<p> The behavior of concrete block walls subjected to vertical compressive loads with out-of-plane eccentricities was investigated both experimentally and analytically. Particular attention was devoted to the effect of wall slenderness on capacity.</p> <p> In the experimental study, 14 full scale walls and numerous small specimens were tested to provide complete and reliable data concerning the behavior of concrete block walls and its components. Plain walls and partially grouted reinforced walls were tested in symmetric single curvature under compressive loads with out-of-plane eccentricities. Reinforced walls were tested in pure bending, as well.</p> <p> Prisms were tested to analyze the behavior of concrete masonry in compression with no slenderness or eccentricity effects. Bond tests were carried out to determine the behavior at interfaces of grout and steel reinforcing bars as well as between mortar and concrete blocks. Material tests were conducted to determine the mechanical properties of the blocks, mortar, grout and steel reinforcement used.</p> <p> A two-dimensional finite element model for the vertical cross section of block masonry walls was developed. It is capable of modeling local failure modes such as cracking, crushing and debonding. Material properties of the concrete blocks, mortar, grout, and steel bars were treated individually. The large deformation analysis allowed for consideration of the slenderness effect. The model was verified through comparison with experimental results. Fairly good agreement was obtained.</p> <p> The material properties of specimens tested during the experimental investigation were the basis of a parametric study. Results of this study were used to investigate the effect of the wall slenderness and the eccentricity of applied loads on the capacity of concrete block walls. They were used to evaluate the current provisions in the Canadian Masonry Code, CAN3-S304-M84. An attempt was made to develop original design equations based on the reduction coefficient approach. The proposed equations for plain and reinforced blockwork were shown to provide more consistent predictions of capacity than current design methods.</p> / Thesis / Master of Engineering (MEngr)

A set of equations describing the motion of a naturally curved and twisted slender elastic rod is determined in this thesis. In particular, a study of the vibration of a helical spring is made, and the natural frequencies from the theory presented are compared with those from a simpler theory. Comparison of the two theories shows that the simpler theory is valid for most springs. The simpler theory is then used to show how the natural frequencies for a helical spring can be obtained when the spring is subjected to any boundary conditions. Finally, an analytical and experimental study of the vibration of a helical spring clamped at both ends is made in order to investigate the validity of the theory presented. / Thesis / Master of Engineering (MEngr)

No description available.

No / Optimum multi-layered feed-forward neural network (NN) models using a resilient back-propagation algorithm and early stopping technique are built to predict the shear capacity of reinforced concrete deep and slender beams. The input layer neurons represent geometrical and material properties of reinforced concrete beams and the output layer produces the beam shear capacity. Training, validation and testing of the developed neural network have been achieved using 50%, 25%, and 25%, respectively, of a comprehensive database compiled from 631 deep and 549 slender beam specimens. The predictions obtained from the developed neural network models are in much better agreement with test results than those determined from shear provisions of different codes, such as KBCS, ACI 318-05, and EC2. The mean and standard deviation of the ratio between predicted using the neural network models and measured shear capacities are 1.02 and 0.18, respectively, for deep beams, and 1.04 and 0.17, respectively, for slender beams. In addition, the influence of different parameters on the shear capacity of reinforced concrete beams predicted by the developed neural network shows consistent agreement with those experimentally observed.

Circular Concrete Filled Tubes are gaining importance in the construction industry due to their advantages insofar as economy and structural efficiency. Due to the recent developments in concrete and steel technology, the usage of high strength materials in these concrete filled tubes is increasing. The governing American specification (AISC 360-16) classifies these composite members as compact, non-compact and slender sections. The allowed section slenderness (ratio of diameter to thickness ratio) in each classification is related to the material properties (ratio of Young's modulus to yield strength ratio). AISC 360-16 is applicable for steels up to 75 ksi and concretes up to 10 ksi. These limits are lower than current available materials and restricts the usage of highly slender sections. As the strength of these tubes is dependent on local buckling, tests on many combinations of high strength steel and concrete are needed to extend these material limits. This preliminary research work focuses on understanding the local buckling behavior of highly slender sections and the effect of concrete infill and its confinement. The research began by compiling a database that highlighted a gap on tests with highly slender sections and high strength materials. To address this issue, a pilot set of experimental tests were conducted on short circular concrete filled members. An analytical evaluation of these experimental results are performed using 3D finite element analysis models. The critical buckling load is determined using J2 deformation theory, which proves to give a good estimate when compared with the experimental results. The main objective of the work is to determine if a simplified test like the one used in this work could be used for the large experimental study that will be necessary to expend the material limits in AISC 360-16. The limited data developed in this study indicates that the test can provide satisfactory results with a few improvements and refinements. / Master of Science

Master of Science / Department of Architectural Engineering and Construction Science / Kimberly W. Kramer / This report uses and references (Analysis of Vertical Reinforcement in Slender Reinforced Concrete (Tilt-up) Panels with Openings & Subject to Varying Wind Pressures) (Bartels, 2010) to investigate the design philosophy and assumptions used in Section 14.8 of the ACI 318-08 (ACI Committee 318, 2008). The design philosophy and assumptions are analyzed to determine the applicability and accuracy of Section 14.8 of the ACI 318-08 (ACI Committee 318, 2008) to the design and analysis of slender concrete panels with openings. Special emphasis is placed on identifying and quantifying the degree of effect that each assumption has on the final design of the panel. These topics include stress distribution around openings, the effect of varying stiffness of the member on the P-delta effect, stiffness variations due to workmanship and tolerances, and the effect of axial load on the stiffness of the member. This is accomplished through the use of specially designed computer analyses that isolate an assumption or effect to determine its impact on the final design. This study shows that two-way effects are almost non-existant, the portion of the panel above the opening has very little effect on the P-delta effects, the code specified reduction in bending stiffness due to workmanship and tolerances appear to be appropriate, and the effective area of reinforcement overestimates the stiffness of the panel.

[pt] Trata-se de um estudo experimental do comportamento de pilares de alta resistência submetidos à flexão composta reta e oblíqua. Foram ensaiados oito pilares com seção transversal de 25x15 cm e comprimento de 300 cm, compondo duas séries de 4 pilares cada uma. Na primeira série, a resistência do concreto foi de 40 MPa e os quatro pilares foram ensaiados à flexão composta oblíqua. Na segunda série, a resistência do concreto foi de 70 MPa e os quatro pilares foram ensaiados à flexão composta reta. Em cada série, a variável foi a taxa de armadura longitudinal que assumiu os valores 1,3%, 2,1%, 3,2% e 4,3%. A finalidade foi verificar os valores da excentricidade de segunda ordem que devem ser considerados no dimensionamento de pilares de concreto de alta resistência. Os resultados experimentais foram comparados com os obtidos pelos métodos do Pilar Padrão com Curvatura Aproximada e do Pilar Padrão com Rigidez Aproximada que constam na NBR 6118:2003. Essa comparação mostrou que o método da curvatura aproximada apresenta valores das excentricidades de 2ª ordem próximos dos reais no caso de pilares submetidos à flexão composta reta e oblíqua, enquanto que o método da rigidez aproximada é contra a segurança só na maioria dos ensaios de pilares submetidos à flexão composta reta. / [en] This work presents an experimental study of the behavior of slender high strength concrete columns under uniaxial and biaxial eccentric compression loads. Eight columns with cross-section of 15x25 cm and height of 300 cm were tested, divided into two series. In the first series, the concrete strength was 40 MPa and the four columns were tested under biaxial compression. In the second series, the concrete strength was 70 MPa and the four columns were tested under uniaxial compression. In each series, the variable was the longitudinal reinforcement ratio which assumed the values 1,3%, 2,1%, 3,2% e 4,3%. The objective was to verify the values of the eccentricity of second order that should be taken into account in the design of slender high strength concrete columns. The experimental results were compared with theoretical results obtained by the models of the approximated curvature and approximated stiffnes methods prescribed in the NBR 6118:2003 code. This comparison showed that the method of curvature approximate present values of the eccentricities of second order close to the real in the case of columns under uniaxial and biaxial eccentric compression loads, while the method of stiffness approximate is lower security in columns under uniaxial eccentric compression load.

Os silos verticais são estruturas com elevado índice de deformações excessivas e ruptura causados, principalmente, pelo desconhecimento da variabilidade nas pressões devidas ao produto armazenado. O objetivo deste trabalho é apresentar um estudo teórico, numérico e experimental das pressões exercidas pelos produtos armazenados granulares nas paredes de silos esbeltos, com a proposta da incorporação de parâmetros com propriedades estocásticas, nos modelos de pressões apresentados na literatura. Os parâmetros mais relevantes dos modelos de pressões foram ajustados aos dados experimentais obtidos em um silo-piloto, utilizando a técnica de estimação de parâmetros por máxima verossimilhança (EMV), e, para isso, foram empregados os algoritmos genéticos (AGs) como procedimento de otimização. As avaliações experimentais no silo-piloto foram conduzidas com três produtos: soja, milho e ração. Com as variabilidades dos parâmetros dos modelos de pressões encontrados nos experimentos, a confiabilidade estrutural dos silos verticais metálicos cilíndricos de chapas onduladas e fundo plano foi avaliada por meio da técnica de simulação de Monte Carlo (SMC). Os resultados mostraram que os modelos de pressões de Janssen (1895) e de Jenike et al. (1973) podem ser utilizados para o cálculo das pressões com as variabilidades dos parâmetros representadas pela distribuição lognormal. A avaliação da probabilidade de falha para este sistema está acima dos limites recomendados internacionalmente, indicando que atenção especial deve ser dada aos projetos de silos verticais esbeltos. / Vertical silos are structures with a large number of deformations and failures mainly due to misunderstanding of pressure variability of the storage products. The aim of this work is theoretical, numerical and experimental study of wall pressure in slender silos with the incorporation of stochastic properties of the parameters in pressures models used in the international literature. The most relevant parameters of the pressure models were adjusted to the experimental data obtained from a pilot-silo using maximum likelihood function, and for this purpose, genetic algorithms (GA) were used in the optimization procedure. The experimental evaluation in pilot-silo was conducted with three different bulk solids, which are: maize, soy and animal feed mixture. With the pressures models parameters, the structural reliability of flat bottom corrugated cylindrical steel silos with was evaluated using Monte Carlo simulation (SMC) to simulate a stochastic process. The results showed that Janssen (1895) and Jenike et al. (1973) pressure models can be used to evaluate the pressures with the parameters uncertainties modeled to lognormal distributions. The reliability index determined in this structural system was less than international recommended values for the design of slender silos.

Como conseqüência do atual desenvolvimento tecnológico dos materiais aço e concreto, várias pesquisas têm surgido com vistas a um melhor aproveitamento da capacidade desses dois materiais, exigindo um maior conhecimento sobre o comportamento dos elementos, inclusive sobre sua vulnerabilidade a estados limites últimos. Sendo a instabilidade um estado limite último possível de ocorrer em configurações de equilíbrio de peças de concreto armado submetidas a determinadas solicitações normais, seu estudo torna-se fundamental para que seja possível propor soluções estruturais seguras e economicamente viáveis. Este trabalho apresenta a análise de alguns aspectos que interferem no estudo da estabilidade de pilares esbeltos de concreto armado, através de uma abordagem envolvendo aspectos teóricos, como também aspectos práticos oriundos da resolução de exemplos. O estudo é feito com base nos métodos geral e do equilíbrio, com os processos exato e do pilar padrão, através de um software (SISTEMA FLEXOR), desenvolvido por CADAMURO Jr. (1997). O objetivo é testar a viabilidade desses métodos a fim de propor soluções e, com isso, tornar mais amplo e acessível o uso de pilares esbeltos de concreto armado, incentivando a adoção de projetos mais arrojados sem subutilização dos materiais. / As a consequence of the actual technological development of the materials steel and concrete, many researches have come up with proposal of better use of these two materials capacity, demanding a bigger knowledge about the behaviour of the elements, included your vulnerability to ultimate limit states. Being the instability a possible ultimate limit state of reinforced concrete columns equilibrium configuration, this study has been fundamental to make possible to propose safe and economically reasonable structural solutions. This work presents the analysis of some aspects that interfere in the study of slender reinforced concrete columns stability, through an approach involving theoretical and practical aspects derived from numerical solutions. The scheme is based in the General and Equilibrium Methods with the Exact Process and Model Column Method, through a software (SISTEMA FLEXOR) developed by CADAMURO Jr. (1997). The objective is to testify the practicability of these methods, to propose solutions and to render wider and more practical the use of slender reinforced concrete columns, stimulating the adoption of projects bolders without underutilisation of the materials.

A maioria dos silos existentes no mundo não apresenta condições ideais de operação devido ao insuficiente conhecimento das pressões, do fluxo e do grande número de variáveis que afetam o comportamento dos produtos armazenados. Isso explica também, a grande quantidade de acidentes e colapsos em silos. Uma análise dos principais códigos normativos indica a existência de divergências entre eles, principalmente quando se referem à determinação das pressões exercidas pelo produto armazenado sobre a estrutura, o mesmo ocorrendo entre as teorias propostas por pesquisadores. Este trabalho tem por finalidade apresentar um estudo teórico das pressões e fluxo em silos verticais esbeltos (h/d&#8805;1,5) exercidas pelo produto armazenado. Para isso, um estado da arte das teorias de pressões e fluxo propostas pelos mais importantes pesquisadores e normas internacionais sobre o assunto foi desenvolvida. Como exemplo de aplicação, foram analisadas as pressões em um silo vertical esbelto com fundo cônico, para as situações de fluxo de massa e fluxo de funil, para dois produtos granulares. Com base nos resultados obtidos, foi elaborada uma proposta de norma brasileira para a determinação das pressões exercidas pelo produto armazenado para essas unidades, tendo em vista que o Brasil ainda não possui uma norma específica para o projeto e construção de silos. Além disso, foi desenvolvido um programa computacional de cálculo das pressões. / Silos are structures that usually present process and failures problems due to insufficient knowledge of bulk solids pressures and flow. An analysis of the principal international theories and standards shows divergences, mainly in the pressures determination due to the storage of bulk solids. This work presents a theoretical study of the pressures and flow in slender vertical silos (h/d&#8805;1,5) due the storage of the bulk solids. An state of the art of the theories of pressures and flow proposed by the most important researchers and international standards on the subject is presented. As a practical example, the pressures were determined in a slender vertical silo with conical bottom, for mass and funnel flow patterns and for two granular materials. Based on the study, a proposal of Brazilian standard was elaborated for the determination of the pressures due the bulk solids for slender silos, considering that Brazil doesn't still have a specific standard for the design and construction of silos. A software for pressures determination was also developed.