Earthquakes have always been a major type of natural disaster in Taiwan. In order to build up Taiwan's resilience, the National Science and Technology Council (NSTC) is vigorously promoting research on disaster prevention and mitigation, and has guided NARLabs' National Center for Research on Earthquake Engineering (NCREE) as it works to impROVe the evaluation of quake-resistant design and reinforcement technology, thereby enhancing the nation's overall seismic safety and creating a more sustainable homeland.
To ensure quality, all construction projects in Taiwan need to follow regulations set by the government. Reviewing and revising the seismic safety regulations for buildings is one of the most effective ways to impROVe their overall earthquake resistance. Since 2005, NCREE has been responsible for assisting the Ministry of the Interior in reviewing and revising seismic safety regulations for buildings. After two revisions in 2006 and 2011, plus an 11-year interval, the new Seismic Design Specifications and Commentary of Buildings was officially put into effect in October of this year. These new regulations incorporate the latest technological research to effectively enhance the earthquake resistance of buildings in Taiwan.
The new regulations involve four major revisions: increasing seismic safety near fault zones, impROVing the earthquake resistance of buildings with weak ground floors, refining soil liquefaction data and anti-liquefaction design, and ensuring the design quality and effectiveness of seismic isolation and damping elements.
Increasing Seismic Safety Near Fault Zones
When an earthquake is triggered by fault movement, the neighboring fault areas often experience significant ground displacement and intense shaking. This is more likely to cause strong damage to buildings nearer to the fault zone, and this phenomenon has been widely studied by the research community since the 1999 Jiji earthquake.
NCREE carefully analyzed the impact areas of known active faults in Taiwan and the possible damage they could cause to adjacent zones and adjusted the seismic safety regulations for these zones to ensure that buildings can withstand the "near-fault effect." For example, the earthquake resistance of new buildings designed in accordance with the new regulations in the area near Chishan Fault will be increased by 20-30%. This can effectively impROVe the seismic safety of buildings, and the cost of construction will only increase by about 5%.
ImpROVing Earthquake Resistance in Buildings with Weak Ground Floors
The collapse of the Weiguan Jinlong residential complex and King's Town Bank in the 2016 Meinong earthquake and the collapse of the Marshal Hotel and the Yun Men Tsui Ti Building in the 2018 Hualien earthquake were all cases where the ground floor(s) collapsed while the top half of the structure remained relatively intact. Buildings with weak ground floors (commonly known as "soft-legged shrimps" in Chinese) are like this mainly due to the fact that the lower floors are open spaces for public use with fewer structural and non-structural walls. If the building also incorporates a traditional pedestrian arcade, the ground floor will have little earthquake resistance.
Such buildings should undergo thorough assessment and structural reinforcement as soon as possible. To avoid damage to the structure of such buildings due to strong earthquakes before reinforcement is complete, the new regulations stipulate "eliminating damage to weak floors." Buildings that are assessed to be in need of mandatory impROVement can undergo phased reinforcement to pROVide short-term protection measures before full reinforcement or rebuilding. The regulations also pROVide complementary seismic safety evaluation procedures and reinforcement methods to assist the owners of such buildings in selecting appropriate methods to reduce the risk of collapse due to ground floor weakness during an earthquake.
Refining Soil Liquefaction Data and Anti-Liquefaction Design
If liquefaction occurs in the soil at a building's foundation and the foundation is not properly designed to resist it, it may cause serious subsidence or tilting of the building. The 1999 Jiji earthquake was a case where such building liquefaction damage occurred. Another example is the 2018 earthquake, which caused a large area of the Port of Hualien to sink up to 50 centimeters; had there been buildings there, the consequences would have been unthinkable.
In view of this, NCREE put together more than 300 cases of soil liquefaction in Taiwan and over 300 cases from other countries, and used these cases to analyze and calculate the liquefaction resistance of soil in different areas of Taiwan. Then, they developed a localized soil liquefaction assessment method which has been included in the new seismic safety regulations. This way, localities can follow the same standards when producing liquefaction risk maps, which will also impROVe accuracy and representation for national risk maps. Design engineers can use the impROVed liquefaction data to more accurately identify the liquefaction risk of a construction area and its impact area, allowing them to propose proper and reliable liquefaction-resistant designs to ensure building safety.
Ensuring the Design Quality and Effectiveness of Seismic Isolation and Damping Elements
Since 2006, when the seismic safety regulations for buildings first included a chapter on seismic isolation and damping element design, these elements have been used in numerous building engineering designs. In 2009, roughly 80 buildings in Taiwan incorporated seismic isolation and damping. This number has increased to more than 1,000 buildings in 2022. However, the quality and performance of seismic isolation and damping elements must be verified through proper performance testing in order to meet the design requirements. The new regulations for performance testing and quality control of these elements are more stringent and detailed to ensure their quality and performance so that their role in earthquake safety can be performed as it should.
NCREE hopes that through the revised regulations, new buildings can withstand collapse after large earthquakes, be repairable after medium earthquakes, and be undamaged after small earthquakes. NCREE will continue to strengthen and refine the Seismic Design Specifications and Commentary of Buildings to assist the Ministry of the Interior in creating regulations that can effectively protect living safety in Taiwan.