Investigation into ultra high performance concrete for pedestrian bridge design: A Cape Town railway case study

Rohrbeck, Alicia (2022-04)

Thesis (MEng)--Stellenbosch University, 2022.

Thesis

ENGLISH ABSTRACT: The need for e cient bridge structures with enhanced load-bearing capacity and lower maintenance is continuously increasing, and the development of cost-e ective solutions to satisfy these demands remains a never-ending challenge. Ultra High Performance Con crete (UHPC) is an advanced bre reinforced cement-based material with exceptional strength- and performance properties that far surpass that of conventional concrete, and o ers a promising solution to improve bridge design. The successful development of locally-produced UHPC in recent years has raised the possibility of its utilisation in local design practice. In order to enable its structural application, a comprehensive understanding of the mechanical behaviour and consequent structural response is needed to accurately characterise the behaviour of UHPC for design purposes. With the aim of addressing this issue, this research investigates the utilisation of locally-developed UHPC in pedestrian bridge design. The study focuses on the devel opment and implementation of a comprehensive design methodology within the context of a single case study that incorporates appropriate constitutive modelling techniques and design principles of UHPC into local pedestrian bridge design practice. Subsequently, the structural response of the developed design concept is assessed in order to gain insight into the structural design and behaviour of UHPC pedestrian bridges. The results reveal the di culties that arise in describing the behaviour of UHPC in design. Constitutive modelling of UHPC, especially its tensile behaviour, must be sup ported by su cient empirical data to accurately characterise its behaviour. Experimental testing and high quality control is therefore crucial in order to utilise UHPC in structural design. Despite the considerable e ort with regards to characterising UHPC for design, the ndings demonstrate the advantageous strength and performance of UHPC structural components. Owing to the material's intrinsically high sti ness, it is observed that UHPC pedestrian bridges are less susceptible to excessive deformations during their service life. Moreover, the bending- and shear forces that arise due to imposed loads can be sustained by the tensile strength provided by UHPC, consequently reducing the need for additional reinforcement in the cross section. This enables the design of thin and lightweight struc tural components without compromising on strength. In view of the implementation of UHPC in local bridge design practice, this research demonstrates that with careful assessment of experimental testing results and in-depth in sight into the mechanical behaviour of UHPC, the characterisation of UHPC for structural design in local practice can be derived from constitutive modelling techniques proposed in literature and the utilisation of UHPC for pedestrian bridges in South Africa is achievable.

AFRIKAANSE OPSOMMING: Die behoefte vir brug strukture met verbeterde dravermoë en vermindere instandhouding neem voortdurend toe, en die ontwikkeling van doeltre ende oplossings om hieraan te voldoen bly `n nimmereindigende uitdaging. Ultra-Hoë Werkverrigting Beton (UHWB) is `n gevorderde sement-gebaseerde materiaal met uitsonderlike sterkte en werkverrigting seienskappe wat `n belowende oplossing bied. Die suksesvolle ontwikkeling van plaaslik-vervaardigde UHWB laat die moontlikheid ontstaan om hierdie materiaal aan te neem in die plaaslike ontwerpspraktyk. Ten einde die strukturele toepassing daarvan moontlik te maak, is `n omvattende begrip van die gedrag en ook die gevolglike strukturele reaksie van UHWB nodig om die gedrag vir on twerp doeleindes akkuraat te beskryf. Met die doel om hierdie kwessie aan te spreek, word die gebruik van plaaslik-ontwikkelde UHWB vir voetgangerbrugontwerp ondersoek in hierdie navorsing. Die studie fokus op die ontwikkeling van `n omvattende metodolo gie wat toepaslike konstitutiewe modelleringstegnieke en ontwerpsbeginsels van UHWB in plaaslike ontwerpspraktyk inkorporeer. Hierdie metodologie word vervolgens geïmple menteer binne die konteks van `n enkele gevallestudie om insig te verkry in die ontwerp en gedrag van UHWB voetgangerbrûe. Die resultate onthul die probleme wat ontstaan om die gedrag van UHWB vir on twerpsdoeleindes te beskryf. Konstitutiewe modellering van UHWB, veral die gedrag in trek, moet deur voldoende empiriese data ondersteun word om sodoende die gedrag akku raat te karakteriseer. Genoegsame eksperimentele toetse, asook hoë kwaliteit beheer, is dus van kardinale belang om UHWB in strukturele ontwerp te gebruik. Ten spyte van die aansienlike moeite met betrekking tot die karakterisering van UHWB, demonstreer die bevindinge die voordelige sterkte en werkverrigtingseienskappe van UHWB strukturele komponente. As gevolg van die materiaal se intrinsieke hoë styfheid, is UHWB voet gangerbrûe minder vatbaar vir oormatige vervormings gedurende hul leeftyd. Boonop kan die buig- en skuif kragte wat ontstaan ondersteun word deur die treksterkte wat deur UHWB verskaf word, wat gevolglik die behoefte vir addisionele versterking in die dwarssnit verminder. Dit maak die ontwerp van dun en liggewig strukturele komponente moontlik sonder om op sterkte in te boet. Hierdie navorsing toon dat - met noukeurige assessering van eksperimentele toetsre sultate en diepgaande insig vain die meganiese gedrag van UHWB - die karakterisering van UHWB afgelei kan word van modelleringstegnieke wat in literatuur voorgestel word. Met die oog op die implementering van UHWB in plaaslike brugontwerpspraktyk, toon hierdie navorsing verder dat die gebruik van UHWB vir voetgangerbrûe in Suid-Afrika haalbaar is.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/124818
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