| Name: | Description: | Size: | Format: | |
|---|---|---|---|---|
| Documento principal | 4.68 MB | Adobe PDF |
Authors
Advisor(s)
Abstract(s)
A presente dissertação tem como objetivo o estudo do comportamento de pilares prismáticos de granito com capitéis nas extremidades, no que se refere às vantagens e desvantagens quando sujeitos a compressão axial. Em [4] foram estudados provetes semelhantes aos do presente estudo, mas sem capitel, tendo-se verificado em ensaios experimentais que a rotura se iniciou quase sempre na secção de aplicação de carga. Com a introdução de um elemento de transição, na zona de aplicação do carregamento, conseguiu-se que essa zona deixasse de ser condicionante para a rotura do provete.
Através da recolha bibliográfica efetuada constatou-se que são diversos os casos em que se faz recurso ao capitel como elemento de remate, desempenhando um papel estrutural importante nos pilares, nomeadamente de minas e de pontes, independente dos aspetos estéticos.
Através de uma análise numérica foram estudados diversos modelos de capitel, tendo-se chegado a geometrias com maior probabilidade de propiciar melhores resultados experimentais quando o pilar é sujeito a esforços de compressão axial. A realização da análise numérica foi fundamental para excluir a hipótese de ensaio dos modelos menos adequados ao problema em causa. Verificou-se que nos modelos em que a secção de aplicação de carga era maior do que a secção do pilar, ocorreu uma concentração de tensões de compressão na interface pilar-capitel, sendo essa concentração maior nos modelos com capitel paralelepipédico. Também se concluiu que as chapas de aço que ficam em contacto com os topos do provete durante o ensaio experimental devem ter a mesma dimensão do provete, a fim de evitar a concentração de tensões de compressão nas arestas do capitel.
O ensaio experimental permitiu, por comparação dos valores de tensão média de rotura dos provetes com capitel com os provetes de referência (sem capitel), verificar que nos provetes em que o capitel possui uma secção de aplicação da carga maior do que a secção do pilar a resistência do provete aumenta. Verificou-se que o grupo de provetes mais resistentes foi o que possuía capitel de faces planas com inclinação de 20%. A análise experimental permitiu concluir que o elemento de transição “capitel” proporciona um aumento da resistência global do provete quando sujeito a forças de compressão axial. Conclui-se ainda que o capitel faz com que a secção de aplicação de carga não seja condicionante no processo de rotura do provete.
This thesis aims to study the behavior of prismatic granite columns with capitals in the extremities, when subjected to axial compression. Test samples similar to those of this study were already investigated in [4], but without capital, and it was found in experimental studies that the rupture zone almost always started in the load application section. With the introduction of a transition element in the zone of load application, it was found that those end zones were not conditioning the strength of the specimens. Through a bibliographic review, it was found that there are several cases in which the use of capitals in the top or bottom of columns plays an important structural role, namely in mine and bridge pillars, regardless of aesthetic aspects. Through a numerical analysis, many capital models were studied, aiming to find most favorable geometries for capitals to provide better experimental results when the pillar is subjected to axial compressive forces. The realization of the numerical analysis was essential to exclude the hypothesis of testing models less suitable to the problem. It was found that the models in which the load application section was larger than the section of the pillar, a concentration of compressive stresses occurred at the interface pillar-capital, being this concentration higher in models with parallelepiped capital. It was also found that steel sheets which are in contact with the tops of the capitals during the test must have the same stone size in order to avoid concentration of compressive stresses at the edges of capital. The laboratory tests allowed the comparison of the average strength of specimens with capital and reference specimens (without capital). It could be verified that the breaking load increased for specimens with a load application section greater than the column section. It was found that the group of more resistant specimens was the one of capitals with plane inclined faces with a slope of 20%. Experimental analysis confirmed that the transition element “capital” provides increased overall strength of the columns when subjected to axial compression forces. It could be also conclude that the capital has influence in the rupture modus, in which the load application section is not conditioning the global specimen strength.
This thesis aims to study the behavior of prismatic granite columns with capitals in the extremities, when subjected to axial compression. Test samples similar to those of this study were already investigated in [4], but without capital, and it was found in experimental studies that the rupture zone almost always started in the load application section. With the introduction of a transition element in the zone of load application, it was found that those end zones were not conditioning the strength of the specimens. Through a bibliographic review, it was found that there are several cases in which the use of capitals in the top or bottom of columns plays an important structural role, namely in mine and bridge pillars, regardless of aesthetic aspects. Through a numerical analysis, many capital models were studied, aiming to find most favorable geometries for capitals to provide better experimental results when the pillar is subjected to axial compressive forces. The realization of the numerical analysis was essential to exclude the hypothesis of testing models less suitable to the problem. It was found that the models in which the load application section was larger than the section of the pillar, a concentration of compressive stresses occurred at the interface pillar-capital, being this concentration higher in models with parallelepiped capital. It was also found that steel sheets which are in contact with the tops of the capitals during the test must have the same stone size in order to avoid concentration of compressive stresses at the edges of capital. The laboratory tests allowed the comparison of the average strength of specimens with capital and reference specimens (without capital). It could be verified that the breaking load increased for specimens with a load application section greater than the column section. It was found that the group of more resistant specimens was the one of capitals with plane inclined faces with a slope of 20%. Experimental analysis confirmed that the transition element “capital” provides increased overall strength of the columns when subjected to axial compression forces. It could be also conclude that the capital has influence in the rupture modus, in which the load application section is not conditioning the global specimen strength.
Description
Keywords
Granito de alta resistência Granito de alta resistência - Estruturas em cantaria Pilares - Resistência à compressão Pilares com capitéis - Resistência à compressão