Evaluation of the Equivalent Slip Modulus of Nailed Connections for Application in Linear Analysis of Plywood Timber Beams

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)The study of the stiffness of laterally loaded semi-rigid connections in plywood-timber beams is justified by the influence that the deformation of the connection has on the overall displacements of the structure. Semi-rigid connections are characterized by the occurrence of a slip between the connected pieces. The characterization of a connection is usually based on an isolated single connector behavior, which is described by its load-slip relationship expressed by the slip modulus, and so it is extended to the group of connectors. Although the method of analysis is well established, the concept of equivalent slip modulus, defined as the slip modulus per unit length of a connection, has not been totally explored. In this study, we focus on the experimental determination of the equivalent slip modulus for mechanically analyzing plywood-timber beams with continuous connections. The results demonstrated that the test is suitable for obtaining experimental values of the equivalent slip modulus.112151157Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [00/00953-8

Wooden framed structures with semi-rigid connections: Quantitative approach focused on design needs

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Mechanical connections are recognized as extremely important elements in the aspect of strength and structural safety. However, classical structural model does not consider the connection stiffness properties, and are based oil models with pinned or rigid joints only. In fact, mechanical connections are deformable and behave not linearly, affecting the whole structure and inducing nonlinear behavior as well. The quantification of this effect, however, depends oil the description of the working of the connectors and the wood response under embedment. The theoretical modeling of wood Structures with semi-rigid connections involves not only the structural analysis, but also the modeling of both single and grouped moment resisting connectors and the study of the wood properties under embedment. The proposal of this paper is to approach these aspects, and to quantitatively study the influence of the moment resistant connection in wooden framed Structures. Comparisons between rigid and semi-rigid connections and between linear and nonlinear analysis lead to quantitative results.313315331Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [00/00953-8

Determination of Poisson's ratios in relation to fiber angle of a tropical wood species

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)This study examines the numerical variation of Poisson's ratio with fiber direction for the tropical wood species Goupia glabra, whose products have significant applications in civil construction. Knowledge of mechanical properties is necessary when applying numerical methods to wood structure design, especially large-span structures, such as bridge structures with orthotropic plates. A theoretical elastic rectilinear orthotropic model with three principal directions of elasticity: longitudinal (L), radial (R), and tangential (T) has been adopted in development of this study. To determine Poisson's ratios and their values, compression tests are performed on small prismatic test specimens. The numerical variation in two principal planes of elasticity, LR and LT, is verified. The results from both experimental tests and an orthotropic model approach are compared. The average differences between the theoretical and experimental values for the Poisson's ratios are in the range of 2-15%, except for the angle 75 for the plane LT and for the angle 90 for the both planes. Considering wood's heterogeneity and anisotropic behavior, the results of Poisson's ratios indicate a satisfactory fit. In general, such results provide numerical information on this elastic parameter of a tropical wood species, extensively used in construction. (C) 2013 Elsevier Ltd. All rights reserved.41691696Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPESP [2004/15481-5]CNPq [301504/2004-0

COMPARISON BETWEEN TSAI-WU FAILURE CRITERION AND HANKINSON'S FORMULA FOR TENSION IN WOOD

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)For wood a material with anisotropic characteristics and strength asymmetry, Hankinson's formula was the first successful expression to predict the strength in non-parallel orientation to the grains. However, with the emergence of new materials, with directional properties, there was a need to formulate broader failure criteria. One of these criterions is Tsai-Wu's general failure theory for anisotropic materials. This research seeks to investigate the use of this failure criterion for wood, considering its directional properties. The failure parameters of Tsai-Wu criterion were determined from uniaxial tension and compression in specimens of the wood species Goupia Glabra, at inclined directions with respect to the fibers (15 degrees, 30 degrees, 45 degrees, 60 degrees, 75 degrees), shear and biaxial compression test. The estimates of Tsai-Wu criterion are compared to the values from Hankinson's formula. The results were in general appropriate and thus reveal an interesting way to be followed for future research.564499510Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [2004/15481-5

Study of concrete-timber composite beams using an analytical approach based on the principle of virtual work and experimental results

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Composite structures have been used in construction as an alternative to conventional structures, providing reduced costs, environmental benefits and maintaining structural safety. The mechanical performance of a composite structure depends, in general, on the efficiency of the connection. A composite interface is designed to transmit shear longitudinal forces at the interface between the two materials along the length of the structure and, at the same time, to prevent vertical detachment. This study contributes to the analysis of the mechanical behavior of concrete-timber composite beams with an emphasis on determining the vertical displacements by solving a set of analytical equations that describe the equilibrium system, using a finite element program and, in special, the principle of virtual work. The latter approach was developed based on the theory of structures to address to systems of composite beams. The proposed formulation is self-consistent, and the results agree well with the experimental data from tested beams. (C) 2012 Elsevier Ltd. All rights reserved.46302310Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Finite element analysis of stress-related degrade during drying of Corymbia citriodora and Eucalyptus obliqua

With the use of experimental wood properties and input moisture content field data, a predictive 3D stress–strain finite element analysis (FEA) model was developed allowing to predict the development of stress-related end splitting and surface checking degrade during conventional and vacuum wood drying. Simulations were carried out for two Australian hardwood species, messmate (Eucalyptus obliqua) and spotted gum (Corymbia citriodora), as these species contrast, in terms of wood properties, drying rates and stress degrade susceptibility. The simulations were performed using a 1/8 symmetry model where the full board dimensions are 1900 mm long × 30 mm thick × 100 mm wide. Moisture content field data model simulations were utilised in a three-dimensional FEA model by extruding a 2D moisture content field computed in the T–L plane across the radial direction to create a 3D model. Material mechanical properties and shrinkage were calculated in relation to moisture content, over discrete time intervals, using a quasi-static solver. End split failure was investigated at the board end, and surface check failure at the board surface, using a Tsai–Wu failure criterion. Simulations showed that messmate was more susceptible to end splitting than spotted gum and that conventionally dried messmate was more susceptible to surface checking than vacuum-dried messmate. The same results were observed from drying trials. The locations of predicted surface check failure also matched drying trials and are compared