Master of Science / Department of Architectural Engineering / Kimberly W. Kramer / Recent years have witnessed the advent of many innovative materials to the construction industry. These materials often offer benefits to the projects on which they are used, but only if they are utilized in the proper applications. Among these new materials is high-strength reinforcing steel for use in reinforced concrete structural elements. This material is not new from the perspective of chemical composition, but rather the applications that it is being selected for. The following paper details the evaluation of the use of high-strength steel reinforcement in the design of reinforced concrete tilt-up panels and compares those designs to that of standard strength reinforcement. For the purpose of this study, standard strength is defined as reinforcement having a tensile yield stress of 60ksi while high-strength reinforcement refers to reinforcing steel with a tensile yield stress of 80ksi. 120 panels are designed for both high-strength and standard strength reinforcement, and the resulting steel spacings are compared. This study provides data from which designers and contractors can improve their ability to provide quality tilt-up panel designs.

Made available in DSpace on 2016-06-02T20:09:19Z (GMT). No. of bitstreams: 1 5795.pdf: 7169522 bytes, checksum: 82089f61a5b06c7100940687172cc2e6 (MD5) Previous issue date: 2014-02-19 / Universidade Federal de Minas Gerais / The resistance to compression is the property that determines the use of masonry as a structural system since the great majority of structural elements in such systems are generally subjected to compressive stresses. One of the factors to be taken into account in the design of these compression elements is their slenderness. For design in Brazil it is still used the concept of simplified slenderness where the buckling length is determined by an effective depth (hef) and the radius of gyration is replaced by a parameter called the effective thickness (tef) for calculating a resistance reduction factor. This reduction factor has its origin in very old international standards and building codes, dating back to when these codes used the allowable stresses method for the dimensioning of structural elements; due to its age, an effective explanation and derivation of this factor, therefore, has been lost and is unknown at this time. With the various updates of international standards for structural masonry and the consequent adoption of the limit state design method for dimensioning of elements, this factor has been abolished. In the Brazilian standards, however, even with the adoption of the limit state design method, this factor is still used, which is a contradiction. Studies on the strength reduction due to slenderness effects show that there are large differences when comparing the results given by the simplified method in the NBR with those given by international standards. These differences probably don t lead to loss of structural integrity of structures in Brazil because the slenderness ratio has been limited to low values, particularly in the case of unreinforced masonry. / A resistência a compressão é propriedade determinante no uso da alvenaria como estrutura, uma vez que a grande maioria dos elementos estruturais nesse tipo de sistema construtivo são submetidos preponderadamente ao esforço de compressão. Um dos fatores a ser levado em conta no dimensionamento de elementos comprimidos é a esbeltez desse elemento. Até hoje no Brasil utiliza-se o conceito de esbeltez simplificado, onde o comprimento de flambagem é determinado por uma altura efetiva (hef) e o raio de giração é substituído por um parâmetro chamado espessura efetiva (tef) para cálculo de fator minorador de resistência. Esse fator tem sua origem em normas e códigos de construção internacionais bastante antigos, remontando a épocas em que esses códigos tratavam o dimensionamento pelo Método das Tensões Admissíveis, tendo sido perdida e, portanto, sendo desconhecida a efetiva explicação da sua dedução. Com as diversas atualizações de normas internacionais em alvenaria estrutural e com a consequente adoção do Método dos Estados Limites para dimensionamento, esse fator foi abolido. Na normalização brasileira, mesmo com a adoção do Método dos Estados Limites, esse fator continua vigente, o que gera uma contradição. Estudos sobre o efeito da redução da resistência devido à esbeltez, mostram que existem grandes diferenças nos resultados quando se compara o método simplificado na NBR com os de outras normas internacionais. Essas diferenças provavelmente não induzem a perda de segurança nas estruturas nacionais porque o índice de esbeltez tem sido limitado a valores baixos, em especial no caso de alvenaria não-armada.