Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: This thesis is a study in the use of precast modular construction as an alternative to current methods of school construction in South Africa. Precast Modular Construction is a concept which utilises the principles of prefabrication and precast concrete. Concrete components, be they beams, columns, slabs or full volumetric modules, are manufactured either off-site in factories or in on-site facilities. These components are then assembled on-site to form the structural envelope of a building. This approach contains many inherent advantages: Time is saved due to on-site and off-site work happening concurrently and hence earlier building occupancy results which directly translates to cost reparation; quality is improved due to most of the work being carried out in a controlled factory environment; and health and safety is heightened. However, when viewed from a South African perspective, the fact that less work is done on-site indirectly implicates job loss, a serious issue in the country. Furthermore, implementing a prefabricated approach in the construction of South African schools requires a complete restructuring of the Department of Public Works’ current procurement approach. Prefabrication requires maximum integration between all parties to a project so that design and constructability issues can be addressed at an early stage. The design-build contract strategy is found to be the most integrated approach and allows for optimal collaboration between all project members. However, to only change the procurement route would not suffice as a complete solution. A broader approach is required which addresses issues prevalent in South Africa. These issues include job creation and the establishment of a sustainable and knowledgeable industry. Concepts such as standardisation and strategic partnering, in response, satisfy the need of the manufacturer - for economies of scale, and the employee - for creation of secure working environments. Verification is obtained from all of the aforementioned to propose that the optimal solution to successfully implement Precast Modular Construction for schools in South Africa would be to implement a design-build procurement approach, whereby a single design-build contractor is awarded by the Department of Public Works a contract, via competitive tendering, for the construction of a predetermined number of schools, preferably exceeding 3, over a given contract period using a standardised design and utilising customisable standardised prefabricated precast construction systems, i.e. Precast Modular Construction. This proposal will theoretically result, amongst other things, in the following: - Precast manufacturers will have a confirmed number of orders for products, and can hence be assured of a constant flow of income. This translates directly to an increase in both employment and job security at the manufacturing plant. - The economies of scale principle is satisfied and prefabricated components can therefore be manufactured or ‘mass customised’ in the most feasible way possible. - The design-build contractor will be guaranteed employment for a given period, once again providing job security for its employees, of which the number can also potentially increase. - The design-build contractor carries with it experience and lessons learned from each successfully completed project on to the next, and so becomes more proficient, resulting in better, higher quality schools delivered in shorter periods and with increased efficiency. It is recognised that the proposal is untested in practise but in a socio-economic situation such as South Africa, where large numbers of schools are required quickly, the above proposal makes sense. To additionally develop this hypothesis, further research is required in the fields of design-build procurement and strategic partnering. / AFRIKAANSE OPSOMMING: Hierdie tesis is 'n studie in die gebruik van modulêre voorafvervaardigte beton konstruksie as 'n alternatief vir die huidige metodes van skool konstruksie in Suid-Afrika. Modulêre voorafvervaardigte beton konstruksie bevat baie inherente voordele. Tyd word bespaar as gevolg van werk wat gelyktydig op en van die terrein af gebeur. Dus word die gebou vroeër betrek wat direk lei tot kostebesparings. Kwaliteit verbeter as gevolg van meeste van die werk wat in 'n beheerde fabriek omgewing uitgevoer word en as sulks lei tot beter gesondheid en veiligheid van werkers. Egter, vanuit 'n Suid-Afrikaanse perspektief impliseer die feit dat daar minder werk op die terrein gedoen word indirek werksverlies, 'n ernstige probleem in die land. Die implementering van 'n voorafvervaardigde benadering tot die bou van skole in Suid-Afrika vereis verder 'n volledige herstrukturering van die huidige verskaffing model. Voorafvervaardiging vereis maksimum integrasie tussen alle partye sodat projek ontwerp en boubaarheid op 'n vroeë stadium aangespreek kan word. Die ontwerp-bou kontrak strategie is die mees geïntegreerde benadering en laat toe vir optimale samewerking tussen alle projek lede. Om egter net die verskaffing roete te verander, sou nie voldoen as 'n enkele oplossing nie. 'n Breër benadering word vereis wat kwessies algemeen in Suid-Afrika aanspreek. Hierdie kwessies sluit in werkskepping en die vestiging van 'n volhoubare en kundige industrie. Konsepte soos standaardisering en strategiese vennootskap, as oplossings, voldoen aan die behoeftes van die vervaardiger - vir 'n ekonomieë van skaal, en die werknemer - vir die skepping van 'n versekerde werksomgewing. Die voorafgaande bevestig dat die optimale oplossing vir suksesvolle implementering van Beton Modulêre Konstruksie vir skole in Suid-Afrika sou wees om 'n ontwerp-bou verskaffingsprosedure te volg. Hierdeur kan 'n kontrak aan 'n enkele ontwerp-bou kontrakteur deur die Departement van Openbare Werke toegeken word, deur middel van ‘n mededingende tender proses. Daar word voorgestel dat die projek, vir die konstruksie van 'n voorafbepaalde aantal skole behoort te wees, verkieslik meer as 3, oor 'n bepaalde kontrak tydperk met behulp van 'n gestandaardiseerde ontwerp. Voorts word daar voorgestel om gebruik te maak van aanpasbare gestandaardiseerde voorafvervaardigde beton konstruksie stelsels, dws Beton Modulêre Konstruksie. Hierdie voorstel sal teoreties, onder andere, die volgende gevolge hê: - Beton vervaardigers sal 'n bevestigde aantal bestellings vir produkte hê, en kan dus verseker wees van 'n konstante vloei van inkomste. Dit lei direk tot 'n toename in indiensneming en werksekerheid by die fabriek. - Die ekonomieë van skaal beginsel is bevredig en voorafvervaardigde komponente kan dus vervaardig word in die mees haalbare manier moontlik. - Die ontwerp-bou kontrakteur is gewaarborg van indiensneming vir 'n gegewe tydperk, as sulks ook die verskaffing van werksekerheid vir sy werknemers, waarvan die aantal moontlik ook kan vermeerder. - Die ontwerp-bou kontrakteur neem ondervinding en lesse wat geleer is uit elke suksesvolle voltooide projek saam na die volgende een, en raak dus meer bedrewe, wat lei tot beter, hoër gehalte skole gelewer in korter tydperke en met toenemende doeltreffendheid. Die voorstel is egter ongetoets in die praktyk, maar in 'n sosio-ekonomiese situasie soos die van Suid-Afrika, waar 'n groot aantal skole vinnig benodig word, maak die bogenoemde voorstel sin. Om hierdie hipotese te ontwikkel, is verdere navorsing nodig in die gebied van ontwerp-bou verskaffing en strategiese vennootskappe.

Thesis (MScEng)-- Stellenbosch University, 2013. / ENGLISH ABSTRACT: Concrete is used in most of the modern day infrastructure. It is a building material for which there exist various design codes and guidelines for its use and construction. It is strong in compression, but lacks tensile strength in its fresh and hardened states and, when unreinforced, fails in a brittle manner. The structural use of synthetic fibres in concrete is investigated in this study to determine its effect on enhancing the mechanical properties of concrete. Slabs on grade are used as the application for which the concrete is tested. The material behaviour is investigated in parallel with two floor design theories. These are the Westegaard theory and the Yield-Line theory. The Westegaard theory uses elastic theory to calculate floor thicknesses while the Yield-Line theory includes plastic behaviour. Conceptual designs are performed with the two theories and material parameters are determined from flexural tests conducted on synthetic fibre reinforced concrete (SynFRC) specimens. Large scale slab tests are performed to verify design values from the two theories. Higher loads till first-crack were measured during tests with concrete slabs reinforced with polypropylene fibres than for unreinforced concrete. It is found that the use of synthetic fibres in concrete increases the post-crack ductility of the material. The Westegaard theory is conservative in its design approach by over-estimating design thicknesses. This was concluded as unreinforced slabs reached higher failure loads than predicted by this theory. The Yield-Line theory predicts design thicknesses more accurately while still accounting for the requirements set by the ultimate- and serviceability limit states. By using SynFRC in combination with the Yield-Line theory as design method, thinner floor slabs can be obtained than with the Westegaard theory. / AFRIKAANSE OPSOMMING: Beton word gebruik as boumateriaal in meeste hedendaagse infrastruktuur. Daar bestaan verskeie ontwerp kodes en riglyne vir die gebruik en oprig van beton strukture. Alhoewel beton sterk in kompressie is, het beton ‘n swak treksterkte in beide die vars- en harde fases en faal dit in ‘n bros manier indien onbewapen. Die gebruik van sintetiese vesels in beton word in hierdie projek ondersoek om die invloed daarvan op die eienskappe van die meganiesegedrag van beton te bepaal. Grond geondersteunde vloere word as toepassing gebruik. Parallel met die materiaalgedrag wat ondersoek word, word twee ontwerpsteorieë ook ondersoek. Dit is die teorie van Westegaard en die Swig-Lyn teorie. Die teorie van Westegaard gebruik elastiese teorie in ontwerpsberekeninge terwyl die Swig-Lyn teorie ‘n plastiese analise gebruik. ‘n Konseptuele vloerontwerp is gedoen deur beide die ontwerpsmetodes te gebruik. Materiaalparameters is bepaal deur buig-toetse uit te voer op sintetiesevesel-bewapende beton. Grootskaalse betonblaaie is gegiet en getoets om die akkuraatheid van die twee metodes te verifieer. Die betonblaaie wat bewapen was met polipropileen vesels het groter laste gedra tot by faling as die blaaie wat nie bewapen was nie. Die vesels verbeter die gedrag van beton in die plastiese gebied van materiaalgedrag deurdat laste ondersteun word nadat die beton alreeds gekraak het. Die Westegaard teorie kan as konserwatief beskou word deurdat dit vloerdiktes oorskat. Hierdie stelling is gegrond op eksperimentele data wat bewys dat onbewapende betonblaaie groter laste kan dra as wat voorspel word deur die Westegaard teorie. Die Swig-Lyn teorie voorspel ontwerpsdiktes meer akkuraat terwyl daar steeds aan die vereistes van swigting en diensbaarheid voldoen word. Deur gebruik te maak van sintetiese vesels en die Swig-Lyn teorie kan dunner betonblaaie ontwerp word as met die Westegaard teorie.

Use of fiber reinforced polymer (FRP) material has been a good solution for many problems in many fields. FRP is available in different types (carbon and glass) and shapes (sheets, rods, and laminates). Civil engineers have used this material to overcome the weakness of concrete members that may have been caused by substandard design or due to changes in the load distribution or to correct the weakness of concrete structures over time specially those subjected to hostile weather conditions. The attachment of FRP material to concrete surfaces to promote the function of the concrete members within the frame system is called Externally Bonded Fiber Reinforced Polymer Systems. Another common way to use the FRP is called Near Surface Mounted (NSM) whereby the material is inserted into the concrete members through grooves within the concrete cover. Concrete beam-column joints designed and constructed before 1970s were characterized by weak column-strong beam. Lack of transverse reinforcement within the joint reign, hence lack of ductility in the joints, and weak concrete could be one of the main reasons that many concrete buildings failed during earthquakes around the world. A technique was used in the present work to compensate for the lack of transverse reinforcement in the beam-column joint by using the carbon fiber reinforced polymer (CFRP) sheets as an Externally Bonded Fiber Reinforced Polymer System in order to retrofit the joint region, and to transfer the failure to the concrete beams. Six specimens in one third scale were designed, constructed, and tested. The proposed retrofitting technique proved to be very effective in improving the behavior of non-ductile beam-column joints, and to change the final mode of failure. The comparison between beam-column joints before and after retrofitting is presented in this study as exhibited by load versus deflection, load versus CFRP strain, energy dissipation, and ductility.

Abstract not available

The shear capacity of reinforced concrete pier caps in existing bridge support systems can be a factor which limits the capacity of an existing bridge. In their usual configuration, pier caps behave as deep beams and have the ability to carry load through tied arch action after the formation of diagonal cracks. Externally bonded fiber reinforced polymer (FRP) reinforcement has been shown to increase the shear capacity of reinforced concrete members which carry load through beam action. However, there is an insufficient amount of research to make it a viable strengthening system for beams which carry load through arch action, such as pier caps. Accordingly, this research was aimed at investigating the behavior of reinforced concrete pier caps through a coordinated experimental and analytical program and to recommend an external strengthening method for pier caps with perceived deficiencies in shear strength. The experimental study was performed on laboratory specimens based on an existing bridge in Georgia. A number of factors were examined, including size, percentage longitudinal reinforcement and crack control reinforcement. The results showed that increasing the longitudinal tension reinforcement increased the beam capacity by changing the shape of the tied arch. In contrast, the presence of crack control reinforcement did not change the point at which diagonal cracking occurred, but it did increase the ultimate capacity by reinforcing the concrete against splitting. The results of the experimental study were used in conjunction with a larger database to examine different analytical methods for estimating the ultimate capacity of deep beams, and a new method was developed for the design of external strengthening. Two specimens were tested with externally bonded FRP reinforcement applied longitudinally to increase the strength of the tension tie. The test results correlated well with the proposed method of analysis and showed that increasing the strength of the longitudinal tension tie is an effective way to increase the strength of a reinforced concrete deep beam.

Procurando conhecer o grau de deterioração precoce das estruturas de concreto armado dos edifícios residenciais da Região Metropolitana da Cidade do Recife, Estado de Pernambuco, este trabalho visa, utilizando um método de quantificação dos danos e o uso de ensaios, avaliar as patologias das estruturas estudadas. Estudou-se três edifícios residenciais (ER), com semelhante padrão de construção, idades construtivas aproximadas e inseridos em diferentes classes de agressividade ambiental. Foi realizada inspeção visual e ensaios em amostras dos pilares, vigas, lajes e reservatório inferior do subsolo dos três edifícios. Após análise dos três edifícios, verificou-se que o caso ER 1, localizado em classe ambiental de agressividade forte (III), a mais agredida pelo meio ambiente, e o estudo de caso ER 2, localizado a uma distância significativa da orla marinha em Classe de Agressividade Ambiental II, apresentaram grau de deterioração media (GD) de 36,98 e 31,23 respectivamente, com recomendação para inspeção periódica e intervenção a médio prazo. Já o estudo de caso ER 3, que está localizado dentro da uma classe de agressividade forte (III), em orla marinha, porém com barreiras de proteção que evitam a incidência direta da névoa salina, encontra-se com alto grau de deterioração (GD = 103,94), sugerindo uma intervenção imediata com riscos de colapso / This work aims to evaluate the pathology of residential buildings structures located at the Metropolitan Region of Recife, Brazil using the quantification of damages to measure the degree of early deterioration of reinforced concrete. Three residential buildings (RB) with similar construction standards were studied. All buildings have approximate age and are inserted into environmental aggressiveness distinct. A visual inspection took place as well as a laboratorial sample analysis of their pillars, beams and underground water reservatories. It was verified that the RB1 case, located at a high environmental aggressiveness class (III), and the RB2 case, located significatively far from the sea and classified with a moderate environmental aggressiveness class (II), both presented a medium degree of deterioration (GDE). For both buildings it is suggested a periodic inspection recommendation and a medium term intervention (GD 1 = 36,98 ; GD 2 = 31,23). The third case (RB3), located at a high environmental aggressiveness class (III) and seafront with protection barriers, presented a high degree of deterioration (GD 3=103,94). It is suggested for RB3 an immediate intervention with collapse risks

Em Março de 2004 entrou em vigor a nova versão da norma brasileira para projeto de estruturas de concreto, a NBR 6118(2003), substituindo sua antecessora que estava em vigor desde 1978. Dentre os novos conceitos apresentados, os de maior impacto no meio técnico estão relacionados à questão da durabilidade das estruturas de concreto. Assim o presente trabalho pretende avaliar a magnitude destas alterações, com ênfase à análise de custos, que ocorrem devido à aplicação dos novos conceitos normativos no Projeto estrutural de três edifícios de concreto armado de alturas variadas. Desta forma, será avaliado o impacto econômico sobre o Projeto dos edifícios, para valores de cobrimentos de concreto relativos as classes de agressividade ambiental CAA=II e CAA=III, a influência nos custos das estruturas, do valor da resistência à compressão do concreto fck, as vantagens da utilização dos modelos I e II para o cálculo das armaduras de cisalhamento de vigas. Também serão abordados o Projeto dos pilares com os novos critérios do momento mínimo de 1 ordem e imperfeições geométricas locais, a ordem de grandeza dos esforços devidos ao desaprumo frente aos esforços devidos ao vento, e finalmente o impacto no custo global das estruturas dos edifícios, quando dimensionados segundo os critérios presentes na NBR-6118(1978) e NBR-6118(2003). Os resultados mostraram que, apesar do maior volume de concreto nos projetos de acordo com a NBR 6118(2003), a quantidade de aço foi reduzida, principalmente nos pilares,em relação a NBR 6118(1978). A diferença entre os custos finais das estruturas foi a favor da NBR 6118(2003) / In March of 2004 the new version of the Brazilian Code for design of concrete structures, the NBR 6118(2003), has replaced its predecessor the NBR 6118(1978). Amongst the new presented concepts, the greatest impact is related to the question of the durability of the concrete structures. The present work evaluates the influence of the new normative criteria, with emphasis to the analysis of costs, in the structural design of three buildings of reinforced concrete of varied heights. The influence in the costs of the structures is analyzed, when designed in the different exposure classes related environmental conditions II and III, of the value adopted for the compressive resistance fck, of the use of models I and II for the calculation of the reinforcement of shear of beams, of the influence of the design of them columns with the new criteria of the minimum moment of first local order and geometric imperfections. Finally, it has been compared the global costs of the structures of the three buildings when designed according to criteria of NBR-6118(1978) and NBR- 6118(2003). The results had mainly shown that, despite the increase in concrete volume in accordance with the NBR 6118 (2003), the amount of steel was reduced, in them columns, in relation the NBR 6118(1978). The difference in final costs of the structures was favorable to the NBR 6118(1978), but it can be considered relatively low, in comparison with the increasing quality and durability proportioned by the adoption the NBR 6118(2003)

Apresenta-se neste trabalho a análise numérica de um edifício de 32 pavimentos, em concreto armado, situado na cidade do Recife. Primeiramente foi realizada a modelagem pelo método dos elementos finitos apenas para a estrutura em concreto. Em seguida realizou-se a modelagem considerando o efeito dos painéis de alvenaria de vedação no comportamento estrutural do edifício, através do modelo de barras diagonais equivalentes. E, depois, a modelagem mais refinada de alguns desses painéis, submetidos ao carregamento proveniente dos pórticos. Os resultados obtidos nos processamentos dos modelos com barras equivalentes e sem elas foram comparados entre si, a fim de se analisarem as reações de apoio e deslocamentos no topo do edifício para os dois modelos. Constatou-se um aumento na rigidez do edifício, bem como a redistribuição dos esforços. Foram analisados também os esforços nos painéis de alvenaria a fim de se verificar em que pavimentos e em que geometria de pórticos as alvenarias estavam sujeitas a maiores tensões / The work presents results from numerical analyses performed in a 32-storey reinforced concrete building in Recife. Numerical finite element analyses were performed taking into account the modeling of reinforced concrete members only as well as the masonry infill panels, considered as equivalent diagonal struts. It was also analyzed a more refined model consisting of isolated infill masonry panels subjected to frame loading from 3-D finite element analyses. Support reaction, stress resultants and displacements on the top of the buildings, obtained from performed analyses, were compared. An increase in building stiffness was observed as well as stress resultant redistribution. Infill masonry panel stresses were also investigated in order to find out the places where it is most stressed

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Nos últimos anos, a indústria da construção civil experimentou um forte crescimento na demanda por edifícios de múltiplos pavimentos de concreto armado. Este comportamento do mercado impulsionou construtores a acelerar todas as etapas do processo de construção, a fim de entregar a edificação em um tempo cada vez mais curto. Como decorrência deste fato, as estruturas são carregadas mais precocemente, ocasião em que as suas propriedades de resistência e deformação ainda não se encontram suficientemente maduras para suportar o carregamento construtivo que a solicita. Com a finalidade de compreender quais consequências são provocadas por esse carregamento prematuro da estrutura e analisar a importância dos efeitos construtivos no projeto de edificações de concreto armado, o trabalho traz o resultado de análises não-lineares realizadas com o Método dos Elementos Finitos adotando uma abordagem usualmente referida como staged construction construção em estágios aplicada a uma edificação real, situada na Cidade do Recife, Estado de Pernambuco, Brasil. Nestas análises foram levados em consideração os efeitos da retração, fluência e envelhecimento do concreto. Os resultados obtidos demonstram que os deslocamentos verticais nos pilares, decorrentes dos efeitos construtivos, são fortemente alterados quando comparados com os deslocamentos verticais resultantes da análise sem a consideração dos estágios de construção. A não consideração desses efeitos construtivos podem, em alguns casos, conduzir a manifestações patológicas importantes na edificação. / The building industry has experienced in recent years a strong growth in demand in general and in the case of reinforced concrete buildings this increase has been more marked. This fact has also contributed to accelerate all stages of the production process of these constructions with more pronounced effects on the methodologies used in the constructive steps that influence directly the structural design of the building. Structures loaded at ever earlier ages, in which the strength and deformation properties of materials are not yet sufficiently mature, it is a variable that needs to be taken into account already in the design phase so that the concrete structure behaves within acceptable level of reliability taking into account design code recommendations for service life. To understand the importance of constructive effects and to assess its magnitude in the execution of reinforced concrete buildings, this paper present result from nonlinear analyses using Finite Element Method adopting an approach commonly referred as staged construction applied to a typical building found in the practice. The effects of creep and shrinkage were considered and the results obtained demonstrate that the strains due to constructive effects can, in certain cases, assume representative values which, if ignored, can lead to important pathologies in the building.

Made available in DSpace on 2017-06-01T17:57:20Z (GMT). No. of bitstreams: 1 Elilde Medeiros.pdf: 1143833 bytes, checksum: 753821a53256142f318470c59cb69f82 (MD5) Previous issue date: 2007-08-17 / The work presents results from numerical analyses performed in a 32-storey reinforced concrete building in Recife. Numerical finite element analyses were performed taking into account the modeling of reinforced concrete members only as well as the masonry infill panels, considered as equivalent diagonal struts. It was also analyzed a more refined model consisting of isolated infill masonry panels subjected to frame loading from 3-D finite element analyses. Support reaction, stress resultants and displacements on the top of the buildings, obtained from performed analyses, were compared. An increase in building stiffness was observed as well as stress resultant redistribution. Infill masonry panel stresses were also investigated in order to find out the places where it is most stressed / Apresenta-se neste trabalho a análise numérica de um edifício de 32 pavimentos, em concreto armado, situado na cidade do Recife. Primeiramente foi realizada a modelagem pelo método dos elementos finitos apenas para a estrutura em concreto. Em seguida realizou-se a modelagem considerando o efeito dos painéis de alvenaria de vedação no comportamento estrutural do edifício, através do modelo de barras diagonais equivalentes. E, depois, a modelagem mais refinada de alguns desses painéis, submetidos ao carregamento proveniente dos pórticos. Os resultados obtidos nos processamentos dos modelos com barras equivalentes e sem elas foram comparados entre si, a fim de se analisarem as reações de apoio e deslocamentos no topo do edifício para os dois modelos. Constatou-se um aumento na rigidez do edifício, bem como a redistribuição dos esforços. Foram analisados também os esforços nos painéis de alvenaria a fim de se verificar em que pavimentos e em que geometria de pórticos as alvenarias estavam sujeitas a maiores tensões