Thesis (MScEng (Civil Engineering))--Stellenbosch University, 2008. / The South African code for the design loading of building structures, namely SABS 0160 (1989), was revised with the requirements for seismic design prescribed in SANS 10160: Part 4: Seismic actions and general requirements for buildings. SANS 10160: Part 4 incorporates the seismic design provisions of several seismic codes of practice, however, the influence of the value prescribed for the behaviour factor has not been established with regard to South African conditions. The behaviour factor is used by most seismic design codes to account for the energy dissipating effects of plastification in structural systems when subjected to earthquake ground motion, to reduce the elastically determined forces to be designed for. However, a considerable difference is observed in the values of the behaviour factor prescribed for the design of reinforced concrete walls between the leading international seismic codes. The aim of this study is to assess the value of the behaviour factor prescribed in SANS 10160: Part 4 for reinforced concrete structural walls under the influence of South African seismic conditions and code requirements. A method of quantifying the value of the behaviour factor was developed and implemented in the study by Ceccotti (2008). This method entails estimation of the maximum analytical behaviour factor as the ratio of seismic intensity at failure of the structure to the seismic intensity prescribed by the design code. Such a method is adopted for this study where the lateral force resisting systems of six-, eight- and tenstorey buildings are investigated with nonlinear static analysis to quantify the maximum computationally-determined value of the behaviour factor. Firstly, it is observed that it is possible to quantify the value of the behaviour factor through the use of a computational study. The nonlinear static method of analysis is shown to provide reliable results in the estimation of the behaviour factor for a sixstorey building, however, does not perform well for taller buildings. Further investigation with the use of dynamic time-history analysis is proposed to evaluate the influence of the factors identified in this study. The behaviour of structural walls, designed for reduced forces with the prescribed behaviour factor of 5.0, exhibits high yield strengths and resists the design seismic action entirely elastically. This high strength is found to be due to the reliability/redundancy factor prescribed by SANS 10160: Part 4 and because of the high values of structural overstrength. Similar studies observed high values of structural overstrength for buildings designed for low seismic intensity, which were shown to result from the fact that the resistance required to gravity loading became more critical than the seismic loads in the design of the structural system. This study identifies several factors that influence the value of the behaviour factor, such as the number of walls in the lateral force resisting system; the number of storeys of the buildings; available displacement ductility of the structural system; and the ground type designed for.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: Electric driven overhead travelling bridge cranes (EOHTC) form a vital part of industrial plants where heavy objects require moving. Overhead travelling cranes aid in production by allowing an uninterrupted work process on the ground while heavy loads are moved to their required locations. Various factors need consideration in determining the loads induced by an EOHTC on its support structure. In order to design such a support structure, the designer must understand and take into account the various loads that the support structure will be subject to during its lifetime. The procedure for determining the loads induced by the EOHTC on its support structure is laid out in the SANS 10160-6:2010 code of practice. This document was published in June 2010 and as a result very few worked examples exist to test the coherence of the procedure. This thesis presents an investigation into the procedure for determining the actions induced by overhead travelling bridge cranes adopted in the SANS 10160-6:2010 code of practice. The investigation was conducted by developing a software application to automatically determine the necessary crane actions needed for the design of the crane support structure, given certain input parameters. The motivation behind this was to have a tool that can calculate the crane induced loads automatically. And by developing such a tool the procedure given in the code of practice is better understood. The Java programming language was used to code the calculations with an object oriented programming approach (OOP). NetBeans, the integrated development environment for developing with Java was used to generate the required graphical user interface of the application. In addition, a Microsoft Excel calculation sheet was also developed for the purpose of comparison and verification. Whilst developing the software application, it was found that the model for the acceleration or deceleration of the crane was specific for four wheel cranes only. This model was then extended to accommodate eight and sixteen wheel cranes and incorporated into the algorithm architecture of the application. The application was successfully completed and verified using benchmarked examples. / AFRIKAANSE OPSOMMING: Elektriese oorhoofse brugkrane vorm ‘n belangrike deel van baie nywerheidsprosesse, waar dit gebruik word om swaar laste in die nywerheidsaanleg te verskuif. Oorhoofse brugkrane voeg waarde by die produksie lyn deur te sorg dat die werksproses op die grond onversteurd voortgaan terwyl swaar laste na hul vereiste posisies verskuif word. Verskillende faktore moet in ag geneem word om die nodige kraanlaste te bepaal. Hierdie laste word benodig om die kraan se ondersteuningstruktuur te ontwerp. Die ontwerper moet die nodige kundigheid hê en moet ook die verskeie laste in ag neem wat die ondersteuningstruktuur gedurende sy leeftyd sal dra. SANS 10160-6:2010 verskaf riglyne vir die bepaling van die laste wat deur oorhoofse brugkrane uitgeoefen word. Hierdie dokument is in Junie 2010 gepubliseer dus bestaan daar min uitgewerkte voorbeelde om die korrektheid van die riglyne te toets en toepassing te demonstreer. Hierdie proefskrif ondersoek die riglyne vir die bepaling van oorhoofse brugkraan aksies soos uiteengesit in die SANS 10160-6:2010. Die navorsing is uitgevoer deur middel van die ontwikkeling van ‘n sagteware toepassing wat die nodige oorhoofse brugkraanlaste automaties bepaal, gegee sekere invoer waardes. Die rede hiervoor was om ‘n hulpmiddel te ontwikkel vir die outomatiese bepaling van oorhoofse brugkraan. Deur die bogenoemde hulpmiddel te ontwikkel word die riglyne, soos gegee in die kode beter verstaan. Java is gebruik as programmeringstaal waar die objek geörienteerde programeringstyl toegepas was. Die geintegreerde ontwikkelingsomgewing vir ontwikkeling met Java, naamlik NetBeans is gebruik om die nodige gebruikers koppelvlak op te bou. ‘n Microsoft Excel sigblad is ook ontwikkel vir kontrolerings doeleindes. Gedurende die ontwikkeling van die sagtewarepakket is dit bevind dat die lasmodel vir die versnelling of vertraging van die oorhoofse brugkraan slegs op vierwiel krane van toepasing is. Hierdie lasmodel is dus uitgebrei om agt- en sestienwiel krane ook te bevat. Die lasmodel aanpassing is dan ook in die program se algoritme-argitektuur ingebou. Die sagteware toepassing is suksesvol ontwikkel en gekontroleer met ‘n maatstaf voorbeeld.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Structural design standards based on the principles of structural reliability are gaining worldwide acceptance and are fast becoming the new basis of structural safety verification. The application of these principles to establish a standardised basis for structural design using partial factor limit states design procedures is done in the European Standard for the Basis of Structural Design EN 1990 from which it is adapted to the South African Basis of Design Standard for Building and Industrial Structures SANS 10160-1. The basis of design requirements stipulated in EN 1990 and SANS 10160-1 apply to all aspects of structural design: This includes reliability levels of structural performance and their differentiation and management; identification of various limit states and design situations; the specification of all the basic variables; separate treatment of actions and material-based resistance. However, application of these requirements is then primarily focused on actions whilst the provision for structural concrete is then left to the materials based design standards. This two-part thesis describes a systematic assessment of the degree to which the application of the reliability framework presented in the basis of design requirements has been achieved in the present generation of structural concrete design standards. More importantly, attempts are made to identify ways in which the process can be advanced. Special attention is drawn to issues that are specific to South African conditions and practice in structural concrete. Part One of the thesis focuses on the key elements of the reliability framework presented in EN 1990 and traces to what extent the requirements have been propelled through the design stipulations of the Eurocode Standard for Design of Concrete Structures EN 1992-1-1. The implications of the different reference level of reliability between the Eurocode default value of ß = 3.8 and that characteristic of South African practice ß = 3.0 through various issues are highlighted. The use and advantage of explicit treatment of reliability performance on reliability management related to some aspects of quality control are explored. A critical aspect is the shear prediction model providing unconservative estimates of shear resistance. Part Two of the thesis focuses on characterising the model factor of the EN 1992-1-1 shear prediction model for members requiring design shear reinforcement. This is done by a comparison to a compiled experimental database with special focus on situations with high reinforcement ratios. The significance of the modelling uncertainty in shear prediction is verified by this comparison. The use of the more conceptually rational modified compression field theory (MCFT) to improve on the quality of shear predictions is investigated and proves to yield more precise values with lower scatter hence making it a more reliable tool for predicting shear. The MCFT can then be used as reference for the reliability calibration and possible improvement for the Eurocode procedure. / AFRIKAANSE OPSOMMING: Strukturele ontwerpstandaarde gebaseer op die beginsels van strukturele betroubaarheid verkry wêreldwye aanvaarding en word vinnig die nuwe basis van strukturele veiligheid bevestiging. Die toepassing van hierdie beginsels om ʼn gestandaardiseerde basis vir strukturele ontwerp is bevestig deur gebruik te maak van gedeeltelike-faktorbeperkende stadiums ontwerpprosedures in die Europese Standaard vir die Basis van Strukturele Ontwerp EN 1990 waarvandaan dit herbewerk is na die Suid-Afrikaanse Basis van Ontwerp Standaarde vir Bou en Industriële Strukture SANS 10160-1. Die basis van ontwerpvereistes bepaal in EN 1990 en SANS 10160-1 is van toepassing op alle aspekte van strukturele ontverp: Dit sluit inbetroubaarheidsvlakke van struktureele prestasie en hul diversifikasie en bestuur; identifikasie van verskeie beperkende state en ontwerpsituasies; die spesifikasie van al die basiese veranderlikes; afsonderlike behandeling van aksies en materiaal-gebaseerde weerstand. Desnieteenstaande, die toepassing van hierdie voorwaardes is dan hoofsaaklik gefokus op aksies terwyl die voorsiening van strukturele beton is dan gelaat op die materiaalgebaseerde ontwerpstandaarde. Hierdie tweeledige verhandeling beskryf ʼn stelselmatige beoordeling van die graad waartoe die toepassing van die betroubaarheidsraamwerk aangebied word in die basis van ontwerpvereistes bereik in die huidige generasie van strukturele beton-ontwerp standaarde is. Meer belangrik, pogings is aangewend om die maniere hoe die proses bevorder kan word te identifiseer. Spesiale aandag word gevestig op kwessies wat spesifiek op Suid-Afrikaanse toestande en praktyke in strukturele beton toepaslik is. Deel Een van die verhandeling fokus op die sleutel-dele van die betroubaarheidsraamwerk aangebied in EN 1990 en skets die mate waartoe die vereistes aangespoor word deur die ontwerp voorskrifte van die Eurocode Standard for the Design of Concrete Structures EN 1992-1-1. Die implikasie van die verskillende verwysingsvlakke van betroubaarheid tussen die Eurocode standaardwaarde van ß = 3.8 en die eienskap van Suid-Afrikaanse praktyk ß = 3.0 deur verskillende kwessies word uitgelig. Die gebruik en voordeel van spesifieke behandeling van betroubaarheidsuitvoering op betroubaarheidsbestuur verwantskap met sekere aspekte van kwaliteit kontrole word ondersoek. ʼn Kritiese aspek is die model vir die voorspelling van skuif-weerstand wat die onkonserwatiewe beramings vir skuif-weerstand gee. Deel Twee van die verhandeling fokus op karakterisering die modelfaktor van die EN 1992- 1-1 skuif-weerstand voorspellings-model. Dit word gedoen deur ʼn vergelyking na ʼn saamgestelde eksperimentele databasis met spesifieke fokus op situasies met hoe herbevestigingsvergelykings. Die oorheersing van die modellering- onsekerheid in skuifweerstand voorspelling is bevestig deur hierdie vergelyking. Die gebruik van ʼn meer konseptuele rasionele gemodifiseerde druk-veld teorie (bekend as MCFT) om die kwaliteit van skuif voorspelling te verbeter is ondersoek en verskaf ‘n meer presiese waarde met laer verspreiding wat lei tot ʼn meer betroubaree instrument om skuif mee te voorspel. Die MCFT word dan gebruik as verwysing vir die betroubaarheid-samestelling en moontlike verbetering van die Eurocode prosedures.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Reinforced concrete structures, designed according to proper capacity design guidelines, can deform inelastically without loss of strength. Therefore, such structures need not be designed for full elastic seismic demand, but could be designed for a reduced demand. In codified design procedures this reduced demand is obtained by dividing the full elastic seismic demand by a code-defined behaviour factor. There is however not any consensus in the international community regarding the appropriate value to be assigned to the behaviour factor. This is evident in the wide range of behaviour factor values specified by international design codes. The purpose of this study is to assess the seismic drift of reinforced concrete structural walls in order to evaluate the current value of the behaviour factor prescribed by SANS 10160-4 (2009). This is done by comparing displacement demand to displacement capacity for a series of structural walls. Displacement demand is calculated according to equivalency principles (equal displacement principle and equal energy principle) and verified by means of a series of inelastic time history analyses (ITHA). In the application of the equivalency rules the fundamental periods of the structural walls were based on cracked sectional stiffness from moment-curvature analyses. Displacement capacity is defined by seismic design codes in terms of inter storey drift limits, with the purpose of preventing non-structural damage in building structures. In this study both the displacement demand and displacement capacity were converted to ductility to enable comparison. The first step in seismic force-based design is the estimation of the fundamental period of the structure. The influence of this first crucial step is investigated in this study by considering two period estimation methods. Firstly, the fundamental period may be calculated from an equation provided by the design code which depends on the height of the building. This equation is known to overestimate acceleration demand, and underestimate displacement demand. The second period estimation method involves an iterative procedure where the stiffness of the structure is based on the cracked sectional stiffness obtained from moment-curvature analysis. This method provides a more realistic estimate of the fundamental period of structures, but due to its iterative nature it is not often applied in design practice. It was found that, regardless of the design method, the current behaviour factor value prescribed in SANS 10160-4 (2010) is adequate to ensure that inter storey drift of structural walls would not exceed code-defined drift limits. Negligible difference between the equivalency principles and ITHA was observed. / AFRIKAANSE OPSOMMING: Gewapende beton strukture wat ontwerp is volgens goeie kapasiteitsontwerp-riglyne kan plasties vervorm sonder verlies aan sterkte. Gevolglik hoef hierdie strukture nie vir die volle elastiese seismiese aanvraag ontwerp te word nie, maar kan vir 'n verminderde aanvraag ontwerp word. In gekodifiseerde ontwerpriglyne word so 'n verminderde aanvraag verkry deur die volle elastiese aanvraag te deel deur 'n kode-gedefinieerde gedragsfaktor. Wat egter duidelik blyk uit die wye reeks van gedragsfaktor waardes in internasionale ontwerp kodes, is dat daar geen konsensus bestaan in die internasionale gemeenskap met betrekking tot die geskikte waarde van die gedragsfaktor nie. Die doel van hierdie studie is om seismiese verplasing van gewapende beton skuifmure te evalueer ten einde die waarde van die gedragsfaktor wat tans deur SANS 10160-4 (2009) voorgeskryf word te assesseer. Dit word gedoen deur verplasingsaanvraag te vergelyk met verplasingskapasiteit. In hierdie studie word verplasingsaanvraag bereken deur middel van gelykheidsbeginsels (gelyke verplasingsbeginsel en gelyke energiebeginsel) en bevestig deur middel van nie-elastiese tydsgeskiedenis analises (NTGA). Die effek van versagting as gevolg van nie-elastiese gedrag word in aanmerking geneem in die toepassing van die gelykheidsbeginsels. Verplasingskapasiteit word deur seismiese ontwerpkodes gedefinieer deur perke te stel op die relatiewe laterale beweging tussen verdiepings, met die doel om nie-strukturele skade te verhoed. Om verplasingsaanvraag en -kapasiteit te vergelyk in hierdie studie, word beide omgeskakel na verplasingsduktiliteit. Die eerste stap in kraggebaseerde seismiese ontwerp is om die fundamentele periode te beraam. Die invloed van hierdie eerste kritiese stap word in hierdie studie aangespreek deur twee periodeberamingsmetodes te ondersoek. Eerstens kan die fundamentele periode bereken word deur 'n vergelyking wat 'n funksie is van die hoogte van die gebou. Dit is egter algemeen bekend dat hierdie vergelyking versnellingsaanvraag oorskat en verplasingsaanvraag onderskat. Die tweede metode behels 'n iteratiewe prosedure waar die styfheid van die struktuur gebaseer word op die gekraakte snit eienskappe, verkry vanaf 'n moment-krommingsanalise. 'n Beter beraming van die fundamentele periode word verkry deur hierdie metode, maar as gevolg van die iteratiewe aard van die metode word dit selde toegepas in ontwerppraktyk. Die resultate van hierdie studie toon dat die huidige waarde van die gedragfaktor soos voorgeskryf in SANS 10160-4 (2010) geskik is om te verseker dat die relatiewe laterale beweging tussen verdiepings binne kode-gedefinieerde perke sal bly. Onbeduidende verskil is waargeneem tussen die resultate van gelykheidsbeginsels en NTGA.