After the production cycle of latex, Hevea brasiliensis trees become residual living plants for this activity, although their woody trunks are still potentially subject to industrial utilization. Bio-composites derived from rubberwood particles were manufactured using two different configurations as a strategy to examine the potential of this species with respect to mechanical behavior. Homogeneous panels were developed from particles at the saturation condition, and heterogeneous panels were obtained from dry particles conditioned at 12% moisture content. Both examples were heat-pressed and glued with castor oil-based polyurethane resin. Density,short-term water absorption and thickness swelling, modulus of rupture and modulus of elasticity in the static bending and perpendicular tensile were evaluated. Panels derived from rubberwood particles proved to be viable according to the technical standards.
This paper compares two concepts of composite timber concrete ceilings and their uncoupled alternatives based on a parametric study by comparing the final deflections of individual variants and at the same time considering according to the ultimate limit state. It includes a comparison of coupled and uncoupled variants while maintaining the same boundary conditions as the load, the thickness of the ceiling structure and the load width. By considering other factors, we can achieve more optimal variant, thanks to more accurate consideration of the required boundary conditions such as the complexity of installation or fire resistance. The purpose of this paper is to simplify the optimal selection of the ceiling structure based on the suitability of the supporting structure.
The issue of behavior and deformation of joints of wooden structures is an integral part of the design of timber structures in its entirety. In this article the attention is therefore devoted to joints of timber structures. For testing there were selected joints with glued-in steel rods. These joints are currently, due to the frequent requirement for invisibility of joints in structures, at the forefront of interest. The content of this paper is therefore testing of these joints and determination of their carrying capacity and describing the type of deformation under load. These tests were carried out on a pressure machine EU100 in the laboratory of the Faculty of Civil Engineering VSB-TU Ostrava. The results of the laboratory tests have been statistically evaluated and accompanied by the graphical records of deformation response to loading. Comparison of test carrying capacity results with values determined from calculation according to the current applicable European standard for design of timber structures and numerical modeling are also presented.
The article deals with research of joints with glued-in threaded rods. The introduction provides a brief presentation of the issue. The first part focuses on axially loaded glued-in threaded rods. The second part explains the behaviour of joints with glued-in rods loaded by bending moment. Theoretical analysis was performed on models based on the finite element method. Verification of theoretical results was realized by practical experiments. Tensile tests were carried out on timber blocks with glued-in bars to verify the depth of affixing. Furthermore, the resistance in bending was confirmed on actual beams with glued-in bars in the middle of the span. Results and the follow-up work are summarized in the conclusion.
The content of this article is to analyse destructive testing results of longitudinal solid wood joints of structural size beams with internal and external glued wood-based panels (plywood) stressed in bending, which was mostly focused on simulating the effect of the glued line thickness (1 and 3 mm) and the influence of contact surfaces of longitudinally connected elements when bending loads. The aim of this article is to compare the carrying capacity and the joint real behaviour under load with values obtained using numerical modelling and calculation according to valid standards.
There are simplified and advanced design methods for the determination of the mechanical resistance of timber structures in fire. The simplified methods have some limitations and in case it is not possible to use the simplified methods, it is necessary to use the advanced ones. These advanced design methods can be analytical or numerical. This contribution deals with the determination of the one-dimensional charring rate depending on time by advanced calculations, focusing on the influence of different input parameters, with the results of an experiment being presented for comparison. The aim of this paper is to show that despite the suitability and conservativeness of the method according to Eurocode 5, there are various cases (different moisture, wood species etc.) when it is necessary to perform numerical or analytical analyses without the possibility to apply standard input parameters. Therefore, this contribution compares individual methods for finding of the most appropriate one.
The aim of this work is the probabilistic modeling of the failure of Lovoa trichilioides and Triplochiton scleroxylonspecies. A general presentation of the wood while focusing on the Weibull distributions was carry out. Parameters of the Weibull distribution for each of the materials were determined. We remark that when the Weibull shape parameter is small, the failure stresses dispersion is greater and the Weibull scale parameter increase or decrease depending on the stress. It is also shown that Lovoa trichilioides exhibits a high dispersion of breaking stress in contrast to Triplochiton scleroxylon. A comparison of the experimental data with the statistical laws allowed us to show that the three-parameter Weibull distribution better models the failure than the normal and the two-parameter Weibull distributions. The studies of variance prove that the failure stresses of Triplochiton scleroxylon vary less in comparison with that of Lovoa trichilioides.
Prestressing force and its change is one of the key factors that affect wooden constructions, especially those using methods of transverse prestressing. To achieve a description of a prestress force (P) in transversally prestressed wooden constructions a simulated experiment was done. Prestressing force, external temperature, and moisture were measured during 669 days. The main goal of this article was to model the primary losses of the prestress force at the spruce element of the 138 x 138 mm cross-section with the sensor installed. For this purpose, all measurements were statistically analyzed and the period of primary loss was found. During this period the prestress force was decreasing with time mainly and the influence of temperature and moisture could be omitted. Based on this analysis a mathematical model of losses of the prestress force was found as P = 8.538-0.014.day.