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Resistência à flexão composta de colunas mistas aço-betão
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Abstract(s)
As principais características das estruturas mistas aço-betão, nomeadamente um tempo de construção mais rápido do que as construções tradicionais e ainda o facto de que, para dimensões semelhantes dos elementos estruturais, a solução mista apresenta maior rigidez e capacidade de carga, permitem dotar este tipo de estruturas de uma vasta amplitude e aplicação nos mais variados tipos de construção, o que se comprova com a utilização crescente das mesmas nos últimos anos.
Dentro dos vários elementos das estruturas mistas, as colunas mistas têm uma aplicação também muito vasta, porém são sobretudo usadas em edifícios de média e grande altura, sobretudo pelo facto de geralmente possuírem uma secção transversal menor para resistir a igual esforço axial. Maioritariamente, são usadas colunas com secções transversais bi-simétricas, no entanto, colunas mistas com secções assimétricas podem também ser usadas quando é necessário dimensionar pilares de canto, paredes de canto ou núcleos, para melhor se adaptarem à planta do edifício ou requisitos de excentricidades de carga.
Uma vez que, colunas mistas com este tipo de secção transversal não podem ser estudadas através do método simplificado do Eurocódigo 4, o objetivo principal deste trabalho é o desenvolvimento de um programa de cálculo para analisar a resistência à flexão composta de colunas mistas com secção transversal mono-simétrica, através do cálculo das respetivas curvas de interação para cada tipo de secção. Sendo assim, foram analisadas quatro secções diferentes, todas do tipo concrete filled steel tubes, nomeadamente duas secções bi-simétricas e duas secções mono-simétricas.
O programa de cálculo foi usado para realizar vários estudos paramétricos, nos quais se variou a resistência dos dois materiais, as propriedades geométricas de cada secção, o eixo segundo o qual o momento é calculado e ainda, uma comparação entre as várias secções transversais diferentes. Observou-se que, no caso, das variações da resistência dos materiais e das propriedades geométricas, o traçado da curva de interação depende do parâmetro ou seja, depende da relação entre a resistência do aço e a resistência total da secção.
Um modelo numérico foi também desenvolvido com o objetivo de realizar uma análise global à coluna mista, usando para isso uma coluna mista com secção transversal circular, no qual se compararam vários pares de esforços N-M de colunas com diferentes alturas com a curva de interação obtida pelo programa de cálculo, com o objetivo de validar o mesmo e estudar a influência e a variação das imperfeições com a altura, no momento total da secção.
The main features of steel-concrete composite structures, particularly a faster construction time compared to traditional buildings and the fact that, for similar dimensions of structural elements, the composite solution offers greater rigidity and load-carrying capacity, enable these types of structures to have a wide range of applications in various construction types. This is evident through their increasing use in recent years. Among the various elements of composite structures, composite columns have a very wide range of applications, especially in medium to high-rise buildings, primarily due to their smaller cross-section to resist the same axial load. Mostly, columns with bi-symmetric cross-sections are used. However, composite columns with asymmetric cross-sections can also be used when it is necessary to design corner pillars, corner walls, or core walls to better adapt to the building's layout or load eccentricity requirements. Since composite columns with this type of cross-section cannot be analyzed using the simplified method of Eurocode 4, the main objective of this work is to develop a calculation program to analyze the composite column's resistance to combined bending for mono-symmetric cross-sections, by calculating the respective interaction curves for each cross-section type. Thus, four different sections were analyzed, all of the concrete filled steel tubes type, including two bi-symmetric sections and two mono-symmetric sections. The calculation program was used to perform various parametric tests, varying the strength of the two materials, the geometric properties of each section, the axis about which the bending moment is calculated, and also a comparison between the various different cross-sections. It was observed that, in the case of variations in material strength and geometric properties within the same section, the shape of the interaction curve depends on the parameter , i.e., it depends on the ratio between the strength of steel and the total strength of the section. A numerical model was also developed to perform a comprehensive analysis of the composite column. In this model a circular cross-section was used, and it compared various combinations of axial and flexural loads (N-M) for columns of different heights with the interaction curve obtained from the calculation program. The primary objectives were to validate the program and investigate the influence and variation of imperfections with height on the total bending moment capacity of the section.
The main features of steel-concrete composite structures, particularly a faster construction time compared to traditional buildings and the fact that, for similar dimensions of structural elements, the composite solution offers greater rigidity and load-carrying capacity, enable these types of structures to have a wide range of applications in various construction types. This is evident through their increasing use in recent years. Among the various elements of composite structures, composite columns have a very wide range of applications, especially in medium to high-rise buildings, primarily due to their smaller cross-section to resist the same axial load. Mostly, columns with bi-symmetric cross-sections are used. However, composite columns with asymmetric cross-sections can also be used when it is necessary to design corner pillars, corner walls, or core walls to better adapt to the building's layout or load eccentricity requirements. Since composite columns with this type of cross-section cannot be analyzed using the simplified method of Eurocode 4, the main objective of this work is to develop a calculation program to analyze the composite column's resistance to combined bending for mono-symmetric cross-sections, by calculating the respective interaction curves for each cross-section type. Thus, four different sections were analyzed, all of the concrete filled steel tubes type, including two bi-symmetric sections and two mono-symmetric sections. The calculation program was used to perform various parametric tests, varying the strength of the two materials, the geometric properties of each section, the axis about which the bending moment is calculated, and also a comparison between the various different cross-sections. It was observed that, in the case of variations in material strength and geometric properties within the same section, the shape of the interaction curve depends on the parameter , i.e., it depends on the ratio between the strength of steel and the total strength of the section. A numerical model was also developed to perform a comprehensive analysis of the composite column. In this model a circular cross-section was used, and it compared various combinations of axial and flexural loads (N-M) for columns of different heights with the interaction curve obtained from the calculation program. The primary objectives were to validate the program and investigate the influence and variation of imperfections with height on the total bending moment capacity of the section.
Description
Keywords
Colunas mistas aço-betão Secções bi-simétricas Secções mono-simétricas Eurocódigo 4 Curvas de interação Modelo numérico Steel-concrete composite columns Bi-symmetric sections Mono-symmetric sections Eurocode 4 Interaction Curves Numerical model