日本建築学会構造系論文集
Online ISSN : 1881-8153
Print ISSN : 1340-4202
ISSN-L : 1340-4202
高靱性・高減衰薄板軽量形鋼造耐力壁の開発とその基本力学性能
曽田 五月也脇田 健裕
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ジャーナル フリー

2018 年 83 巻 743 号 p. 201-210

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 A steel framed house consists of walls and floors made by panels that plywood boards and light-gauge cold-formed steel frames are fastened with drill screws. Seismic performance of steel framed houses mainly depends on force-deformation relation of shear walls. Most conventional plywood shear walls show poor ductility because they may suddenly lose strength triggered by the break of the screw or punching out of the board when deflection angle becomes around 1/30[rad]. Therefore the energy absorbing ability of this wall is very low because of its pinching property in load-deflection relations. Since Japan is an earthquake prone country, the use of steel framed houses has been limited to three story buildings until recent years. But the revision of the design code in 2012 made it possible to apply the structure to a medium-rise building up to four stories. However, when we want to build a four-story house using conventional plywood shear walls, the amount of walls often becomes too much, spoiling the flexibility of the construction. In addition, it is a big problem that response acceleration and stress acting on specific parts of a house will become excessive.
 In this paper, we first proposed a method of inserting plywood inside the peripheral frames consist of the light-gauge cold-formed steels and fastening it with drill screws. By using this method, it is possible to prevent the punching failure of drill screw joints and the dropout of the plywood. As a result, it was shown by static loading test that the ductility of this shear wall is improved.
 Then, we proposed a method to install friction devices that consist of lubricated coated galvanized steel tightened with high-strength bolts between the studs and the inserted panel. This method is intended to make use of energy absorption by frictional force caused by the relative deflection generated between the studs and inserted panel. We conducted a number of the static loading tests on this built-in friction mechanism shear wall and found that it has very high ductility and damping capacity compared with conventional plywood shear wall. As a result of the shaking table tests, it is also confirmed that the wall can hold a stable energy absorbing capacity even when subject to repetition of large amplitude ground motions.
 Finally, we investigated the seismic performance of 2-story house models designed with built-in friction mechanism shear walls by earthquake response analyses. In this analytical study, we used seismic waves recorded in Japan with the maximum speed over 50[cm/sec] as waves exceeding the level required by seismic design regulations. We investigated the quantity of walls that can secure safety against these seismic waves comparing with the models designed by using conventional plywood shear walls. As a result of a number of analytical studies, it was shown that the models using built-in friction mechanism shear walls can suppress the responses to severe earthquake ground motions significantly as well as reduce quantity of walls.

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