Outline

When a building is damaged due to a major earthquake, the country researches on the cause of failure and tries to find out the weak points and the seismic performance. Using these new knowledge, the Building Standard Act may be revised so as to prevent future damage due to the same disaster.

With that said, due to the revision of the Building Standard Act in May 1981, the current earthquake resistance standard called "New Earthquake Resistance Design Standard" was constructed.

In seismic diagnosis, we check the buildings designed before the "new earthquake-resistant design standard" against the existing standards, whether the shape is easily damaged, or whether degradation due to aging is a problem. We investigate whether there is a place that can become a weak point at the time of a large earthquake and carefully examine the necessity of re-calculating the seismic performance of the building and providing additional reinforcements.

Work Flow

Sorting of Existing documents and Field Survey	We check the design documents of the structure and the existing calculation sheets.We also check which design policy and materials were used. We shall conduct an actual field survey to check whether the structure is consistent with the design documents. We also perform compression tests on specimens taken from the framed concrete to check the actual material strength and deterioration due to aging.
Preparation Calculation	Based on the results of the field survey, we shall compute for the load according to the present condition of the building and record the column axial force and the seismic force. We shall determine the cross-sectional capacity of members with complicated cross sections such as assembly materials and the strength / toughness (tenacity) of each member.
Seismic Diagnosis	We shall model the structure based on the design documents and field survey results. We shall determine how much horizontal capacity each member has, the failure modes and whether the chance that these failures will lead to the collapse of the building is high. In addition, we will comprehensively assess the seismic performance of the building from various viewpoints, such as the deterioration of the building and whether the shape and balance of the building will yield to the design earthquake load.
Seismic Reinforcement	If an existing building will most likely yield to current standards, we shall consider providing additional reinforcements to improve seismic performance. In case there is a need to use the existing building while construction is on going, or there are restrictions such as limitation on additional reinforcements due to overlapping existing members, a design approach different to the ones used in new constructions may be necessary.

What to keep in mind in Seismic Diagnosis

Maintenance of plants is done on a daily basis. Depending on the result, the range of construction may increase, design drawings may have to be revised, and maintenance procedure and/or methods may be affected. Adherance to the deadline is also important.

As described above, seismic diagnosis influences the entire process and the cost and time will have to be sacrificed. To avoid this, there should be regular communication with everyone, and work schedule must be prepared together.

For unknown and/or inconsistent parts, it is better to visit the site and explain personally to obtain sufficient understanding and to ensure a safe design.