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3. Semi-rigid behaviour of plane timber structures

Author

Man, Steve Ka Fai

Subjects
624.184, TA Engineering (General). Civil engineering (General)
Abstract

It is common practice in the analysis of structural frames, to either assume that the joints are pinned or rigid. In fact the real behaviour of a joint is neither pinned nor rigid, and lies somewhere between the pinned and rigid assumption. This is referred to as the semi-rigid behaviour. Semi-rigidity not only refers to the rotational behaviour of the joint as commonly studied, but also in axial and shear actions. The moment distribution between pinned and rigid analysis differs substantially and therefore a more accurate method of modelling the semi-rigid joint is necessary to predict the overall structure response. The level of semi-rigid behaviour varies in different joints due to the material, construction and type of connector. The degree of semi-rigidity can be determined through physical tests. The type of joint for this study is the Metal Plate Connector (MPC) for timber trusses, 6 chosen connector used in residential trusses. An extensive test program was carried out in this study. Four different types of joints of a Queen truss were tested. In addition, the effect of combined loads on the joint characteristics was investigated. The loading arrangement in the tests allowed independent control of the bending moment and axial load. A novel approach is adopted to measure displacement, using high-resolution digital photogrammetry and specially developed software. The data produced gave details of timber movement in cartesian co-ordinates and measurement of plate deformation. From these tests, semi-rigid bending moment and axial stiffness values were determined for use in the theoretical study. An attempt to measure shear stiffness is also presented. Further tests were carried out on full-scale trusses under two different load conditions. The theoretical work comprises two approaches to truss modelling. The first is an automated structural analysis program, which accounts for non-linear semirigid joint characteristics derived from the joint tests using the Foschi power function. The effects of stability and geometrical non-linearity are also implemented into the analysis. The second approach calculates truss response using Finite elements where 2-D planar elements were used to calculate the response of the truss. Parameters for the connection strength are derived from the joint tests. Moment stiffness and axial stiffness values of the connections were determined. Combined load tests showed that there is indeed a measurable effect on joint stiffness and capacity due to combined loads, some of which actually contribute to the stiffness, but also some which are detrimental. There is good correlation between the truss test results and the FE model using semi-rigid joints. However, results of the simpler non-linear frame analysis, did not compare so well, but nevertheless exhibited fundamental characteristics of the truss.

Published
2004

4. Produção e caracterização mecânica de painéis de cross laminated timber (CLT) para aplicação como placas de piso

Author

Ecker, Taienne Winni Paiz, Miotto, José Luiz, Rigobello, Ronaldo, Góes, José Luiz Nunes de, Universidade Estadual de Maringá, Centro de Tecnologia, Departamento de Engenharia Civil, and Programa de Pós-Graduação em Engenharia Civil

Subjects
Estruturas de madeira, Cross laminated timber (CLT) - Análise experimental, Madeira laminada colada cruzada (MLCC), Cross laminated timber (CLT) - Elemento estrutural, 624.184, Engenharias, Engenharia Civil
Abstract

Orientador: Prof. Dr. José Luiz Miotto Dissertação (mestrado em Engenharia Civil)--Universidade Estadual de Maringá, 2017 Resumo: O desenvolvimento sustentável na construção civil é um tema que está em ascensão, e devido esse setor ser responsável por enormes impactos ambientais, a busca por soluções que visam atenuar esses impactos é de suma importância. Com isso, apresentam-se como alternativa sustentável os painéis de Cross Laminated Timber (CLT), um produto composto por camadas de lamelas de madeira coladas transversalmente às camadas adjacentes, que pode ser utilizado tanto como elemento de laje quanto de parede, permitindo a construção de edificações com múltiplos pavimentos. Por ser um produto recente no mercado, é primordial a realização de estudos referentes ao seu desempenho estrutural, a fim de que seu emprego na construção civil possa ser feito com economia e segurança. Com isso, neste trabalho analisou-se o desempenho de painéis de CLT para utilização como placa de piso, formados por três camadas ortogonais de lamelas de madeira de pinus, ligadas por adesivo poliuretano monocomponente, através de ensaios de flexão e cisalhamento realizados com base na norma ASTM 198:2009, conforme solicitado pela ANSI/APA PRG 320:2012. Avaliou-se, também, a eficiência da colagem das lamelas por meio da variação da quantidade de adesivo aplicado nos ensaios de flexão. Para o ensaio de cisalhamento foram produzidos 12 painéis com quantidade de adesivo correspondente a 200 g/m². Já para o ensaio de flexão foram produzidos 12 painéis com diferentes quantidades de adesivos, sendo elas, 120 g/m², 160 g/m² e 200 g/m². Por meio dos resultados obtidos, pode ser observada a relação do módulo de elasticidade dos painéis com o módulo de elasticidade das lamelas utilizadas para sua produção. Além disso, evidencia-se a influência da quantidade de adesivo aplicada no desempenho mecânico dos painéis de CLT e recomenda-se um consumo de adesivo igual ou superior a 200 g/m², para melhor desempenho dos painéis. Os painéis testados à flexão, produzidos com uma quantidade de adesivo correspondente a 200 g/m², exibiram valores médios de 34,21 MPa para o módulo de ruptura e 10.200 MPa para o módulo de elasticidade, similares aos requeridos pela norma ANSI/APA PRG 320:2012 Abstract: Sustainable development is a rising topic, and the construction industry being a great responsibility for carrying considerable environmental impacts, the pursuit for solutions aimed at mitigating these impacts is of paramount importance. As a sustainable alternative, Cross Laminated Timber (CLT) panels, a product composed of layers of lamellae glued transversely to the adjacent layers, can be used as a slab or wall element, allowing the construction of multifloor buildings. Being a recent product on the market, it is essential to carry out studies related to its structural performance, so that its application in the construction industry can be done economically and safely. In this work, the performance of CLT panels for use as a floor plates, formed by three orthogonal layers of pine wood lamellae, bonded by one-component polyurethane adhesive, were evaluated through bending and shear tests performed based on ASTM 198:2009 standard, as requested by ANSI/APA PRG 320:2012 standard. It was also evaluated the efficiency of the lamella bonding by varying the amount of adhesive applied in the bending tests. Twelve panels with a quantity of adhesive corresponding to 200 g/m² were produced for the shear tests, while for the bending test 12 panels were produced with different quantities of adhesives, which were 120 g/m², 160 g/m² and 200 g/m². Through the obtained results, it is observed the panels modulus of elasticity compared with the modulus of elasticity of the lamellae used for its production. Furthermore, it is evident the influence of the amount of adhesive applied in the mechanical performance of the CLT panels and is recommended an adhesive consumption equal to or greater than 200 g/m² for improved performance of the panels. The bending tested panels produced with 200 g/m² of adhesive displayed average values of 34.21 MPa for the modulus of rupture and 10.200 MPa for the modulus of elasticity, similar to those required by ANSI/APA PRG 320:2012 standard

Published
2017

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