Thesis (MEng)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: The compound sharp-crested weir, which consists of two or more notches at different elevations, is the most common type of flow gauging structure found in South Africa. The Department of Water Affairs and Forestry (DWAF) is responsible for the operation of these weirs. They are currently experiencing the following problems regarding flow measurement with compound sharp-crested weirs: 1. During free-flow conditions, also known as modular flows, there is uncertainty about the accuracy of the discharge formulas. Although reliable formulas exist for single notch weirs, it is not clear how they should be modified for compound weirs. Whilst methods have already been developed to deal with compound weirs their accuracy needs to be investigated further. 2. When the weirs become submerged during floods, the upstream water head is affected by downstream water levels and the original formulas are not applicable. It has so far been impossible to calculate discharge accurately under these so-called non-modular flow conditions. This report summarises the findings of an extensive study which addressed the issues mentioned above. A comprehensive test programme was completed during which variations of compound sharp-crested weirs were tested under both modular and non-modular flow conditions. In the development of new methods care was taken to adhere to internationally accepted standards. This should make South African practice acceptable to others. One important characteristic of compound weirs is the presence of end contractions. It was found that they have a significant effect on discharge measurement. Generally, the more a weir is contracted, the lower its coefficient of discharge becomes. It was also established that end contractions can ensure excellent aeration for compound weirs. For modular flow conditions it was possible to develop a discharge formula based on the IMFf equation, which is included in the ISO standards. This new method was found to produce the smallest errors when compared to other existing formulas (average error 0.6%). During non-modular flow conditions it was noted that end contractions also play an important role, at least during the early stages of submergence. In full-width weirs the upstream water level tends to drop first (due to de-aeration) before it rises again with increasing submergence. Weirs with end contractions do not suffer from this problem. It was further established that the effect of submergence could be described in terms of an energy loss occurring at the drowned weir. This energy loss is a function of the velocities at the so-called vena contracta of the weir and at the downstream river cross section. As the difference between these velocities increases, the energy loss increases as well. Two methods were tested to estimate the discharge under submerged conditions. The Villemonte formula works well if the energy losses at the weir are relatively high, while the Wessels method is reliable if the energy losses become smaller. A procedure was developed which indicates when each method is applicable. The test data indicated that the maximum error is up to ±10% at high submergence ratios (S> 0.80) if this procedure is followed. / AFRIKAANSE OPSOMMING: Multikeep-skerpkruinmeetstrukture bestaande uit twee of meer kepe op verskillende vlakke word meestal gebruik om vloeie in Suid-Afrikaanse riviere te meet. Die Departement van Waterwese en Bosbou (DWAF) is verantwoordelik vir die instandhouding van sulke meetstrukture. Hulle ervaar tans die volgende probleme met vloeimeting by multikeepskerpkruine: 1. Gedurende modulêre (onversuipte) toestande bestaan daar nog onsekerheid oor die akkuraatheid van die formules wat gebruik word om vloeitempo's te bereken. Alhoewel betroubare formules ontwikkel is vir enkelkepe, is dit nie duidelik hoe hulle aangepas kan word sodat hulle ook vir multikepe gebruik kan word nie. Die akkuraatheid van sommige bestaande metodes vir multikepe moet ook ondersoek word. 2. Onder versuipte toestande word die stroom-op watervlak beïnvloed deur die stroom-af watervlak en die formules vir vry-vloei toestande is nie geldig nie. Dit was tot nou toe nie moontlik om vloeitempo ' s akkuraat te bereken onder hierdie nie-modulêre toestande nie. Hierdie verslag bied 'n opsomming van die bevindinge van 'n navorsingsprojek wat bogenoemde probleme aangespreek het. 'n Toetsprogram is uitgevoer wat moontlike konfigurasies van multikepe ingesluit het. Die modelle van die meetstrukture is onder beide vry-vloei en versuipte toestande bestudeer. Gedurende die ontwikkeling van nuwe formules vir die berekening van vloeie is daarna gestreef om so veel as moontlik gebruik te maak van internasionale standaarde. Dit behoort Suid-Afrikaanse praktyke vir andere aanvaarbaar te maak. 'n Belangrike eienskap van multikepe is die voorkoms van end-kontraksies. Hulle het 'n groot invloed op vloeimeting en oor die algemeen het 'n keep met groot end-kontraksies 'n laer vloei koëffisient as 'n vol-wydte keep. End-kontraksies is ook baie effektief om skerpkruine te belug. Vir vry-vloei toestande is gevind dat 'n metode gebaseer op die IMFT vergelyking (ingesluit in ISO standaarde) baie goeie resultate lewer. In vergelyking met ander bestaande metodes gee dié metode die kleinste foute met 'n gemiddelde fout van 0.6%. Onder versuipte toestande speel end-kontraksies ook 'n belangrike rol, ten minste by beperkte versuiping. As vol-wydte kepe beskou word, kan gesien word dat die stroom-op watervlak eers daal voordat dit weer styg (weens ontlugting). Kepe met end-kontraksies ly nie aan hierdie probleem nie. Dit is verder bevestig dat versuipte toestande beskryf kan word in terme van 'n energie verlies wat by die versuipte meetstruktuur voorkom. Hierdie energie verlies is 'n funksie van die snelhede by die vena contraeta van die keep en by die stroom-af rivier snit. As die verskil tussen die twee snelhede groot is, is die energie velies ook groot. Twee bestaande metodes vir versuipte toestande is getoets. Villemonte se vergelyking werk goed as die energie verliese groot is, terwyl Wessels se metode beter werk as die verliese klein raak. 'n Prosedure is ontwikkel wat dit moontlik maak om die regte metode te kies vir 'n spesifieke toestand. Vanaf die toetsdata is bepaal dat die maksimum fout ±10% is by hoë grade van versuiping (S> 0.80) wanneer bogenoemde prosedure gevolg word.

Thesis (MEng)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: As part of a previous WRC project, three types of sluicing flumes were developed for use in compound weirs in combination with sharp-crested and crump weirs, (Rossouw et al., 1998). These sluicing flumes have several advantages which make them ideal structures for flow measurement in South African rivers. These are a high modular limit, stable modular flow characteristics, an ability to measure a wide range of flows accurately, as well as good sediment handling characteristics. These three flumes have been calibrated under modular or free flow conditions in combination with sharpcrested and crump weirs. There is a high degree of variability of flow in South African rivers. Flood discharges are part of this variability, and can form an important part of the mean annual runoff. Measuring weirs cannot always be built so that they do not become submerged during floods, but it is nevertheless important that flood discharges be recorded. It is therefore important that these compound weirs be calibrated for flow measurement under non-modular or submerged conditions. The purpose of the research undertaken for this WRC project is to find a method to calculate the non-modular discharge over compound weirs consisting of sluicing flumes in combination with sharp-crested and crump weirs. By analysis of existing data from the previous WRC project, as well as data from laboratory tests undertaken as part of this project, the submergence effect of sluicing flumes has been quantified. A range of configurations of sharp-crested weirs as well as crump weirs in combination with the sluicing flume have been tested. A new method has been developed to calculate the submerged discharge over these compound weirs. This method is suitably accurate, and can be recommended to the DWAF for use. The calculation procedure that must be followed in order to calculate the submerged discharge over these compound weirs becomes rather complicated due to the iterations that must be carried out. In order to clarify these procedures, flow charts are provided which set out the steps that must be followed. Calibration curves for all the combinations of compound weirs analysed in this report are also provided. These can be used to obtain estimates of the discharge in the field, and can also be used as a check on any calculations carried out. The principal goal of this project, namely that of finding a suitably accurate method to calculate the non-modular discharge over these compound weirs has therefore been achieved. / AFRIKAANSE OPSOMMING: As deel van 'n vorige Water Navorsings Kommisie (WNK) projek, is drie spoelgeute ontwikkel vir gebruik in saamgestelde meetwalle in kombinasie met skerp-kruin en Crump oorlope, (Rossouwet al., 1998). Die spoelgeute het eienskappe wat hulle gunstig maak vir vloeimeting in Suid Afrikaanse riviere. Vanhierdie eienskappe is 'n hoë modulêre limiet, stabiele modulêre vloei eienskappe, goeie sediment hanterings eienskappe en 'n vermoë om oor 'n wye bereik vloeie akkuraat te kan meet. Hierdie drie geute is in kombinasie met skerpkruin en Crump oorlope gekalibreer onder vryvloei toestande. Vloeie varieër baie in Suid Afrikaanse riviere. Vloede is deel van hierdie variasies en maak 'n belangrike deel uit van die gemiddelde jaarlikse afloop. Meetwalle kan nie altyd gebou word sodat hulle nie versuip tydens vloede nie, maar dit is nogtans belangrik dat hierdie vloeie gemeet word. Daarom is dit belangrik dat saamgestelde meetwalle gekalibreer is vir vloeimeting onder versuipte of nie-modulêre toestande. Die doel van die navorsing wat gedoen is vir hierde WNK projek was om 'n geskikte metode te ontwikkel om die nie-modulêre vloeie oor saamgestelde meetwalle, wat bestaan uit spoelgeute in kombinasie met skerpkruin en Crump oorlope, te kan bereken. Met die analise van bestaande data van die vorige WNK projek, asook data van labratoriumtoetse wat gedoen is as deel van hierdie projek, is die versuiping van spoelgeute beskryf. 'n Hele reeks skerpkruin asook crump oorlope is getoets in kombinasie met die spoelgeute. 'n Nuwe metode is ontwikkel om die nie-modulêre vloei oor hierdie saamgestelde meetstrukture te kan bereken. Hierdie metode IS akkuraat genoeg om aan die Departement van Waterwese te kan aanbeveel. Die berekingsproses wat gevolg moet word om die versuipte vloei oor die saamgestelde meetstrukture te bereken, raak ingewikkeld as gevolg van die iterasies wat uitgevoer moet word. Vloeidiagramme is opgestel wat hierdie prosedures duidelik uiteensit. Kalibrasie kurwes is ook ontwikkel vir al die kombinasies van saamgestelde meetwalle wat geanaliseer is in hierdie verslag. Hierdie kurwes kan gebruik word om skattings te maak van vloeie in die veld, maar ook om enige berekings wat gedoen is te kontroleer. Die hoofdoel van hierdie projek, naamlik om 'n geskikte metode te ontwikkel wat die nie-modulêre vloeie oor saamgestelde meetwalle akuraat kan bereken, is bereik.

Thesis (M.ScEng.)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: Historically, urban waterresources have too often been managed without recognition that the flow in a river integrates many landscape and biological features. This has often resulted in the elimination of natural processes and their replacement by man-made streamlined structures with the effects of increased urbanisation being primarily addressed from an engineering and economics point of view to the detriment of environmental and social issues. Catchment Management, as legislated in the Water Act, No. 36 of 1998, is a management approach to address the negative consequences of an urban stormwater design philosophy restricted to flood restriction. It is a systems approach that integrates engineering and scientific skills, socio-economic concerns, and environmental constraints within a new multidisciplinary decision-making process that recognises the different components of the hydrological and aquatic cycles are linked, and each component is affected by changes in every other component. In order to make effective management decisions, catchment managers require tools to provide reliable information about the performance of alternative arrangements of stormwater management facilities and to quantify the effects of possible management decisions on the water environment. A deterministic hydrological model is such a tool, which provides the link between the conceptual understanding of the physical catchment characteristics and the empirical quantification of the hydrological, water quality and ecological response. In order to provide effective computer based decision support, the hydrological model must be part of an integrated software application in which a collection of data manipulation, analysis, modelling and interpretation tools, including GIS, can be efficiently used together to manage a large potion of the overall decision process. This decision support system must have a simple and intuitive user interface able to produce easily interpreted output. It must have powerful graphical presentation capabilities promoting effective communication and be designed to solve ill-structured problems by flexibly combining statistical analysis, models and data. The Great Lotus River canal, situated on the Cape Flats, Cape Town, has been designed and controlled through extensive canalisation and the construction of detention pond facilities to avoid the flooding of urban areas of the catchment. This approach has resulted in these channels becoming stormwater drains, transporting waste and nutrients in dissolved and particulate forms, and reducing their assimilatory capacity for water quality improvement. In order to investigate the use of hydrological modelling in decision support for Catchment Management, the semi-distributed, physically based model, SWMM, was applied to the Great Lotus River canal. SWMM consists of a number of independent modules allowing the hydrological and hydraulic simulations of urban catchments and their conveyance networks on an event or continuous basis. In order to ease the application of the Fortran based SWMM model, the GUl, PCSWMM98, was developed by Computational Hydraulics Inc (CH!). This provides decision support for SWMM through large array of tools for file management, data file creation, output visualisation and interpretation, model calibration and error analysis and storm dynamic analysis thus easing any simulations with SWMM. In addition, PCSWMM was developed with a GIS functionality for graphically creating, editing and/or querying SWMM model entities and attributes, displaying these SWMM layers with background layers and dynamic model results, and exporting data to SWMM input files thus providing an interface between a GIS and SWMM. In terms of Catchment Management, the above DSS can be used effectively to assist decisionmaking. This is to address tensions between the fundamental catchment management considerations of physical development, social considerations and maintaining ecological sustainability. It is at the stages of Assessment and Planning that the model can play the most significant role in providing decision support to the Catchment Management process. Assessment in the Catchment Management process refers to the collection, storage, modelling and interpretation of catchment information. It is in this quantification, interpretation and assessment of catchment information that a hydrological model contributes to an increase in knowledge in the Catchment Management process. In identifying and quantifying, at a sufficient temporal and spatial scale, the dominant cause and effect relationships in the urban physical environment, a hydrological model is able to highlight the main contributing factors to an issue. This is used in the Planning stage of the Catchment Management process and when combining these contributing factors with assessments of the socio-economic and administrative environments, enables the prioritisation of the principal issues requiring attention in a Catchment Management Strategy. It is possible to link the multiple decision-making requirements of Catchment Management with the abilities of a hydrological model to provide information on these requirements in a conceptual framework. This framework consists of the fundamental catchment considerations of Physical Development, Environmental Management and Social Development and resolves these considerations into the various management issues associated with each consideration ~s well as its management solution. The management solutions are linked to the model through formulating the solution in terms of the model parameters and perturbing the affected parameters in ways to simulate the management solution. This results in model output and graphical interpretation of the effects of the suggested management solution. A comparison between the simulated effects of each management solution allows the Catchment Management body to identify optimal management solutions for the various management Issues. The present model of the Great Lotus River catchment is sufficient to simulate the overland and subsurface flows from individual parts of the catchment and to route these flows and associated pollutant loadings to the catchment outlet. At its present level of complexity, the finely discretised model subcatchment and conveyance network provides decision support for Catchment Management through the simulation, at a pre-feasibility stage, of various Catchment Management issues and their proposed solutions. Given more detailed canal and drainage network dimensions and water quality data, it is possible for the model to incorporate hydraulic calculation routines to assess the implications of alternative river rehabilitation techniques and waste management strategies. This would allow greater capability in assessing the role of the various BMPs in ameliorating stormwater impacts and pollutant loading. In addition, a detailed level survey of the stormwater pipe and canal network could result in hydrological modelling being utilised to identify critical areas where stormwater upgrading would be necessary. In order to facilitate future complex, finely discretised catchment hydrological models, it is imperative that complete and detailed drainage patterns and stormwater network characteristics are available. In addition, to minimise model generation costs and time of model setup, this spatially representative data must be captured in a GIS for rapid inclusion into the model. Furthermore, complete spatially representative precipitation datasets are necessary to ensure that model error is reduced. These two issues of available spatial data and comprehensive precipitation records are crucial for the generated models to function as effective decision support systems for Catchment Management. / AFRIKAANSE OPSOMMING: Histories is stedelike waterbronne te dikwels bestuur sonder inagneming dat die vloei van die rivier baie landskap- en biologiese kenmerke insluit. Dit het dikwels daartoe gelei dat natuurlike prosesse uitgeskakel is en vervang is deur mensgemaakte, stroombelynde strukture waarvan die effek van toenemende verstedeliking hoofsaaklik aangespreek word vanuit 'n ingenieurs- en ekonomiese oogpunt tot nadeel van omgewings- en sosiale kwessies. Opvangsgebiedsbestuur, soos bepaal deur die Waterwet, Wet 36 van 1998, is 'n bestuursbenadering om die negatiewe gevolge van 'n stedelike stormwaterontwerpfilosofie wat beperk is tot vloedbeperking aan te spreek. Dit is 'n stelselbenadering wat ingenieurs- en wetenskaplike vaardighede, sosio-ekonomiese probleme en omgewingsbeperkings integreer in 'n nuwe multidissiplinêre besluitnemingsproses wat erkenning daaraan gee dat die verskillende komponente van die hidrologiese en watersiklusse verbind is, en elke komponent beïnvloed word deur veranderings in elke ander komponent. Om doeltreffende bestuursbesluite te neem, benodig opvangsgebiedsbestuur die hulpmiddels om betroubare inligting oor die prestasie van alternatiewe moontlikhede VIr stormwaterbestuurfasiliteite en om die effek van moontlike bestuursbesluite op die wateromgewing te kwantifiseer. 'n Deterministiese hidrologiese model is so 'n hulpmiddel wat die skakel daarstel tussen die konseptueie begrip van die fisiese opvangsgebiedskenmerke en die empiriese kwantifisering van die water-, waterkwaliteit- en ekologiese reaksie. Om doeltreffende rekenaarbesluitnemingsteun te verskaf, moet die hidrologiese model deel wees van 'n geïntegreerde sagteware-aanwending waarin 'n versameling datamanipulasie-, analise-, modellerings- en interpreteringshulpmiddels, insluitend GIS, doeltreffend saam gebruik kan word om 'n groot deel van die algehele besluitnemingsproses te bestuur. Hierdie besluitnemingsteunstelsel moet 'n eenvoudige en intuïtiewe gebruikersvlak hê wat in staat is om maklik interpreteerbare uitsette te lewer. Dit moet goeie grafiese voorleggingsvermoëns hê wat doeltreffende kommunikasie vergemaklik en ontwerp wees om swak gestruktureerde probleme deur die buigsame samevoeging van statistiese analise, modelle en data op te los. Die Groot Lotusrivierkanaal op die Kaapse Vlakte, Kaapstad is ontwerp en word beheer deur uitgebreide kanalisasie en die konstruksie van detensiedamfasiliteite om die oorstroming van stedelike opvangsgebiede te vermy. Hierdie benadering het daartoe gelei dat hierdie kanale stormwaterafvoerpype geword het wat afval en nutriënte in opgelosde en partikelvorm vervoer en hulle assimilasievermoë vir die verbetering van waterkwaliteit verminder. Om die gebruik van hidrologiese modelle in besluitnemingsteun vir Opvangsgebiedsbestuur te ondersoek, is die semi-verspreide, fisiesgebaseerde model, SWMM, op die Groot Lotusrivierkanaal toegepas. SWMM bestaan uit 'n aantalonafhanklike modules wat die hidrologiese en hidroulika simulasies van stedelike opvangsgebiede en hulle vervoemetwerke per geleentheid of deurlopend monitor. Om die aanwending van die Fortran gebaseerde SWMM model te vergemaklik is die GUl, PCSWMM98 deur Computational Hydraulics Inc (CHD ontwikkel. Dit verskaf besluitnemingsteun vir SWMM deur 'n groot aantal hulpmiddels vir lêerbestuur, die skep van datalêers, uitsetvisualisering en interpretasie, modelkalibrasie, foutanalise en stormdinamikaanalise om enige simulasies met SWMM te vergemaklik. Daarby is PCSWMM ontwikkel met 'n GIS funksionaliteit vir die grafiese daarstelling, redigering en/of navraagfunksie van SWMM model entiteite en kenmerke, wat hierdie SWMM vlakke met agtergrondvlakke en dinamiese modelresultate vertoon en data in SWMM inset1êers plaas en op daardie manier 'n koppelvlak tussen 'n GIS en SWMM verskaf. Volgens Opvangsgebiedsbestuur kan bogenoemde DSS doeltreffend gebruik word in besluitneming. Dit IS om die spanning tussen fundamentele opvangsgebiedsbestuursoorwegings van fisiese ontwikkeling, sosiale oorwegings en ekologiese volhoubaarheid aan te spreek. Dis in die stadiums van Waardebepaling en Beplanning wat die model die belangrikste rol kan vervul in die verskaffing van besluitnemingsteun vir die Opvangsgebiedsbestuursproses. Waardebepaling in die Opvangsgebiedbestuursproses verwys na die versameling, berging, modellering en interpretasie van opvangsgebiedsinligting. Deur hierdie kwantifisering, interpretasie en waardebepaling van opvangsgebiedsinligting dra 'n hidrologiese model by tot 'n verhoging in kennis in die Opvangsgebiedsbestuur. Deur die identifisering en kwantifisering, op 'n ruim genoeg tydelike en ruimtelike skaal, van die dominante oorsaak en gevolg verhoudings in die stedelike fisiese omgewing, kan die hidrologiese model die hoof bydraende faktore uitlig. Dit word gebruik in die Beplanningsfase van die Opvangsgebiedproses en wanneer hierdie bydraende faktore by die waardebepaling van die sosio-ekonomiese en administratiewe omgewings saamgevoeg word, maak dit moontlik om die belangrike kwessies wat aandag behoort te kry in 'n Opvangsgebiedsbestuurstrategie in volgorde van voorrang te plaas. Dit is moontlik om die verskeidenheid besluitnemingsvereistes van Opvangsgebiedsbestuur met die vermoëns van 'n hidrologiese model te koppel om inligting oor hierdie vereistes in 'n konseptuele raamwerk te verskaf. Die raamwerk bestaan uit die fundamentele opvangsgebiedsoorwegings van Fisiese Ontwikkeling, Omgewingsbestuur en Sosiale Ontwikkeling en los hierdie oorwegings op in die verskillende bestuursaangeleenthede wat met elke oorweging en die bestuuroplossing geassosieer word. Die bestuursoplossings word aan die model gekoppel deur die formulering van die oplossing volgens die modelparameters en versteuring van die relevante parameters op sekere manier om die bestuursoplossing te simuleer. Dit lei tot modeluitset en grafiese interpretasie van die effek van die voorgestelde bestuursoplossing. 'n Vergelyking tussen die gesimuleerde effek van elke bestuursoplossing laat die Opvangsgebiedsbestuursliggaam toe om die optimale bestuursoplossings vir die verskeie bestuursaangeleenthede te identifiseer. Die huidige model van die Groot Lotusrivieropvang is genoegsaam om die bo- en ondergrondse vloei vanaf individuele dele van die opvangsgebied te simuleer en om die watervloei en geassosieerde besoedelstofladings na die opvangsgebiedsuitlaatplek te lei. Op sy huidige vlak van kompleksiteit verskaf die fyn gediskretiseerde model subopvangsgebied en vervoernetwerk besluitnemingsteun aan Opvangsgebiedsbestuur deur die simulasie, teen 'n voor-lewensvatbaarheidstudie, van verskeie opvangsgebiedsbestuurkwessies en die voorgestelde oplossings. Indien meer gedetailleerde kanaal- en dreineringsnetwerkdimensies- en waterkwaliteitdata ingevoer word, is dit moontlik vir die model om hidroulikaberekeningsroetines te inkorporeer om die implikasies van alternatiewe rivierrehabilitasietegnieke en afvalbestuurstrategieë te beoordeel. Dit sou die vermoë verbeter om die waarde van die verskeie BMPs te bepaal om die impak van stormwater en besoedelstoflading te versag. Daarby kan 'n gedetailleerde vlakopname van die stormwaterpyp en -kanaalnetwerk daartoe lei dat hidrologiese modelle gebruik kan word om kritieke areas te identifiseer waar stormwateropgradering nodig is. Om toekomstige komplekse, gediskretiseerde opvangsgebiedshidrologiese modelle te verbeter, is dit noodsaaklik dat volledige en gedetailleerde dreineringspatrone en stormwaternetwerkkenmerke beskikbaar is. Om die model-ontwikkelingskoste en tyd bestee aan die opstel van 'n model te minimiseer, moet hierdie ruimtelik verteenwoordigende data ingelees word in 'n GIS vir vinnige insluiting in die model. Daarbenewens is volledige, ruimtelik verteenwoordigende presipitasie datastelle nodig om te verseker dat modelfoute verminder word. Hierdie twee kwessies van beskikbare ruimtelike data en omvattende presipitasierekords is van die uiterste belang sodat die gegenereerde modelle as doeltreffende besluitnemingsteun vir Opvangsgebiedsbestuur kan funksioneer.

Thesis (MScEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: First-order second-moment structural reliability methods are used to assess the reliability of a prestressed concrete beam. This beam was designed for imposed office floor loads and partitions following the limit states design method as provided for by the applicable South African structural codes, viz SABS 0100-1:1992 and SABS 0160:1989. The reliability is examined at two limit states. At the ultimate limit state of flexure the ultimate moment of resistance must exceed the applied external moment at the critical section, while at the serviceability limit state of deflection the deflection must satisfy the codespecified deflection criteria. Realistic theoretical models are selected to express the flexural strength and deflection of the prestressed concrete member, while appropriate probabilistic models are gathered from the literature for loading, resistance and modelling uncertainties. The calculated reliability index at the ultimate limit state of flexure (3.10) is lower than expected in view of the fact that this represents a non-critical limit state in the case of a Class 2 prestressed concrete member. This condition can be explained with reference to the relatively high uncertainty associated with the modelling error for flexural strength. The calculated reliability index at the serviceability limit state of deflection (l.67) compares well with acceptable practice. The study further focuses on the sensitivity of the reliability at the two limit states of interest to uncertainty in the various design parameters. The ultimate limit state of flexure is dominated by the uncertainty associated with the modelling error for flexural strength, while the contribution to the overall uncertainty of the ultimate strength and area of the prestressing steel and the effective depth is less significant. In comparison the reliability at the serviceability limit state of deflection is not dominated by the uncertainty associated with a single basic variable. Instead, the uncertainty associated with the modelling error, creep factor and prestress loss factor are all significant. It was also demonstrated that the variability in beam stiffness is not a major source of uncertainty in the case of a Class 2 prestressed concrete member. It is recommended that the present code provisions for ultimate strength and deflection should be reviewed to formulate theoretical models with reduced systematic and random errors. The effect of the uncertainty associated with the creep and prestressed loss factors should also be adressed by adjustment of the partial material factor for concrete at the serviceability limit state of deflection. Furthermore, research must be directed towards formulating an objective failure criterion for deflection. The uncertainty in the deflection limit must therefore be quantified with a probability distribution. / AFRIKAANSE OPSOMMING: Eerste-orde tweede-moment struktuur betroubaarheid metodes word ingespan om die betroubaarheid van 'n voorspanbeton balk te bereken. Hierdie balk is ontwerp vir opgelegte kantoor vloerbelasting en partisies volgens die grenstoestand ontwerp metode soos beskryf in die toepaslike Suid-Afrikaanse boukodes, naamlik SABS 0100-1: 1992 en SABS 0160: 1989. Die betroubaarheid word ondersoek by twee grenstoestande. By die swiglimiet van buiging moet die weerstandsmoment die eksterne aangewende moment oorskrei by die kritieke balksnit, terwyl die defleksie die kriteria soos voorgeskryf deur die kode moet bevredig by die dienslimiet van defleksie. Realistiese teoretiese modelle word gebruik om die buigsterkte en defleksie van die voorspanbeton balk te bereken. Verder is geskikte waarskynlikheid modelle uit die literatuur versamelom die belasting, weerstand en modelonsekerhede te karakteriseer. Die betroubaarheid indeks soos bereken vir die swiglimiet van buiging (3.10) is laer as wat verwag sou word in die lig van die feit dat hierdie nie 'n kritieke grenstoestand verteenwoordig in die geval van 'n Klas 2 voorspan element nie. Dit kan verklaar word met verwysing na die relatiewe groot onsekerheid wat geassosieer word met die modellering fout vir buigsterkte. Die berekende betroubaarheid indeks vir die dienslimiet van defleksie (1.67) vergelyk goed met aanvaarde praktyk. Die studie fokus verder op die sensitiwiteit van die betroubaarheid by die twee grenstoestande onder beskouing ten opsigte van die onsekerheid in die verskillende ontwerp parameters. By die swiglimiet van buiging word die onsekerheid oorheers deur die bydrae van die modelering fout vir buigsterkte. Die bydraes tot die totale onsekerheid deur die swigsterkte en area van die voorspanstaal sowel as die effektiewe diepte is minder belangrik. By die dienslimiet van defleksie word die betroubaarheid nie oorheers deur die onsekerheid van 'n enkele basiese veranderlike nie. In stede hiervan is die onsekerheid van die modellerings fout, kruipfaktor en voorspan verliesfaktor almal noemenswaardig. Daar word verder aangetoon dat die veranderlikheid in balkstyfheid nie 'n belangrike bron van onsekerheid in die geval van 'n Klas 2 voorspan element is nie. Daar word aanbeveel dat die bestaande voorskrifte in die kode vir buigsterkte en defleksie aangespreek moet word deur teoretiese modelle met klein modelonsekerhede te formuleer. Die uitwerking van die onsekerheid van die kruip- en voorspan verliesfaktore kan aangespreek word deur 'n aanpassing te maak in die parsiële materiaalfaktor vir beton in die geval van die dienslimiet van defleksie. Navorsing moet verder daarop gemik wees om 'n objektiewe falingskriterium vir defleksie te formuleer. Die onsekerheid van die toelaatbare defleksie moet dus gekwatifiseer word deur 'n waarskynlikheidsverdeling.

Thesis (M.Ing.)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: A road safety remedial programme has as an objective the improvement of road transportation safety by applying road safety engineering remedial measures to hazardous road network elements in a manner that will be economically efficient. Since accident data is the primary manifestation of poor safety levels it must be analysed in manner that will support the overall objective of economic efficiency. Three steps in the process of implementing a road safety remedial programme, that rely on the systematic analysis of accident data, are the identification of hazardous locations, the ranking of hazardous locations and the evaluation of remedial measure effectiveness. The efficiency of a road safety remedial programme can be enhanced by using appropriate methodologies to measure safety, identify and rank hazardous locations and to determine the effectiveness of road safety remedial measures. There are a number of methodologies available to perform these tasks, although some perform much better than other. Methodologies based on the Empirical Bayesian approach generally provide better results than the Conventional methods. Bayesian methodologies are not often used in South Africa. To do so would require the additional training of students and engineering professionals as well as more research by tertiary and other research institutions. The efficiency of a road safety remedial programme can be compromised by using poor quality accident data. In South Africa the quality of accident data is generally poor and should more attention be given to the proper management and control of accident data. This thesis will report on, investigate and evaluate Bayesian and Conventional accident data analysis methodologies. / AFRIKAANSE OPSOMMING: Die doel van 'n padveiligheidsverbeteringsprogram is om op die mees koste effektiewe manier die veiligheid van onveilige padnetwerkelemente te verbeter deur die toepassing van ingenieursmaatreëls. Aangesien padveiligheid direk verband hou met verkeersongelukke vereis die koste effektiewe implementering van 'n padveiligheidsverbeteringsprogram die doelgerigte en korrekte ontleding van ongeluksdata. Om 'n padveiligheidsverbeteringsprogram te implementeer word die ontleding van ongeluksdata verlang vir die identifisering en priortisering van gevaarkolle, sowel as om die effektiwiteit van verbeteringsmaatreëls te bepaal. Die koste effektiwiteit van 'n padveiligheidsverbeteringsprogram kan verbeter word deur die regte metodes te kies om padveiligheid te meet, gevaarkolle te identifiseer en te prioritiseer en om die effektiwiteit van verbeteringsmaatreëls te bepaal. Daar is verskeie metodes om hierdie ontledings te doen, alhoewel sommige van die metodes beter is as ander. Die 'Bayesian' metodes lewer oor die algemeen beter resultate as die gewone konvensionele metodes. 'Bayesian' metodes word nie. in Suid Afrika toegepas nie. Om dit te doen sal addisionele opleiding van studente en ingenieurs vereis, sowel as addisionele navorsing deur universiteite en ander navorsing instansies. Die gebruik van swak kwaliteit ongeluksdata kan die integriteit van 'n padveiligheidsverbeteringsprogram benadeel. Die kwaliteit van ongeluksdata in Suid Afrika is oor die algemeen swak en behoort meer aandag gegee te word aan die bestuur en kontrole van ongeluksdata. Die doel van hierdie tesis is om verslag te doen oor 'Bayesian' en konvensionele metodes wat gebruik kan word om ongeluksdata te ontleed, dit te ondersoek en te evalueer.

Thesis (MScEng)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: This investigation arose out of the pressing need for alternatives to ineffective existing methodologies for low flow measurement in boulder bed rivers, with particular focus on the mountain streams in the Western Cape. Both empirical and mathematical verification were regarded as important if progress was to be made towards identifying a suitable approach. Historically the inability to determine the frictional effect of the streambed on the flow rate has been a major obstacle limiting the accuracy of flow calculations. From literature, the most likely relationship appears to be a power function, utilising hydraulic variables derived from physical parameters characteristic of a section of stream. Local Western Cape data was thus collected from various typical mountain streams, so that relevant analysis could be done. Testing of existing equations from literature sources on this set of data revealed limited applicability. Subsequent empirical experimentation has shown that particle size is a dominant variable in determining boulder bed flow resistance under low flow conditions. A mathematical approach was sought to provide a more suitable base for a locally applicable formula. Sediment transport theory, based on simple power conservation laws, was successfully implemented, partially bridging the gap between the applications for sand bed and boulder bed flow conditions respectively. After a certain degree of empirical adjustment, an equation form was finalised that is believed to be the most suitable for Western Cape mountain streams, with definite potential for wider application, provided further research is done. / AFRIKAANSE OPSOMMING: Hierdie ondersoek spruit uit die dringende behoefte aan bruikbare alternatiewe vir bestaande laagvloei meetmetodes in riviere met bodems bestaande uit spoelklip, met spesifieke klem op die bergstrome van die Wes Kaap. Dit is as belangrik beskou om beide empiriese en wiskundige bevestiging te vind vir 'n verbeterde metode. Histories is die akkuraatheid van vloeitempo berekeninge hoofsaaklik beperk deur die onvoorspelbaarheid van die ruheidseffek van die rivierbodem op die vloei. Uit bestaande literatuur blyk dit dat die mees geskikte verwantskap waarskynlik 'n magsfunksie is, wat saamgestel is uit hidrouliese veranderlikes verkry vanaf fisiese parameters kenmerkend aan die spesifieke riviersnit. Plaaslike Wes-Kaapse data is dus versamelop verskeie tipiese bergstrome in die gebied sodat geskikte ontledings gedoen kon word. Verskeie bestaande formules is getoets teen hierdie stel data en ongeskik gevind vir direkte aanwending. Empiriese toetse het gevolg en getoon dat partikel grootte 'n dominante invloed het op die vloeiweerstand van spoelklip bodems onder laagvloei omstandighede. 'n Wiskundige benadering is daarna gevolg om 'n beter basis te verskaf waaruit 'n plaaslik bruikbare vergelyking kon volg. Sedimentvervoer beginsels, wat gebaseer is op basiese drywingsteorie, is suksesvol aangewend vir hierdie doel, en het in 'n mate die gaping tussen aanwending op sand en klip bodems oorbrug. Na afloop van empiriese verstelling is 'n formule gefinaliseer wat beskou word as die mees geskikte vir Wes-Kaapse bergstrome, maar wat ook die potensiaal besit vir wyer aanwending, mits verdere navorsing gedoen sou word.

Thesis (MScEng)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: AP230 of STEP is an application protocol for structural steel-framed buildings. Product data relating to steel structures is represented in a model that captures analysis, design and manufacturing views. The information requirements described in AP230 were analysed with the purpose of identifying a subset of entities that are essential for the description of simple industrial steel frames with the view to being able to describe the structural concept, and to perform the structural analysis and design of such structures. Having identified the essential entities, a relational database model for these entities was developed. Planning, analysis and design applications will use the database to collaboratively exchange data relating to the structure. The comprehensiveness of the database model was investigated by mapping a simple industrial frame to the database model. Access to the database is provided by a set of classes called the database representative classes. The data-representatives are instances that have the same selection identifiers and attributes as corresponding information units in the database. The datarepresentatives' primary tasks are to store themselves in the database and to retrieve their state from the database. A graphical user interface application, programmed in Java, used for the description of the structural concept with the capacity of storing the concept in the database and retrieving it again through the use of the database representative classes was also created as part of this project. / AFRIKAANSE OPSOMMING: AP230 van STEP is 'n toepassingsprotokol wat staal raamwerke beskryf. Die produkdata ter beskrywing van staal strukture word saamgevat in 'n model wat analise, ontwerp en vervaardigings oogmerke in aanmerking neem. Die informasie vereistes, soos beskryf in AP230, is geanaliseer om 'n subset van entiteite te identifiseer wat noodsaaklik is vir die beskrywing van 'n eenvoudige nywerheidsstruktuur om die strukturele konsep te beskryf en om die struktuur te analiseer en te ontwerp. Nadat die essensiële entiteite geïdentifiseer is, is 'n relasionele databasismodel van die entiteite geskep. Beplanning, analise en ontwerptoepassings maak van die databasis gebruik om kollaboratief data oor strukture uit te ruil. Die omvattenheid van die databasis-model is ondersoek deur 'n eenvoudige nywerheidsstruktuur daarop afte beeld. Toegang tot die databasis word verskaf deur 'n groep Java klasse wat bekend staan as die verteenwoordigende databasis klasse. Hierdie databasis-verteenwoordigers is instansies met dieselfde identifikasie eienskappe as die ooreenkomstige informasie eenhede in die databasis. Die hoofdoel van die databasis-verteenwoordigers is om hulself in die databasis te stoor asook om hul rang weer vanuit die databasis te verkry. 'n Grafiese gebruikerskoppelvlak, geprogrammeer in Java, is ontwikkel. Die koppelvlak word gebruik om die strukturele konsep te beskryf, dit te stoor na die databasis en om dit weer, met behulp van die databasis-verteenwoordigers, uit die databasis te haal.

Thesis (MEng)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: This study sets out to explore the possibilities and accuracy of flow measurement at natural controls, focussing specifically on Western Cape cobble-bed rivers. These rivers are regarded as being difficult in terms of flow measurement, mostly due to their large scale roughness and very turbulent and uneven flows. The aim is to determine a system through which various types of natural controls can be calibrated, by establishing a relationship between the discharge coefficient and the physical characteristics of each control type. This was achieved by conducting an extensive field investigation, focussing on the identification and gauging of both critical and uniform natural controls. Two types of critical controls were identified and investigated, namely step-pool controls and horizontal constriction controls as well as one type of uniform flow control, namely the plane bed control. Step-pool controls were found to be very robust controls which provided efficient critical controls for a wide range of flows. Horizontal constriction controls proved to be reasonably accurate measurement sites and, because of their physical characteristics, they are able to measure the full range of flows from low to flood flows. Uniform controls are widely used for flow measurements on deep rivers, but such measurements become highly unreliable when flow depths are small and bed roughness high as is the case with cobble-bed rivers. Under conditions of high roughness, generally speaking critical controls can be calibrated more accurately than uniform controls and are therefore to be preferred. The field study was followed by a series of laboratory tests, focussing on horizontal constriction controls. Calibration equations were derived by which the discharge coefficient value can be determined for a given constriction ratio and upstream energy head. Results from both the fieldwork and laboratory work were analysed and integrated to determine a calibration system applicable to natural controls in Western Cape cobbleand boulder-bed rivers. Reasonably accurate values of the discharge coefficients for different types of natural controls were established, which should be widely applicable. Additionally, guidelines were drawn up for the measurement of flow at natural controls, to be used by both engineers and non-engineers. Discharge measurement at natural controls in the Western Cape was found to be a viable and reasonably accurate way of determining river discharge. It proves to be an environmentally acceptable way of measurement, using the natural river characteristics rather than seriously interfering with them or damaging them. These advantages make discharge measurement at natural controls a promising means of determining river discharge in the future. / AFRIKAANSE OPSOMMING: Die beste posisie vir vloeirneting in riviere is waar die topografie van die rivier 'n unieke verhouding tussen die deurstroming en die water diepte bewerkstellig. Hierdie studie ondersoek die uitvoerbaarheid en akkuraatheid van vloeirneting by natuurlike kontroles met die fokus op Wes-Kaapse spoelklip riviere. Vloeirneting in spoelklip riviere word as baie ingewikkeld beskou weens die grootte van die bedpartikels relatieftot die vloeidiepte en gevolglike onewe, turbulente vloeie. Die doel van die studie was om 'n stelsel te ontwikkel waardeur verskillende tipes natuurlike kontroles gekalibreer kan word deur verwantskappe te bepaal tussen die deurstromings koëffisiënt en die stroom-op energie hoogte. Bogenoemde is bepaal met behulp van 'n uitgebreide veldstudie waarin die hoof tipes natuurlike kontroles, nl. die kritiese vloei kontrole en die uniforme vloei kontrole, geidentifiseer en gekalibreer is. Twee tipes kritiese vloei kontroles is ondersoek, naamlik die trap-poel ("step-pool") kontrole en die horisontale vernouing kontrole. Daar is bevind dat beide die trap-poel kontrole en die horisontale vernouing baie effektiewe kritiese kontroles is, waarmee 'n wye reeks van vloeie gemeet kan word. Uniforme vloei kontroles word algemeen vir vloeimeting in diep vloeiende riviere gebruik, maar sulke metings word hoogs onbetroubaar wanner die vloeidiepte klein is relatief tot die partikel grootte van die rivierbed, soos in die geval van spoelklip riviere. Onder hierdie omstandighede kan kritiese kontroles in die algemeen meer akkuraat gekalibreer word en word hul gevolglik bo uniforme vloei kontroles verkies. Die veldstudie is gevolg deur 'n reeks laboratorium toetse, wat fokus op die horisontale vernouing kontrole. Kalibrasie vergelykings is afgelei waarmee die deurstromings koëffisient vir 'n gegewe stroom-op energiehoogte en vernouings-verhouding bereken kan word. Resultate van beide die veldstudie en die laboratorium toetse is geanaliseer en geïntegreer om 'n kalibrasie stelsel te bepaal wat van toepassing is op natuurlike kontroles in Wes-Kaapse spoelklip riviere. Aanvaarbare waardes vir die deurstromings koëffisiente vir verskeie tipes natuurlike kontroles is bepaal, wat algemeen toepasbaar behoort te wees. Riglyne vir die meting van riviervloei by natuurlike kontroles is opgestel vir die gebruik deur beide ingenieurs en nie-ingenieurs. Vloeimeting deur middel van natuurlike kontroles is 'n lewensvatbare metingsmetode waarmee riviervloei redelik akkuraat bepaal kan word. Dit is 'n omgewingsaanvaarbare metings metode wat die natuurlike karakter van die rivier gebruik, eerder as om ernstig daarmee in te meng of dit te beskadig. Hierde positiewe eienskappe maak vloeimeting deur middel van natuurlike kontroles 'n belowende metingsmetode vir die toekoms.

Thesis (MEng)--Stellenbosch University, 1994. / ENGLISH ABSTRACT: Various aspects affecting the inlet capacities of modified stormwater kerb inlets were investigated. Investigations centred on the influence of effective inlet length, ratios of upstream transition section length to inlet section length and road crossfall. The suitability of existing design curves for use in the design of modified kerb inlets was verified and new more "user-friendly" design curves were developed. Attempts were made to develop a sound theoretical model to predict inlet capacities for stormwater kerb inlets as the lack of such a model had previously been identified as a major shortcoming in the design of stormwater kerb inlets. A detailed study of relevant literature and of various full scale model test results confirmed the fact that the effective inlet length is the most important variable affecting the inlet capacity at stormwater kerb inlets. Model studies on various combinations of transition section lengths and inlet section lengths have indicated that in the case of supercritical flow the inlet capacity of stormwater kerb inlets is not sensitive to changes in the ratio between the inlet section length and the upstream transition section length. Furthermore no marked effect on the inlet capacity of a modified stormwater kerb inlet was detected when the road crossfall was increased from 2% to 3%. The inlet capacities predicted by the existing design curves were found to be consistent, although on the conservative side, when compared to the inlet capacities obtained from the full scale model tests. New design curves derived from the existing design curves were developed to provide a less cumbersome procedure in the design of stormwater kerb inlets. The development of an improved comprehensive theoretical model based on pure hydraulic principles was not possible due to the extremely complex nature of flow conditions at stormwater kerb inlets. The most important findings emanating from this research project are: - The confirmation of the "effective inlet length” concept, whereby a part of the expensive inlet section is replaced by an equivalent length of inexpensive transition section upstream of the kerb inlet. which does not affect the inlet capacity of the kerb inlet negatively and thereby results in a substantial saving in the cost of stormwater kerb inlets. - Model tests revealed that for supercritical flows the upstream transition section can be made up to 6 times longer than the inlet section with a maximum length of 6m. without any negative effect on the inlet capacity of the kerb inlet. Similarly an analysis of previous research results has indicated that even in cases of subcritical flow the upstream transition section can be made twice the length of the inlet section. - The full scale model tests also indicated that an upward adjustment of 30% in the inlet capacities as predicted by the existing design curves was justified. The modified design curves proved to be suitable for the design of conventional stormwater kerb inlets as well as for modified stormwater kerb inlets where part of the inlet section is replaced by a transition section. A new set of "easy to use" design curves was developed specifically for urban applications. - Guidelines for determining upstream transition section lengths were drawn up for use in conjunction with the existing and new design curves for the design of stormwater kerb inlets. / AFRIKAANSE OPSOMMING: Verskeie aspekte wat die inlaatkapasiteit van verbeterde randsteeninlate belnvloed is ondersook. Die belangrikste aspekte wat ondersoek is, was die invlood van effektiewe inlaatlengte en die moontlike verhouding van die stroomop oorgangslengte tot die werklike inlaatlengte sowel as dwarshelling. Die ontwerpgrafieke wat tans gebruik word om randsteeninlaatlengtes te bepaal is ook ondersoek aan die hand van modeltoetse op volskaalse modelle om die grafieke se akkuraatheid te toots. Meer gebruikersvriendelike ontwerpgrafieke is ook ontwikkel. 'n Belangrike tekortkoming tot op datum, naamlik 'n geskikte teoretiese model om die inlaatkapasiteit van randsteeninlate te beskryf, is aangespreek. 'n Voorvereiste vir so 'n model was dat die model gebaseer moes word op suiwer hidrouliese beginsels. Die bestudering van vorige navorsing asook die uitvoering van verskeie modelstudies op volskaalse randsteeninlate het die effektiewe inlaatlengte as die belangrikste veranderlike wat die inlaatkapasiteit van randsteeninlate bepaal geYdentifiseer. Tydens tootse uitgevoer op volskaalse modelle onder superkritiese vlooitoostande met verskillende kombinasies van oorgangslengtes en inlaatlengtes, vir die dieselfde totale lengte het dit geblyk dat die inlaatkapasiteit grootliks onatbanklik is van die verhouding van die oorgangslengte tot die inlaatlengte. Vit die modeltootse het dit oak geblyk dat paddwarsval 'n baie beperkte invlood op die inlaatkapasiteit van ransteeninlate gehad het toe die paddwarsval verander is van 2%na 3%. Die resultate wat verkry is uit die modeltoetse het ook aangetoon dat die bestaande ontwerpgrafieke konserwatief is in hul voorspelling van inlaatkapasieit van randsteeninlate. Die bestaande ontwerpgrafieke is voorts gebruik om nuwe meer gebruikersvriendelike ontwerpgrafieke te ontwikkel. Die ontwikkeling van 'n teoretiese model am inlaatkapasiteite volledig te voorspel was egter nie moontlik nie vanwee die uiters komplekse aard van die vloei by randsteeninlate. Die belangrikste bevindinge van hierdie studie kan soos volg opgesom word: - Afdoende bewyse is gevind dat die "effektiewe inlaatlengte" konsep, waarvolgens 'n gedeelte van die duur inlaatgedeelte met 'n goedkoper oorgangsstuk van dieselfde Iengte vervang kan word sonder om inlaatkapasiteit in te boet, weI suksesvol aangewend kan word om kostes in die ontwerp van stOlIDwater randsteeninlate te bespaar. - Afdoende bewyse is gevind dat die "effektiewe inlaatlengte" konsep, waarvolgens 'n gedeelte van die duur inlaatgedeelte met 'n goedkoper oorgangsstuk van dieselfde Iengte vervang kan word sonder om inlaatkapasiteit in te boet, weI suksesvol aangewend kan word om kostes in die ontwerp van stOlIDwater randsteeninlate te bespaar. - Afdoende bewyse is gevind dat die "effektiewe inlaatlengte" konsep, waarvolgens 'n gedeelte van die duur inlaatgedeelte met 'n goedkoper oorgangsstuk van dieselfde Iengte vervang kan word sonder om inlaatkapasiteit in te boet, weI suksesvol aangewend kan word om kostes in die ontwerp van stOlIDwater randsteeninlate te bespaar. - Riglyne is ook ontwikkel vir die bepaling van stroomop oorgangslengtes. Die riglyne kan saam met die bestaande en die nuwe ontwerpgrafieke gebruik word by die ontwerp van stormwater nmdsteeninlate.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2006. / The predominately manual, time-consuming and error-prone procedure currently used in engineering offices for the calculation of preliminary column forces in multi-storey buildings constitutes the motive for the research described in this study. Identifying the current procedure as in need of improvement, techniques and prototype software posing a semi-automated alternative, are developed. Influence areas used for load-assignment are established with the use of a Voronoi diagram calculated for a specific floor geometry. The forces transferred to the columns are based solely on the size of the influence areas thus calculated. The definition of the floor geometry, as well as the definition of loads and other necessary input parameters, are performed in a CAD-system, into which the Voronoi functionality is integrated. The accuracy of the forces obtained with the implemented procedure and, consequently, the accuracy of the forces as they are calculated in current practice, is determined through comparison with the results of finite element analyses. The comparative analysis of a sample of typical floor geometries allows an evaluation of the results and the identification of tendencies observed regarding the errors obtained. It is concluded that calculating column forces based on influence areas, i.e. solving a geometrical problem without taking any stiffness properties into account, is unsafe. The implication hereof is twofold. Firstly, it serves as a warning concerning the technique currently used in practice and secondly, it steers the investigation in the direction of a finite element analysis: using the influence areas as a basis for automatic meshing, a semi-automated analysis can be performed relatively inexpensively, using plate elements.