Abstract
Significance of the experiments
Timber structure should be strengthened by using bolts and metal fasteners. However, in case of traditional or esthetic design of wood building, as columns and roof trusses are disclosed, exposed metal fasteners are apt to be unsightly. One of the ideas to solve this problem is to apply adhesives at the tenon-mortise joints of the construction on site. To secure final resistance (fall-safe) of the joint, L shaped metal connector could be nailed inside the wall covering. These reinforcements make a frame stiffer and stronger against lateral forces without any bearing wall or bracing. The adhesives used here should have the following properties,
(1) “Open time” should be long enough for use on site. (2) Not subject to insensible any change of temperature and moisture when it is hardening. (3) Keeps ductility after setting.
The author chose a modified Urethane glue for this purpose.
To examine stiffness and strength of the T joint, 135 test-pieces were tested by 27 categories of tests to know the influence of, (1) species of the member, (2) sectional dimension of the member, (3) length of the tenon, (4) effect of the angle piece metal reinforcement.
Test results and summary
The experiments were conducted applying a lateral force to the top of the column 70 cm apart from the sill. Rigidity of the joint could be determined by measuring angle of deformation caused by the load. Results are as follows;
(1) Species …HINOKI (Japanese Cypress) was the best not only in stiffness but also strength, as well as ductility. BEITSUGA (Hem-fir) followed hext a little lower, and SUGI (Japanese Cedar).
(2) Sectional dimension…The wider the better in stiffness and strength especially in case of the short tenon.
(3) Length of the tenon…Specimens having long tenon are 1.5 times stronger than the shorter ones. Long tenon was often broken at the last stage of the test. While short tenon was pulled out from the hole.
(4) Method of fastening…Glued joints are superior to mechanical fasteners are we assumed. A series of experiments were successful. And it is effective to use metal fastener with glued joint for increasing rigidity, strength and ductility.
(5) Possibility of the wood rahmen structure …According to the above mentioned results, a column with adequately fastened lateral members is expected to endure in certain extent against lateral forces caused by earthquake or heavy wind. Allowable load is estimated as 104 kg (12 cm sq.) to 141 kg (13.5 cm sq.) in case of HINOKI. And we have learned for our survey that 0.5-1.0 columns are existing in a contemporary wood house. This plan has a good chance to establish another system of house construction taking place the bearing wall system. Development of the' adhesives for this use and trial the construction in the hearest occasion should be the way to realize beautiful and strong wooden houses.
