A Windows based post processor for the design of reinforced concrete space frames is developed. The post processor is capable of designing beams and columns of reinforced concrete space frames in accordance with the ACI specification. The program is developed in C++ using the object oriented programming approach. The objects used in the program represents a one to one analogy with objects in the real world. The computer model of a structure is composed of objects like members, joints, loads, beams and columns. The development of the post processor is discussed and the program architecture is presented. The design results obtained from the post processor are compared with those obtained from several commercial structural design programs to ensure the correctness of the design. It was concluded that the application of object oriented programming techniques results in programs that are easier to develop and maintain and also greatly reduces the effort required for developing applications for graphical user interfaces. / Master of Science

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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.

The results of an experimental investigation are presented which examine the seismic adequacy of pre-1970 reinforced concrete (RC) corner beam-column joints and the efficacy of carbon fiber-reinforced polymer (CFRP) composites for both pre- and post-earthquake retrofit of such joints. Four full-scale corner beam-column-slab subassemblages built with identical dimensions and pre-1970 reinforcement details were subjected to a reverse-cycle bidirectional displacement history consisting of alternate and simultaneous cycles in the two primary frame directions before and/or after retrofit. Two of the specimens were first subjected to severe and moderate levels of damage, respectively, then repaired by epoxy injection, and strengthened by adding a #7 reinforcing bar within the clear cover at the column inside corner and by externally bonding multiple layers of carbon fabric to form a carbon-epoxy retrofit system. Two other specimens, one of which had a significantly lower concrete compressive strength, were strengthened in their as-built condition. The CFRP scheme was improved in light of the findings as the experimental program progressed. Pre-1970 RC corner beam-column joints were found to be severely inadequate in meeting seismic demands because of column bar yielding, joint shear failure, loss of anchorage of beam bottom bars, failure of column lap-splices, and the resulting loss of stiffness and strength that dominate their behavior even at relatively low interstory drift levels. Bidirectional loading played a significant role in such response. It was shown, however, that such joints can be strengthened easily both before and after earthquake damage by using CFRP composite schemes. Regardless of the level of existing damage and concrete strength, a "rigid" joint behavior up to interstory drift ratios of at least 2.4% and joint shear strength factors ranging from 1.06 to 1.41√MPa were achieved; such shear strength factors are larger than the value of 1.00√MPa recommended for use with seismically designed, code-conforming corner beam-column joints. A ductile beam hinging mechanism was achieved and energy dissipation capacity was improved efficiently for joints with concrete strengths ranging from 26 to 34 MPa. The subassemblage with significantly low-strength concrete (15 MPa) had low overall lateral stiffness and reduced reinforcement anchorages which prevented the formation of beam hinging. In cases of such low-strength concrete, more invasive operations may be required so that the improved joint shear strength can be mobilized. It is recommended that bidirectional loading be always considered in both pre- and post-retrofit evaluation of corner joints.

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