The development of precast concrete housing systems provides an opportunity to easily and inexpensively incorporate solar energy collection by casting collector tubes into the roof structure. A design is presented for a precast solar water heating system used to aid in meeting the space and domestic water heating loads of a single family residence. A three-dimensional transient collector model is developed to characterize the precast solar collector's performance throughout the day. The model describes the collector as a series of segments in the axial direction connected by a fluid flowing through an embedded tube. Each segment is represented by a two-dimensional solid model with top boundary conditions determined using a traditional flat plate solar collector model for convection and radiation from the collector cover plate. The precast collector is coupled to a series solar assisted heat pump system and used to meet the heating needs of the residence. The performance of the proposed system is compared to the performance of a typical air to air heat pump. The combined collector and heat pump model is solved using Matlab in conjunction with the finite element solver, Femlab. Using the system model, various non-dimensional design and operating parameters were analyzed to determine a set of near optimal design and operating values. The annual performance of the near optimal system was evaluated to determine the energy and cost savings for applications in Atlanta, GA and Chicago, IL. In addition, a life cycle cost study of the system was completed to determine the economic feasibility of the proposed system. The results of the annual study show that capturing solar energy using the precast collector and applying the energy through a solar assisted heat pump can reduce the electricity required for heating by more than 50% in regions with long heating seasons. The life cycle cost analysis shows that the energy savings justifies the increase in initial cost in locations with long heating seasons but that the system is not economically attractive in locations with shorter heating seasons. / Master of Science

Lap splices are used in reinforced concrete structures to transfer tension forces across discontinuous reinforcing bars to allow for continuity of load path in structural elements. Lap splices of straight reinforcing bars present a number of disadvantages when used in connections of large precast concrete elements typical of bridge substructure. Most importantly, lap splices of large (e.g., No. 11) straight bars are substantially long. Since the closure joint connecting two precast elements must be at least long enough to fit the lap splice, traditional lap splices result in impractically large closure joints, offsetting the benefits of using precast concrete elements. To address this problem, bridge designers are using hooked bars in noncontact lap splices to connect precast elements, presuming that hooked bars will allow for shorter required splice lengths. However, there exists neither substantial design guidance nor studies of the behavior of hooked bar lap splices in large precast elements justifying this design philosophy. To develop design guidance permitting the use of noncontact hooked bar lap splices and address the knowledge gap regarding the behavior of such splices, an extensive experimental and computational research program was conducted which is described in this dissertation. Fifty-eight large-scale beam-splice specimens containing hooked bar lap splices were tested to physically study the behavior of hooked bar lap splices and develop a dataset to justify design guidance permitting the use of such splices in practice. Bond variables were parametrically varied among the test specimens to produce guidance applicable over the wide range of geometric configurations and material properties expected in bridge design. The specimens were subjected to monotonic, four-point loading and were designed to fail in a mode related to anchorage to study splice behavior. Nonlinear finite element analyses were conducted to examine the mechanism of force transfer in hooked bar lap splices and numerically assess splice configurations not experimentally studied. A simple approach to modelling hooked reinforcing bars in solid concrete elements which accounts for conditions of imperfect bond was developed and validated using the experimental results. Test results from the 58 specimens were used to assess the appropriateness of using existing guidance for hooked bar anchorages to design hooked bar lap splices. Because the existing guidance was found to be deficient for this application, descriptive and design equations characterizing hooked bar lap splices were developed using power regression analyses. The results demonstrated that all else being equal, a bottom-cast hooked bar lap splice can develop approximately 40% greater stress than contact lap splices of straight bars. Accordingly, hooked bars can be used to splice bars over a substantially shorter length than straight bars. Noncontact hooked bar lap splices without secondary reinforcement (e.g., ties) can fail due to a mode termed "hook side bulging", resulting from eccentricity between the lapped bars. Splices with secondary reinforcement typically fail due to more typical modes observed in the literature, such as side-face blowout and concrete crushing. Unlike as suggested by code authorities and some researchers for noncontact lap splices of straight bars, noncontact hooked bar lap splices were found to exhibit weaker splice strengths than contact splices as the splice spacing increased. The use of steel fibers and increases in lap length, concrete compressive strength, cover depth, amount of secondary reinforcement, or the number of lap splices allowed for greater stress on average to be developed in spliced bars. All else being equal, an increase in either bar size or the number of spliced reinforcement layers decreased the stress that could be developed in the spliced bars. A descriptive equation characterizing splice strength with an average test-to-calculation ratio and coefficient of variation of 6% was developed. The descriptive equation was adapted to develop a design equation for the minimum required lap length of hooked bars which uniformly characterizes the influence of the bond variables over the ranges explored in this study. Design examples and code language facilitating technology transfer of the design equation into immediate practice were developed. / Doctor of Philosophy / Precast concrete is widely used in highway bridges to enable more rapid and economical construction than could be achieved using cast-in-place concrete. However, the connection of two or more precast, prefabricated bridge elements introduces several difficulties which may inhibit construction, thereby reducing overall economy. One of the most significant difficulties is that connections of substructure elements supporting the superstructures are impractically long using a common, code-approved detail―lap splices of straight reinforcing bars. Such splices are quite long (e.g., 5 ft in length) since large bars are typically used in substructure elements, requiring long splice lengths to transfer the large forces in each bar across the connection. Details which would shorten the required splice length would consequently reduce the required connection length, thereby reducing the amount of cast-in-place concrete construction required in the field. Consequently, the speed of construction, economy, and worker safety would increase. This dissertation thus summarizes an extensive experimental and numerical study aimed at validating the use of noncontact hooked bar lap splices to shorten the required splice length of large precast elements. In support of this objective, the anchorage behavior of noncontact hooked bar lap splices was studied through static load testing of 58 large-scale beam-splice specimens and nonlinear finite element models accounting for bond-slip behavior. These efforts revealed that hooked bar lap splices can develop on average approximately 40% more stress over the same lap length than contact splices of straight bars. Existing design provisions which might presently be used to design hooked bar lap splices were evaluated against the experimental results and were found to be deficient in characterizing splice strength. Thus, a design equation was developed for the splice length of hooked bars which accurately characterizes anchorage behavior and allows for significantly shorter splices lengths than what could be achieved with straight bars.

Thesis (MScEng (Civil Engineering))--Stellenbosch University, 2008. / Introduction South Africa is currently experiencing a significant increase in infrastructure investment. Forecasts by BMI-BRSCU have shown that the building and construction industry is expected to grow considerably to 2010, before languishing slightly to 2015. This growth will be driven in particular by investment in non-residential building (41% growth) and construction (73% growth) activities. Even beyond 2015 however, the demand will still be high on the construction industry to provide infrastructure for South Africa’s growing population. South Africa is also facing a serious shortage of engineers, technicians and other skilled workers in the construction industry. This places high demands on designers and contractors to provide services and to realise projects in ever-reducing time periods and at less cost. These conditions have made it increasingly difficult to maintain the required quality of construction in an industry where mistakes can lead to disastrous consequences. Recent advances in structural materials, structural systems and the way in which projects are handled, now enables a new look at the possibilities of combining pre-fabrication with on site work. This method, known as Hybrid Concrete Construction (HCC), has the potential to revolutionize the South African construction industry if applied correctly. Local research into this technique is however required and it is the aim of this thesis to draw attention to this subject. Key Findings Hybrid Concrete Construction (HCC) can be applied to any structural project, it will however not necessarily be successful. A structure needs to be adapted from the very start to suit a particular construction method. This ensures that all the advantages of the selected construction method may be achieved. Adapting a structure to a different construction method requires a mutual understanding and commitment from all project participants, including the architect, engineer, contractor and client. HCC also requires a certain degree of repetition in a project to be financially viable. A theoretical cost exercise was performed where only the material and erection costs were considered. In this exercise, HCC was found to be slightly less expensive than other construction methods for the Office Building of more than 10 storeys. HCC was also found to be significantly faster than other construction methods for the Office Building of more than 3 storeys. The time calculation was however based on the simplified time estimates from one source. Because of HCC’s shorter estimated construction period, the client can expect to earn revenue from a much earlier date. This decreases the relative cost of a HCC project. This advantage, however, needs to be quantified for chosen South African projects. On-site safety is still an important issue with HCC projects. Labourers are not accustomed to this construction method and it may be necessary to alter current skill development programs to include a crane safety course. The training of qualified riggers and crane operators should receive priority if HCC is to develop in South Africa. This preliminary investigation has shown that Hybrid Concrete Construction (HCC) can be feasible for the South African market. Further investigation is however required to determine the parameters for which HCC would be the preferred construction method. Recommendations Based on the findings and conclusions of this investigation, the following recommendations are made. The following actions should be undertaken by individual South African companies: · Develop relationships with external project partners · Train competent riggers and crane operators The South African concrete industry should invest in the following actions: · Invest in mass-producing precast concrete facilities · Develop a central database of South African projects with information on time, costs, project concepts and layouts to be used as a guideline for decision making · Develop local guidelines for the production and application of self compacting concrete · Compile guidelines for the design and construction of HCC and precast concrete construction in South Africa · Develop a local hidden corbel type connection to its full potential

Adoption of a streamlined BIM workflow throughout the AEC projects’ lifecycle will provide the project stakeholders with the rich information embedded in the parametric design models. Users can incorporate this rich information in various activities, improving efficiency and productivity of project activities and potentially enhancing accuracy and reducing errors and reworks. Two main challenges for such a streamlined information flow throughout the AEC projects that haven’t been sufficiently addressed by previous research efforts include lack of semantic interoperability and a large gap and misalignment of information between available BIM information provided by design activities and the required information for performing preconstruction and construction activities. This research effort proposes a framework for a knowledge-based system (KBS) that encapsulates domain experts’ knowledge and represents it through modularized rule set libraries as well as connected design automation and optimization solutions. The research attempts to provide a methodology for automatic semantic enrichment of design models as well as automated detailed design to fill the information gap between design and preconstruction project activities, streamlining BIM workflow and enhancing its value in the AEC projects.

O método construtivo com painéis portantes de concreto é economicamente viável, porém relativamente novo no cenário nacional, sobretudo no caso dos pré-moldados. As incertezas referentes às peculiaridades desse método, bem como a nova norma brasileira de painéis pré-moldados, ainda em elaboração, vem a motivar uma análise probabilística dos critérios de projeto disponíveis. Utilizando-se a técnica da confiabilidade estrutural, é possível propagar as incertezas referentes às variáveis a uma resposta final no índice de confiabilidade, sendo um cálculo totalmente probabilístico. Neste trabalho, emprega-se tal técnica com informações estatísticas referentes a lajes de concreto moldadas in loco para verificar, de maneira mais verossímil, a segurança dos critérios de projeto impostos pelo Precast Concrete Institute Design Handbook - Precast and Prestressed Concrete - 7th Edition (2010) às fases transitórias (desforma, transporte e içamento) e pela Norma Brasileira ABNT NBR 6118: 2014 - Projeto de estruturas de concreto, à fase em uso. Prossegue-se a uma análise crítica dos resultados bem como sugestões para diminuir a variação dos resultados, sobretudo pela calibração de novos coeficientes parciais de segurança, processo para o qual este trabalho pode servir de base. / The shear wall building method is economicaly viable, but relatively new in the brazillian scene, that is specially true for precast members. The uncertainty pertaining this method, and the new brazillian design code for precast shear walls, still in development, serve as motivation for a probabilistic analysis of available project criteria. Using the structural reliability technique, it is possible to forward the variables uncertainties to a final answer in the form of the reliability index, being that this method is entirely probabilistic. In this study, this technique is used with statistical data pertaining cast-in-place concrete slabs to ascertain, with a higher degree of verisimilitude, the safety of the design criteria imposed by the Precast Concrete Institute Handbook - Precast and Prestressed Concrete - 7th Edition (2010) to the temporary states (stripping, transit and lifting) and by the Brazillian Code ABNT NBR 6118: 2014 - Concrete structures design, to the working state. The study then proceeds to a critical analysis of the results and to suggestions to reduce their variability, specially through calibration of new partial safety factors, a procedure to which this study might serve as a basis.

Os danos ambientais causados pela construção civil são fonte de preocupação nesta área da engenharia, e reduzi-lo é interesse comum a todos. Pensar em sustentabilidade já na fase de projeto é um modo viável de se reduzir este impacto. A escolha pelo concreto pré-moldado oferece alguns benefícios iniciais quando se compara este ao concreto moldado no local e, dentre estes, estão a racionalização do canteiro de obras, a redução do desperdício e uma melhoria na produtividade. Uma qualidade adicional, que ainda não está tão clara, é a redução do impacto ambiental que se pode ter com o emprego do concreto pré-moldado. A proposta deste trabalho envolve a análise de fatores que influenciam a sustentabilidade ambiental de estruturas de concreto pré-moldado e a aplicação de um algoritmo de otimização para determinação dos valores ótimos que conduzem ao mínimo impacto ambiental. Para isso, optou-se por minimizar as emissões de CO2, associadas à forma estrutural adotada, à produção, ao transporte e à montagem dos elementos pré-moldados. Estudos de otimização no projeto de estruturas têm usualmente sido utilizados a fim de reduzir custos e, entre as técnicas de otimização utilizadas em engenharia estrutural, os algoritmos genéticos têm sido reconhecidos como uma forte tendência por serem fáceis de implementar e fornecerem excelentes resultados. Com o código de otimização de emissão de CO2 foram processados diversos exemplos, variando os dados de entrada um a um e, avaliando a influência da variação destes na emissão de CO2. Considerando um edifício de 30 m x 30 m, uma adição de pavimento representa um acréscimo aproximado de 35% de emissão de CO2. Para o mesmo prédio, um aumento de 10 m em uma das direções significa aumentar em 30% a emissão de CO2. Variaram-se também as larguras e alturas máximas das vigas, tamanho de vão mínimo entra pilares, distância da fábrica à obra, cargas atuantes, número de indivíduos da população, número de indivíduos para elitismo, numero máximo de gerações, taxa de cruzamento e taxa de mutação. Ao variar estes parâmetros as porcentagens de variação de emissão de CO2 chegam a valores próximos de 5%. Foi encontrado também um valor de emissão por m³ aproximado de 430 kg/m³. Além disso, a saída de dados do código de otimização de emissão de CO2 foi comparada com a do código de otimização de custo, e foi constatado que as configurações estruturais apresentadas para um mesmo edifício processado com os dois códigos são semelhantes entre si e semelhantes à solução estrutural utilizada para esta edificação. Também foi constatado que pode se relacionar emissão de CO2 com custo. Deste modo, foi proposto um fator que relaciona as duas grandezas, chamado Fator Emissão-Custo, ou Fec. Observou-se que o Fec varia com o acréscimo de pavimentos, mostrando que o custo e a emissão de CO2 são afetados de forma diversa pelo número de pavimentos. Para um edifício de 4 pavimentos o Fec médio encontrado foi de 1,53 kgCO2/R$. Os resultados encontrados permitiram atestar a validade do método dos algoritmos genéticos à engenharia de estruturas, bem como a importância que o concreto pré-moldado tem para a industrialização da construção civil. / The environmental impact caused by civil constructions is a source of concern in this area of engineering, and reducing it is a common interest to all. Thinking about sustainability already in the design phase is a feasible way to reduce this impact. The choice for precast concrete offers some initial benefits when compared to the cast- on-site concrete and, among these, are streamlining the construction site, reducing waste and improving productivity. An additional quality, which is not yet so clear, is to reduce the environmental impact that one can have when using precast concrete. The purpose of this work is to develop a method of optimization of the elements of precast concrete structures in relation to the sustainability of the product. To do so, it is proposed to minimize the CO2 emission associated to the structural solution, production, transportation and assembly of precast concrete. Studies on optimization design of structures have been commonly used to reduce costs and, among the optimization techniques in structural engineering, genetic algorithms have been recognized as a strong trend for being easy to implement and providing excellent results. With the CO2 emission code were processed several examples, varying the input data one by one, then was assessed the influence of each variation on CO2 emission. Considering one building with the size 30 m x 30 m, each floor added represents an approximated increase about 35% on CO2 emission. For the same building one increase of 10 m on each direction means add 30% on CO2 emission. Was varied on the code the maximum heights and widths of the beam, the minimum span between pillars, distance from the building to the factory, loads acting, maximum population individuals number, number of individuals to elitism, maximum generation number, outcrossing rate and mutation rate. Varying these parameters, the variations percentage of CO2 emission reaches values next to 5%. Was found too an approximated value to CO2 emission per m³ as about 430 Kg/m³. Furthermore, the CO2 emission optimization code data output was compared with the cost optimization code data output, and it was verified that the structural configuration presented on outputs was similar between them both and similar with the real structural solution used on this building. It was verified too that the CO2 emission and cost could be related. On this way was proposed a factor which relates the two quantities called Emission-Cost Factor, or Fec. It was noticed that Fec varies when floors are added, which means that the cost does not vary at the same way that the CO2 emission does when the number of floors are changed. For a building with 4 floors the medium value of Fec was found 1,53 kgCO2/R$. The results permitted attest the validity of using genetic algorithms in structural engineering, as well as highlighting the precast concrete contribution on the industrialization of civil construction.

Os galpões de concreto pré-moldado, formados por pórticos atirantados, são muito utilizados, no Brasil. Porém, para o projeto dessas estruturas, a bibliografia é limitada. Além disso, vários critérios de projeto são adaptados dos relativos a estruturas de concreto moldado no local e de múltiplos pavimentos. O objetivo deste trabalho é contribuir para a análise desse tipo de estrutura, introduzindo conceitos que dificilmente são considerados na prática, tais como: rigidez da ligação viga-pilar, análise não-linear física e geométrica, deformação excessiva e fluência. A pesquisa foi desenvolvida por meio de análises estruturais, usando modelos de galpões comuns na prática. Cada conceito citado anteriormente foi analisado em exemplos. A rigidez da ligação viga-pilar foi avaliada com base no parâmetro de restrição à rotação, \'alfa\'R. A não-linearidade física (NLF) do concreto foi considerada pelo método de Branson. Para a não-linearidade geométrica (NLG), foram utilizados os parâmetros \'alfa\' e o processo P.\'delta\'. A deformação excessiva, incluindo a fluência, foi discutida tendo em conta os aspectos normativos. Constatou-se que a ligação viga-pilar pode ter comportamento semi-rígido em alguns casos, mas, se corretamente dimensionada, apresenta, de fato, comportamento rígido. A consideração da NLF apresentou resultados melhores que a análise elástica linear, sendo possível, para o exemplo estudado, utilizar um coeficiente redutor de inércia igual a 0,5, para as vigas e para os pilares do pórtico. Concluiu-se, também, que a consideração da NLG deve ser feita sistematicamente para esse tipo de estrutura, uma vez que alguns exemplos apresentaram acréscimos de momentos superiores a 10% e \'alfa\' > \'alfa\' lim. Além disso, observou-se que a verificação do estado limite de deformação excessiva (ELS-DEF) pode ser determinante na escolha das seções transversais do pórtico, sendo obrigatória a consideração da fluência. Nesse sentido, o presente trabalho contribui para a literatura técnica sobre a análise estrutural dos galpões atirantados, auxiliando projetistas no cálculo dessas estruturas e servindo de referência nos cursos sobre esse assunto. / Sheds of precast concrete formed by tied portal frames are widely used in Brazil. However, there are few works on the design of these structures. In addition, several design criteria are adapted from those relative to the structures of cast in place concrete and multi-storey buildings. The objective of this work is to contribute to the analysis of this type of structure, introducing concepts that are hardly seen in practice, such as: rigidity of beam-column connection, physics and geometric nonlinear analysis, excessive deformation, and creep. The research was developed by mean of structural analysis, using models of sheds common in practice. Each concept previously mentioned was analyzed in examples. The stiffness of the beam-column connection was evaluated with base on the restriction parameter of the rotation, \'alfa\'R. The physics non-linearity (PNL) of concrete was considered by the method of Branson. For the geometric non-linearity (GNL) the parameter \'alfa\' and the process P.\'delta\' were used. The excessive deformation including creep was discussed taking in account the aspects of brazilian codes. It was found that the beam-column connection may have semi-rigid behavior in some cases, but, if properly designed, it has in fact rigid behavior. The consideration of the PNL had better results than the linear elastic analysis, and, for the sample studied, was possible to use a reduction coefficient of inertia equal to 0.5 for the beams and columns of the portal frame. It was also concluded that the consideration of GNL should be done systematically for this type of structure, since as some examples showed increase of moments above 10% and \'alfa\' > \'alfa\' lim. Furthermore, it was observed that the verification of deflection serviceability can be decisive in the choice of the portal frame cross sections, being obligatory the consideration of creep. In this sense, the present work contributes to the technical literature on the structural analysis of the tied portal frame sheds, helping engineers in the design of these structures and serving as reference in courses about this subject.

Esta pesquisa visa analisar a transferência de tensões de compressão entre elementos de concreto pré-moldado através de almofadas de argamassa modificada. A argamassa foi modificada com as adições de fibras de polipropileno, látex estireno-butadieno e vermiculita termo-expandida. A caracterização da argamassa foi realizada com ensaios de compressão, de tração por compressão diametral e de módulo de elasticidade, além de ensaios de rigidez de almofada, que medem a capacidade da peça de se deformar sob tensão de compressão uniforme. As análises de transferência de tensões foram realizadas intercalando uma almofada entre dois blocos de concreto e submetendo o corpo de prova formado a ensaios de compressão. Os parâmetros variados nesses ensaios foram: rugosidade superficial e resistência mecânica dos blocos ligados, excentricidade de carregamento, solidarização ou não da almofada ao bloco inferior de concreto e carregamento monotônico e cíclico. Em relação à massa do cimento, a argamassa das almofadas possuía 30% de agregados, dos quais 95% eram areia fina e 5% eram vermiculita, 10% de látex, 2% de taxa volumétrica de fibras de polipropileno e relação água / cimento de 0,25, além da água incorporada no látex. A argamassa apresentou resistência à compressão média de 27,65 MPa, resistência à tração de 3,62 MPa e módulo de elasticidade igual a 11,53 GPa. Os principais resultados dos ensaios de ligação foram: a) para compressão centrada, a presença da almofada aumentou a resistência em 20% para espessuras de saliências de 0,5 mm e 30% para saliências de 1,0 mm; b) ganho de efetividade da almofada à medida que se reduziu a resistência do concreto; c) em ligações excêntricas, a dispersão dos resultados não permitiu uma correta avaliação dos resultados; d) para carregamento cíclico, a almofada de apoio aumentou em 45% a resistência da ligação. / This research aims to analyze the compressive stresses transfer between precast concrete elements by modified mortar pads. The mortar was modified with additions of polypropylene fibers, styrene-butadiene latex and heat-expanded vermiculite. Mortar characterization was performed in compression, tension and elastic modulus tests, further pad rigidity tests, that measure the pad capacity to deform under uniform compressive stress. Stress transfer analyzes were performed interleaving a bearing pad between two concrete blocks and subjecting the specimen formed in the compression tests. Varied parameters in these tests were: surface roughness and mechanical strength of the connected blocks, loading eccentricity, solidarization or not of the bearing pad to the bottom concrete block and monotonic and cyclic loading. In relation to the cement weight, the mortar of the pads showed 30% of aggregates, which 95% were fine sand and 5% were vermiculite, 10% of latex, 2% of volumetric rate of polypropylene fibers and water / cement ratio of 0,25, in addition of water incorporated into the latex. The mortar showed compression strength of 27,65 MPa, tension strength of 3,62 MPa and elastic modulus equal to 11,53 GPa. The main results of connection test were: a) for centered compression, presence of pad increased the strength in 20% for thicknesses of imperfections of 0,5 mm and 30% for imperfections of 1,0 mm; b) gain of effectiveness of the bearing pad when the concrete strength was reduced; c) in eccentrical connections, the dispersion of results did not allowed a correct evaluation of results; d) for cyclic loading, the bearing pad increased in 45% the connections strength.

A maioria dos edifícios de concreto pré-moldado, construídos no Brasil e no exterior, é constituída por lajes alveolares. Este trabalho considera o estudo da continuidade dessas lajes. No cálculo desses elementos, a prática comum é considerá-los como simplesmente apoiados. Para melhorar o desempenho, é possível promover a continuidade nos apoios intermediários. Isso pode ser feito colocando armadura na região tracionada da ligação, no interior da capa, ou através de barras concretadas dentro dos alvéolos. O objetivo deste trabalho é investigar o comportamento de pavimentos formados por lajes alveolares com continuidade, com armadura na capa. Para isso, foi realizado um estudo envolvendo análise teórica e experimental em três modelos. Esses modelos, em escala real, foram submetidos a um carregamento transversal, distribuído de forma linear. Os estudos teóricos consideraram uma simulação numérica com elementos de viga e a fórmula de Branson para descrever o comportamento não linear físico do material. Além disso, foram avaliadas as expressões dos principais códigos nacionais e internacionais, no que diz respeito à ruptura por cisalhamento da seção transversal e da interface laje-capa. Os resultados da análise experimental indicaram que o modelo 1 rompeu por cisalhamento da seção transversal, com o mecanismo de tração diagonal do concreto. O modelo 2 apresentou ruptura por cisalhamento da interface. No modelo 3, a ruptura foi por flexão. O comportamento dos modelos ensaiados foi governado pela fissuração da capa na região de momento negativo. A análise teórica com elementos de barra representou de forma satisfatória o comportamento dos modelos ensaiados. As únicas formulações que apresentaram resultados coerentes com os três ensaios foram: EUROCODE 2:2004, para o cálculo da resistência ao cisalhamento da interface, e FIB MODEL CODE 2010, para o cálculo da resistência ao cisalhamento da seção transversal. Conclui-se que a continuidade melhora o desempenho das lajes alveolares, uma vez que reduz os deslocamentos no meio do vão e aumenta a capacidade de carga. / Most buildings of precast concrete built in Brazil and abroad consist of hollow core slabs. This paper considers the study of the continuity of these slabs. In design of these elements the common practice is to consider them as simply supported. To improve the performance it is possible to promote the continuity in the intermediate supports. This can be done by placing reinforcement in the tensioned region of the connection, inside the topping, or by bars concreted inside the voids. The aim of this work is to investigate the behavior of hollow core floors with continuity, with reinforcement in the topping. For this, a study involving theoretical and experimental analysis was conducted in three models. The full-scale models were subjected to a transverse loading distributed linearly. The theoretical studies have considered a numerical simulation with beam elements and the Branson formula to describe the physical nonlinear behavior of the material. Furthermore, the specifications of the major Brazilian and international codes were evaluated, with respect to failure by shear of the cross section and the slab-topping interface. The results of the experimental analysis indicated that the model 1 failed by shear of the cross section with the mechanism of diagonal tension of the concrete. Model 2 presented shear failure of the interface. In model 3, the failure was by flexure. The behavior of the tested models was ruled by cracking of the topping in region of negative bending moment. Theoretical analysis with beam elements represented satisfactorily the behavior of the tested models. The only formulations that presented consistent results with the three tests were: EUROCODE 2:2004, to calculate the shear strength of the interface, and FIB MODEL CODE 2010, for calculating of the shear strength of the cross section. It is concluded that the continuity improves the performance of the hollow core slabs, as it reduces the displacements at mid-span and increases the bearing capacity.

A utilização de concreto leve decorre especialmente dos benefícios promovidos pela redução da massa específica do material, tais como menores esforços nas estruturas, economia com fôrmas e cimbramento, além de diminuição dos custos com transporte e montagem de construções pré-fabricadas. Atualmente, além das questões técnicas e econômicas, a escolha dos materiais de construção deve levar em conta os aspectos ambientais. Portanto, o uso de poliestireno expandido (EPS) na produção de concreto pode abrir portas para o emprego de resíduos de materiais dessa natureza, e ainda usufruir de sua baixa massa específica nas aplicações estruturais. Este trabalho teve como objetivo determinar as principais características do concreto leve com pérolas (esferas) de EPS, também conhecido como Concreto Ultraleve® ou Concreflex®, características essas necessárias para projetar elementos estruturais, e analisar o comportamento de lajes produzidas com esse novo material. Mais especificamente, foram determinadas características mecânicas, tais como: resistência à compressão, módulo de elasticidade e resistência à tração, na compressão diametral e na flexão, além de características de deformação de longo prazo, como retração e fluência. Também foi determinada a massa específica e avaliada sua relação com as características mecânicas, além dos ensaios de modelos de lajes unidirecionais produzidas com esse concreto. Para analisar a possibilidade de aplicação prática do concreto leve com EPS em lajes, foram elaboradas tabelas para pré-dimensionamento de lajes unidirecionais e bidirecionais com o novo material, nas quais essas lajes foram comparadas com as de concreto comum. Com base no procedimento experimental e nos resultados dos ensaios, o objetivo de determinar as características necessárias para projetar elementos estruturais de Concreto Leve com EPS foi alcançado. Pode-se ainda afirmar que o concreto estudado, com aproximadamente metade da massa específica dos concretos convencionais, apresenta características compatíveis com a produção e o uso comercial de lajes maciças, principalmente pré-moldadas, o que pode ser estendido a outros elementos que não necessitem de concretos com resistência muito alta. Também foi avaliado o comportamento de modelos de lajes de concreto leve com poliuretano (PU), de maneira semelhante ao estudo realizado com EPS, incluindo a caracterização do concreto de cada modelo. Para complementar a análise de desempenho do concreto leve com EPS, apresentou-se um estudo de carbonatação, que comprovou a excelente condição desse novo material com relação à durabilidade. / The use of lightweight concrete is mainly due to the benefits provided by reducing the density of the material such as smaller efforts on structures, economy of molds and scaffolding, as well as lower costs of transportation and erection of precast constructions. Currently, besides the technical and economic issues, the choice of building materials should take into account environmental aspects. Therefore, the use of expanded polystyrene (EPS) in the concrete production can open doors for the use of waste materials of this nature, and still to take advantage of its low density in structural applications. This study aimed to determine the main characteristics of the lightweight concrete with EPS beads (spheres), also named Ultra Lightweight Concrete, characteristics which are necessary to design structural members, and analyze the behavior of slabs produced with this new material. More specifically mechanical properties were determined, such as compressive strength, modulus of elasticity, and splitting and flexural tensile strength, as well as long term deformation properties such as shrinkage and creep. The density was also determined and evaluated its association with the mechanical characteristics, besides the tests of unidirectional slab models produced with this concrete. To analyze the possibility of use of the lightweight concrete with EPS in slabs, tables were compiled for pre-design of unidirectional and bidirectional slabs with this new material, in which these slabs were compared with those of common concrete. Based on the experimental procedure and results of tests, the aim of determine the characteristics necessary to design structural elements of lightweight concrete with EPS has been achieved. Can be also said that the studied concrete, with about half the density of conventional concrete, presents mechanical characteristics compatible with commercial production and use of slabs, mainly precast, conclusion which can be extended to other components that do not require concretes with very high strength. It was also assessed the behavior of slab models of lightweight concrete with polyurethane (PU) in a similar way to the study carried out with EPS, including the characterization of concrete for each model. To complement the performance analysis of the lightweight concrete with EPS a study of carbonation was presented, which proved the excellent condition of this new material with respect to durability.