For this research, prestress losses were monitored in six HPC bridge girders. These measured losses were compared to predicted losses according to four sources. Prestress loss predictive methods considered for this research were: 1- AASHTO LRFD 2004, 2- AASHTO LRFD 2004 Refined, 3- AASHTO LRFD 2007, and 4- AASHTO LRFD Lump Sum method. On the other hand, the camber prediction methods used in the present research were: 1- Time dependent method described in NCHRP Report 496, 2- PCI multiplier method, and 3- Improved PCI Multiplier method. For the purpose of this research, long-term prestress losses were monitored in select girders from Bridge 669 located near Farmington, Utah. Bridge 669 is a three-span prestress concrete girder bridge. The three spans have lengths of 132.2, 108.5, and 82.2 feet long, respectively. Eleven AASHTO Type VI precast prestressed girders were used to support the deck in each span. The deflection of several girders from a three-span, prestressed, precast concrete girder bridge was monitored for 3 years. Fifteen bridge girders were fabricated for the three span-bridge. Ten girders from the exterior spans had span length of 80 feet, and five girders from the middle span had span length of 137 feet. From the results of this research, in both the 82- and 132-foot-long, the AASHTO LRFD 2004 Refined Method does a better job predicting the prestress loss and it can be concluded that all the prediction methods do a better job predicting the loss for the larger girders. The Lump Sum method predicted very accurately the long term prestress loss for the 132-foot-long girders.

<p> A computer program is written to calculate the deflections and stresses in a shell of general nature.</p> <p> An oblique. truncated pyramid, built of aluminium plates is used for illustration and experimental analysis. </p> <p> Theoretical values of deflections and stresses are compared with the experimental results. </p> / Thesis / Master of Engineering (MEngr)

Yes / For composite cellular beams, additional deflections occur due to the loss of bending and shear stiffness at the opening positions and also due to slip in the shear connectors caused by partial shear connection. Design formulae are presented for the additional deflection of composite beams with circular openings or for cellular beams as a function of the proportionate depth of the openings. The simplified formulae are calibrated against finite element results for both cellular and solid web beams and also against measured deflections of a 15.3 m composite cellular beam test. This additional deflection is presented as a function of flexural and shear terms that are a function of the span:depth ratio. For modelling of cellular beams to determine deflections, the circular opening may be represented by an equivalent rectangular opening of length equal to 70% of the opening diameter.

Lajes-cogumelo são sistemas estruturais que apresentam uma série de vantagens em relação aos sistemas convencionais. Por outro lado, com a retirada das vigas, podem surgir problemas como o deslocamento transversal das lajes, a instabilidade global do edifício e a punção da laje pelo pilar. Este trabalho concentra-se no estudo dos deslocamentos transversais das lajes-cogumelo, procurando-se fazer a comparação entre deslocamentos calculados por diferentes processos: o das vigas cruzadas, o de Rangan e o dos elementos finitos. São abordados conceitos básicos para o cálculo desses deslocamentos, o estado de fissuração a ser adotado na determinação da rigidez e os efeitos da fluência e da retração do concreto, que foram baseados no ACI 209R-92. São apresentados três exemplos de aplicação. Com base nos resultados obtidos, verifica-se que os valores dos deslocamentos calculados pelos diferentes processos dependem muito da rigidez considerada, uma vez que é grande a influência do estado de fissuração nos deslocamentos da laje. Nos dois primeiros exemplos, pode-se observar que a diferença de resultados entre o processo de Rangan (que adota um estado padrão de fissuração) e a análise por elementos finitos (considerando a fissuração) é muito variável; os resultados diferem de 1% a 200%. Os resultados obtidos com dois programas de elementos finitos (que consideram a fissuração de formas diferentes) não apresentam diferenças maiores que 14%. / Flat plates are structural systems that present some advantages when compared to slabs with beams. On the other hand, when beams are removed some problems can arise, such as slab deflections, global instability of the building and punching shear. This work deals with the flat plate deflections, comparing computed deflections using different procedures: crossing beam method, Rangan method and finite element method. Basic concepts for the calculation of these deflections, the cracking stage to be adopted in order to determine the stiffness and the effects of concrete creep and shrinkage using the ACI 209R-92 are presented. Three examples are developed. Based on the results, it is noticed that the computed deflections using different procedures depend on the esteemed stiffness, since the influence of cracking stage in the slab deflections is great. In the first two examples, the difference between the results calculated using the Rangan method (which adopts a standard cracking stage) and the finite element method (considering cracking) is very variable; the results differ within a range of 1% to 200%. The results calculated with two finite element program (which consider cracking by different ways) do not present differences greater than 14%.

Neste trabalho, são estudados os deslocamentos de vigas, lajes e pavimentos completos em concreto armado, submetidos a carregamentos perpendiculares aos seus eixos e planos. Utiliza-se para tanto o programa ANPAV, desenvolvido no SET-EESC-USP, que permite o cálculo dos deslocamentos considerando-se o comportamento não-linear do concreto armado por meio de todos os fenômenos modernamente considerados com esse objetivo. Assim, a partir de elementos finitos estratificados em filamentos, no caso de elementos de barra tridimensional, ou camadas, no caso dos elementos de placa, podem ser considerados os efeitos da fissuração, da retração, da fluência, e da colaboração do concreto tracionado entre as fissuras para a rigidez à flexão dos elementos. Inicialmente, então, são calculados os deslocamentos de um elevado número de lajes e vigas isoladas e, a partir da análise dos resultados, é avaliada a influência dos parâmetros envolvidos neste cálculo. Sugerem-se, tanto para lajes quanto para vigas, expressões para o cálculo de coeficientes multiplicadores dos deslocamentos imediatos para a avaliação dos deslocamentos diferidos no tempo, e também são feitas propostas para a determinação de uma altura mínima para esses elementos. Com a utilização dessas alturas mínimas, pode-se garantir que o estado limite de deformação excessiva não será atingido, dispensando-se a necessidade do cálculo dos deslocamentos propriamente ditos e simplificando-se enormemente o trabalho de projetistas dessas estruturas. Por fim, são estudados pavimentos de edifícios residenciais e seus deslocamentos são calculados a partir de análises linear e não-linear, sendo os resultados obtidos comparados de forma a se validar alguns modelos e expressões desenvolvidas na análise dos elementos isolados. / This work presents an analysis of deflections for reinforced concrete beams, slabs and floors under perpendicular loading. The ANPAV program - a finite-element program developed at SET-EESC-USP that allows estimating the deflections considering reinforced concrete non-linear behavior - is used. With finite layered-elements for beams and plates it is possible to evaluate deflections taking into account cracking, shrinkage, creep and tension stiffening. Firstly, deflections for a wide range of isolated beams and slabs cases are calculated in order to evaluate the influence of several important parameters. Then, multiplier coefficients for assessing long term deflections from immediate deflections and minimum thickness expressions to ascertain serviceability limit states are suggested, both for beams and slabs. Finally, deflections for residential building floors are calculated for linear and non-linear analysis and the results are compared in order to validate the models and parameters obtained from isolated beams and slabs.

Corrosion of steel reinforcement in concrete structures results in significant repair and rehabilitation costs. In the past several years, new fiber reinforced polymer (FRP) reinforcing bars have been introduced as an alternative to steel reinforcing bars. Several national and international organizations have recently developed standards based on preliminary test results. However, limited validation testing has been performed on the recommendations of these standards. High variability of the tensile properties, degradation of tensile strength, direct shear capacity, predicted deflections due to creep, cracking behavior of FRP-reinforced concrete flexural members, bond behavior and development length, and effects of thermal expansion on cracking of FRP reinforced concrete have all been reported, but are areas that need further investigation and validation. The objective of this study is to evaluate the characteristics of glass FRP reinforcing bars and provide recommendations on the design and construction of concrete structures containing these bar types with regard to the areas described. The recently developed ACI 440 design guidelines were analyzed and modifications proposed.

This dissertation describes the development and effectiveness of a mathematical model used to predict the behavior of cantilever beams whose loading conditions include parallel combinations of evenly distributed loads and endpoint forces. The large deflection of cantilever beams has been widely studied. A number of models and mathematical techniques have been utilized in predicting the endpoint path coordinates and load-deflection relationships of such beams. The Pseudo-Rigid-Body Model (PRBM) is one such method which replaces the elastic beam with rigid links of a parameterized pivot location and torsional spring stiffness. In this paper, the PRBM method is extended to include cases of a constant distributed load combined with a parallel endpoint force. The phase space of the governing differential equations is used to store information relevant to the characterization of the PRBM parameters. Correction factors are also given to decrease the error in the load-deflection relationship and extend the angular range of the model, thereby further aiding compliant mechanism design. The calculations suggest a simple way of representing the effective torque caused by a distributed load in a PRBM as a function of easily calculated model parameters.

In this research, nonlinear structural analysis along with finite element analysis were carried out for a pretensioned concrete beam at different levels of pretension in order to examine the effect of the change in the tendon force on the geometric stiffness of the beam. Several results were obtained for deflection, horizontal displacement and surface strains to investigate how they are affected by the level of pretension under the application of the same load in each case. These computations were compared with the tendon force to conclude whether they can be used to estimate the pretension level by means of simple measurements. The purpose was to develop a methodology for quantifying the prestress losses by taking advantage of the dependence of the prestressed concrete beam stiffness on the tendon force. / text

Corrosion of steel reinforcement in concrete structures results in significant repair and rehabilitation costs. In the past several years, new fiber reinforced polymer (FRP) reinforcing bars have been introduced as an alternative to steel reinforcing bars. Several national and international organizations have recently developed standards based on preliminary test results. However, limited validation testing has been performed on the recommendations of these standards. High variability of the tensile properties, degradation of tensile strength, direct shear capacity, predicted deflections due to creep, cracking behavior of FRP-reinforced concrete flexural members, bond behavior and development length, and effects of thermal expansion on cracking of FRP reinforced concrete have all been reported, but are areas that need further investigation and validation. The objective of this study is to evaluate the characteristics of glass FRP reinforcing bars and provide recommendations on the design and construction of concrete structures containing these bar types with regard to the areas described. The recently developed ACI 440 design guidelines were analyzed and modifications proposed.

Lajes-cogumelo são sistemas estruturais que apresentam uma série de vantagens em relação aos sistemas convencionais. Por outro lado, com a retirada das vigas, podem surgir problemas como o deslocamento transversal das lajes, a instabilidade global do edifício e a punção da laje pelo pilar. Este trabalho concentra-se no estudo dos deslocamentos transversais das lajes-cogumelo, procurando-se fazer a comparação entre deslocamentos calculados por diferentes processos: o das vigas cruzadas, o de Rangan e o dos elementos finitos. São abordados conceitos básicos para o cálculo desses deslocamentos, o estado de fissuração a ser adotado na determinação da rigidez e os efeitos da fluência e da retração do concreto, que foram baseados no ACI 209R-92. São apresentados três exemplos de aplicação. Com base nos resultados obtidos, verifica-se que os valores dos deslocamentos calculados pelos diferentes processos dependem muito da rigidez considerada, uma vez que é grande a influência do estado de fissuração nos deslocamentos da laje. Nos dois primeiros exemplos, pode-se observar que a diferença de resultados entre o processo de Rangan (que adota um estado padrão de fissuração) e a análise por elementos finitos (considerando a fissuração) é muito variável; os resultados diferem de 1% a 200%. Os resultados obtidos com dois programas de elementos finitos (que consideram a fissuração de formas diferentes) não apresentam diferenças maiores que 14%. / Flat plates are structural systems that present some advantages when compared to slabs with beams. On the other hand, when beams are removed some problems can arise, such as slab deflections, global instability of the building and punching shear. This work deals with the flat plate deflections, comparing computed deflections using different procedures: crossing beam method, Rangan method and finite element method. Basic concepts for the calculation of these deflections, the cracking stage to be adopted in order to determine the stiffness and the effects of concrete creep and shrinkage using the ACI 209R-92 are presented. Three examples are developed. Based on the results, it is noticed that the computed deflections using different procedures depend on the esteemed stiffness, since the influence of cracking stage in the slab deflections is great. In the first two examples, the difference between the results calculated using the Rangan method (which adopts a standard cracking stage) and the finite element method (considering cracking) is very variable; the results differ within a range of 1% to 200%. The results calculated with two finite element program (which consider cracking by different ways) do not present differences greater than 14%.