Allowable stress calculation and seismic resistance grade 3

Let's take a closer look at allowable stress calculations and seismic resistance grade 3.

In particular, understanding allowable stress calculations and seismic resistance level 3 is the first step to creating safer buildings.

Importance of allowable stress calculations and seismic design based on seismic grade 3

Whether it's wood, steel frame, or other construction methods, earthquake resistance grade 3 is the pass mark.

The probability of a magnitude 8 to 9 earthquake occurring in the Nankai Trough is"50% or more within 90 years, 30-70% within 80 years."How to get through this safelyEarthquake resistance grade 3 is requiredThis is common knowledge among construction professionals.

Most people believe that steel-framed buildings are strong, while wooden buildings are not, but there are steel-framed buildings with Class 1 (same level as the Building Standards Act) and wooden buildings with Class 3 seismic resistance. Naturally, in this case, regardless of the type of structure, Class 3 seismic resistance is overwhelmingly stronger.

No matter which company you go to, they'll present catalogs and sales pitches claiming, "Our building is strong because we use the XX construction method." This can be confusing for the average person, but as long as the building meets seismic resistance level 3 or higher, the structure is acceptable . Thinking this way will free you from unnecessary worry.

Simulation for each seismic resistance grade

In fact, there is a video that shows a simulation in which 1 houses built with strengths ranging from 3 (very weak) to 1.5 (extremely high earthquake resistance) are shaken by the seismic waves of the Great Hanshin Earthquake, assuming that the strength defined by the Building Standards Act is 0.5 and seismic resistance grade 2 is 16. If you watch this, you will see the results clearly.

It can be seen that the only houses that survived the earthquake waves were the last four buildings in the row and the two buildings on the right side of the second row from the back, that is, houses with a seismic resistance rating of 4 (= 2 or higher).

Seismic dampers: They don't just withstand vibrations, they control it

However, for those with more stringent requirements, such as "I want to reduce the shaking itself when a major earthquake hits," or "I want to maintain the initial strength as much as possible even if there are hundreds of aftershocks," or in areas where microtremor surveys show that the shaking during an earthquake is expected to be particularly intense, it is also possible to install "seismic dampers."

There are many seismic dampers on the market. Most use the frictional heat of rubber, but many have significant differences in properties depending on the temperature, and the risk of deterioration over time cannot be completely eliminated. Our company recommends the Mu-Dam seismic damper, which is the only seismic damper that does not have such concerns and is also recommended by Mr. Sato of the Structural Engineering School.

There's something important to keep in mind here: "Installing seismic dampers on houses with a seismic resistance rating of 1 or 2 is practically meaningless ." This is something that any reputable seismic damper manufacturer will state themselves. However, in reality, after the Kumamoto earthquake, there was a constant stream of contractors in the surrounding area who were loudly advertising houses with low seismic resistance ratings as "highly earthquake-resistant" simply by installing seismic dampers. This is similar to contractors who rush to install underfloor air conditioning without improving insulation or airtightness.

"Basic performance trumps equipment!!" Please don't forget that this is the fundamental principle.