specifically chosen because of its ability to simulate relatively larger catchment areas
(it can handle catchment scales from less than 1km2 to 2500km2), its ability to
simulate erosion in channels, gullies and landslides, its applicability to a wide range
of land-use types and ability to simulate land use changes. Another model, ACRU
(Smithers et al., 2002) was also reviewed.
The aim of the model evaluation was to provide a conceptual understanding of
catchment sediment yield modelling processes comprising model set up, calibration,
validation and simulation. The detailed evaluation of the SHETRAN model was done
through a case study of Glenmaggie Dam in Australia. The flow was calibrated and
validated using data from 1975 to 1984, and 1996 to 2006 respectively. The results
for both the calibration and validation were reasonable and reliable. The sediment
load was validated against turbidity derived sediment load data from 1996 to 2006.
The model was used to identify sources of sediment and areas of higher sediment
yield. The land use of a selected sub-catchment was altered to analyse the impact of
land use and vegetative cover on the sediment yield. Based on the results, the
SHETRAN model was confirmed to be a reliable model for catchment sediment yield
modelling including simulation of different land uses. / AFRIKAANSE OPSOMMING: ‘n Studie van die stand van damtoeslikking in Suid-Afrika toon dat daar ernstige
toeslikkingsprobleme by baie reservoirs bestaan. ’n Ontleding van die
toeslikkingsyfers gegrond op damkomopmetings toon dat omtrent 25% van die totale
getal reservoirs tussen 10 en 30% van hulle oorspronklike opgaarvermoë verloor het.
Die gemiddelde tempo van damtoeslikking in Suid-Afrika is 0.3%/jaar, wat laer is as
die wêreld gemiddeld van 0.8%/jaar.
Die oogmerk met hierdie navorsing was om sedimentlewering voorspellingsmetodes
te ontwikkel deur gebruik te maak van analitiese metodes en wiskundige modellering.
Die sedimentlewering voorspellingsmetodes kan gebruik word vir die beplanning en
bestuur van waterbronne en veral vir damtoeslikking beheer. Die opvangsgebied
erosie en die sedimentlewering modelleringsmetodes kan toegepas word in
tydveranderlike en ruimtelike ontleding van sedimentlewering. Hierdie inligting
word benodig vir die detail ontwerp van waterhulpbronne en veral vir die
identifisering van kritiese erosiegebiede, bronne van sediment en die formulering van
opvangsgebied-bestuur strategië.
‘n Literatuuroorsig oor die huidige metodes vir die voorspelling van erosie en
sedimentlewering is gedoen.
Nege sedimentasie streke is afgebaken in Suid-Afrika, gegrond op waargenome
damtoeslikkingsdata en opvangsgebied-eienskappe. Proefondervindelike en
waarskynlikheidsbenaderinge is ondersoek. Die waarskynlikheidsbenadering is
gegrond op die ontleding van waargenome damtoeslikking wat bereken is uit
reservoir opmeting data en rivier gesuspendeerde sediment data, asook data oor
gronderosie.
Die proefondervindelike metode se vergelykings is afgelei vanuit regressie ontleding
van die veranderlikes wat ‘n belangrike invloed het op die erosie en sedimentlewering
in Suid-Afrika. Daar is bevestig dat die ontwikkelde proefondervindelike (empiriese)
vergelykings ‘n akkurate en betroubare voorspellingsvermoë in ses van die nege
streke het. Die waarskynlikheidsbenadering is aanbeveel vir die voorspelling van sedimentlewering in die ander drie streke, waar betroubare regressie vergelykings nie
afgelei kon word nie. Die voorspellingsakkuraatheid van albei metodes is nagegaan
en bevestig deur gebruik te maak van die teenstrydigheidsverhouding en grafieke van
die waargenome en berekende data.
Analitiese metodes van sedimentleweringsvoorspelling is nodig vir ‘n volle
opvangsgebied, terwyl wiskundige modellering om sedimentlewerings te voorspel
gebruik kan word om ‘n meer in diepte ontleding van die sedimentlewering binne ‘n
opvanggebied te doen. ‘n Evaluasie van beskikbare wiskundige modelle wat
opvangsgebied sedimentlewering kan voorspel, is gedoen. Die hoofkriteria vir die
keuse van ‘n model vir gebruik by gedetailleerde ontleding is gegrond op die
volgende: die vermoëns van die model, wat verbruikers benodig en die aanwending
van die model. Die SHETRAN model (Ewen et al., 2000) is spesifiek gekies weens
sy vermoë om relatief groter opvangsgebiede te simuleer (dit kan opvangsgebiede
van 1km2 tot 2500km2 wees) asook om erosie in kanale, dongas en grondverskuiwing
simuleer. Dit kan toegepas word op ‘n wye reeks grondtipes en kan ook die gevolge
simuleer as die gebruik van die grond verander. ‘n Ander model, ACRU (Smithers
et al., 2002) is ook ondersoek.
Die doel van die modelevaluering was om ‘n konseptuele begrip te kry van
sedimentlewering modelleringsprosesse wat die opstelling, kalibrasie, toetsing en
simulasies insluit. Die volledige evaluasie van SHETRAN is gedoen deur middel van
‘n gevalle-studie van die Glenmaggiedam in Australia. Die riviervloei is gekalibreer
en getoets deur gebruik te maak van data wat strek van 1975 tot 1984, en van 1996 tot
2006 onderskeidelik. Die resultate van beide die kalibrasie en die toetswas redelik en
betroubaar. Die sedimentlading is gekalibreer teen velddata van 1996 tot 2006. Die
model is gebruik om bronne van sediment te identifiseer, asook gebiede met ‘n hoër
sedimentlewering. Die gebruik van die grond op ‘n gekose sub-opvangsgebied is
verander om die impak van grondgebruik en plantbedekking op sedimentlewering te
ontleed. Die resultate bewys dat die SHETRAN model ‘n betroubare model is vir groot
opvangsgebied sedimentlewering modellering, asook vir die simulasie van
verskillende grondgebruike.
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The cross-shore distribution of grain size in the longshore transport zoneSoltau, Christoph 12 1900 (has links)
Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Calculation of longshore sediment transport rates is a typical part of coastal engineering work.
One of the important inputs to such calculations is the sediment grain size. A single,
representative grain size is typically required. The inter-tidal beach is the most convenient and
common area from which grain size data can be obtained. Yet only a fraction of the longshore
transport occurs at the beach, with the bulk of the transport occurring in the surf zone, where
sampling is difficult. Sediment transport calculations can be improved if the representative
grains size is also characteristic of this area. A better understanding how the grain size in the
longshore transport zone compares to the beach grain size is required.
A review of relevant literature indicates that limited attention has been given to quantifying
the grain size in the longshore transport zone. No previous investigations were found that
tried to link the longshore transport zone grain size to that found on the beach. A
comprehensive analysis of beach and longshore transport zone grain sizes was therefore
undertaken and is described in this thesis.
Beach grain sizes were compared to those in the longshore transport zone for three different
locations around the world: Published grains size information, together with detailed wave
and profile data, was obtained from the US Army Field Research Facility at Duck; a second
data set was obtained from measurements done at Bogenfels in Namibia; a third dataset was
compiled from sampling undertaken by the author in Table Bay, South Africa. A total of 189
samples were collected at four sampling lines in Table Bay between September 2005 and
September 2006. Samples were collected across the entire profile from the primary dune to a
water depth of 10 m. Samples were collected by grab in the offshore, and by swimming and
diving in the surf zone. The location of the four Table Bay sampling lines was chosen so as to
obtain data from beaches with different wave and grain size characteristics. Together with the
Duck and Bogenfels data, data from six different beaches was therefore available for study.
A settling tube was used to determine the grain sizes. Verification of the settling tube analyses
against conventional sieving indicated a good comparison. However, the settling tube proved
unsuitable for processing of samples with coarse to very coarse material, for which sieving
was conducted instead.
The grain size at the mid-tide level has been used to characterise the beach. The limits of the
longshore transport zone were defined by calculating the cross-shore distribution of longshore
transport with the Unibest model. Simpler methods, such as the depth of closure, either
overestimated or underestimated it, depending on which wave condition was used in the depth
of closure formula.
It was found that the beaches with steeper mid-tide beach slopes, such as Bogenfels and
northern Table Bay, had coarser median grain sizes than more gently sloping beaches such as
found in the south of Table Bay. On energetic beaches, the mid-tide beach grain sizes were
significantly coarser than those in the surf zone, by more than twice. At less exposed
locations, such as Duck and the central Table Bay beaches, this difference was less. At
sheltered locations, such as the southern sampling lines in Table Bay, the mid-tide beach grain
sizes are virtually the same as those found in the surf zone. The surf similarity parameter was
used to compare the characteristics of the different sites. This parameter was defined using the
average wave height seaward of breaking, and the mid-tide beach slope. The ratio between the
longshore transport zone grain size and the mid-tide beach grain size was found to be similar
to the inverse of the surf similarity parameter for the six beaches that were studied.
These findings have led to an improved understanding of the grain size in the longshore
transport zone and allow a better characterisation of the representative grain size to use for
sediment transport calculations. / AFRIKAANSE OPSOMMING: In kusingenieurswese word langstrandse sedimentvervoer (langsvervoer) gereeld bereken.
Belangrike invoer vir sulke berekeninge is die verteenwordigende korrelgrootte van die sand.
Die sandkorrelgrootte van die benatte strand is die maklikste om te bepaal, al vind net ‘n klein
gedeelte van die langsvervoer op die benatte strand plaas. Die grootste gedeelte van die
langsvervoer kom in die brandersone voor, waar dit moeilik is om monsters te neem.
Sedimentvervoerberekeninge kan verbeter word as die korrelgrootte ook hierdie sone
verteenwoordig. Dit is dus van belang om te verstaan hoe die korrelgrootte van die benatte
strand met die gemiddelde korrelgrootte oor die algehele langsvervoersone vergelyk.
‘n Literatuursoektog dui aan dat min aandag al gegee is aan hoe die korrelgrootte op die
benatte strand met dié in die langsvervoersone vergelyk. ‘n Ontleding van sandkorrelgroottes
op die benatte strand en in die langsvervoersone is dus onderneem en word in die tesis
uiteengesit.
Strandkorrelgroottes word met dié in die langsvervoersone vergelyk vir drie verskillende
gebiede in die wereld : (1) Gepubliseerde data oor korrelgroottes, sowel as strandhellings en
golwe, is van die Field Research Facility by Duck in die VSA verkry ; (2) ‘n tweede stel data
is van opmetings by Bogenfels in Namibie verkry; (3) die derde stel data is saamgestel deur
die skrywer tydens opmetings in Tafelbaai, Suid-Afrika. ‘n Totaal van 189 monsters is tussen
September 2005 en September 2006 by vier verskillende opmetingslyne in Tafelbaai geneem.
Monsters is geneem van die duin tot in 10 m waterdiepte. In dieper water is grypmonsters
geneem, terwyl dié in the brandersone verkry is deur te duik. Die posisie van die vier
Tafelbaaise opmetingslyne is gekies om strande met verskillende golftoestande en
korrelgroottes te dek. Tesame met die data van Duck en Bogenfels is dus ses datastelle vir
ontleding beskikbaar.
‘n Valbuis is gebruik om die korrelgroottes te bepaal. Die valbuismetode het goed met
gewone sifresultate vergelyk, behalwe vir monsters met baie growwe korrels. Hiervoor is
sifwerk gebruik.
Die korrelgrootte van die benatte strand is gebruik om die strand te karakteriseer. Die grense
van die langsvervoersone is bepaal deur die dwarsstrandse verdeling van die langsvervoer met
die Unibest-model te bereken. Eenvoudiger metodes, soos die berekening van die
sluitingsdiepte, het minder betroubare resultate gelewer.
Daar is gevind dat steiler benatte strande, soos Bogenfels en Noord-Tafelbaai se strande,
groter gemiddelde korrelgroottes as platter benatte strande, soos dié in suidelike Tafelbaai,
het. Op blootgestelde strande is die benatte strand se korrelgrootte tot meer as twee keer
groter as dié in die brandersone. By gedeeltelik beskutte strande, soos Duck en Sentraal-
Tafelbaai se strande, was die verskil minder. Op beskutte strande, soos die Suid-Tafelbaai se
strande, is gevind dat die benatte strand se korrelgrootte amper dieselfde as dié in die
brandersone is. Die brandergelyksoortigheidsfaktor is gebruik om die verskillende strande te
vergelyk. Die golfhoogtes net buite die branderlyn en die benatte strandhelling is gebruik om
die veranderlike te bereken. Daar is gevind dat by die ses strande wat ondersoek is, die
verhouding van die korrelgrootte in die langsvervoersone en dié van die benatte strand
ongeveer gelyk aan die omgekeerde brandergelyksoortigheidsfaktor is.
Die bevindings het tot ‘n beter begrip van die wisseling van die korrelgroottes in die
langsvervoersone gelei. Gevolglik kan ‘n akkurater verteenwoordigende sandkorrelgrootte
bepaal word.
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Evaluation of incipient motion criteria for rock in Reno mattresses and rip rapStoffberg, Francis W 12 1900 (has links)
Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2005. / There has always been some debate in the past about the most effective and economical type of revetment to be used to combat or prevent erosion in rivers and channels. Some of the most common materials used for these mitigation measures are gabions, Reno mattresses and rip rap. A study done by the Colorado State University (CSU, 1984), comprised hydraulic tests of Reno mattresses used as a channel bed revetment. The result were compared with those of rip rap. This thesis mainly deals with the evaluation of incipient motion conditions for rock used in Reno mattresses and as rip rap. In this thesis the results of the CSU study and the design criteria of Maccaferri are evaluated and compared with the result obtained when applying the stream power theory and the Shields' theory with respect to incipient motion. This thesis includes the theory with respsect to incipient motion conditions, background to the CSU study and comparisons of the results of the CSU study and Maccaferri's design criteria with theoretical calculations. A cost comparison of Reno mattresses and rip rap as channel bed revetment measures, as well as conclusions and recommendations with regard to the design and use of these options, are also included. The frame of reference for this thesis is the set of CSU test results. The calibrations achieved, proposals made and accuracy of conclusions thus depend on those results.
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An investigation into the feasibility of hybrid concrete construction in South AfricaJurgens, Christiaan Johannes 03 1900 (has links)
Thesis (MScEng (Civil Engineering))--Stellenbosch University, 2008. / Introduction
South Africa is currently experiencing a significant increase in infrastructure investment.
Forecasts by BMI-BRSCU have shown that the building and construction industry is expected
to grow considerably to 2010, before languishing slightly to 2015. This growth will be driven
in particular by investment in non-residential building (41% growth) and construction (73%
growth) activities. Even beyond 2015 however, the demand will still be high on the
construction industry to provide infrastructure for South Africa’s growing population.
South Africa is also facing a serious shortage of engineers, technicians and other skilled
workers in the construction industry. This places high demands on designers and contractors
to provide services and to realise projects in ever-reducing time periods and at less cost. These
conditions have made it increasingly difficult to maintain the required quality of construction
in an industry where mistakes can lead to disastrous consequences.
Recent advances in structural materials, structural systems and the way in which projects are
handled, now enables a new look at the possibilities of combining pre-fabrication with on site
work. This method, known as Hybrid Concrete Construction (HCC), has the potential to
revolutionize the South African construction industry if applied correctly. Local research into
this technique is however required and it is the aim of this thesis to draw attention to this
subject.
Key Findings
Hybrid Concrete Construction (HCC) can be applied to any structural project, it will however
not necessarily be successful. A structure needs to be adapted from the very start to suit a
particular construction method. This ensures that all the advantages of the selected
construction method may be achieved. Adapting a structure to a different construction method
requires a mutual understanding and commitment from all project participants, including the
architect, engineer, contractor and client. HCC also requires a certain degree of repetition in a
project to be financially viable.
A theoretical cost exercise was performed where only the material and erection costs were
considered. In this exercise, HCC was found to be slightly less expensive than other
construction methods for the Office Building of more than 10 storeys. HCC was also found to
be significantly faster than other construction methods for the Office Building of more than 3
storeys. The time calculation was however based on the simplified time estimates from one
source.
Because of HCC’s shorter estimated construction period, the client can expect to earn revenue
from a much earlier date. This decreases the relative cost of a HCC project. This advantage,
however, needs to be quantified for chosen South African projects.
On-site safety is still an important issue with HCC projects. Labourers are not accustomed to
this construction method and it may be necessary to alter current skill development programs
to include a crane safety course. The training of qualified riggers and crane operators should
receive priority if HCC is to develop in South Africa.
This preliminary investigation has shown that Hybrid Concrete Construction (HCC) can be
feasible for the South African market. Further investigation is however required to determine
the parameters for which HCC would be the preferred construction method.
Recommendations
Based on the findings and conclusions of this investigation, the following recommendations
are made.
The following actions should be undertaken by individual South African companies:
· Develop relationships with external project partners
· Train competent riggers and crane operators
The South African concrete industry should invest in the following actions:
· Invest in mass-producing precast concrete facilities
· Develop a central database of South African projects with information on time,
costs, project concepts and layouts to be used as a guideline for decision making
· Develop local guidelines for the production and application of self compacting
concrete
· Compile guidelines for the design and construction of HCC and precast concrete
construction in South Africa
· Develop a local hidden corbel type connection to its full potential
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Investigation of marine components of large direct seawater intake & brine discharge systems for desalination plants, towards development of a general design approachLe Roux, Maria 03 1900 (has links)
Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: This investigation focused on the marine components of large direct seawater intake and brine
discharge systems for seawater desalination plants, with the main aim to provide an overall design
approach for these components.
Due to its complexity, an overall and systematic design approach, addressing all the components
(feedwater requirements, plant technology, marine structures and environmental issues) is required to
ensure an optimum design. A literature review was done on the various desalination technologies,
the main components of a seawater desalination plant, as well as the physical, hydraulic, operational
and environmental issues regarding seawater extraction facilities, marine pipelines and discharge
structures (diffuser).
In order to obtain practical input to the development of an overall design approach, information
regarding the marine structures of ten of the largest existing seawater desalination plants throughout
the world were obtained and compared with each other and the available technologies.
By way of example, the recently designed marine components of a new seawater reverse osmosis
desalination plant in Namibia were reviewed and, as part of this thesis, alternative conceptual
concepts which will include two additional components (sump and brine reservoir) were designed.
The alternative design was compared with the actual design in order to determine the feasibility of the
alternative in terms of operation and cost and subsequently provide input to the overall design
recommendations.
Furthermore, from the literature review it seems that there are still significant uncertainties regarding
the required performance of a brine (dense) outfall and this required more attention in terms of
environmental and hydraulic performance. Based on the Namibian plant, the diffuser configuration
was analysed in terms of its hydraulic and environmental performance and subsequently some
general guidance with specific respect to a brine diffuser was developed, which in turn formed part of
the overall design approach for the marine components.
Finally, the design approach for seawater intake structures, brine outfalls and the connecting marine
pipelines is provided in the form of flow diagrams. / AFRIKAANSE OPSOMMING: Hierdie ondersoek handel oor die mariene komponente van groot en direkte toevoer van seewater en
die sout-uitvloeisisteme van ontsoutingsaanlegte van seewater. Die doel is om ‘n oorsigtelike
ontwerpbenadering vir hierdie component te verskaf.
As gevolg van die kompleksiteit, is ‘n oorsigtelike en sistimatiese benadering, wat al die komponente
(vereistes vir toevoerwater, tehnologie by die aanleg, mariene omstandighede en omgewingsfaktore)
in ag neem noodsaaklik om die beste ontwerp te verseker.
‘n Literêre oorsig is gedoen ten opsigte van die tegnologie van verskeie ontsoutingsmetodes, die
hoofkomponente van ‘n seewater-ontsoutingsaanleg, asook die fisiese, hidrouliese, operasionele en
omgewingskwessies rakende die fasiliteite om die seewater te onttrek, die mariene pyplyne en die
strukture vir die afvloei.
Ten einde die optimum ontwerp te ontwikkel, is inligting oor die tegnologie en strukture van tien van
die grootste bestaande onsoutingsaanlegte in die wêreld bekom, bestudeer en vergelyk Hulle is met
mekaar vergelyk, asook met beskikbare tegnologie.
As ‘n voorbeeld is die nuut ontwerpte mariene komponente van die nuwe ontsoutingsaanleg in
Namibië, waar ontsouting d.m.v. omgekeerde osmose gedoen word ondersoek en as deel van hierdie
tesis, is ‘n alternatiewe konsep, wat twee bykomende komponente – ‘n opvangput en reservoir vir die
afloop – ontwerp. Hierdie alternatiewe ontwerp is met die werklike aanleg vergelyk om die
uitvoerbaarheid van die onderneming en die koste daaraan verbonde te toets. Dit is gebruik as
aanbeveling vir die oorhoofse ontwerp.
Uit die literêre oorsig blyk dit dar daar nog groot onsekerheid is oor die vereistes van die (digte)
waterafloop en dat meer aandag aan die omgewings- en hidrouliese aspekte gegee moet word. Met
die Namibiese aanleg as voorbeeld, is die struktuur van die spreiers t.o.v. hidrouliese werkverrigting
en die omgewing ontleed. Voortspruitend daaruit is algemene riglyne vir ‘n spesifieke spreier vir
afloopwater ontwikkel, wat op sy beurt weer deel vorm van die oorhoofse ontwerp vir mariene
komponente.
Laastens is die ontwerp vir die strukture vir seewater-invloei, die afloopwater en die mariene
verbindingspyplyne as vloeidigramme aangetoon.
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Laboratory accelerated curing protocol for bitumen stabilized materialsMoloto, Percy Kgothatso 03 1900 (has links)
Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The research conducted in this study forms part of the Phase II process of the Bitumen
Stabilized Materials (BSMs) Guideline improvement initiative. The initiative aims to address
areas of concern in the cold mix design procedures for BSMs.
Current road rehabilitation using the bitumen stabilization process requires testing of
representative specimens as means to evaluate pavement performance over time. In order to
adequately acquire specimens representative of field conditions, it is necessary to condition the
materials in a process called curing. Although curing procedures have been standard in many
countries on different continents, the protocols are varied and an acceptable procedure is
currently not available.
In order to develop an acceptable curing protocol for BSMs, both field and laboratory
environments were investigated. Considering that curing takes time in the field, production of
representative samples intended for laboratory testing must undergo accelerated curing in the
laboratory. Given the complexities involved in achieving close correlations between field and
laboratory environments, the research strived to reconcile field and laboratory material
behaviour. In particular, the main objective of the research was to unify the curing protocol for
BSMs, with the standardization of the curing protocol being top priority.
In this study, laboratory results have confirmed that the different natures of curing mechanisms
inherent in a BSM-foam and BSM-emulsion contribute to irreconcilable material behaviour(s).
Results have confirmed that curing of BSM-foam is largely a function of water repulsion, with the
addition of active filler dominating material performance almost immediately. Unlike BSM-foam,
curing of BSM-emulsion is both a function of the breaking of emulsion during the initial phase
and the gradual release of moisture with time. In this instance, BSM-emulsion material
performance resembled active filler influences past the breaking of the emulsion cycle.
Consequently, given the observed differences regarding material behaviour(s), the unification of
the curing protocol for BSMs has not been successful.
In terms of accommodation of active filler in the final curing protocol for BSMs, findings in this
research have revealed that active filler’s tendency to absorb moisture in the initial stages
requires longer curing time to help extract the absorbed moisture during the curing process.
Although the use of active filler has an impact on curing, its inclusion in a BSM does not justify
its extension in the curing time as cementation is not one of the desired properties of these
materials. BSMs are primarily desirable for their flexibility in pavement structures. For this
reason, active filler was omitted in the final curing protocol due to reasons of simplifying the mix
design process.
In conclusion, different curing protocols were tested and developed to help produce reconcilable
material behaviour in both the field and laboratory environments. Through the reconciliation of
key material properties such as the resilient modulus, long term equilibrium moisture conditions
and shear parameters, an acceptable standardized curing protocol for BSM-foam and BSMemulsion
intended for application in industrial laboratories across South Africa was successfully
developed. / AFRIKAANSE OPSOMMING: Die navorsing tydens hierdie studie gedoen, vorm deel van die Tweede fase van die Bitumen
Gestabiliseerde Materiale Riglyne verbeteringsinisiatief. Die inisiatief het ten doel om areas van
bekommernis in die kouemengsel-ontwerp-prosedures vir Bitumen Gestabiliseerde Materiale
aan te spreek.
Huidige padrehabilitasie wat gebruik maak van die Bitumen Gestabiliseerde Materiale proses,
vereis toetsing van verteenwoordigende monsters om sodoende plaveiselgedrag oor ‘n tydperk
te evalueer. Materiale moet deur die verouderingsproses gekondisioneer word, om sodoende
monsters te verkry wat akkuraat verteenwoordigend van veldtoestande is. Alhoewel
verouderingsprosesse in meeste lande - op verskillende kontinente - gestandariseerd is, is die
protokol verskillend en ‘n aanvaarbare prosedure is nie tans beskikbaar nie.
Beide veld- en laboratoriumomgewings is ondersoek, om sodoende ‘n aanvaarbare
verouderings-protokol vir Bitumen Gestabiliseerde Materiale te ontwikkel. Wanneer in ag
geneem word dat veroudering in die veld tydrowend is, moet vervaardiging van
verteenwoordigende monsters vir laboratoriumgebruik versnelde veroudering in die
laboratoruim ondergaan. Gegee die kompleksiteite betrokke om goeie korrelasie tussen velden
laboratoriumomgewings te verkry, het die navorsing daarna gestreef om die veld- en
laboratoriummateriaalgedrag te verenig. Die hoofdoel van die navorsing was om die
verouderingsprotokol vir Bitumen Gestabiliseerde Materiale te verenig met die stardaardisering
van die verouderingsprotokol as top prioriteit.
In hierdie studie het laboratorium resultate bevestig dat die verskillende aard van
voorbereidings- meganismes inherent in BSM-skuim en BSM-emulsie bydra tot onversoenbare
materiaalgedrag. Resultate het bevestig dat voorbereiding van BSM-skuim ’n funksie van
waterrepulsie het en met die byvoeging van aktiewe vullers dominieer dit die materiaalgedrag
byna onmiddelik. Anders as BSM-skuim is die voorbereiding van BSM-emulsie beide ’n funksie
vir die breek van emulsie tydens die begin fase en die geleidelike vrystelling van vog oor tyd. In
hierdie geval het BSM-emulsie se materiaalgedrag die invloed van aktiewe vuller getoon nadat
die emulsie gebreek het. Gevolglik, weens die waargenome verskille rakende materiaalgedrag
is die vereniging van die voorbereidings- protokols vir BSMs nie suksesvol nie.
In terme van inagneming van aktiewe vullers in die finale voorbereidingsprotokol vir BSM’s, is
deur navorsing bevind dat aktiewe vullers neig se neiging om vog te absorbeer in die
beginstadia dit benodig dus ‘n langer verouderingstyd vir die ontrekking van die geabsorbeerde
vog. Hoewel die gebruik van aktiewe vullers ’n impak het op die voorbereiding, reverdig dit nie
die verlenging van die verouderingstyd vir die insluiting daarvan in BSM nie, siende dat
sementering nie een van die gewenste eienskappe van hierdie materiaal is nie. BSMs word
hoofsaaklik verkies vir sy buigsaamheid in paveiselsturkture. Om die mengselontwerp prosesse
te vereenvoudig, was aktiewe vullers dus weggelaat in die finale voorbereidingsprotokol.
Ter afsluiting was verskeie voorbereidings protokolle getoets en ontwikkel om te help met die
vervaardiging van versoenbare materaalgedrag in beide veld-en-laboratoriumomgewings. Deur
die versoening van kern materiaal eienskappe soos die elastisiteitsmodulus, lang
termynewewigvog kondisies en skuifparameters, is ’n aanvaarbare gestandariseerde
voorbereidingsprotokol vir BSM-skuim en BSM-emulsie bedoel vir aanwending in industriele
laboratoriums regoor Suid Afrika suksesvol ontwikkel.
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