Nowadays, "seismic isolation structure" is regarded as a technology to prevent damage or collapse of buildings from earthquake. Seismic isolation bearing can prevent damage to buildings, it is also effective to ensure the safety inside the building.
Seismic Isolation structure (bearing) is a technology to protect lives and assets. In Japan, it's used for many buildings, such as apartment, hospital, city hall, office, factory and warehouse etc. Its effectiveness had been proven in Kobe earthquake, Niigata Chuetsu earthquake, Fukuoka West Offshore earthquake and recent Tohoku Pacific earthquake. What is about "seismic isolation structure", the structure of seismic-isolated building, mechanism, effect and mechanism of seismic isolation bearing will be explained in this contents.
When the large earthquake energy is transmitted to buildings, the buildings may suffer from damage or collapse. How to deal with earthquakes, methods of construction or structure has been devised and measured by earthquake prone country, Japan. The buildings have 3 types of structure, seismic isolation, seismic vibration control and seismic resistant structures.
Illustration below describes the differences of each other.
Seismic isolated building is mounted on seismic isolation bearings. While supporting the weight of building ,seismic isolation bearings can perform large horizontal movement to protect the building from earthquake.
In this video,
- Structure of seismic isolation building
- Structure of seismic isolation bearing which is supporting the weight of building
- You can see the deformation of seismic isolation bearing during an earthquake by animation.
This video introduce an example of assumed seismic response results after earthquakes for indoor or structural members(column/ beam / wall etc.) by using actual structural design and ground motion [which is a very rare earthquake (occurs at once in hundred of years) notification waves; Kobe phase] to perform the earthquake simulation of seismic isolation, seismic vibration control and seismic resistant structures.
Simulation results vary depending on building/ ground motion. Let's perform the earthquake simulation for reinforced concrete structure 14F apartment* with following outline of design.
* X direction: Shear wall Y direction: rigid frame
During massive earthquake, indoor furniture is likely to fall apart from damages to the building.
In case of seismic isolation structure, due to the effectiveness of seismic isolators the building will be shaken gently that prevent furniture fall down and ensure the safety.
This video is taken based on the shaking table test with full scale house model on actual seismic waves. The effectiveness of seismic isolation structure can be observed when comparing the indoor condition between seismic isolation structure and non-seismic isolation structure.
Video source: Ichijo Komuten
In order to ensure that seismic isolation structure exhibits the required seismic isolation function and maintain the safety of building in future, inspection and verification by the owner and building administrator are needed. (Refer to Article 8 and 12 of Building Standard Law)
Inspection and verification shall be carried out including the surrounding of building, seismic isolation pit, plumbing as well as the seismic isolation bearings.
In this video, as an example of actual seismic isolation structure, you can see the inspection works and description of inspection items conducted by professional inspector(seismic isolation structure inspection engineer)
* For more information about the inspection, please refer to "Maintenance standard of seismic isolated building ,2010" The Japan Society of Seismic Isolation.
"Maintenance of seismic isolation structure" Part I (6 minutes 44 seconds)
- Inspection at seismic isolation pit
"Maintenance of seismic isolation structure" Part II (3 minutes 31 seconds)
- Inspection for surrounding of building
- Notes of caution