Experimental Study on the Strength Characteristics and Easy Seismic Retrofitting of Traditional Japanese Hanging Walls With Slits

Abstract eng:
Traditional Japanese houses are made of a wooden framework and a mud wall that is one of the main earthquake-resisting elements of the house. There is a growing tendency toward seismic retrofitting of traditional houses, and while there are choices in the way seismic retrofitting of houses can be realized, for example, increase the quantity of the mud in the wall, the reinforcement of joints, and setting viscous dampers, one effective way is to increase the wall size. Many restoring force characteristics of earthquake-resisting elements have been clarified by experiment; the characteristics of walls in old houses, however, are often different from those of the walls examined in these experiments. For example, the wall above the ceiling of an old house is not considered in structural design. When structural design is executed, the strength of a wall with a slit should be reduced, rather than a wall without a slit. The method for reducing this strength, however, has not yet been clarified. It is thought that such a slit should be filled up at the time of retrofit work. This work, however, is very difficult considering time and cost, since the floor and the ceiling, both sides of the wall need to be demolished and restored when the slit is filled up. Given this condition, we conducted experiments on mud walls with slits on their upper side, assuming that the wall above the ceiling is not constructed, and clarified their restoring force characteristics. Our experiments comprised static cyclic lateral loading tests. Considering the ease of construction, we examined the seismic retrofit construction method wherein the slit is filled up from one side of the wall; although this method is simple, we hoped that it could provide the required change in strength to make a retrofit practically possible. We used five hanging mud walls with different specifications, but with common properties as follows: a height of 2.73m, a length of 1.82m, a hanging wall height of 0.91m, a column of 0.105 × 0.105m, a beam of 0.105 × 0.18m, a ground sill of 0.105 × 0.105m, and a wall thickness of 0.06m. The slit width on the wall’s upper side was 0.15m. We examined two methods for filling up the slit, one with wall clay and one with wooden boards. In this paper, we present experimental results of the strength, ductility, and energy dissipating capacity of these walls. The conclusions obtained are summarized as follows. First, the strength of the wall with the slit is 0.875 times less than that of the wall without the slit. Second, if the slit is filled up by wall clay from one side of the wall, a wall with the same strength as that of the wall without a slit is obtained, and a seismic retrofit effect could be expected. Third, if the slit is filled up with wooden boards, the strength does not increase, and a seismic retrofit effect is not expected.

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