Tensile Strength Properties of Tropical Hardwoods in Structural Size Testing
In Malaysia, there is no research done on the tensile strength of structural size timber. The tension stress found in the Malaysian code of practice, MS 544: Part 2: 2001, was not determined directly and it was taken as 60% of the bending strength values of small clear specimens. This paper presents the results of the tensile test on structural size timber specimens from selected Malaysian Tropical hardwoods namely Kedondong (Canarium spp), Keruing (Dipterocarpus spp) and Bintangor (Calophyllum spp) under the strength group SG5. A special tensile grip was fabricated using the model suggested in ASTM D198 and the tests were also conducted according to ASTM D198. The tensile strength characteristics evaluated include tensile strength, modulus of elasticity and Poisson’s ratio, and the data were analyzed statistically. In this study it was found that the grade stresses for structural size specimens were higher than that published in the Malaysian code of practice. Index Term— tensile strength, structural size, Malaysian
Stochastic Model for Localized Tensile Strength and Modulus of Elasticity in Lumber
Localized modulus of elasticity (MOE) and tensile strength (T) were modeled for two visual grades of Douglas-fir laminating lumber. These material property models will be used as input to other structural analysis models that predict the strength and reliability of glued-laminated beams. Tensile strength and MOE are important material properties since most glued-laminated (glulam) timber beam failures initiate in the tension zone. Localized MOE and T exhibited significant within-piece variability as well as between-piece variability. These localized properties were also spatially correlated. A method that uses a transformation of the multivariate normal distribution was developed to simulate these localized properties for lumber up to 8-ft long. This method preserved the probability distributions of localized MOE and T as well as the spatial correlations between the localized property values. Procedures were described for expanding the model to simulate boards of any length. The method was also used to simulate long-span tensile strength. Mean simulated tensile strengths compared favorably with test results. Test results also confirmed a reduction in tensile strength as test span increased.
AN ACCELERATED ABRASION TEST1
A suitable abrasion apparatus is described which is capable of measuring the wear resistance of flooring materials having widely varying physical properties. The requisite conditions of wear necessary to produce results comparable to those obtained in actual service are given. Other abrasion methods and their shortcomings for use in this problem are summarized.