Mechanical behaviour of wood T-joints. Experimental and numerical investigation

Results of a double-shear single-dowel wood connection tested under monotonic quasi-static compression loading are presented and discussed in this paper. The wood used in this study was a pine wood, namely the Pinus pinaster species, which is one of the most important Portuguese species. Each connection (specimen) consists of three wood members: a centre member, loaded in compression along the parallel-tograin direction and two simply supported side members, loaded along the perpendicular-to-grain direction (Tconnection). The load transfer between wood members was assured by means of a steel dowel, which is representative of the most common joining technique applied for structural details in wooden structures. The complete load-slip behaviour of the joint is obtained until failure. In particular, the values of the stiffness, the ultimate loads and the ductility were evaluated. Additionally, this investigation proposed non-linear 3D finite element models to simulate the T-joint behaviour. The interaction between the dowel and the wood members was simulated using contact finite elements. A plasticity model, based on Hill’s criterion, was used to simulate the joint ductility and cohesive damage modelling was applied to simulate the brittle failure modes (splitting) observed in the side members of the joint. The simulation procedure allowed a satisfactory description of the non-linear behaviour of the T-joint including the collapse prediction

Mechanical behaviour of wood T-joints. Experimental and numerical investigation

Results of a double-shear single-dowel wood connection tested under monotonic quasi-static compression loading are presented and discussed in this paper. The wood used in this study was a pine wood, namely the Pinus pinaster species, which is one of the most important Portuguese species. Each connection (specimen) consists of three wood members: a centre member, loaded in compression along the parallel-tograin direction and two simply supported side members, loaded along the perpendicular-to-grain direction (Tconnection). The load transfer between wood members was assured by means of a steel dowel, which is representative of the most common joining technique applied for structural details in wooden structures. The complete load-slip behaviour of the joint is obtained until failure. In particular, the values of the stiffness, the ultimate loads and the ductility were evaluated. Additionally, this investigation proposed non-linear 3D finite element models to simulate the T-joint behaviour. The interaction between the dowel and the wood members was simulated using contact finite elements. A plasticity model, based on Hill’s criterion, was used to simulate the joint ductility and cohesive damage modelling was applied to simulate the brittle failure modes (splitting) observed in the side members of the joint. The simulation procedure allowed a satisfactory description of the non-linear behaviour of the T-joint including the collapse prediction

Sombreamento de cafeeiros durante o desenvolvimento das gemas florais e seus efeitos sobre a frutificação e produção Shading of coffee plants during floral buds development and its effects on fructification and production

O objetivo neste trabalho foi avaliar a influência do sombreamento, durante o período de desenvolvimento de gemas florais, sobre o desenvolvimento e maturação dos frutos, produção e tamanho dos grãos de Coffea arabica L. O experimento foi conduzido com cafeeiros adultos no Município de Londrina, os quais foram sombreados nos meses de abril, maio, junho, julho e agosto de 2004, com malhas de sombrite com 50% de sombreamento. As coberturas foram retiradas, simultaneamente, no início de outubro do mesmo ano. A interceptação de 50% da radiação incidente sobre o dossel dos cafeeiros em diferentes épocas do desenvolvimento de gemas florais não alterou o crescimento e o desenvolvimento dos frutos. As altas temperaturas e a deficiência hídrica anteciparam a maturação dos frutos, porém sem diferenças significativas nos estádios de maturação entre os tratamentos. O sombreamento, em diferentes épocas, também não afetou a produção e o tamanho dos grãos.<br>The objective of this paper was to evaluate the influence of shading during the period of floral buds development on the growth and maturation of coffee fruits, production and grain size of Coffea arabica L. The experiment was carried out in Londrina, PR, Brazil. Plots of adult coffee plants were shaded monthly in April, May, June, July and August of 2004 using shading screens with 50% of porosity. The coverings were removed simultaneously at the beginning of October of the same year. The interception of 50% of incident radiation over the coffee canopy in different periods of floral buds development did not alter fruit growth and development. Fruit maturation was anticipated due to high temperatures and water deficit, however without significant differences on maturation periods among treatments. Grain yield and size were not affected by shading in the different periods

Dificuldades no desenvolvimento da lectoescrita: o papel das habilidades metalinguísticas

Este estudo investigou a relação entre habilidades metalingüísticas (consciência fonológica e sintática) e desempenho na leitura e na escrita (ortografia) de palavras isoladas. Foram formados três grupos de sujeitos: 20 crianças com dificuldades em leitura e escrita, cursando 3ª e 4ª séries (grupo 1); 20 crianças da 1ª série, com o mesmo nível de leitura e escrita dos sujeitos do grupo 1 (grupo 2) e 20 crianças da 3ª e 4ª séries, com a mesma idade cronológica dos sujeitos do grupo 1 (grupo 3). Esperava-se que o grupo 1 apresentasse escores inferiores nas habilidades metalingüísticas, quando comparado aos outros grupos. A hipótese foi confirmada apenas para os escores em consciência fonológica. Em relação à consciência sintática, não se observou diferença significativa entre os grupos 1 e 2, os quais tiveram um desempenho inferior ao do grupo 3. Os resultados mostraram que as dificuldades em leitura e escrita estão relacionadas predominantemente com problemas de natureza fonológica