Este trabalho enfoca a análise estrutural de um dos tipos de laje que vem ganhando espaço no mercado brasileiro, que é a laje formada por vigotas de concreto protendido. O objetivo principal do trabalho é contribuir na avaliação do comportamento desse tipo de laje com relação aos momentos fletores negativos no apoio, mediante análise teórica. Esta análise foi realizada a partir da relação momento x curvatura proposta pelo CEB-90 em conjunto com a técnica do carregamento incremental para a consideração da não-linearidade física do concreto. Esse método foi avaliado através da comparação com resultados experimentais de painéis alveolares encontrados na literatura, verificando que o modelo teórico representa satisfatoriamente o comportamento estrutural de lajes formadas por elementos pré-moldados protendidos. A partir disto, fez-se análises em situações representativas de projeto de lajes formadas por vigotas protendidas, chegando-se as seguintes conclusões: a) a utilização da continuidade favorece fortemente a redução dos deslocamentos; b) os deslocamentos praticamente independem da taxa de armadura de continuidade; c) a evolução do momento fletor negativo no apoio e momento fletor positivo máximo no vão apresentou um comportamento padrão para os casos analisados; d) esse comportamento foi independente da taxa de armadura de continuidade e e) a taxa de armadura de continuidade afetou praticamente o valor da carga última. / This work aims the structural analysis in a type of slabs that is increasing its utilization in Brazil. These slabs are made by precast prestressed joists. The main objective of this work is the evaluation of the behavior of this type of slabs by theoretical analysis of the bending moments on the supports of continuous slabs. In the theoretical analysis was carried out the consideration of the non-linear of the concrete behavior through the moment x curvature relationship of Model Code CEB-90 add incremental load technique. This methodology was appraised with experimental results of panels of hollow core slabs and this methodology was able to represent satisfactorily the behavior of slabs made by precast prestressed elements. Analysis of representative cases of slabs with precast prestressed joists was carried out and the main conclusions were: a) the use of continuity aids highly to decrease the displacements; b) displacements were practically independent of reinforcement ratio on the support; c) the development profiles of the bending moments had a standard behavior to the analysed cases; d) this behavior was independent of reinforcement ratio on the support and e) the reinforcement ratio on the support affected practically the ultimate load value.

Precast, prestressed concrete panels (PCPs) have been widely used in Texas as stay-in-place formwork in bridge deck construction. Although PCPs are widely popular and extensively used, Texas is experiencing problems with collinear cracks (cracks along the strands) in panels. One reason for the formation of collinear cracks is thought to be the required level of initial prestress. Currently, PCPs are designed assuming a 45-ksi, lump-sum prestress loss. If the prestress losses are demonstrated to be lower than this value, this could justify the use of a lower initial prestress, probably resulting in fewer collinear cracks. For this purpose, 20 precast, prestressed panels were cast at two different plants. Half of those 20 panels were fabricated with the current TxDOT-required prestress of 16.1 kips per strand, and the other half were fabricated with a lower prestress of 14.4 kips per strand based on initially observed prestress losses of 25 ksi or less. Thirteen of those panels were instrumented with strain gages and monitored over their life time. Observed losses stabilized after five months, and are found to be about 24.4 ksi. Even with the reduced initial prestress, the remaining prestress in all panels exceeds the value now assumed by TxDOT for design. / text

Thesis (Ph. D.)--University of Canterbury, 2009. / Typescript (photocopy). "July 2009." Includes bibliographical references. Also available via the World Wide Web.

Este trabalho enfoca a análise estrutural de um dos tipos de laje que vem ganhando espaço no mercado brasileiro, que é a laje formada por vigotas de concreto protendido. O objetivo principal do trabalho é contribuir na avaliação do comportamento desse tipo de laje com relação aos momentos fletores negativos no apoio, mediante análise teórica. Esta análise foi realizada a partir da relação momento x curvatura proposta pelo CEB-90 em conjunto com a técnica do carregamento incremental para a consideração da não-linearidade física do concreto. Esse método foi avaliado através da comparação com resultados experimentais de painéis alveolares encontrados na literatura, verificando que o modelo teórico representa satisfatoriamente o comportamento estrutural de lajes formadas por elementos pré-moldados protendidos. A partir disto, fez-se análises em situações representativas de projeto de lajes formadas por vigotas protendidas, chegando-se as seguintes conclusões: a) a utilização da continuidade favorece fortemente a redução dos deslocamentos; b) os deslocamentos praticamente independem da taxa de armadura de continuidade; c) a evolução do momento fletor negativo no apoio e momento fletor positivo máximo no vão apresentou um comportamento padrão para os casos analisados; d) esse comportamento foi independente da taxa de armadura de continuidade e e) a taxa de armadura de continuidade afetou praticamente o valor da carga última. / This work aims the structural analysis in a type of slabs that is increasing its utilization in Brazil. These slabs are made by precast prestressed joists. The main objective of this work is the evaluation of the behavior of this type of slabs by theoretical analysis of the bending moments on the supports of continuous slabs. In the theoretical analysis was carried out the consideration of the non-linear of the concrete behavior through the moment x curvature relationship of Model Code CEB-90 add incremental load technique. This methodology was appraised with experimental results of panels of hollow core slabs and this methodology was able to represent satisfactorily the behavior of slabs made by precast prestressed elements. Analysis of representative cases of slabs with precast prestressed joists was carried out and the main conclusions were: a) the use of continuity aids highly to decrease the displacements; b) displacements were practically independent of reinforcement ratio on the support; c) the development profiles of the bending moments had a standard behavior to the analysed cases; d) this behavior was independent of reinforcement ratio on the support and e) the reinforcement ratio on the support affected practically the ultimate load value.

The object of this study was to investigate the recent developments in the use of precast prestressed concrete members for buildings in the United States and Iran. In the United States, the study was concerned with developments in the usage of members such as slabs, wall panels, beams and columns. The latest technical and engineering reports, along with personal interviews, were used, and a number of case studies were conducted on recently built structures. The author also studied the newest developments in the precast concrete industry in Iran. A questionnaire was formulated in both Persian (native language of Iran) and English, and was sent to twelve of the largest precast concrete manufacturers in Iran. This study was extended to include the use of precast concrete members in alleviating Iran's housing shortage, which is one of the greatest problems facing the country today. From these studies the following observations have been made with respect to the United States: There is a vast variety of precast concrete units designed and manufactured in the country. The majority of precast concrete units in buildings are assembled by using simple connections. There has been great improvement in the quality of sealant materials. In the case studies conducted, it was evident that proper planning in design, production, transportation and erection of members were the major reasons in lowering the cost of precast concrete structures as compared to cast-in-place structures. The rapid increase in the use of precast concrete members is due to repetition of similar members, increase in strength and serviceability by prestressing, rapid construction, better quality control, improvement in handling and fire resistance qualities. In the case of Iran, the following observations have been made: The use of precast concrete members has increased rapidly in the last decade. Precast concrete construction, with proper sheer design, appears suitable in areas where there is stronger and more frequent earthquake occurrence. Precast concrete members are considered to be suitable for low-cost housing projects because of the availability of cement and steel reinforcement, an inadequate supply of wood and also because of the advantages of precast concrete mentioned above.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Pre-cast sections have the advantages of structural efficiency, better quality control and less construction time, which enable them to be widely used in building structures. The connections of pre-cast buildings play a vital role for the stability and strength of structures. Nowadays, more attention is drawn to the aesthetical appearance of building structures, especially by architects. The Hidden Corbel Connection (HCC) was then developed to make the building structures stable and aesthetically pleasing. A modified HCC was designed and investigated in this study. Amongst all the mechanisms in the connection zone, the mechanism of the end anchorage length of tension reinforcement plays a key role in the economy of the connection and is hence further investigated. In order to investigate whether the end anchorage length of tension reinforcement can be reduced for a simply supported beam, a 2D non-linear finite element model is used to analyze the stress distribution inside the connection zone. Based on the stress distribution in the connection zone, the tensile force was calculated at the face of the support, which directly correlates to the required end anchorage length of tension reinforcement. The confinement in the connection zone increases the bond stress, which in turn reduces the required anchorage length of tension reinforcement. Therefore, a 3D model is used to analyze the region inside the modified HCC to find the position of the best confinement. By comparing the finite element (FE) results with Eurocode 2 (2004), and SABS 0100-1 (2000), it is demonstrated that the FE results require the shortest anchorage length, while the longest anchorage length is specified in SABS 0100-1 (2000). Based on the comparison between the FE results and the design codes, a laboratory experiment was then performed to determine if the end anchorage length of tension reinforcement can be reduced. Four beams with different support conditions and with different end anchorage length of tension reinforcement were tested. The results of the laboratory experiment indicate that the end anchorage length for simply supported beams can be shortened from the specification of SABS 0100-1 (2000).

Thesis (M.Tech - Marketing, Faculty of Management Sciences)--Vaal University of Technology, 2010 / This study provides a framework for customer-supplier relationships and service quality measurement in a precast concrete manufacturing firm with the use of the universally accepted SERVQUAL model. Within an increasingly competitive precast concrete market, customer satisfaction is a critical goal for manufacturers of all types. Customer-supplier relationships and service quality were therefore investigated in this study. A quantitative research approach was used in the study to analyse the data. This approach enabled the researcher to obtain an accurate measure of all constructs that relate to service quality improvement for the particular concrete manufacturing firm amongst contractors, civil consultants, government institutions and end users. A sample size of 246 respondents from Gauteng Province was used. Descriptive statistics were used to explain the characteristics of sample data. In addition, factor analysis was used to condense the variables into five factors in order to capture the essence of service quality within a cementitious products organisation. Five dimensions, responsiveness, problem- solving, physical aspects, service personnel and physical appearance were extracted to measure service quality. Results showed that satisfied customers tend to re-patronise suppliers who enhance their service outputs provided to the customers. Thus it is imperative to enhance customer satisfaction and ultimately customer loyalty. These results suggest that improved service qualities can be useful for building customer loyalty and long- lasting relationships. The reliability analysis produced a Cronbach alpha which ranged from 0.700 to 0.815 which were deemed acceptable. The Pearson correlation analysis showed that service quality is associated with customers' future buying behaviour in terms of their decisions to purchase and recommend the supplier to others. Customers felt that service personnel were friendly, courteous and possessed the knowledge to answer customer questions. They exhibited a favourable image of the company and its services. This service dimension was ranked first in terms of importance by the customers therefore, the precast concrete manufacturer ought not be complacent but rather seek innovative ways in maintaining the service personnel dimension of service quality. The overall mean score of expectation of service quality by customers was 4.71. This indicates that the service provided by this company is satisfactory. It therefore suggests that, it is necessary for managerial intervention to prioritise in all these areas to develop a strategy of service quality improvement. Training of personnel is an essential component of service quality enhancement especially with complaints and the complaints-handling procedures. The management team of the organisation needs to play an active role in ensuring that all personnel are adequately trained and highly motivated to understand the user‟s specific problems and in the process to provide competent solutions to problems. Based on literature and results emanating from the empirical survey, these findings may assist the organisation in the enhancement of its service-quality levels. Hence, service-quality levels should be monitored carefully on a continuous basis.

O objetivo principal deste trabalho é apresentar um modelo de análise probabilística do comportamento ao longo do tempo de estruturas de concreto. Para isso, é realizada a análise probabilística em conjunto com análise numérica. A análise numérica é realizada através de um programa computacional, baseado no método dos elementos finitos, que considera o comportamento não-linear e dependente do tempo dos materiais, assim como o processo evolutivo da construção. Para determinar o efeito das incertezas dos parâmetros é realizada uma análise probabilística, utilizando o método de amostragem por hipercubo latino. O modelo apresentado pode ser aplicado para a análise probabilística do comportamento ao longo do tempo das estruturas de concreto em geral. No entanto, foi aplicado na análise das flechas diferidas de lajes pré-moldadas formadas por vigotas com armação treliçada. Com esta análise, pôde-se propor um coeficiente multiplicador das flechas imediatas para a avaliação das flechas diferidas no tempo. O coeficiente multiplicador obtido para as lajes pré-moldadas formadas por vigotas com armação treliçada pode alcançar valores muito superiores ao fator 'alfa'f recomendado pela NBR 6118 (2003) para o caso de vigas de concreto armado. / The goal of this research is to present a probabilistic analysis model of the long-term behavior of concrete structures. For that, the probabilistic analysis is carried out together with numerical analysis. The numerical analysis is carried out using a software based on the finite element method that takes into account the nonlinear and time dependent behavior of the materials, as well as the evolutionary construction process. A probabilistic analysis is carried out in order to determine the effects of the uncertainties of the parameters, using latin hypercube sampling method. The presented model can be applied in the probabilistic analysis of the long-term behavior of concrete structures in general. However, it was applied in the analysis of the long-term deflections of precast slabs made by joist with lattice reinforcement. By this analysis, a multiplier coefficient of immediate deflections to evaluate long-term deflections could be proposed. The multiplier coefficient obtained for precast slabs made by joist with lattice reinforcement can reach values much higher than the factor 'alfa'f recommended by NBR 6118 (2003) for the case of reinforced concrete beams.

Essa pesquisa apresenta um estudo a respeito de cálices de fundação com colarinho. O trabalho foi elaborado a partir de uma análise crítica e síntese de resultados de estudos experimentais e numéricos desenvolvidos na Escola de Engenharia de São Carlos - Universidade de São Paulo (EESC-USP) sobre a ligação pilar-fundação por meio de cálice para estruturas de concreto pré-moldado. Esses estudos englobam uma tese de doutorado e três dissertações de mestrado, em que foram abordadas diversas situações de projeto dessa ligação. A partir dos resultados dessas pesquisas são elaboradas recomendações para o projeto do cálice com interface lisa e rugosa e da base do pilar pré-moldado. Incluem-se ainda avaliação da situação de montagem e disposições construtivas gerais a respeito da ligação por meio de cálice. Mediante aplicações, são avaliadas as recomendações de projeto e simulados casos reais de emprego da ligação pilar-fundação por meio de cálice. Com base nesse estudo, as principais conclusões incorporadas às recomendações foram em relação: a) a posição de aplicação da resultante de pressão superior na parede frontal; b) ao comportamento das paredes transversais; c) a força normal com pequena excentricidade; d) a determinação da espessura mínima da parede do colarinho e; e) adaptação do modelo de comportamento da base do pilar pré-moldado com o modelo do cálice. Ao final, são elaborados exemplos de dimensionamento da ligação cálice de fundação com interface lisa e rugosa e da base do pilar pré-moldado, além de um roteiro simplificado com recomendações de projeto desses elementos. / This research presents a study about the socket base with pedestal walls. The paper was drawn from a review and synthesis of results of experimental and numerical studies carried out at the Engineering School of São Carlos University of São Paulo (EESC-USP) about the socket base connection by pedestal walls in precast concrete structures. These studies include a Phd thesis and three MSc dissertations, which addressed several situations of design of that kinf of connection. From the results, recommendations are drawn for the design of socket with smooth and rough interface and precast column base. Included also evaluated at the erection situation and constructive provisions regarding socket base. With some applications are analyzed the design recommendations and simulated real cases of use of column-base connection by socket. Based on this study, the main conclusions that were incorporated into the recommendations were about: a) local of application of the top pression resultant; b) behavior of transversal walls; c) normal force with small eccentricity; d) determination of the thickness of pedestal wall and; e) adaptation of column base model with the socket model. Finally, examples are drawn about socket foundation design with smooth and rough interface and of the precast column base, beyond simplified script with recommendations for the design of these elements.

Neste trabalho é enfocada a análise estrutural de lajes pré-moldadas formadas por vigotas treliçadas. Esta análise foi realizada mediante o modelo de grelha, considerando a não-linearidade do concreto armado utilizando-se a relação momento x curvatura e carregamento incremental. O modelo da não-linearidade do concreto armado foi avaliado com resultados experimentais de vigas bi-apoiadas e painéis de laje contínua. O trabalho inclui uma análise teórico-experimental de uma laje pré-moldada bidirecional isolada e simulações numéricas de casos representativos de arranjos estruturais das lajes treliçadas. As principais conclusões do trabalho foram: a) o modelo de grelha é bastante adequado para a análise de lajes nervuradas pré-moldadas; b) os resultados da análise teórico-experimental da laje pré-moldada indicam que os deslocamentos foram fortemente influenciados pela rigidez à torção e c) a redistribuição de momentos fletores nas lajes contínuas é relativamente pequena. / This work aims the structural analysis in precast slabs made by lattice joist. The scheme was carried out by using the grillage model considering the non-linear of the reinforced concrete through the relationship moment x curvature and incremental loads. The non-linear model of the reinforced concrete was appraised with experimental of simply supported beams and panels of continuos slabs. The work includes a theoretical-experimental analysis of a isolated bidirectional precast slabs and numeric simulations of representative cases of structural arrangements of the slabs witch lattice joist. The main conclusions of the work were: a) the grillage model is quite appropriate for precast ribbed slabs; b) the results of theoretical-experimental analysis of the precast slabs point out the relevance the torsional in the deflections and c) the bending moments redistribution in the continuous slabs are quite small.