In this article, we would like to show you how to make your wooden house more resistant to earthquakes.
In Japan, the following methods are widely used to assess the seismic resistance of a building. Firstly, the required strength of the building is calculated, then the specification and layout of the walls, the specification and soundness of the foundation, and so on, are calculated. The numerator is the strength of the building and the denominator is the strength required for the building. This figure is known as the “Upper Structure Rating”.
According to this method of assessment, the strength of the building before the renovation was a low value of 0.11. The main reasons for this are the lack of seismic walls, especially on the ground floor, and the heavy weight of the tiled roof on the first floor. In addition, the balance of the walls is skewed towards the north, which is another weak point of the building.
The renovation plan was therefore to add more walls, mainly on the ground floor.
↑This diagram shows the arrangement of the walls on the ground floor of the house before the renovation. The red dots represent the centre of the weight of the building and the green dots represent the centre of the total strength of the walls. It has been found that if the red and green points are far apart, the building is more likely to break when it takes a large force in an earthquake.
↑This diagram then shows the arrangement of the walls on the ground floor of the house after the renovation. In addition to increasing the total strength of the walls by increasing the number of columns and walls, the positions of the red and green dots have been kept as close as possible so that they are less likely to break when the house is struck by an earthquake.
The roof could also be renovated to reduce its weight. As a result, the “superstructure grade” of the renovated building is 0.73. If it were possible, we would have aimed for a score of 1.0 or so, but this was not realistic and we decided against it.
In the area where the walls are to be added, seismic wall panels are to be installed to increase the resistance to horizontal forces in the event of an earthquake. This photo shows the construction of the wall panels.
The outer wall panels are also made of materials that act as seismic walls.
Before the renovation, the floor plan had very many windows and few walls, but after the renovation, the amount of walls has been increased to improve the seismic strength.