Abstract
This paper reports the results of the tests which were made to examine the strength properties of commercial timbers and to check the values of allowable unit stresses and of moduli of elasticity provided in AIJ Standard for Structrual Design of Timber Structure. The species of timbers selected from market were Sugi and Hinoki for columns and Matsu for beams, and the number of specimens were 31, 28 and 10, respectively. The nominal cross section of full-size specimens were 10.5×10.5 or 12×12cm in columns, and 12×18, 12×21 or 12×24cm in beams. Static bending and compression tests were made on full-size specimens and on knot-free small specimens taken from both ends of each full-size specimen. The test results indicate that: 1) The values of proportional limit obtained from the tests on columns range 1.2 to 1.4 times the allowable unit stresses, regardless of species, structural grades and kinds of stresses. 2) Ther atio of the allowable unit stress for "higher grade structual lumber" to that for "ordinary grade structual lumber", which is shown in AIJ Structural Standard, is appropriate for both bending and compression. 3) It is to be desired that allowable unit stress for compression and modulus of elasticity in Sugi are decreased down to 80 and 90% of the values shown in AIJ Standard, respectively. Except the above-mentioned, the provided values of allowable unit stresses and of moduli of elasticity in Sugi and Hinoki and the relationships among them are almost appropriate.
