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Construction in in-situ cast flat slabs using steel fibre reinforced concrete

dc.contributor.advisorBoshoff, W. P.en_ZA
dc.contributor.authorJarrat, Roberten_ZA
dc.contributor.otherStellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.en_ZA
dc.date.accessioned2011-11-22T12:16:47Zen_ZA
dc.date.accessioned2011-12-05T13:05:47Z
dc.date.available2011-11-22T12:16:47Zen_ZA
dc.date.available2011-12-05T13:05:47Z
dc.date.issued2011-12en_ZA
dc.identifier.urihttp://hdl.handle.net/10019.1/17861en_ZA
dc.descriptionThesis (MScEng)--Stellenbosch University, 2011.en_ZA
dc.description.abstractENGLISH ABSTRACT: Fibre reinforced concrete (FRC) transforms concrete from a characteristically brittle material to one with a post-crack tensile residual capacity. Its application in industry has varied over the past of which the tensile properties have generally been used in the form of crack mitigation. More recently, the introduction of steel fibres has broadened this scope to structural applications in which the resisting tensile stresses that develop within a steel FRC (SFRC) element can be rather significant. This thesis reviews the existing practices and design models associated with SFRC and the suitability of its implementation as the sole form of reinforcement in in-situ cast flat slab systems. As a material SFRC is dependent on a number of factors which include the fibre type and volume, fibre distributions, element size, as well as the support and applied load conditions. Thus, its performance can be considered rather variable in comparison to conventional concrete should the incorrect practices be implemented. In order to adequately define the material characteristics, it is necessary to use test procedures that accurately reflect on the intended structural application. As a result a number of test procedures have been developed. In addition to this, the post-crack material performance is associated with a non-linear behaviour. This attribute makes the design of structural SFRC elements rather difficult. In an attempt to simplify this, existing design models define stress-strain or stress-crack width relations in which assumptions are made regarding the cross-sectional stress distribution at specified load states. This thesis takes on two parts in defining the suitability of SFRC as the sole form of reinforcement in flat slab systems. The first is a theoretical investigation regarding the micro and macro scale material performance of SFRC, the practices that exist in defining the material properties and its application in structural systems (particularly suspended slab systems), and a breakdown of the existing design models applicable to strain softening deflection hardening SFRC materials. The second part is an experimental program in which the fresh state and hardened state material properties of specified SFRC mix designs defined through flow and beam testing respectively. These properties are then implemented in the design and construction of full scale flexural and punching shear test slabs in an attempt to verify the theory applied. The investigation reveals that the use of SFRC significantly improves the ductility of concrete systems in the post-crack state through fibre crack bridging. This ductility can result in deflection hardening of flat slab systems in which the redistribution of stresses increases the load carrying capacity once cracking has taken place. However, the performance of large scale test specimens is significantly influenced by the construction practices implemented in which the material variability increases as a result of non-uniform fibre distributions. The results indicate that the load prediction models applied have potential to adequately predict the ultimate failure loads of SFRC flat slab systems but however cannot account for possible non-uniform fibre distributions which could result in premature failure of the system.en_ZA
dc.description.abstractAFRIKAANSE OPSOMMING: Vesel versterkte beton (VVB) verander beton van die kenmerkende uiters bros material na ‘n material met ‘n residuele post-kraak trekkapasiteit. Die toepassing daarvan in die bedryf het in die verlede gewissel en die trek eienskappe is oor die algemeen gebruik vir kraak vermindering. Meer onlangs het die bekenstelling van staal vesel hierdie omvang verbreed na die strukturele toepassings waar trekspannings wat ‘n VVB element kan weerstaan noemenswaardig kan wees. Hierdie tesis ondersoek bestaande praktyke en ontwerpmodelle met die oog op staalvesel versterkte beton (SVVB) en die geskiktheid van die implementering daarvan as die enigste vorm van bekisting in in-situ gegiete plat blad stelsels. As ‘n materiaal, is SVVB afhanklik van ‘n aantal faktore wat die tipe vesel en volume, vesel verspreiding, element grootte, sowel as die randvoorwaardes tipe aangewende las insluit. As gevolg hiervan, kan die gedrag van SVVB, wat korrek geïmplimenteer word, as redelik varieerbaar beskou word wanneer dit met konvensionele beton vergelyk word. Ten einde die materiaaleienskappe voldoende te definieer, is dit noodsaaklik dat prosedures wat die strukturele toepassing akuraat voorstel, getoets word en daarom is ‘n aantal toets prosedures ontwikkel. Verder het die post-kraak materiaalgedrag ‘n nie-lineêre verband wat struktuurontwerp met SVVB redelik moeilik maak. Om dit te vereenvoudig, definieer bestaande ontwerpmodelle spanning-vervorming of spanning-kraakwydte verhoudings waarin aannames gemaak word ten opsigte van die spanningsverdeling oor ‘n snit, gegewe sekere lastoestande. Hierdie studie bestaan uit twee dele wat die geskiktheid van SVVB as die enigste vorm van bikisting in plat blad stelsels definieer. Die eerste deel bestaan uit ‘n teoretiese ondersoek wat handel oor die mikro- en makro-skaal materiaalgedrag van SVVB, die praktyke wat bestaan om die materiaaleienskappe en toepassing in strukturele sisteme (spesifiek opgelegde blad stelsels) te definieer, en ‘n uiteensetting van die bestaande ontwerpmodelle wat van toepassing is vir defleksie as gevolg van vervormingsversagting wat SVVB material verhard. Die tweede deel bestaan uit ‘n eksperimentele program waarin die materiaaleienskappe van gespesifiseerde SVVB meng-ontwerpe in die vars toestand en in die verharde toestand gedefinieer word deur middel van vloei- en balktoetse onderskeidelik. Hierdie eienskappe word dan toegepas vir die ontwerp en konstruksie van volskaalse buig- en ponsskuif toetsblaaie ten einde die modelle en teorie wat toegepas is, te bevestig. Die ondersoek toon dat die gebruik van SVVB die duktiliteit van beton sisteme noemenswaardig verbeter in die post-kraak toestand deur kraak oorbrugging. Hierdie duktiliteit kan defleksie verharding van plat blad stelsels veroorsaak waarin die herverdeling van spannings, nadat kraking plaasgevind het, die lasdraende kapasiteit verhoog. Die gedrag van die grootskaalse toetsmonsters word egter noemenswaardig beïnvloed deur die konstruksiemetodes wat geïmplementeer word waarin die materialveranderlikheid toeneem as ‘n gevolg van nie-uniforme vesel verdelings. Die resultate dui daarop dat die modelle wat toegepas is om die laste te voorspel, die potensiaal het om die grens falingslas van SVVB plat blad stelsel voldoende te voorspel, maar neem nie moontlike nie-uniforme veselverdelings wat kan lei tot vroeë faling van die stelsel in ag nie.af
dc.format.extent185 p. : ill.
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.subjectConcrete slabsen_ZA
dc.subjectIn-situ cast flat slabsen_ZA
dc.subjectSteel fibre reinforced concreteen_ZA
dc.subjectFibre reinforced concrete (FRC)en_ZA
dc.subjectDissertations -- Civil engineeringen_ZA
dc.subjectTheses -- Civil engineeringen_ZA
dc.titleConstruction in in-situ cast flat slabs using steel fibre reinforced concreteen_ZA
dc.typeThesisen_ZA
dc.rights.holderStellenbosch Universityen_ZA


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