Second-order behavior and carrying capacity of 3D asymmetric steel frames with bracing elements

Non-linear P-delta behavior of three-dimensional frames with plan and elevation asymmetries is studied, using a parametric variation of geometry in plan and a stiffness variation along the height. Some behavioral aspects of a calibration frame have been addressed to ascertain the importance of the nodal rigidity (modeled with laminar elements of the type shell with implicit formulation of thick plate or modeled with elastic stiff springs) in the modeling of the geometric non-linearity and stability of such calibration frame. Eurocode 3 criteria for second order analyses is briefly addressed in connection with the 2D frame classification with respect to sway behavior; however for 3D structures the calculated carrying capacity is independent of this classification. So a parametric study of the critical load factor of asymmetric three dimensional frames, unbraced and braced, permits to characterize their carrying capacity with respect to overall structural stability.info:eu-repo/semantics/publishedVersio

Simplified methods to obtain efforts in the joint lines of metal connectors of wood truss

This paper presents a simplified method to obtain the distributions efforts in the joint lines in a wood truss node connected by metal plates fasteners, as function on the efforts transferred by each wooden element to the connection node. Although this verification is simple to solve in cases of simple joint geometries and/or symmetrical loading in relation to the node. The problem becomes complex in cases where the connection is composed of more than one joint line, without axis of symmetry and/or cases in which the loads are not symmetrical in relation to the node. This work aims to verify and compare three method to obtain the distribution efforts in the joint lines. Method 1 is based on the static balance between the efforts in anchors and their distribution over the adjacent joint lines. Method 2 (fictitious line) was presented to obtain the distributions efforts in the rupture lines from the distribution of efforts into composite lines (ensuring the balance of efforts on the fictitious line and the transmission of these efforts to the various rupture lines). Method 3 (obtaining the distribution by numerical models, in this case the MEF) allows to obtain the distribution along the line(s) for any configuration and composition of this(s), in addition it also allows to introduce the real stiffness of the plate and consequently a more realistic deformation/stress. The checks are carried out through Eurocode 5 EN 1995-1-1: 2004 [1] and through the CSI (Combined Stress Index), which represents the structural efficiency, in order to conclude the veracity of the method.info:eu-repo/semantics/publishedVersio

Computational modeling of joint lines in punched metal plate fasteners

Punched metal plate fasteners (nail plates) are currently the top choice in the wooden-truss industry because of its high mechanical capacity and easy automated assembly. Here, a computational modelling is proposed to evaluate the force distribution within the plate’s anchorage area and in the rupture lines, a structural system that in most cases is highly hyperestatic and does not feature an analytical solution. This method can be applied to areas with multiple gaps (rupture lines) and therefore its analysis is discussed from a quantitative and qualitive point of view.info:eu-repo/semantics/publishedVersio

Simplified methods to obtain efforts in the joint lines of metal connectors of wood truss

This paper presents three simplified methods to obtain the distributions efforts in the joint lines in a wood truss node connected by metal plates fasteners, as function on the efforts transferred by each wooden element to the connection node. Although this verification is simple to solve in cases of simple joint geometries and/or symmetrical loading in relation to the node. The problem becomes complex in cases where the connection is composed of more than one joint line, without axis of symmetry and/or cases in which the loads are not symmetrical in relation to the node. This work aims to verify and compare three methods to obtain the distribution efforts in the joint lines. Method 1 is based on the static balance between the efforts in anchors and their distribution over the adjacent joint lines. Method 2 (fictitious line) was presented to obtain the distributions efforts in the rupture lines from the distribution of efforts into composite lines (ensuring the balance of efforts on the fictitious line and the transmission of these efforts to the various rupture lines). Method 3 (obtaining the distribution by numerical models, in this case the MEF) allows to obtain the distribution along the line(s) for any configuration and composition of this(s), in addition it also allows to introduce the real stiffness of the plate and consequently a more realistic deformation/stress. The checks are carried out through Eurocode 5 EN 1995-1-1: 2004 [1] and through the CSI (Combined Stress Index), which represents the structural efficiency, in order to conclude the veracity of the method.info:eu-repo/semantics/publishedVersio

Computational modeling and parametric study of pile groups

Geotechnics and the study of the behavior of soil with the construction inserted in it is of extrema importance. This study aims at the computational analysis of a group of three rein- forced concrete piles with axial and horizontal loads. The piles were inserted in non-cohesive soil (medium and dense sand). The geometric parameters of the piles (diameter, distance be- tween them, and length) and physical parameters of the soil (stratification and angle of fric- tion between them) were varied. The GEO5 "Pile Group" program, the NAVFAC DM 7.2 method was used to determine the bearing capacity. The Poulos & Davis (1980) and FEM methods for settlement, and the p-y method (FEM) to determine the internal forces distribu- tion. The efficiency of the piles is more sensitive the more the distance between them varies. For settlement, Poulos & Davis values are sensitive to distance and diameter, and in FEM they are more sensitive to diameter and length variation.info:eu-repo/semantics/publishedVersio

Desempenho não linear geométrico de pórticos metálicos contraventados sob acções verticais

A necessidade da utilização de contraventamentos em estruturas porticadas tridimensionais obriga a uma selecção criteriosa, por parte do projectista, das dimensões e da localização dos elementos estruturais de forma a garantir melhoria do comportamento local e global, assim como uma economia do material estrutural utilizado. Numa primeira análise estudam-se pórticos planos contraventados e relaciona-se a variação de vários parâmetros (comprimentos, inércias e áreas) com o comportamento da estrutura face às acções verticais. Uma vez que as estruturas reais apresentam configurações tridimensionais, o passo seguinte consiste na determinação das relações existentes entre os pórticos que constituem a estrutura e o seu desempenho, em função dos sistemas de contraventamento adoptados. Para proceder a comparações recorreu-se à utilização de um software de cálculo automático (INST3D) baseado numa formulação exacta das matrizes de rigidez através das funções de estabilidade de Livesley e Chandler e que, através da equação matricial incremental de equilíbrio, permite obter os parâmetros críticos para as diversas configurações estudadas. Finalmente através de um estudo paramétrico, conclui-se qual a melhor solução a adoptar para cada estrutura analisada e apontam-se conclusões que melhor se adaptam ao pórtico (2D ou 3D) em estudo.info:eu-repo/semantics/publishedVersio

Desempenho não linear geométrico de pórticos metálicos 3D assimétricos

Neste trabalho estuda-se a importância de vários parâmetros na análise geometricamente não linear (2ª ordem) de pórticos metálicos 3D. Este estudo visa identificar as variáveis que condicionam o desempenho não-linear geométrico das estruturas analisadas e, assim, possibilitar uma maior carga de instabilidade global. Com base nos estudos paramétricos efectuados conclui-se qual a situação estrutural, incluindo disposição dos contraventamentos, que maximiza a capacidade resistente da estrutura relativamente ao modelo de análise não-linear geométrica utilizado.info:eu-repo/semantics/publishedVersio

Modelos de comportamento não linear geométrico de pórticos assimétricos tridimensionais

Neste trabalho pretende-se relacionar o comportamento não linear geométrico de pórticos tridimensionais com configuração irregular em planta, admitindo a variação de parâmetros geométricos e de rigidez previamente escolhidos, através da comparação entre os resultados obtidos com software desenvolvido pelos autores e com software comercial. A utilização da formulação da matriz de rigidez no software desenvolvido permite aferir o seu grau de precisão, face aos softwares comerciais utilizados. O estudo determina comparativamente o factor de carga para cada caso, e poderá permitir desenvolver tabelas e gráficos que traduzam de forma simplificada a melhor solução para cada configuração das estruturas tridimensionais analisadas.info:eu-repo/semantics/publishedVersio

Avaliação das frequências verticais de vibração em pontes em arco de pedra através de medições in-situ

As pontes de alvenaria são geralmente estruturas antigas com valor histórico e patrimonial, construídas com base em conhecimentos empíricos para um nível de tráfego consideravelmente diferente daquele que hoje se verifica em estruturas deste tipo. Considerando a grande preocupação da engenharia moderna de evitar o fenômeno da ressonância, o estudo das propriedades dinâmicas dessas estruturas é fundamental, pois permitirá conhecer seu comportamento frente aos carregamentos dinâmicos impostos à estrutura. O presente estudo baseia-se na determinação de parâmetros dinâmicos, nomeadamente frequências próprias associadas aos modos de vibração vertical para um conjunto de trinta e três pontes de arco de alvenaria localizadas no distrito de Bragança, Portugal. Esses parâmetros foram obtidos através de ensaios de vibração ambiental realizados in-situ e a identificação das próprias frequências foi realizada no domínio da frequência utilizando a técnica peak-piking. A identificação das frequências próprias permitiu comparar a influência de alguns parâmetros geométricos das pontes e sua relação e aproximação com a faixa de frequência da fonte de excitação, sendo que 36,36% das pontes apresentam frequências na faixa de frequência naturais dos veículos.info:eu-repo/semantics/publishedVersio

Direct shear tests: experimental setup based on a labview approach - experimental results in a silty sand soil

This work describes an experimental setup that was developed in order to automate the direct shear tests, with the objective of characterizing the mechanical resistance of the soil. This experimental setup ensures repeatability and automation in data acquisition, avoiding human errors, mainly when the test data vary with high dynamics. The described setup is based on LabVIEW approach, LVDT sensors and a 16-bit data acquisition board. For the direct shear test, the procedures guided by ASTM D-3080/D-3080M-11 "Standard Method for Direct shear Tests on soils under Consolidated Drained Conditions". This paper exposes the applicability study of the direct shear test to an existing silty sand soil, from the city of Bragança-Portugal, in order to verify the applicability of this test with the instrumented apparatus. The results obtained and the main conclusions are presented.info:eu-repo/semantics/publishedVersio