This time, I will explain the true meaning of earthquake resistance grade 3. This time, I would like to explain earthquake countermeasures based on the proposal given by Professor Sato in response to the large earthquake that occurred in the Noto region on New Year's Day 2024. In the previous video, I talked about how many people probably think of a safe house when they think, "I want a safe and secure house," and that a safe house is one that protects lives in an earthquake and allows you to live even after an earthquake occurs, and that one indicator that can reliably guarantee this is earthquake resistance grade 3. This time, I would like to explain this earthquake resistance grade in more depth. In the real world, it is said that there are three ways to check the safety, or strength, of a building in our field. One is what is called the specification provisions of the Building Standards Act. This is whether the amount of walls of the building is sufficient, whether the balance of the walls of the building is well arranged, and whether the fixing strength of the column head and base of the building's columns is sufficient. It is decided that such things should be considered. Therefore, this is the minimum standard, and in terms of earthquake resistance grade, it is 1. The method of checking this is the basis. As a step higher level of confirmation, there is a law called the Housing Quality Assurance Promotion Act. This law gave rise to terms such as building performance indication and seismic resistance grade. The term "long-term quality housing," familiar to those considering new construction, was also created within the constraints of this law. The Quality Assurance Act calls for a more strict and rigorous review of specifications and construction of houses with seismic resistance grades 2 and 3. The term seismic resistance grades 2 and 3 is mentioned here. You may think that it's okay because it's seismic resistance grade 3, which Mr. Morishita is talking about a lot, but there is actually another step higher in safety confirmation. It is an advanced calculation method called allowable stress calculation. This is what can be called structural calculation. The specification regulations and the Quality Assurance Act look like structural calculations, but they are not structural calculations. I'll get in trouble for saying this, but I think it's best to think of them as quasi-structural calculations or pseudo-structural calculations. The difference between allowable stress calculations and the specification regulations/quality assurance act is the actual route and precision of the calculations. I'll explain it with a picture by Professor Sato. Although the term is the same, "earthquake resistance grade 3," it is said that there is a difference between the level of detail required by the allowable stress calculation and the root level required by the Quality Assurance Act. I have been asked by customers, "What is the difference?" and I was at a loss for an explanation. I will explain it using the explanation I gave at that time, which somehow seemed to make the customer understand. Here are diagrams of two structures. There are pillars, beams, and foundations, and the battens on the second floor are diagonal braces, so think of them as walls. At first glance, they look the same, but there is one difference: one of the diagrams has another pillar under the pillar. In a video I released a long time ago, I explained the direct hit rate. I talked about how houses with matching walls on the second and first floors are strong. It's the same story. For example, when an earthquake force is applied horizontally and this wall itself is pushed horizontally, a strong rotational force is applied and transmitted to the beam. At that time, the way the force is transmitted is different when there is a pillar on the first floor and when there is not. When there is a column on the first floor, the force transmitted from the column is transmitted directly to the column below and then to the foundation. It feels like it is being firmly supported. On the other hand, if there is no column below, the force is dispersed. It is not good just because the force is dispersed, but as it is dispersed, a lot of stress is placed on the beam. It may deform or even come off. And because the force is spread out, it is weaker and less able to withstand the earthquake force than if it were directly supported. However, in terms of the amount of walls, both are the same. In this way, structures change subtly depending on how they are assembled, the thickness and size of the structure, etc. In this way, the allowable stress calculation is not just a two-dimensional view of the amount of walls, but a three-dimensional view of how the force is applied at the joints between the beams and columns, and is a way to seek safety in detail. As a conclusion of the analysis of an enormous number of structural strengths by many structural experts, here is a diagram comparing the specification regulations, the quality assurance law, and the allowable stress calculation. For example, it shows the difference between seismic resistance grade 1 in the specifications and seismic resistance grades 2 and 3 calculated under the Quality Assurance Act, in a sense. Since there is variation depending on the building, it is a sense value. Generally, seismic resistance grade 2 is 1.25 times stronger so that it can withstand an earthquake that occurs once every 100 years. Seismic resistance grade 3 is about 1.5 times stronger so that it will not collapse even in a strong earthquake that occurs once every 500 or 300 years, which is a longer span. In this way, it is calculated as 1.25 or 1.5 times seismic resistance grade 1, but if you apply it to the image diagram, seismic resistance grade 1 in the allowable stress calculation is suddenly about as strong as seismic resistance grade 2 in the Quality Assurance Act. As for seismic resistance grade 2, it is slightly higher than seismic resistance grade 3, which is considered OK in the Quality Assurance Act. And, although the name is the same, seismic resistance grade 3 is much higher in the allowable stress calculation than in the Quality Assurance Act. Of course, it may not be a simple calculation of how many times, but at least the difference in distribution is about this much. I'm sure that everyone thought that in order to protect their lives after this earthquake, they absolutely had to clear the new earthquake resistance standard of earthquake resistance grade 1. You may think that it's a little scary, and that you don't want to save your life but not be able to live in it, so you want earthquake resistance grade 2 or 3, or if you're building a new house, you want grade 3. However, I want you to know that there is actually a wide range depending on how you check safety. Of course, there are various constraints and difficulties when strengthening an existing house. In that situation, you may need to determine a realistic compromise, or a point where you'll go for now. However, when it comes to new construction, it doesn't necessarily cost a huge amount of money to make it earthquake-resistant. In my opinion, it probably won't cost hundreds of thousands to 1 million yen. Large earthquakes may be rare, but since there are quite a lot of earthquakes now, they may not be rare. In other words, a house that you can continue to live in even if there is an earthquake is like insurance. When you think about it like that, I think people still want to take measures for things like that. I think that everyone has been affected by the damage caused by this earthquake. When you want or want a house with seismic resistance grade 3, please be aware that there is a wide range depending on how you check the safety. There is also a similar term, "equivalent to seismic resistance grade 3." There is no strict definition, but some people use this term. I thought that it was used to mean something like "If we achieve the 3 of the quality assurance law, it is equivalent to seismic resistance grade 3," but I was wrong. When I listen to the stories of customers who actually live in houses equivalent to seismic resistance grade 3, some people say, "It is equivalent to 3 because it has 1.5 times the wall volume specified in the specifications." I think that is a bit of an exaggeration, and I think it will be misunderstood and misconstrued, so please be careful. I hope that you will know this as knowledge and use it to build your own house in the future and protect your life. Please refer to it. -------------------- Here is the homepage. https://www.m-athome.co.jp/ Here is the new model house. https://www.m-athome.co.jp/modelhouse... Here is high-performance renovation. https://www.m-athome.co.jp/lp/renovat... We are accepting reservations for tours. https://www.m-athome.co.jp/eventinfo/... #MorishitaAtHome #earthquake #earthquakeresistance #BuildingCode #Himeji #builders #customhomes