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In this paper a new method for the derivation of settings for grading machines is proposed based on the fulfillment of basic statistic principles of regression, as well as the assumption that the distribution of the non-destructive indicating property of the machine and the model residuals are known. A system is introduced to quantify the uncertainty of the observations with the actual population they should describe. To verify the method the theoretical distribution of assigned strength grades is constructed together with a 90% confidence interval over which the destructive observations are expected. The strength grading system in Europe is based on strength, stiffness and density. Although in some cases stiffness or density may be the governing property this paper will focus on the case that the bending strength is the governing grade determining property. In this paper the principle of the proposed method is explained on simulated data and afterwards verified on real data for strength only. This shows good application for uses in practice. The verification showed that an incorrect combining of samples gives inaccurate settings for the intended grading area. With the proposed method the variation between samples can easily be taken into account. [ABSTRACT FROM PUBLISHER]

Recent research in Europe is bringing a wider range of wood species to the construction market as structural timber and glue laminated products. This option would also open markets for currently underused UK species, foremost hardwoods, but testing efforts when developing strength grading assignments for any minor UK species are prohibitive, as the resource is small and scattered. Grading approaches that require less material for destructive testing could be employed to open routes to market for structural hardwood products. In addition, the European hardwood research has been revealing some gaps and uncertainties in grading standards. In particular, data are lacking to support adjustment equations for size, moisture content, and testing arrangement for hardwoods. This paper outlines a new PhD project that will focus on these problems and aims to develop an easier route for strength grading hardwoods. [ABSTRACT FROM AUTHOR]

This work presents the results of a numerical investigation on the effect of light timber retrofit systems on the global response of URM cavity-wall buildings. The building object of the study is a two-storey cavity-wall terraced house, retrofitted with OSB panels and timber frames. The Applied Element Method, was chosen for the numerical analyses. Numerical models, calibrated on experimental data of both retrofitted and non-retrofitted walls, were validated through the simulation of a shake-table test of a full-scale retrofitted specimen. A parametric study was then conducted to investigate the influence of different retrofit layouts on the building's global seismic response. [ABSTRACT FROM AUTHOR]

The application of frequency-resonance method (FRM) for precise log bending testing is limited by complex geometry; usually the cone with variable cross. This case study presents the relationship among non-destructively tested material parameters of sugar maples and the numerical analysis of effect of simplifications in FRM. Four standing stems were measured to find basic geometry parameters, 3D scanned for precise geometry description, tested by pulling test (PT) to obtain elastic parameters, and, finally, cut down to process the logs. Four logs were measured by stress wave propagation (SWP) using an acoustic tomography (AT) device to obtain longitudinal sound velocities and then evaluated by the FRM to obtain natural frequencies in bending and longitudinal vibrations. Comparison was made between the dynamic moduli of elasticity (MOE), calculated from SWP and the FRM, and the static MOE calculated from the PT. In-situ experimental evaluation was accompanied by modal analysis by finite element method (FEM) working at three levels of geometry simplification (beam model, simplified solid model, and scan-based solid model); the natural frequencies of bending and longitudinal mode shapes were analyzed. The influence of geometry precision on the resulting dynamic response of logs was found regarding comparison to the experimental values. [ABSTRACT FROM AUTHOR]

Wood has a very high variability compared to other construction materials. Such variability may be more important in the Congo Basin forest, in which hundreds of species are regularly exploited for trading in international markets. Reducing such a variability in construction applications is a major challenge since the characteristic values of strength properties may have penalizing effects on wood. The main objective of this work was to specify the mechanical strength variability of tropical timber species from the Congo Basin. Eighty-nine timber species were considered. Their mechanical properties were derived from small and clear specimen. The first step of the study consisted in identifying the mechanical groups in which the timber species may be assigned, by using the principle of variance's decomposition. In the second step, the Monte-Carlo simulations were used in order to quantify the variability of the strength properties for each species. We found that the strength of the timbers can be organized in six distinct groups. The variability analysis revealed with a more precise information, the potential of the timber species to be assigned simultaneously to several strength categories. Potential applications may concern reliable and interchangeable uses of tropical timber species and a more efficient processing and grading. [ABSTRACT FROM AUTHOR]

Copyright of China Forest Products Industry is the property of China Forest Products Industry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The present research work had the goal of assessing the use of ultrasound for determining the physical-mechanical properties of clear wood in Eucalyptus camaldulensis from a 5-year-old forest stand located in the municipality of Sinop, Mato Grosso State, Brazil. The selection of trees was carried out according to the diameter at breast height (DBH) and height (H). Forty trees were harvested and a 2 m long log was obtained from each tree for the assessment of physical-mechanical properties. In physical properties, the specific gravity, shrinkage (radial, tangential and volumetric) and anisotropic factor were determined. The dynamic modulus of elasticity (MOE) was estimated by ultrasound applied in the longitudinal direction of the samples. The highest correlation with the mechanical test results was found for dynamic MOE, with R2 values in the range of 0.30–0.75. Wood density was highly positively correlated with the dynamic MOE of the wood. The use of ultrasound as a non-destructive method was feasible to determine the selected physical-mechanical properties of Eucalyptus camaldulensis wood as a function of propagation speed and the MOE dynamic in most of the assays. [ABSTRACT FROM AUTHOR]

The usage of hardwoods for engineered wood products, such as glulam, requires defined mechanical properties reflecting the actual tensile strength of the material. Currently, the European strength class system EN 338 only covers profiles for hardwoods tested in bending. In this study, the material properties of medium-density hardwoods are analysed with the focus on a total of 3663 European ash (Fraxinus excelsior) and European beech (Fagus sylvatica) specimens tested in different loading modes (tension, compression, bending, and shear). The relationships between the material properties—tensile strength, stiffness, and density—are analysed on grouped data of both graded and ungraded specimens. As a result, a tailored ratio of tensile strength to tensile MOE and density is given, which allows to utilize a higher tensile strength of hardwoods (ft,0,k over 30 N/mm²) compared to softwoods. Furthermore, the relationship of the test values and the derived values is checked. The equations for deriving the compression and bending strength from tensile strength are verified based on available data. For tensile and compression strength perpendicular to the grain and for shear strength of both beech and ash, higher strength values than the ones listed in EN 338 are possible. The relationship between the mechanical properties are combined to tensile strength profiles for hardwoods. [ABSTRACT FROM AUTHOR]

Copyright of Bautechnik is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Hardwood is becoming more in focus and more important in timber structures. The natural higher strength increases the potential of timber structures and power to compete with steel or concrete. However, for designing connections, the performance parameters stiffness and load-carrying capacity based on, e.g. embedment strength or withdrawal capacity need to be known but these are less standardized compared to softwood. Since not all types of connections are relevant to be used as high-performing connections in hardwood, structural systems, parameters of connections are summarized and discussed with a focus on relevance for their use in hardwood. For the connection types with glued-in rods and steel dowels, the assembling procedure, the load-carrying capacity and failure behaviour is investigated in relation to the necessary design parameters as a first part of the relevant connections. First, the results of their design and influencing parameters are presented, summarized and compared regarding current design equations. [ABSTRACT FROM AUTHOR]

This paper analyzes the usability of different dynamic moduli of elasticity and wood density for the prediction of mechanical properties - static modulus of elasticity and modulus of rupture - in samples with grain deflection from the longitudinal direction. Five tropical hardwoods (Afzelia bipindensis, Intsia bijuga, Millettia laurentii, Astroniwn graveolens and Microberlinia brazzavillensis) with different grain characteristics were used for this purpose. The fiber deflection was caused by the presence of interlocked grain or the working process. The three nondestructive techniques used in this study - longitudinal and flexural resonance method and ultrasound method -- provided higher values of modulus of elasticity than the static bending test, but close correlation was observed between these variables. The weakest correlation was found for the ultrasound method which is probably caused by its measuring mechanism. The prediction of the modulus of rupture is less accurate when the dynamic modulus of elasticity is compared with the static modulus of elasticity; on the other hand, it was still good in comparison with the density model, which is inapplicable when grain deflection occurs in wood. In the wood of Zebrano where the interlocked grain was strongly developed, almost all of the correlation coefficients showed the lowest values and the prediction of modulus of rupture by nondestructive techniques was unsatisfactory. [ABSTRACT FROM AUTHOR]

In this study; bending properties of beech wood (Fagus orientalis) were predicted using stress - wave method and compared with static bending tests. First, lumbers which were different in length and cross section were weighed and dimensions were measured. Then, moisture contents were obtained via moisture meter. By using the density, moisture, and dimensions of the samples in MTG Timber Grader device, dynamic modulus of elasticity values were determined. And then, samples were subjected to 3 point bending test. Modulus of elasticity and bending strengths were calculated using load- deformation curves. Regression models were developed to interpret relationships between dynamic modulus elasticity and bending properties. Results showed that there is a high regression coefficient (0,86) between dynamic modulus of elasticity and static modulus of elasticity. Regression coefficient between dynamic modulus of elasticity and static bending strength was measured as (0,72) and regression coefficient between static modulus of elasticity and static bending strength was measured as (0,74). Results indicate that bending properties of beech wood lumber can be predicted using stress wave method. [ABSTRACT FROM AUTHOR]

Bending properties of Turkish red pine (Pinus brutia Ten.) lumber pieces were predicted using the stress wave method. The lumber samples were taken from 30- to 80-year-old red pine trees harvested from a southwest site in Turkey. MTG timber grader was utilized to predict modulus of elasticity (MOE) and modulus of rupture (MOR) values of lumbers with 40 mm x 90 mm in cross section and 3 meters in length. Static MOE and MOR values of the lumber pieces were determined using a three-point bending test. The coefficient of determination between measured and predicted MOEs was 0.84 and that between dynamic MOE and bending strength was 0.69. However, the coefficient of determination between bending MOE and strength was only 0.45. It seems that dynamic MOE has better prediction capability for bending strength than static MOE. Effects of some variables such as log and visual grades on dynamic MOE values were also determined statistically. Natural frequency of the lumbers showed far more significant effects than other variables. It is apparent that the stress wave method has the potential to predict the bending properties of Turkish red pine lumber. [ABSTRACT FROM AUTHOR]