Publicação
Influence of the joints stiffness in the monotonic and cyclic behaviour of traditional timber trusses. Assement of the efficaccy of different strengthenning techniques
| Resumo: | Connections are the key element in the behaviour of traditional timber trusses. The overall behaviour and stresses distribution are function of connections strength and stiffness, in particular under non-symmetric loads and extreme events. In these situations, the connections are loaded well beyond their pseudo-elastic limit. Normally, traditional timber connections are assumed as hinges or rigid. However, even without any strengthening device, they have a significant rotational stiffness and may be better classified as semi-rigid and friction-based. It is the misunderstanding of the connections behaviour that normally leads to the replacement of old timber structures, instead of their retrofitting to satisfy safety. In order to better predict and understand the behaviour of timber structures, analytical models of connections are crucial. Semi-rigid models, using nonlinear laws and hysteretic rules, intend to represent the behaviour of timber structures with a comparable level of detail for all the structural components. In this thesis, structural analysis of some full-scale timber trusses is presented. After a primary survey an extensive experimental program, using fullscale connections investigating the monotonic and cyclic behaviours of traditional timber connections, identifying, and evaluating suitable strengthening techniques with metal devices was performed. Based on the test results a numerical analysis over unstrengthened connections was carried out aiming to extend the parameters evaluated through tests. Then, semi-rigid models for the analysis of traditional timber connections are presented. Synthetic laws are calibrated and the tests performed are modelled. Full-scale timber trusses examples were loaded under symmetric and non-symmetric cyclic loads and the test results were compared to the numerical analysis using the semi-rigid models proposed. Two dismantled Italian King-post truss examples were tested and strengthened in laboratory facilities and one Portuguese Queen-post truss example was tested in field conditions. |
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| Autores principais: | Branco, Jorge M. |
| Ano: | 2008 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | português |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | Connections are the key element in the behaviour of traditional timber trusses. The overall behaviour and stresses distribution are function of connections strength and stiffness, in particular under non-symmetric loads and extreme events. In these situations, the connections are loaded well beyond their pseudo-elastic limit. Normally, traditional timber connections are assumed as hinges or rigid. However, even without any strengthening device, they have a significant rotational stiffness and may be better classified as semi-rigid and friction-based. It is the misunderstanding of the connections behaviour that normally leads to the replacement of old timber structures, instead of their retrofitting to satisfy safety. In order to better predict and understand the behaviour of timber structures, analytical models of connections are crucial. Semi-rigid models, using nonlinear laws and hysteretic rules, intend to represent the behaviour of timber structures with a comparable level of detail for all the structural components. In this thesis, structural analysis of some full-scale timber trusses is presented. After a primary survey an extensive experimental program, using fullscale connections investigating the monotonic and cyclic behaviours of traditional timber connections, identifying, and evaluating suitable strengthening techniques with metal devices was performed. Based on the test results a numerical analysis over unstrengthened connections was carried out aiming to extend the parameters evaluated through tests. Then, semi-rigid models for the analysis of traditional timber connections are presented. Synthetic laws are calibrated and the tests performed are modelled. Full-scale timber trusses examples were loaded under symmetric and non-symmetric cyclic loads and the test results were compared to the numerical analysis using the semi-rigid models proposed. Two dismantled Italian King-post truss examples were tested and strengthened in laboratory facilities and one Portuguese Queen-post truss example was tested in field conditions. |
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