130 research outputs found
Evaluation of batch test for measurement of active biomass in activated sludge mixed liquor
No full textIncludes bibliographical references.Over the past two decades significant advances have been made in the areas of engineering (design) and technology (implementation and operation) of the single sludge activated sludge system. Activated sludge systems have been successfully designed and implemented at full-scale for the biological removal of carbon (C), nitrogen (N) and phosphorus (P). This implementation has been aided by the development of a suite of steady state design models (e.g. WRC, 1984; Wentzel et aI., 1990; Maurer and Gujer, 1994) and kinetic simulation models (e.g. Dold et al., 1980, 1991; Van Haandel et aI., 1981; Henze et al. , 1987; Wentzel et aI., 1992; Henze et al., 1995)
Prime-boost regimens with adjuvanted synthetic long peptides elicit T cells and antibodies to conserved regions of HIV-1 in macaques.
No full textAbstract
OBJECTIVES:
Administration of synthetic long peptides (SLPs) derived from human papillomavirus to cervical cancer patients resulted in clinical benefit correlated with expansions of tumour-specific T cells. Because vaginal mucosa is an important port of entry for HIV-1, we have explored SLP for HIV-1 vaccination. Using immunogen HIVconsv derived from the conserved regions of HIV-1, we previously showed in rhesus macaques that SLP.HIVconsv delivered as a boost increased the breath of T-cell specificities elicited by single-gene vaccines. Here, we compared and characterized the use of electroporated pSG2.HIVconsv DNA (D) and imiquimod/montanide-adjuvanted SLP.HIVconsv (S) as priming vaccines for boosting with attenuated chimpanzee adenovirus ChAdV63.HIVconsv (C) and modified vaccinia virus Ankara MVA.HIVconsv (M).
DESIGN:
Prime-boost regimens of DDDCMS, DSSCMS and SSSCMS in rhesus macaques.
METHODS:
Animals' blood was analysed regularly throughout the vaccination for HIV-1-specific T-cell and antibody responses.
RESULTS:
We found that electroporation spares DNA dose, both SLP.HIVconsv and pSG2.HIVconsv DNA primed weakly HIVconsv-specific T cells, regimen DDDCM induced the highest frequencies of oligofunctional, proliferating CD4(+) and CD8(+) T cells, and a subsequent SLP.HIVconsv boost expanded primarily CD4(+) cells. DSS was the most efficient regimen inducing antibodies binding to regions of trimeric HIV-1 Env, which are highly conserved among the four major global clades, although no unequivocal neutralizing activity was detected.
CONCLUSION:
The present results encourage evaluation of the SLP.HIVconsv vaccine modality in human volunteers along the currently trialled pSG2.HIVconsv DNA, ChAdV63.HIVconsv and MVA.HIVconsv vaccines. These results are discussed in the context of the RV144 trial outcom
Communication for porverty alleviation : The case study of Plan, An international Humanitarian, Child focused Development Organisation working in Zambia
No full textPoverty affects nations in many different ways. Many people in Zambia especially in rural areas live in poverty. Plan an international humanitarian, child-focused development organisation without religious or political affiliation is among many non-governmental organisations that are
lighting against poverty. The author was attached to Plan in Zambia from March to May 2004. The attachment provided the author with a rare opportunity to work for an international organisation. Plan has undertaken a number of programmes to improve the food security of its target
beneficiaries. Plan has spent a lot of resources on capacity building so that the communities can sustain the programmes after completion of its programmes. The groundnuts seed multiplication project in Chadiza and the livestock restocking project in Mazabuka have assisted a lot of people to improve their food security. Communication is vital in the successful implementation of any project. The researcher recommends that Plan in Zambia should publicise its activities so that people can know about its programmes. Communication strategies should put emphasis on dissemination of information about its programmes and how to sustain these programmes
Cloning, expression, purification and drug targeting of Plasmodium falciparum hypoxanthine guanine xanthine phosphoribosyltransferase (HGXPRT)
No full textIncludes bibliographical references.The research concerns sub-cloning the gene for HGXPRT from Plasmodium falciparum from a vector with a His-tag facility to one without, expression of the protein in E. coli, and purification. On an analytical scale (40 ml culture), a purification procedure was developed that involves extraction of contaminating proteins by anion exchange chromatography (HGXPRT does not bind under the conditions used), followed by Reactive Red 120 agarose affinity chromatography
Urban poverty as a challenge for ministry within the Malawian context
No full textThesis (DTh)--Stellenbosch University, 2002.ENGLISH ABSTRACT: This dissertation develops a theory for doing Malawian urban ministry called "Holistic hermeneutical practical theology." The effects of urbanization: secularization, disorientation, poverty and pollution in Malawi's urban centers make it difficult for the CCAP to implement successful ministry that deals with the shantytowns' circumstances. Chapter one: The first chapter describes the Malawian urban context. It defines the five components of the researcher's topic of study: "Urban poverty as a challenge for ministry within the Malawian (African) context" and the three components of the methodology: "Holistic hermeneutical practical theology." Four relational hypotheses are formulated to guide the study. Different research methods applied to gathering information for chapters of this dissertation are documented at the end of this chapter. Chapter two: The second chapter examines the CCAP's existing ministry practice and addresses the first hypothesis: "Its rural background and theory of ministry prevent the CCAP from developing an effective urban ministry that adequately addresses the problems of the poor." The missionaries introduced a comprehensive ministry approach to the early leaders of the CCAP Nkhoma Synod. In the process of blending the missionary approach to ministry in the local Chewa context, a philosophy of ministry that emphasizes spiritual salvation (neglecting the physical needs) was developed in the CCAP Nkhoma Synod. This approach poses a problem for the Church to adequately address the physical needs and realities of Malawians in the cities. Chapter three: The third chapter discusses the poverty situations of Malawian and South African shantytowns and slums and is the result of research conducted in order to examine the validity of the four hypotheses. The responses of the groups interviewed were helpful for an understanding of the current congregational challenges and ministry opportunities in urban areas. This chapter addresses issues of this thesis positively: research objectives, the population growth data of urban inter-censal, a brief historical description of Malawian cities, the government efforts to address urban challenges and problems, the CCAP ministry approach to urban ministry, and a brief description of two South African poverty scenarios. The research reveals that the church and the government work independently of each other. In this way the validity of the third hypothesis: "A holistic approach to urban ministry with joint forums for development is needed to address urban poverty problems," is confirmed. Chapter four: This chapter describes the extent of poverty in Malawi, which is most disturbing. The recent studies on Malawian poverty indicate that the poverty scenario is a pervasive problem affecting approximately 60% of the population; urban poverty, in particular, is 65%. Furthermore, chapter four discusses a number of issues, some of which are: a description and Christian views of the poor, an overview definition of urban poverty, the causes of poverty and the vocation of the urban church. The cities' informal economies can make a huge difference in the lives of the poor. All of the four hypotheses form the background to this chapter. Chapter five: Chapter five examines four different approaches of the urban ministry in poverty areas. The purpose of this chapter is to understand the approaches of current work in poverty areas. Various approaches are discussed: community organization, effective congregationally based advocacy ministries, a liberation model, and a church in solidarity with the poor and oppressed. This chapter repeatedly confirms the first and the fourth hypotheses. Chapter six: In this chapter the theory of a holistic, hermeneutical practical theology is applied to a number of activities called pillars, juxtapositioning it with the four hypotheses. This is presented as a model for doing urban ministry in Malawian (African) cities. In the process of describing or developing the model, the four hypotheses - that have already been thoroughly proved and discussed - now serve as orientation markers pointing the CCAP towards its future role in urban ministry. The model emphasizes a hermeneutic-communicative praxis, which makes it constantly concerned with understanding the Christian meaning produced in the past, and relating it to interaction with the present-day faith community. Thus, the church in urban Malawi will address the challenges presented by the effects of urbanization and industrialization. The model's ten pillars are discussed: i) ministry in a new era and context, ii) urban ministry among the poor requires community participation, iii) proclaiming the Gospel in word and deed, iv) Christian faith development, v) urban evangelism, vi) effective pastoral care, vii) the need to build faith communities, viii) the need to equip the urban mission, ix) moving towards ecumenical alliances in African cities, and x) the importance of congregational studies. Chapter seven is a summary and conclusion of the dissertation. It discusses issues of this thesis positively: orientation of the study hypotheses, congregational study methods used in each chapter, the study's path and results, the contribution the study has made to the existing knowledge, and the conclusion of the whole dissertation. Urbanization is Africa's new missionary challenge for this century. The Christian task in Africa is the mission of the continent, which is in the process of rapid urbanization. If the church delays its adaptation to the urban context (the theories of which are changing constantly) it will forsake her strategic mission of being a foreign body in the world, where the old and new overlap in her, rendering her too early for heaven and too late for the earth.AFRIKAANSE OPSOMMING: Hierdie proefskrif ontwikkel 'n teorie vir die Malawiese stadsbediening wat beskryf
word as 'n "Holistiese hermeneutiese praktiese teologie." Die invloed van
verstedeliking, sekularisasie, disorientasie, armoede en besoedeling in Malawi se
stedelike sentra maak dit moeilik vir die CCAP om suksesvolle bediening, onder
plakkersdorp-omstandighede, te implementeer.
Hoofstuk een: Die eerste hoofstuk beskryf die Malawiese stedelike konteks. Dit
omskryf die vyf komponente van die navorser se studie-onderwerp, "Stedelike
armoede as 'n uitdaging vir die bediening binne die Malawiese (Afrika) konteks" en
die drie komponente van die metodologie, "Holistiese hermeneutiese praktiese
teologie." Vier verwante hipoteses is geformuleer om as riglyn vir die studie te dien.
Verskillende navorsingsmetodes, toegepas vir die inwin van inligting vir hierdie tesis
se hoofstukke, word aan die einde van hierdie hoofstuk beskryf.
Hoofstuk twee: Die tweede hoofstuk ondersoek die CCAP se huidige
bedieningspraktyk en is gerig tot die eerste hipotese: "Die CCAP se landelike
agtergrond en teorie van bediening verhinder die kerk om 'n doeltreffende stedelike
bediening te ontwikkel wat die armes se probleme toereikend kan aanspreek." Die
sendelinge het 'n omvattende bedieningsbenadering vir die vroee leiers van die CCAP
Nkhoma Sinode ingestel. In die proses om die sendingbenadering tot die bediening in
die plaaslike Chewa konteks in te voer, is 'n filosofie van bediening wat die geestelike
verlossing beklemtoon (terwyl fisieke behoeftes verwaarloos word) in die CCAP
Nkhoma Sinode ontwikkel. Hierdie benadering veroorsaak 'n probleem vir die Kerk
om die fisieke behoeftes en realiteite van stedelike Malawiers toereikend aan te
spreek.
Hoofstuk drie: Die derde hoofstuk bespreek die Malawiese en Suid-Afrikaanse
plakkersdorpe en agterbuurtes se toestande van armoede. Die hoofstuk is die produk
van navorsing wat die geldigheid van die vier hipoteses ondersoek het.
Die reaksies van die groepe met wie onderhoude gevoer is, het bygedra tot 'n begrip
van die huidige gemeentelike uitdagings en bedieningsgeleenthede in stedelike
gebiede. Die proefskrif spreek die volgende kwessies in hierdie hoofstuk aan:
navorsingsdoelstellings, die tussentydse data van die bevolkingsgroei van stedelike
gebiede, 'n kort historiese beskrywing van Malawiese stede, die regering se pogings
om stedelike uitdagings en probleme aan te spreek, die benadering van die CCAP tot
stedelike bediening en 'n kort beskrywing van twee Suid-Afrikaanse armoede-tonele.
Die navorsing toon dat die kerk en die regering onafhanklik van mekaar werk. Dus,
die geldigheid van die derde hipotesis: "'n Holistiese benadering tot die stedelike
bediening met gemeenskaplike forums vir ontwikkeling is nodig om stedelike
armoedeprobleme aan te spreek" is hiermee bevestig.
Hoofstuk vier: Hierdie hoofstuk beskryf die ontstellende impak van armoede in
Malawi. Die onlangse studies, met betrekking tot Malawiese armoede, toon dat die
armoede-toneel 'n deurdringende probleem is wat ongeveer 60% van die bevolking
raak; stedelike armoede, in die besonder, is 65%.
Hoofstuk vier bespreek 'n aantal kwessies, sommige hiervan is: 'n beskrywing en
Christelike perspektief op armoede, 'n oorsigtelike definisie van stedelike armoede,
die oorsake van armoede en die roeping van die stedelike kerk. Die stede se informele
ekonomiee kan 'n baie groot verskil in die lewens van die armes maak. Al vier
hipoteses vorm die agtergrond van hierdie hoofstuk.
Hoofstuk vyf: Hierdie hoofstuk ondersoek vier verskillende benaderinge tot
stedelike bediening in areas van armoede. Die doel van hierdie hoofstuk is om die
benaderinge in arm dele te verstaan. Verskeie benaderinge word bespreek:
gemeenskapsorganisasie, doeltreffende gemeentelik-gebaseerde voorspraakbedienings,
'n bevrydingsmodel en 'n kerk in solidariteit met die armes en verdruktes. Hierdie
hoofstuk bevestig herhaaldelik die eerste en die vierde hipoteses.
Hoofstuk ses: In hierdie hoofstuk word die teorie van 'n holisties-hermeneutiese
praktiese teologie toegepas op 'n aantal aktiwiteite, wat pillare genoem word, en stel dit naas die vier hipoteses. Dit word voorgestel as 'n model vir stedelike bediening in
Malawiese (Afrika) stede. In die proses om die model te beskryf of ontwikkel, dien
die vier hipoteses (wat reeds deeglik bewys en bespreek is) nou as orientasie merkers
wat die pad vir die CCAP vir sy toekomstige rol in die stedelike bediening aanwys.
Die model beklemtoon 'n hermeneuties-kommunikatiewe praktyk, wat gedurig in
verband gebring word met die verstaan van die Christelike betekenis wat in die
verlede teweeggebring is en wat dit, deur interaksie met die huidige
geloofsgemeenskap, in verband bring. Dus, die kerk in stedelike Malawi sal die
uitdagings wat deur die uitwerking van verstedeliking en industrialisasie gebied word,
aanspreek. Die model se tien pilare word bespreek: i) bediening in 'n nuwe era en
konteks, ii) stedelike bediening onder die armes benodig gemeenskapsdeelname, iii)
die verkondiging van die Evangelie in woord en daad, iv) Christelike
geloofsontwikkeling, v) stedelike evangelisasie, vi) doeltreffende pastorale sorg, vii)
die behoefte vir die opbou van geloofsgemeenskappe, viii) die behoefte om die
stedelike sending toe te rus, ix) die vorm van ekurneniese alliansies in die stede van
Afrika, en x) die belangrikheid van gemeentelike studies.
Hoofstuk sewe is 'n opsomming en afsluiting van die proefskrif. Dit bespreek hierdie
proefskrif se hoofpunte: die orientasie en die hipoteses van die studie, die
navorsingsmetodes geimplementeer in elke hoofstuk, die studie se ontwikkeling en
resultate, die bydrae van die studie tot die bestaande kennis, en die afsluiting van die
werk. Afrika se stede is die nuwe sendinguitdaging. Die Christelike taak in Afrika is
die evangelisasie van die vasteland wat tans in die proses van snelle verstedeliking is.
Indien die kerk in gebreke bly om in die stedelike konteks aan te pas, sal die kerk sy
strategiese missie versaak om lig in die wereld te wees.Doctora
From paternalism to partnership : the sensitive handover
No full textThis article forms part of the research in progress as part of the degree PhD (Missions) at the University of Pretoria.This article seeks to address the handover process of missions work from pioneer missionaries to indigenous leaders. It posits that this can only be done in a biblical way if paternalism yields to partnership. The article justifies paternalism in the commencement of missions work, but argues that there is a point beyond which paternalism becomes unjustifiable and crippling to the work of God's kingdom. Instead of simply condemning the crippling paternalism, the author goes on to point to the way in which true partnership can be birthed. It is through mutual respect and admiration between the missionaries and the indigenous leaders. The author uses the Bible to show that church planting missions work should go through at least three phases of development. He then ends his article by showing how mutual respect and admiration between missionaries and indigenous leaders enhances the handover process. In the light of the difficulties experienced at this juncture of missions work, and in view of the shift of the future of missions from the Western world to the Majority World, this article addresses a very pertinent subject.am2013mn201
Levels of interest among prospective and enrolled undergraduate students in learning through online and blended modes
No full textIn many developing countries, at least in Africa, many colleges and universities continue to deliver undergraduate level education in the in-person, face-to-face, mode. Many of these institutions are slow in adopting and embracing the online learning mode. This study investigated levels of interest among prospective and enrolled undergraduates for the full-online or blended learning mode. The study also assessed the factors that stimulated the interest of these groups for the preferred delivery mode. Based on a sample of 414 prospective and enrolled undergraduates from private and public colleges and universities in the context of Botswana, and using a survey design that involved questionnaires, and regression analysis, the study found that majority (56%, n=414) of the sample was interested in and preferred some form of online or blended learning, compared to the face-to-face learning mode. The proportion of individuals with keen interest in the blended learning mode, at undergraduate level, is surprisingly high. The motivational drivers for the student choice are linked to greater flexibility and convenience, and perceived better opportunity for interactions with professors and classmates (OR=10.9; 95% CI: 5.4 – 22.1). The COVID-19 outbreak and the requirements for social distancing may have also accounted for the level of interest reported. The findings have major significance for curriculum design and development, instructional design in higher education, education technology infrastructure development, and long-term enrolment planning
Development of analytical flexural models for steel fibre-reinforced concrete beams with and without steel bars
No full textThesis (MScEng)--Stellenbosch University, 2011.ENGLISH ABSTRACT: There is an increasing demand for the development and use of innovative materials with
reduced cost of construction while offering improved structural properties. Steel fibre
reinforced concrete (SFRC) can be used as a structural material to substitute the conventional
reinforcing bars partially or fully. However, there is little or no codified approach on the
design procedures for SFRC members in the latest guidelines outlined in the draft 2010
Model code.
It is against this background that analytical methods are derived in this study for the
determination of the flexural capacity of strain-softening, deflection-hardening SFRC with
and without steel reinforcing bars. Models used for the determination of the flexural capacity
of SFRC rectangular sections are based on equivalent stress blocks for both compression and
tensile stresses. These are derived from an elastic-perfect plastic model for compression and
either an elastic-constant post-peak response or Rilem’s multi-linear model for tension, in
which strain compatibility and force equilibrium theories are used. By employing the
equivalent stress blocks for both tensile and compressive stress states, parameters are defined
by converting the actual stress-strain distribution to an equivalent stress block, depending on
the ratio of yield (or cracking) strain and post-yield (post-cracking) strains. Due to the
simplicity of a drop-down tensile model and a bilinear compression model, these material
models are used for the subsequent derivation of the flexural models for both SFRC with and
without steel reinforcing bars.
An experimental program is designed and executed for model verification. This includes
material characterisation experiments for the determination of material model input
parameters, and main beam flexural experiments for the determination of the beam bending
capacity. An indirect tensile test is used for the characterisation of the tensile behaviour while
a four-point bending test is used for beam bending behaviour.
Both flexural models for SFRC with and without reinforcing bars have been verified to fairly
predict the flexural capacity of the beams. However, the flexural model for SFRC with steel
bars offers some challenges as to whether the synergetic effect of using both steel bars and
steel fibres should be incorporated at the low fibre volumes as used in the verification
exercise. Furthermore, the use of indirect methods to characterise tensile behaviour added
some uncertainties in the material model parameters and hence may have affected the
predictability of the model. More research on the verification of the models is required to
enable the use of a wider concrete strength spectrum for the verification and possible
modification of the models. Studies on the model uncertainty may also help determine the
reliable safety factor for the use of the model in predicting design strength of beam sections at
a prescribed reliability index.AFRIKAANSE OPSOMMING: Daar is ‘n groeiende aanvraag na die ontwikkeling en gebruik van innoverende materiale met
verminderde konstruksiekoste maar verbeterde strukturele eienskappe. Staalvesel-gewapende
beton (SVGB) kan gebruik word as strukturele materiaal om die konvensionele
wapeningstawe gedeeltelik of ten volle te vervang. Daar is egter min of geen gekodifiseerde
benaderings tot die ontwerpprosedures vir SVGB-dele in die nuutste riglyne uitgestippel in
die konsepweergawe van die 2010 Modelkode nie.
Dit is teen hierdie agtergrond dat in hierdie studie analitiese metodes afgelei is vir die
bepaling van die buigkapasiteit van spanning-versagtende, defleksie-verhardende SVGB met
en sonder staalbewapeningstawe. Modelle wat gebruik is vir die bepaling van die
buigkapasiteit van SVGB reghoekige snitte is gebaseer op ekwivalente spanningsblokke vir
beide druk- en trekspannings. Hierdie is afgelei van ‘n elasties-perfekte plastiese model vir
druk en óf ‘n elasties-konstante post-piek respons óf Rilem se multi-lineêre model vir
spanning, waarin teorieë vir drukkapasiteit en krag-ewewig gebruik is. Deur die ekwivalente
spanningsblokke vir beide trek- en drukspanningstoestande te implementeer, is parameters
bepaal deur die werklike verspreiding van spanningsdruk om te wissel na ‘n ekwivalente
spanningsblok, afhangend van die verhouding van swig- (of kraak-)spanning en post-swig
(post-kraak) spannings. Te wyte aan die eenvoud van ‘n aftrek trekmodel en ‘n bilineêre
kompressiemodel, is hierdie materiaalmodelle gebruik vir die daaropvolgende afleiding van
die buigingsmodelle vir beide SVGB met en sonder staalbewapeningstawe. ‘n Eksperimentele program vir modelkontrolering is ontwerp en uitgevoer. Dit sluit eksperimente in vir materiaalbeskrywing, om invoerparameters van materiaalmodelle te
bepaal, asook eksperimente vir hoofbalkbuigings, om balkbuigingskapasiteit te bepaal. ‘n
Indirekte trektoets is gebruik vir die beskrywing van die trekgedrag, terwyl ‘n vierpuntbuigingstoets
gebruik is vir balkbuiggedrag.
Dit is bewys dat beide buigingsmodelle vir SVGB met en sonder staalbewapeningstawe die
buigingskapasiteit van die balke redelik akkuraat kan voorspel. Nietemin, bied die
buigingsmodel vir SVGB met staalbewapeningstawe sekere uitdagings: die vraag ontstaan
rondom die insluiting van die sinergetiese effek van die gebruik van beide staalstawe en
staalvesels met die lae veselvolumes soos gebruik in die kontroleringsoefening. Verder het
die gebruik van indirekte metodes om die buigingsgedrag te bepaal, onsekerhede gevoeg by
die materiaalmodelparameters en dit mag dus as sulks die voorspelbaarheid van die model
beïnvloed. Meer navorsing moet uitgevoer word oor die kontrolering van die modelle sodat
‘n wyer spektrum van betonsterkte gebruik kan word vir die verifikasie en moontlike
aanpassing van die modelle. Navorsing oor die wisselvalligheid van die modelle mag ook
help om die betroubare veiligheidsfaktor te bepaal vir die model se gebruik in die berekening
van ontwerpkrag van balkdele teen ‘n voorgeskrewe betroubaarheidsindeks
A History of the care of orphans in pre-colonial and colonial Zambia, 1880-1964
No full textThe main purpose of the study was to present the care of orphans in pre-colonial and colonial Zambia as one of the most important welfare services besides education and health which have been the main focus in the historiography of welfare services in Zambia. The study also examined the causes and impacts of orphanhood. In addition, the roles of different institutions in the care of orphans were identifies such as the extended family system, missionary societies and the Colonial Government especially after 1948. Lastly, the study examined the impact of the institutionalization of orphans in orphanages.Research data for the study was obtained from the University of Zambia Library, the National archives of Zambia, the Ministry of Community Development’s Documentation Department, The Faith Encounter and Spiritual Centre of Zambia, Kasisi Orphanage (Children’s Home) and the Catholic Secretariat’s Social Welfare Department. In addition oral interviews were conducted to establish the possible impacts of the institutionalization of orphans in orphanages.The study has established the presences of orphans in pre-colonial and colonial Zambia and their plight contrary to many casual observers views’ that there were no orphans during the period under study. The study has presented evidence of the presence of oral traditions in form of folklore on the existence of orphans in African societies. During the colonial period and as a result of the socio-economic policies of the colonial government, there was a notable increase in the number of orphans in both the rural and urban centres according to Social Services Reports and Legislative Council debates. The stakeholders in the care of orphans were the extended family system, the missionaries who established orphanages such as Kasisi, Kalene Hills and Kabompo Orphanages and the government.Despite many concerns the colonial period raised over the possible negative impacts of institutionalization of orphans in orphanages, many orphans who were brought up in orphanages and left the orphanages when they became adults benefitted through academic and professional training. Hence they were better equipped and were easily integrated in the new society after independence. The author hopes the study will contribute to the historiography of social welfare in Zambia
Nonlinear truss modelling of masonry infill frames towards sustainable residential buildings
No full textThesis (PhD)--Stellenbosch University, 2018.ENGLISH ABSTRACT: With significant international efforts focused on sustainable development goals, the role of engineers in achieving sustainable infrastructure development cannot be over-emphasised. However, one of the challenges in ensuring implementation of sustainable infrastructure development for building infrastructure among engineers is lack of clear integrated structural performance and sustainability performance assessment. This research work is part of the effort in establishing a proper linkage between structural performance and sustainability performance of building infrastructure. Both structural performance and sustainability performance are evaluated on a building structure with clear definition of its structural topology, building materials and construction, use of the building and all relevant information about the location. Sustainability assessment requires further information on the material sourcing and the processes involved in material production and the supply chain. Thus, a case-study-based evaluation approach is adopted to ensure an integrated approach for structural and sustainability performance is conducted. Infill RC framed residential buildings in Western Cape, South Africa are selected for evaluation, but the approach can be applied to load-bearing masonry buildings, of which a significant stock currently exists in the region. The region is susceptible to moderate seismic events. A simplified nonlinear structural performance evaluation procedure for the infill RC frames is developed through evaluation of the infill behaviour and the bare frame behaviour. Both experimental and numerical data is used to verify the proposed procedure. Two modelling approaches for the infill RC frames are used, the truss system and frame-strut system.
Infill frame modelling utilises the equivalent strut concepts, with the cross-sectional areas for the equivalent strut established using existing models in literature. Models that incorporate the contribution of the frame stiffness and the infill wall to the equivalent strut width or cross-sectional area are considered. Use of the equivalent struts for the infill is a simplification, developed based on observed infill behaviour when subjected to lateral loading. Thus, it provides an ‘averaged’ behaviour at macro-level concealing the detailed behaviour at micro-level. Notwithstanding this weakness, the equivalent strut modelling offers a simplified approach for infill frame modelling. Much research has been done on the improvement of the macro-modelling of the infill frames, with various configurations for the equivalent struts being suggested, such as single strut, double strut, multi-struts and incorporation of shear links within the equivalent strut. Some of these models are reviewed in this study. Analytical relationships for the equivalent strut behaviour are developed based on the key infill failure modes, namely corner crushing, diagonal compression or cracking and sliding shear failures. Stress zones representing these dominant stress behaviours are used to evaluate the infill behaviour. A parametric study for the infill RC frames is conducted to develop and calibrate the analytical models for the equivalent struts.
Apart from examining the behaviour for the infill, parametric evaluation of the bare frame behaviour is performed. Second moment of areas and the lengths for the beam and the columns are varied using the second moment ratios and aspect ratios respectively, to cover what may be an inclusive range in applied infill frame geometries and configurations encountered in practice. The behaviour of the bare frame is captured through the yield and ultimate strength, and their respective deformations. Trends in the yield and ultimate strength and their deformations across the aspect ratios and the second moment of area ratios of the beam and columns are used to develop analytical relationships for the bare frame behaviour. The bare frame lateral deformation characteristics can be represented by a truss system, where a diagonal strut is introduced. Apart from the parametric-based definition for the diagonal strut behaviour, the diagonal behaviour is also calibrated based on the column properties. This assumes that column properties have significant contribution to the lateral behaviour for the bare frames.
The truss and frame-strut system models for the infill RC frames are validated using experimental and numerical data for the infill RC frames. These models utilise the infill strut properties while the truss modelling also incorporates the diagonal strut properties used to convert the frame into a truss. Though the truss model gives higher values of resistance than the frame-strut model, both models give reasonable predictions. It is recommended that improvements in material behaviour characterisation, infill frame experimental evaluation can improve the model predictions and refine the analytical relationships proposed.
Integration of structural performance assessment with sustainability performance assessment for development of sustainable infrastructure is possible. Work by Lepech et al. (2015) provides the basis for the integration, with structural performance generating the timeline (durability) with which the sustainability impacts are measured. The sustainability impact of the building from construction to end of its life and incorporating the structural repairs can be established using probabilistic approaches. However, this approach requires more data for probabilistic characterisation of both the impacts and the timelines for specific activities within the life cycle of the building.
The dissertation presents a simplified assessment method of structural walling systems of infrastructure, which is intended to enable assessment of complex structural systems in either the conceptual design stage, or possibly for existing structures at the stage of structural renovation or rehabilitation. Whilst complex nonlinear finite element approaches could be performed instead, the simple, but nevertheless rigorously derived proposed approach, enables feasible analysis and assessment of structural performance, be it capacity for lateral, seismic resistance, or other regional dominating actions like high wind or even flooding and subsidence. The feasible approach is argued to enable incorporation of structural integrity in broader sustainability assessment frameworks for appropriate decision making by potential or existing owners and their professional teams.AFRIKAANSE OPSOMMING: Met noemenswaardige internasionale navorsingsaktiwiteit gefokus op volhoubare ontwikkelingsdoelwitte, kan die rol van ingenieurs in die bereiking van volhoubare infrastruktuur nie genoeg beklemtoon word nie. Een van die uitdagings in implementering van volhoubare infrastruktuurontwikkeling deur ingenieurs, is egter die gebrek aan geïntegreerde assessering van struktuurgedrag én volhoubaarheid van geboue. Beide struktuurgedrag en volhoubaarheid van ’n gebou-struktuur word hier evalueer, met duidelike definisie van die strukturele topologie, boumateriale en konstruksie, gebruik van die gebou en alle relevante inligting oor die lokasie. Volhoubaarheidsassessering verg verdere inligting oor bronne van materiaal, en die prosesse betrokke in materiaalprosessering in materiaalvervaardiging, en die toevoerketting. Dus word ’n gevallestudie-benadering gevolg vir strukturele gedrag- en volhoubaarheidsassessering. Messelwerk invul gewapende beton (RC) residensiële geboue in die Wes-Kaap, Suid-Afrika word geselekteer vir evaluering, maar die benadering kan toegepas word op lasdraende messelwerk muur geboue, waarvan ’n groot aantal in die streek voorkom. Die streek val in ’n ligte tot matige seismiese gebied. ’n Vereenvoudigde nie-lineêre struktuurgedrag evalueringsprosedure vir die invul RC rame word ontwikkel deur evaluering van die invul gedrag, en afsonderlik dié van die RC rame. Beide eksperimentele en numeriese data word gebruik om die voorgestelde prosedure te verifieër. Twee modelleringsbenaderings vir die invul RC rame word gebruik, naamlik die vakwerk sisteem, en ’n raam-diagonale stut sisteem.
Invul raam modellering maak gebruik van die ekwivalente diagonale stut konsep, en die dwarssnit afmetings vir die stut word bepaal met bestaande modelle in die literatuur. Modelle wat die bydrae van die raamstyfheid en die invul muur tot die ekwivalente stut inagneem, word beskou. Gebruik van die ekwivalente stut vir die invul is ’n vereenvoudiging, ontwikkel op basis van waargenome invul gedrag onderhewig aan dwarsbelasting. Dit voorsien dus ‘n ‘gemiddelde’ gedrag op makro-vlak, sonder om gedetaileerde gedrag op mikro-vlak te onthul. Nieteenstaande hierdie swakheid, bied die ekwivalente stut modellering ’n vereenvoudigde benadering vir die invul raam modellering. Veel navorsing is gedoen ter verbetering van die makro-modellering van die invul rame, en verskeie konfigurasies is voorgestel vir die ekwivalente stut, insluitend ’n enkel stut, ’n dubbel stut, veelvoudige stutte, en inkorporering van skuifweerstand in die ekwivalente stut. Van hierdie modelle word in hierdie studie bestudeer. Analitiese verwantskappe vir die ekwivalente stutgedrag word ontwikkel op basis van die sleutel invul falingsmodes, naamlik hoekvergruising, diagonale vergruising/kraakvorming, en skuif-glip falings. Spanningsones wat dominante spanningsgedrag verteenwoordig word gebruik ter evaluering van die invul gedrag. ’n Parametriese studie word vir die invul RC rame uitgevoer, ter ontwikkeling en kalibrasie van die analitiese modelle vir die ekwivalente stutte.
Benewens die bestudering van die invul gedrag, is parametrise evaluering van die RC rame afsonderlik uitgevoer. Tweede momente van area en die lengte van die balk en kolomme word geverifieër met gebruik van tweede moment van area verhoudings en aspekverhoudings onderskeidelik, om wat beskou word as ’n inklusiewe bereik van invul rame en konfigurasies in die praktyk, in te sluit. Die gedrag van die kaal rame word verteenwoordig deur die vloei- en ultieme weerstand, en geassosieerde deformasies. Tendense in die vloei- en ultieme weerstand en ooreenstemmende deformasies oor die spektrum van verhoudings in tweede momente van area van die balk en kolomme word gebruik om analitiese verbande vir die kaal raamgedrag te ontwikkel. Die kaal raam se dwarsdeformasie karakteristieke kan verteenwoordig word deur ’n vakwerk sisteem, waarin ’n diagonale stut geplaas word. Afgesien van die geparametriseerde definisie vir die diagonale stut se gedrag, word die stut se gedrag ook gekalibreer op grond van die kolom eienskappe. Dit aanvaar dat die kolom noemenswaardig bydra tot die dwarsverplasingsgedrag van die kaal rame.
Die vakwerk en raam-stut sisteem modelle vir invul RC rame word valideer deur gebruik van eksperimentele en numeriese data vir invul RC rame. Hierdie modelle gebruik die invul stut eienskappe, terwyl die vakwerk modellering ook die diagonal stut-eienskappe gebruik om die raam na ’n vakwerk om te skakel. Al gee die vakwerkmodel hoër waardes van weerstand as die raam-stut model, gee beide modelle redelike voorspellings. Dit word aanbeveel dat verbeteringe in materiaalgedrag karakterisering en invul raam eksperimentele evaluering kan help om die modelvoorspellings te verbeter, en om die voorgestelde analitiese verwantskappe te verfyn.
Integrasie van strukturele gedrag-assessering met volhoubaarheidsassessering vir die ontwikkeling van volhoubare infrastruktuur is moontlik. Navorsing van Lepech et al. (2015) voorsien ‘n basis vir integrasie, met struktuurgedrag wat die tydslyn (duursaamheid) skep, waarteen die volhoubaarheidsimpak gemeet word. Die volhoubaarheidsimpak van die gebou vanaf konstruksie tot einde van sy leeftyd en inkorporasie van strukturele herstel kan beskryf word aan die hand van waarskynlikheidsbenaderings. Hierdie benadering verg egter meer data vir die karakterisering van beide die impak en tydslyn vir spesifieke aktiwiteite in die lewensiklus van die gebou.
Die proefskrif bied ‘n vereenvoudigde assesseringsmetode vir strukturele muursisteme vir infrastruktuur, wat die assessering van komplekse strukturele sisteme in óf die konsepontwerp fase, óf die strukturele renovering of rehabilitering van bestaande geboue moontlik maak. Terwyl komplekse nie-lineêre eindige element benaderings uitgevoer sou kon word, maak die vereenvoudigde maar sorgvuldig afgeleide voorgestelde benadering die analise en assessering van struktuurgedrag koste-effektief uitvoerbaar, hetsy dit die kapasiteit onder seismiese opwekking is, of ander streeksgebonde dominerende aksies soos hoë windsnelheid en selfs vloede en versakking. Dit word aangevoer dat die uitvoerbare benadering die inkorporasie van strukturele integriteit in breër volhoubaarheidsassessering raamwerke moontlik maak, vir geskikte besluitneming deur potensiële eienaars en hulle professionele spanne.Doctora
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