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News Release

Bangkok

Making existing buildings earthquake safer is possible

There are many seismic retrofitting techniques. But all of these come to a level of cost that will be determined by the level of safety that the building owner wants to ensure and is prepared to invest in.


With the recent seismic activity in Japan and Myanmar, issue has arisen on how safe the buildings are in Thailand.  Most of the modern high-rise buildings in the country have been designed to withhold an Earthquake of up to 5 Richter with some having been over compensated to withstand much greater.  However, whether they be low-rise, mid-rise, or high-rise buildings, risk may still remain with some. In retrospective, the only way to make these buildings earthquake “safer” is to retrofit them, according to Michael Tang, Head of Project and Development Services at Jones Lang LaSalle in Thailand. 
 
“Simply, seismic retrofitting is the modification of existing structures to make them more resistant to seismic activity.  The current practice of retrofitting is predominantly concerned with structural improvement, essentially to reduce the hazards and losses from the non-structural elements,” said Michael. “It is also important to keep in mind that there is no such thing as an earthquake-proof structure. Therefore, the amount of investment that a building owner wants to put back into the building would be based on where the building lies in the seismic zone – low, medium and high area,” he added.
 
 
According to the Performance Based Earthquake Engineering (PBEE) applied in the US, there are four key levels for the retrofitting – 1) public safety, 2) structural survivability, 3) structural functionality and 4) structure unaffected.
 
Among these four PBEE objectives, the most common is Public Safety which is to protect human life, ensuring that the structure would not collapse upon its occupants or passersby, and that the structure could be safely exited.  Under severe seismic conditions, the structure would need to be totally demolished.
 
The next level is Structural Survivability.  The goal is that the structure, while remaining safe for exit, may require extensive repairs before it is general useful for occupation.
 
Structural Functionality applies to primary structure undamaged and the structure is undiminished in utility for its primary application.  This requires a high level of retrofit and after seismic activity, only ‘cosmetic’ repairs would be required.
 
Structure Unaffected is a retrofit that is the highest of all which usually applies to high cultural significance.
 
“There are many retrofitting techniques ranging from ad-hoc additional support of structural element, base isolator, infilling of sheer trusses, active control system, exterior bracing, etc,” said Michael.  “More and more retrofitting exercises are being done to existing buildings in developed countries, especially in the US.  These exercises are not a requirement by law, but insurance lead, which will lower the premium of the building insurance.”
 
“Obviously all of these come to a level of cost that will be determined by the level of safety that the building owner wants to ensure and is prepared to invest in,” he concluded.