The recent seismic regulation in Thailand has been officially announced on 4 March 2021 which will be enforced in the next 180 days.
There are several aspects of the new regulation which will have some impacts to not only the structural engineers, but also developers and architects.
Some key changes and impacts from the B.E. 2564 Seismic Regulation are discussed in this article.
Seismic Zones
Similar to the old regulation, there are still three seismic hazard zones in the B.E. 2564 regulation, but they are re-named as follows:
Zone 1 (formerly “Observation zone”) represents a low seismic zone.
Zone 2 (formerly “Zone 1”) represents a moderate seismic zone.
Zone 3 (formerly “Zone 2”) represents a high seismic zone.
Twenty one provinces are added to the B.E. 2564 regulation, resulting in a total of 43 provinces with seismic design enforcement. This is nearly double the areas required in the B.E. 2550 regulation (22 provinces).
"The eastern area is now the only region in the country which does not require seismic design."
There are 4 new provinces from the northeastern region added to the new regulation. The eastern area is now the only region in the country which does not require seismic design.
Three provinces in the south; namely, Ranong, Phang Nga, and Phuket, are changed from the low seismic zone to the moderate seismic zone.
Building Categories
There are 12 building categories added to the new regulation resulting in a total of 30 building categories required seismic design consideration.
Eight additional building categories are added to Seismic Zones 1 and 2, while another 4 additional categories are added to Seismic Zone 3.
Criteria for Enforcement
In general, the criteria for seismic design enforcement are similar to the old regulation which are based on Usage/Function, Height, and Column spacing. A significant change is that the criterion based on number of people in the building is now replaced by the building area, which will be more straightforward.
"... the criterion based on number of people in the building is now replaced by the building area."
Overall criteria are generally more stringent. For example, all community malls with area over 1,500 m2 in Seismic Zones 1 and 2 (e.g. Bangkok and vicinities, etc.) are now required to consider seismic design. As for Zone 3, a seismic design is now required for residential houses and shop houses as defined under the Land Development Law regardless of building height.
These new criteria have a tendency to significantly impact the project investment cost and will need to be properly assessed.
Minimum Seismic Demand
Apart from those general requirements for seismic design familiar with by most structural engineers, e.g. building geometry, irregularities, etc., stability of those non-structural elements and architectural features in the building are now required to consider under this new regulation.
"Stability of those non-structural elements and architectural features in the building are now required to consider under this new regulation."
Minimum seismic demand will need to follow a relevant Ministerial Announcement. This specific announcement; expecting to be announced by this year, will mainly follow DPT1301/1302-61 standard, implying that seismic demand based on other international codes (e.g. ASCE7, etc.) is no longer allowed by this regulation.
"... , implying that seismic demand based on other international codes (e.g. ASCE7, etc.) is no longer allowed by this regulation."
It shall be noted that, although the DPT1301/1302-61 standard is mainly based on ASCE7 standard, a conventional Response Spectrum Analysis (RSA) is replaced by the Modified Response Spectrum Analysis (MRSA) method. The MRSA method will be more complex and will require deep knowledge in the seismic code to efficiently calculate the seismic demand to achieve both safety and economical design.
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