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A sustainable delivery approach for peri-urban and rural areas.January 2004 (has links)
Challenges of implementing Integrated Development programmes can be seen in the difficulty in aligning different departmental budgets and processes in the implementation phase of projects. This has had many implications for development. However, the use of conventional and single sector approaches to meet development needs has been more apparent. The need to respond to a lack of basic services and poverty in rural and periurban has been growing. Absence of appropriate rural and peri-urban development approaches, and non-alignment of policy and budgets across government structures have resulted in the use of urban based models. This has culminated in the creation of settlements that are unable sustain themselves over time. The dissertation puts forward the hypothesis that "community development through the housing approach is not an appropriate development mechanism for rural and peri-urban areas". It also highlights problems faced in attempting peri-urban and rural areas. This is illustrated by a case study - Intathakusa Integrated Development Programme. This is a peri-urban and rural development programme located within the boundaries of eThekwini Metropolitan Area and is used to illustrate problems faced by a number of areas of similar nature. This project attempted to deliver integrated programmes within the urban edge and the peripheral parts of the city. Qualitative research methods facilitated an in-depth exploration of relevant issues in this dissertation. Development practitioners and community representatives were interviewed to elicit information on the challenges facing peri-urban and rural development and to explore possible alternatives. The dissertation concludes with suggestions for sustainable livelihoods approaches for rural and peri-urban areas. The research also acknowledges that the housing package is perhaps a basic requirement for rural and peri-urban areas. It acknowledges that housing offers a means through which a bundle of basic services (over and above a house) can be delivered. The research concludes by arguing that if this funding mechanism is to be used in rural and peri-urban areas, it should be repackaged to include bigger site sizes and agriculture. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2004.
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Rural road maintenance through labour-based lengthmen system in Zambia.Mwango, Abraham. January 2000 (has links)
Rural road maintenance has received little or no attention in Zambia for a long time,
resulting in an adverse impact on the economy. Meanwhile Road Authorities have
continued to use traditional capital-intensive periodic and routine maintenance at the
expense of scarce foreign exchange. The system has not performed well, hence the current
state of roads.
Labour-based methods for routine maintenance under the Lengthmen System used in
Kenya, Lesotho and other developing countries in the Sub-Saharan Africa have proved to
be technically and economically viable.
In this report the author examines the desirability of using the Labour-Based Lengthmen
System as an alternative to the existing capital -intensive methods in Zambia. This is done
through rev iewing rural road maintenance in Zambia and then carrying out a comparative
analysis of the same bctween Zambia, Kenya and Lesotho
The comparative analysis shows that Zambia is not performing well when compared to
Kenya and Lesotho. Meanwhile, the Lengthmen System is more desirable compared to
other methods under the current economic conditions. Recommendations, based on the
comparative analysis, have been given to improve rural road maintenance in Zambia. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2000.
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Wind induced sediment re-suspension in a shallow lake.Pringle, Justin James. January 2011 (has links)
Wind induced turbidity within shallow lakes can greatly affect the biological functioning
of a system in either a positive or negative manner. This research aims to understand
and model the physical processes that cause sediment re-suspension. Lake St Lucia
on the east coast of South Africa, a UNESCO World heritage site was used as a case
study. Lake St. Lucia is a shallow water system which commonly experiences high
levels of turbidity. Coupled with the naturally shallow depth of the lake, it is currently
drought stricken, resulting in abnormally low water levels. A simple model has been
developed which accounts for sediment re-suspension due to wind-driven waves and
their associated bed shear stresses. The wave heights within a shallow lake such as St
Lucia are controlled either by the fetch (for a large water depth), or the water depth (for
a large fetch). When the wind is strong enough, the wind-driven turbulent mixing
causes the water column to become fully mixed. When the wave-driven boundary layer
becomes turbulent, sediment, being entrained within the water column increases
significantly. The model also accounts for the effects of temporal consolidation on the
re-suspension of sediments by setting a time scale for the erosion processes. It was
found that the median of the monthly turbidity levels over the past ten years exceeded
the average turbidity levels over the past 92 years. In all cases it was shown that mouth
linkage with the uMfolozi resulted in lower turbidity levels than without any linkage due
to the higher average water levels.
The model was then developed to predict the spatial variation in turbidity within the
Southern Lake. This was achieved through the use of existing bathymetric data for the
Lake. This spatial model was then used to show how the turbidity varied for different
wind and water depth conditions. Two conditions were considered, a NE and SW wind
blowing at 8m/s for water levels of 0 EMSL and -0.5 EMSL. The spatial model showed
that a decrease in water level increases the turbidity within the lake significantly. The
wind directions appeared to yield similar results of sediment re-suspension. It was also
shown that the high turbidity values were situated in the shallow depths even though
the wave heights were small in comparison to those in deeper water. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2011.
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The flocculation dynamics of cohesive sediments in the St. Lucia and Mfolozi estuaries, South Africa.Maine, Christopher Mark. January 2011 (has links)
Increasing turbidities due to land use changes and poor catchment management can cause negative impacts on estuaries worldwide. High turbidity has an impact on the biological functioning of estuaries which are amongst our most productive ecosystems. This study focuses on the St Lucia estuary on the east coast of South Africa, a UNESCO World Heritage Site and Ramsar wetland of international importance. Increased turbidity due to suspended inorganic sediments has been identified as an important threat to the sustainability of biodiversity in the St Lucia system. In order to determine the influence of increased cohesive sediment loads on the estuarine system it is necessary to understand how flocculation affects the fate and transport of cohesive sediment. Flocculation describes the processes of aggregate formation and breakup. Suspended sediment concentration, salinity and turbulent shear rates have been identified as key drivers of estuarine flocculation. This study investigates flocculation by measuring how the floc size distribution and settling velocities of flocs vary with the key drivers. A laboratory technique was developed where flocculation was simulated in an agitated beaker. Digital imaging techniques were used to measure changes in the size of flocs within the beaker and floc settling velocities in a still settling column. Results show reduced aggregation and floc size with increases in turbulent shear. Floc settling velocities were observed to increase with floc size while the effective density was observed to decrease. The study is concluded by investigating potential applications for the results obtained. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2011.
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Traffic circles in South Africa : traffic performance and driver behaviour.Krogscheepers, Johann Christoff. January 1997 (has links)
This thesis presents the results of an investigation into traffic operations and driver behaviour at
traffic circles under South African conditions. The scarcity of local traffic circles necessitated the
development of a simulation program (TRACSIM) to assist in the research process. This
microscopic program for single lane circles is based on event updates and was calibrated and
validated based on local data. Because the acceptance of gaps is such a vital part of the operation
of a traffic circle, it was examined in detail. Specific attention was given to the possible use of a gap
acceptance model based on variables other than time. Since the gap acceptance process also depends
on the gap distribution in the circulating stream, the effect of the origin-destination pattern was also
investigated. Two existing analysis techniques are evaluated and verified for local conditions,
improving them where possible. Generally these techniques under-estimate traffic delay at local
circles.
Observations indicate a difference between the acceptance of gaps/lags in the entering and circulating
stream of conflicting traffic as well as a difference between critical gaps and critical lags. The mean
observed critical gaps/lags are larger than in other countries, which indicates that delays at local
circles will be greater. Gap/lag acceptance based on critical distances rather than critical times was
applied successfully in the simulation program TRACSIM. A method is proposed to estimate critical
distances from the geometric layout of the circle. Critical gaps are not fixed, but should vary with
at least the conflicting flows. The investigation of the effect of unbalanced flows on delay, showed
that the variability in drivers' critical gaps is more a function of delay than of conflicting flow. Entry
delays increase because of an increase in conflicting flows or because of an unfavourable imbalance
of conflicting flows. In both instances the drivers' critical gaps will decrease. A variable critical gap
model only based on conflicting flows will show no change in the drivers' critical gaps if the
conflicting volumes remain constant, even though the actual average delay might increase because
of an unfavourable imbalance in conflicting flows. / Thesis (Ph.D.)-University of Natal, Durban, 1997.
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Effective HIV and AIDS management : a South African construction sector model.Harinarain, Nishani. January 2013 (has links)
Abstract available on PDF file. / Ph.D.--University of KwaZulu-Natal, Durban, 2013.
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Anthropogenic impacts and biophysical interactions in Lake St Lucia.Chrystal, Robynne Angela Lawrie. January 2013 (has links)
The St Lucia estuarine lake system in South Africa is part of a UN-
ESCO World Heritage site and a Ramsar wetland of international
importance. Like many estuarine systems worldwide St Lucia has
experienced signi cant anthropogenic impacts over the past century
including catchment land use changes, water diversions/abstractions
and inlet manipulation. In addition, the system has recently su ered
losses in species diversity and abundance following unprecedented hy-
persaline conditions and desiccation. Questions regarding its sustain-
ability have motivated a reevaluation of management decisions made
in the past and of options for the future. To understand the func-
tioning of the system, it is necessary to analyse it holistically in terms
of the physical processes and their interaction with the biology. This
study focusses on aspects of the biophysical interactions in the estu-
arine complex, and aims to provide new knowledge to underpin the
development of improved models for predicting the response of the
system to anthropogenic interventions.
A model for the water and salt budgets was used to investigate what
if scenarios in terms of past anthropogenic interventions, in particular
the e ects of diverting the Mfolozi River from St Lucia. Furthermore,
the risks of hypersalinity and desiccation were assessed for each sce-
nario. Integrating these modeled scenarios with observed biological
responses to physicochemical changes suggested that large long-term
changes in the ecological structure can be expected in the di erent
management scenarios. To validate this, the ecosystem response to
changing environmental responses was quantitatively assessed using
ecological network analysis.
Long-term simulations show that the separation of the Mfolozi and
St Lucia mouths had a signi cant impact on the functioning of the St
Lucia system. The Mfolozi plays a pivotal role in maintaining a more
stable mouth state regime and provides a vital source of freshwater
during dry conditions. The con guration of the Mfolozi/St Lucia inlet
plays a key role in the physico-chemical environment of the system and
in
uences the system's susceptibility to desiccation and hypersaline
conditions. Ecosystem indices revealed that the water level, salinity
and mouth state have a signi cant impact on species abundance and
diversity as well as the ecological structure and functioning of the
system. In addition, ecosystem indices show that the system recovers
rapidly during favourable conditions. The arti cial separation of the
St Lucia and Mfolozi inlets underpins the most signi cant impacts on
the water and salt budget of the lake and its reversal is key to the
sustainability of the system. / Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2013.
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Reliability assessment of structural concrete with special reference to shear resistanceMensah, Kenneth Kwesi 03 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Structural design standards based on the principles of structural reliability are gaining
worldwide acceptance and are fast becoming the new basis of structural safety verification.
The application of these principles to establish a standardised basis for structural design using
partial factor limit states design procedures is done in the European Standard for the Basis of
Structural Design EN 1990 from which it is adapted to the South African Basis of Design
Standard for Building and Industrial Structures SANS 10160-1. The basis of design
requirements stipulated in EN 1990 and SANS 10160-1 apply to all aspects of structural
design: This includes reliability levels of structural performance and their differentiation and
management; identification of various limit states and design situations; the specification of
all the basic variables; separate treatment of actions and material-based resistance. However,
application of these requirements is then primarily focused on actions whilst the provision for
structural concrete is then left to the materials based design standards.
This two-part thesis describes a systematic assessment of the degree to which the application
of the reliability framework presented in the basis of design requirements has been achieved
in the present generation of structural concrete design standards. More importantly, attempts
are made to identify ways in which the process can be advanced. Special attention is drawn
to issues that are specific to South African conditions and practice in structural concrete.
Part One of the thesis focuses on the key elements of the reliability framework presented in
EN 1990 and traces to what extent the requirements have been propelled through the design
stipulations of the Eurocode Standard for Design of Concrete Structures EN 1992-1-1. The
implications of the different reference level of reliability between the Eurocode default value
of ß = 3.8 and that characteristic of South African practice ß = 3.0 through various issues
are highlighted. The use and advantage of explicit treatment of reliability performance on
reliability management related to some aspects of quality control are explored. A critical
aspect is the shear prediction model providing unconservative estimates of shear resistance.
Part Two of the thesis focuses on characterising the model factor of the EN 1992-1-1 shear
prediction model for members requiring design shear reinforcement. This is done by a
comparison to a compiled experimental database with special focus on situations with high
reinforcement ratios. The significance of the modelling uncertainty in shear prediction is verified by this comparison. The use of the more conceptually rational modified compression
field theory (MCFT) to improve on the quality of shear predictions is investigated and proves
to yield more precise values with lower scatter hence making it a more reliable tool for
predicting shear. The MCFT can then be used as reference for the reliability calibration and
possible improvement for the Eurocode procedure. / AFRIKAANSE OPSOMMING: Strukturele ontwerpstandaarde gebaseer op die beginsels van strukturele betroubaarheid
verkry wêreldwye aanvaarding en word vinnig die nuwe basis van strukturele veiligheid
bevestiging. Die toepassing van hierdie beginsels om ʼn gestandaardiseerde basis vir
strukturele ontwerp is bevestig deur gebruik te maak van gedeeltelike-faktorbeperkende
stadiums ontwerpprosedures in die Europese Standaard vir die Basis van Strukturele
Ontwerp EN 1990 waarvandaan dit herbewerk is na die Suid-Afrikaanse Basis van Ontwerp
Standaarde vir Bou en Industriële Strukture SANS 10160-1. Die basis van ontwerpvereistes
bepaal in EN 1990 en SANS 10160-1 is van toepassing op alle aspekte van strukturele
ontverp: Dit sluit inbetroubaarheidsvlakke van struktureele prestasie en hul diversifikasie en
bestuur; identifikasie van verskeie beperkende state en ontwerpsituasies; die spesifikasie van
al die basiese veranderlikes; afsonderlike behandeling van aksies en materiaal-gebaseerde
weerstand. Desnieteenstaande, die toepassing van hierdie voorwaardes is dan hoofsaaklik
gefokus op aksies terwyl die voorsiening van strukturele beton is dan gelaat op die materiaalgebaseerde
ontwerpstandaarde.
Hierdie tweeledige verhandeling beskryf ʼn stelselmatige beoordeling van die graad waartoe
die toepassing van die betroubaarheidsraamwerk aangebied word in die basis van
ontwerpvereistes bereik in die huidige generasie van strukturele beton-ontwerp standaarde is.
Meer belangrik, pogings is aangewend om die maniere hoe die proses bevorder kan word te
identifiseer. Spesiale aandag word gevestig op kwessies wat spesifiek op Suid-Afrikaanse
toestande en praktyke in strukturele beton toepaslik is.
Deel Een van die verhandeling fokus op die sleutel-dele van die betroubaarheidsraamwerk
aangebied in EN 1990 en skets die mate waartoe die vereistes aangespoor word deur die
ontwerp voorskrifte van die Eurocode Standard for the Design of Concrete Structures EN
1992-1-1. Die implikasie van die verskillende verwysingsvlakke van betroubaarheid tussen
die Eurocode standaardwaarde van ß = 3.8 en die eienskap van Suid-Afrikaanse praktyk
ß = 3.0 deur verskillende kwessies word uitgelig. Die gebruik en voordeel van spesifieke
behandeling van betroubaarheidsuitvoering op betroubaarheidsbestuur verwantskap met
sekere aspekte van kwaliteit kontrole word ondersoek. ʼn Kritiese aspek is die model vir die
voorspelling van skuif-weerstand wat die onkonserwatiewe beramings vir skuif-weerstand
gee. Deel Twee van die verhandeling fokus op karakterisering die modelfaktor van die EN 1992-
1-1 skuif-weerstand voorspellings-model. Dit word gedoen deur ʼn vergelyking na ʼn
saamgestelde eksperimentele databasis met spesifieke fokus op situasies met hoe
herbevestigingsvergelykings. Die oorheersing van die modellering- onsekerheid in skuifweerstand
voorspelling is bevestig deur hierdie vergelyking. Die gebruik van ʼn meer
konseptuele rasionele gemodifiseerde druk-veld teorie (bekend as MCFT) om die kwaliteit
van skuif voorspelling te verbeter is ondersoek en verskaf ‘n meer presiese waarde met laer
verspreiding wat lei tot ʼn meer betroubaree instrument om skuif mee te voorspel. Die MCFT
word dan gebruik as verwysing vir die betroubaarheid-samestelling en moontlike verbetering
van die Eurocode prosedures.
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The time-dependent cracking behaviour of strain hardening cement-based compositeAdendorff, Christo Johan 12 1900 (has links)
Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Strain Hardening Cement-based Composite (SHCC) is part of the High Performance Fibre
Reinforced Cement-based Composite (HPFRCC) family and is a relative new concrete
composite. This Fibre Reinforced Cement-based Composite (FRCC) contains randomly
distributed short fibres and when subjected to a uni-axial tensile load multiple cracking
occurs. The multiple cracking generates fine cracks which are normally smaller than 100
μm and achieve a strain capacity of more than 5 %. There are limited publications
regarding the research of sustained tensile tests on SHCC and especially the cracking
behaviour of SHCC under quasi-static uni-axial as well as sustained tensile loads.
The cracking behaviour is described as the average crack width, number of cracks and
descriptive statistical properties which could be used to represent the distribution of the
multiple fine cracks under uni-axial tension. There are two types of tests that were under
consideration to determine the cracking behaviour of SHCC. The first is quasi-static uniaxial
tensile tests and the second is sustained tensile tests. The latter was dependant on the
uni-axial tensile tests in terms of the sustained load applied. The sustained loads ranged
from 40 % to 80 % of the ultimate tensile resistance recorded from the uni-axial tensile
tests that correspond with a strain rate of 0.001 /s. Different strain rates were used for the
uni-axial tensile tests to determine the effect on the cracking behaviour. The cracking
behaviour was determined with the aid of a non-contact optical 3D digital deformation
measuring device called ARAMIS.
The content of this thesis gives a background study of the cracking behaviour and relevant
research performed on SHCC under certain loads as well as some literature about the timedependant
effects of a cement-based composite.
The functioning of the device called ARAMIS is explained as well as the resulting effects
of this device on the preparation of the test specimens. The experimental framework for the
uni-axial and sustained tensile tests is discussed. Thereafter, the experimental results of the tests are depicted and discussed. The results shed
some light on the basic material properties such as the average ultimate stress and average
ultimate strain, Young’s modulus, etc. for the quasi-static tensile tests as well as shrinkage
and creep of SHCC. The cracking behaviour such as the average crack width, number of
cracks, the variance and skewness of the distribution of the crack widths in the test
specimens for the quasi-static uni-axial and sustained tensile tests are depicted and
discussed.
The cracking behaviour when subjected to uni-axial tensile tests with different strain rates
is significantly governed by the formation of new cracks and the average crack width
remains small with increase in strain. There is no significant difference for the cracking
behaviour found when subjected to different strain rates. However, when SHCC is
subjected to a sustained load then the average crack width is dependant on the number of
cracks that form over time as well as the load level. The formation of fewer and wider
cracks was observed for specimens loaded at average 40 % of the ultimate tensile resistance
stress, however at loading percentages of higher than 65 % more cracks developed which
resulted in a smaller average crack width. / AFRIKAANSE OPSOMMING: Vervorming Verharding Sement gebaseerde samestelling “Strain Hardening Cement-based
Composite” (SHCC) is deel van die familie van “High Performance Fibre Reinforced
Cement-based Composite” (HPFRCC) en is ʼn relatiewe nuwe beton samestelling. Hierdie
vesel versterkte sement gebaseerde beton bevat willekeurig verspreide kort vesels en
veelvoudige klein krake vorm onder monotoniese trekkragte. Hierdie veelvoudige klein
krake is minder as 100 μm wyd en lei tot ʼn vervorming van meer as 5 %. Daar is ʼn tekort
aan navorsing oor die kruip van SHCC sowel as die kraak gedrag van hierdie sement
gebaseerde samestelling onderhewig aan trek.
Die kraak gedrag word beskryf as die gemiddelde kraakwydte, aantal krake en ʼn paar
beskrywende statistiese parameters. Hierdie kraak gedrag parameters kan gebruik word om
ʼn verdeling te kan weergee van die veelvoudige klein krake onder ʼn trek belasting. Twee
tipes toetse was uitgevoer om die kraak gedrag te beskryf. Die eerste tipe toets was
monotoniese trek toetse en die tweede tipe was kruip toetse. Die tweede toets was afhanklik
van die monotoniese trek toetse in terme van die belasting wat gebruik was vir die kruip
toetse. Die belasting was gevarieer vanaf 40 % tot 80 % van die breekbelasting wat bepaal
is met die monotoniese trektoetse wat ooreenstem met ʼn vervorming tempo van 0.001 /s.
Verskillende vervorming tempo’s vir die monotoniese trektoetse was uitgevoer om te
bepaal wat die effek is op die kraak gedrag. Die kraak gedrag was bepaal met behulp van ʼn
geen-kontak optiese 3D digitale deformasie meet instrument genoem ARAMIS.
Die inhoud van die tesis bevat ʼn kort opsoming oor ʼn agtergrond studie van die kraak
gedrag en relevante navorsing oor vesel versterkte sement gebaseerde beton, sowel as
literatuur oor die tydafhanklike effekte van ʼn sement gebaseerde samestelling.
Die beheer en gebruik van die meet instrument ARAMIS word verduidelik, sowel as die
effek van hierdie masjien op die voorbereiding vir die eksperimente. Die eksperimentele
uiteensetting vir die monotoniese en kruip toetse word beskryf. Daarvolgens is die resultate van die eksperimentele toetse getoon en verduidelik. Die
resultate verduidelik die basiese materiaal eienskappe, byvoorbeeld die gemiddelde
breekspanning met die ooreenkomstige breekvervorming, Young’s modulus en so voorts
vir die monotoniese trektoetse, sowel as eienskappe met betrekking tot krimp en kruip van
SHCC. Die kraak gedrag naamlik die gemiddelde kraakwydte, aantal krake per meter,
variansie en die skuinsheid van die ontwikkelde krake met die toets proefstukke vir die
monotoniese en kruip trek toetse word weergegee en verduidelik.
Die kraak gedrag van SHCC wanneer getoets word met verskillende monotoniese trektoets
tempo’s word beheer deur die ontwikkeling van nuwe krake en die gemiddelde kraakwydte
is beduidend laag met toenemende vervorming. Daar is geen beduidende verskil in die
kraak gedrag ten opsigte van die verskillende monotoniese trek tempo’s nie. In teendeel,
wanneer SHCC belas word met ʼn konstante las oor tyd word die gemiddelde kraakwydte
beheer deur die ontwikkeling van nuwe krake sowel as die belasting wat aangewend is.
Onder ʼn belasting van so laag as 40 % van die breekbelasting vorm daar minder krake,
maar met ʼn groter gemiddelde kraakwydte. Wanneer belas word met meer as 65 % van die
breekbelasting vorm meer krake wat lei tot ʼn kleiner gemiddelde kraakwydte.
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Assessment of seismic drift of structural walls designed according to SANS 10160 - Part 4Le Roux, Rudolf Cornelis 12 1900 (has links)
Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Reinforced concrete structures, designed according to proper capacity design guidelines, can deform
inelastically without loss of strength. Therefore, such structures need not be designed for full elastic
seismic demand, but could be designed for a reduced demand. In codified design procedures this
reduced demand is obtained by dividing the full elastic seismic demand by a code-defined behaviour
factor. There is however not any consensus in the international community regarding the appropriate
value to be assigned to the behaviour factor. This is evident in the wide range of behaviour factor
values specified by international design codes.
The purpose of this study is to assess the seismic drift of reinforced concrete structural walls in order
to evaluate the current value of the behaviour factor prescribed by SANS 10160-4 (2009). This is
done by comparing displacement demand to displacement capacity for a series of structural walls.
Displacement demand is calculated according to equivalency principles (equal displacement principle
and equal energy principle) and verified by means of a series of inelastic time history analyses (ITHA).
In the application of the equivalency rules the fundamental periods of the structural walls were based
on cracked sectional stiffness from moment-curvature analyses.
Displacement capacity is defined by seismic design codes in terms of inter storey drift limits, with the
purpose of preventing non-structural damage in building structures. In this study both the
displacement demand and displacement capacity were converted to ductility to enable comparison.
The first step in seismic force-based design is the estimation of the fundamental period of the
structure. The influence of this first crucial step is investigated in this study by considering two period
estimation methods. Firstly, the fundamental period may be calculated from an equation provided by
the design code which depends on the height of the building. This equation is known to overestimate
acceleration demand, and underestimate displacement demand. The second period estimation
method involves an iterative procedure where the stiffness of the structure is based on the cracked
sectional stiffness obtained from moment-curvature analysis. This method provides a more realistic
estimate of the fundamental period of structures, but due to its iterative nature it is not often applied in
design practice.
It was found that, regardless of the design method, the current behaviour factor value prescribed in
SANS 10160-4 (2010) is adequate to ensure that inter storey drift of structural walls would not exceed
code-defined drift limits. Negligible difference between the equivalency principles and ITHA was
observed. / AFRIKAANSE OPSOMMING: Gewapende beton strukture wat ontwerp is volgens goeie kapasiteitsontwerp-riglyne kan plasties
vervorm sonder verlies aan sterkte. Gevolglik hoef hierdie strukture nie vir die volle elastiese
seismiese aanvraag ontwerp te word nie, maar kan vir 'n verminderde aanvraag ontwerp word. In
gekodifiseerde ontwerpriglyne word so 'n verminderde aanvraag verkry deur die volle elastiese
aanvraag te deel deur 'n kode-gedefinieerde gedragsfaktor. Wat egter duidelik blyk uit die wye reeks
van gedragsfaktor waardes in internasionale ontwerp kodes, is dat daar geen konsensus bestaan in
die internasionale gemeenskap met betrekking tot die geskikte waarde van die gedragsfaktor nie.
Die doel van hierdie studie is om seismiese verplasing van gewapende beton skuifmure te evalueer
ten einde die waarde van die gedragsfaktor wat tans deur SANS 10160-4 (2009) voorgeskryf word te
assesseer. Dit word gedoen deur verplasingsaanvraag te vergelyk met verplasingskapasiteit.
In hierdie studie word verplasingsaanvraag bereken deur middel van gelykheidsbeginsels (gelyke
verplasingsbeginsel en gelyke energiebeginsel) en bevestig deur middel van nie-elastiese
tydsgeskiedenis analises (NTGA). Die effek van versagting as gevolg van nie-elastiese gedrag word
in aanmerking geneem in die toepassing van die gelykheidsbeginsels.
Verplasingskapasiteit word deur seismiese ontwerpkodes gedefinieer deur perke te stel op die
relatiewe laterale beweging tussen verdiepings, met die doel om nie-strukturele skade te verhoed.
Om verplasingsaanvraag en -kapasiteit te vergelyk in hierdie studie, word beide omgeskakel na
verplasingsduktiliteit.
Die eerste stap in kraggebaseerde seismiese ontwerp is om die fundamentele periode te beraam. Die
invloed van hierdie eerste kritiese stap word in hierdie studie aangespreek deur twee
periodeberamingsmetodes te ondersoek. Eerstens kan die fundamentele periode bereken word deur
'n vergelyking wat 'n funksie is van die hoogte van die gebou. Dit is egter algemeen bekend dat
hierdie vergelyking versnellingsaanvraag oorskat en verplasingsaanvraag onderskat. Die tweede
metode behels 'n iteratiewe prosedure waar die styfheid van die struktuur gebaseer word op die
gekraakte snit eienskappe, verkry vanaf 'n moment-krommingsanalise. 'n Beter beraming van die
fundamentele periode word verkry deur hierdie metode, maar as gevolg van die iteratiewe aard van
die metode word dit selde toegepas in ontwerppraktyk.
Die resultate van hierdie studie toon dat die huidige waarde van die gedragfaktor soos voorgeskryf in
SANS 10160-4 (2010) geskik is om te verseker dat die relatiewe laterale beweging tussen verdiepings
binne kode-gedefinieerde perke sal bly. Onbeduidende verskil is waargeneem tussen die resultate
van gelykheidsbeginsels en NTGA.
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