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Müller Ulrich Ringhofer Andreas Brandner Reinhard Schickhofer Gerhard 《Wood Science and Technology》2015,49(6):1123-1136
Wood Science and Technology - Several studies have dealt with the problem of how to measure the shear modulus of small clear wood specimens, avoiding bias from normal compression, bending, tension... 相似文献
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Tensile strength perpendicular to grain constitutes one of the most vulnerable properties of timber. Due to versatile influencing parameters this property exhibits a high amount of uncertainty. Thus, progress in modeling, in particular by considering stochastics, is seen as worthwhile. This increases the reliability estimates of timber constructions but also their economic efficiency. Test data of tensile properties determined on consecutive board segments of Norway spruce are analyzed. The data consists of four subgroups, classified in regard to segment length and radial position within the log. The correlation in longitudinal direction of perpendicular to grain tensile strength and elastic modulus as well as of density is examined. This is done depending on the radial position of structural timber within the log. A second-order hierarchical model together with equicorrelation is used. The results outline the applicability of the model and allow the quantification of equicorrelation coefficients of all three properties. The outcome provides a valuable and necessary input for state-of-the-art mechanics-stochastic modeling of the resistance perpendicular to grain tensile strength and elastic modulus of unjointed and jointed structural timber, but in particular of products available in large dimensions, like glued and cross-laminated timber. Additionally, the spatial correlation of density is discussed which is seen as worthwhile for the estimation of group action of fasteners. The necessity to differentiate between the variability within and between segments of structural timber is clearly demonstrated. 相似文献
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Reinhard Stürzenbecher Karin Hofstetter Gerhard Schickhofer Josef Eberhardsteiner 《Wood Science and Technology》2010,44(2):205-223
The interrelationships between microstructural characteristics and anisotropic elastic properties of strand-based engineered
wood products are highly relevant in order to produce custom-designed strand products with tailored properties. A model providing
a link between these characteristics and the resulting elastic behavior of the strand products is a very valuable tool to
study these relationships. Here, the development, the experimental validation, and several applications of a multiscale model
for strand products are presented. In a first homogenization step, the elastic properties of homogeneous strand boards are
estimated by means of continuum micromechanics from strand shape, strand orientation, elastic properties of the used raw material,
and mean board density. In a second homogenization step, the effective stiffness of multi-layer strand boards is determined
by means of lamination theory, where the vertical density profile and different layer assemblies are taken into account. On
the whole, this model enables to predict the macroscopic mechanical performance of strand-based panels from microscopic mechanical
and morphological characteristics and, thus, constitutes a valuable tool for product development and optimization. 相似文献
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Development of high-performance strand boards: engineering design and experimental investigations 总被引:1,自引:0,他引:1
Reinhard Stürzenbecher Karin Hofstetter Thomas Bogensperger Gerhard Schickhofer Josef Eberhardsteiner 《Wood Science and Technology》2010,44(1):13-29
Strand-based engineered wood products such as oriented strand boards enjoy great popularity in structural engineering and
are widely used for a variety of applications. To strengthen their competitiveness and to enlarge their range of utilization
particularly in the load-bearing sector, the mechanical properties of these products need to be improved. This motivated the
research efforts to use large-area, slender veneer strands for the production of strand boards with increased stiffness and
strength. Target-oriented development of these products requires comprehending the effects of the relevant (micro-)characteristics,
such as wood quality, strand geometry, and strand orientation and compaction during the production process, as well as layer
assembly and density profile, on the mechanical properties of the finished strand boards. Comprehensive test series, in which
these effects on tension, bending and shear properties of the boards have been studied individually, are presented in this
paper. The obtained results provided insight into the microstructural load-carrying mechanisms and, thus, yielded valuable
knowledge for product optimization and further improvement of custom-designed strand-based engineered wood products. 相似文献
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