An Experimental Study on Bearing Strength in Compression for Bolted Joint of Plywood

Abstract

In recent years, in the field of wood industry, especially in Japan, it is required that planed raw materials switch from import materials to domestic lumber and development of new usage suitable for domestic lumber is strongly demanded. To promote and increase the demand of domestic cedars, the various types of products or building members by use of plywood has been suggested in Japan. We suggested the combined structure which sandwiched a steel material in plywood. And also, to investigate the structural resistant mechanism and performance under compression, the loading test of the sandwiched members has been conducted. Furthermore, we assume that the combined structural system would apply to sheet lightweight section steel structures, and the examination about the stiffening effect with the system is done, too. In addition, it is thought that it is necessary to establish enough clearance between the hole of plywood and bolt because of the accuracy of finishing of materials and precision of constructions. On the other hand, it is desirable that the clearance becomes small as much as possible, because the excessive clearance causes a drop of the structure unity of the combined material and invites the paths for thermal air environmental and humidity. Then, the moderate clearance around the joint would be inevitable, it is necessary to clarify the influence on the stress transfer mechanism and modification quality by the bearing pressure of the circumference of a bolt joint, and the above. In this research, the two types of filling up method for the clearance are studied; the first is a wet construction method by use of filler, and the other is a dry construction method with steel hardware. Herein, to develop and propose the above filling up methods, the structural resistant performance is not only evaluated, the difficulties of production, the costs and the human body effects are estimated. To select the suited filler materials, the construction examination and material testing were carried out. Form this selection, an urethane, an epoxy and a cement were picked up. And the bearing pressure experiment tests with the parameter of materials, the size of clearance, i.e. the thickness of filler, and the procuring period were conducted. The next, the steel hardware is designed with consideration the absorbing the gap resulted from construction and production errors. And the bearing pressure experiment study is conducted. From the experimental result, the relations of rigidity and strength with the parameters of fillers are clarified. And also, from the comparison of the results of filler and the ones of steel hardware, it can be said the steel hardware becomes the one of the most suitable methods.