In a world constantly grappling with the devastating consequences of earthquakes, the imperative for robust seismic design and evaluation cannot be overstated. Year after year, global regions experience seismic events that result in significant property damage and loss of human lives. From the Niigata earthquake in Japan (2007) to the Haiti earthquake (2010) and the more recent Christchurch earthquake in New Zealand (2011), the recurrence of seismic disasters underscores the urgency to fortify structures against the relentless force of nature.
Global Seismic Challenges
The seismic landscape is dynamic, as evidenced by recent earthquakes with magnitudes ranging from 6.3 to 9.0, causing widespread destruction. The seismic vulnerability is not confined to a specific region, as earthquakes in Japan, Peru, China, Italy, and New Zealand demonstrate the worldwide impact of these natural disasters. The need for comprehensive seismic design and evaluation is underscored by the continuous threat of seismic events, emphasizing the global imperative to minimize both property and human losses.
Seismic Preparedness in Korea
While Korea has not experienced a significant earthquake since 1905, neighboring countries like China and Japan have faced escalating damages. The proximity of the Korean peninsula to seismic hotspots necessitates proactive measures to mitigate the potential direct and indirect impacts of earthquakes. Although efforts are underway to enhance seismic resilience in schools through the Green School project, a critical gap remains in addressing seismic vulnerabilities in various building types, especially in middle and low-rise structures.
Challenges in Seismic Design Criteria
The seismic design criteria in Korea, established in 1998, primarily apply to buildings with six or more stories and a total floor area exceeding 100,000 square meters. This leaves a considerable portion of buildings, particularly middle and low-rise structures, without adequate seismic design considerations. The urgent need for seismic performance evaluation and reinforcement in these structures cannot be overstated.
Research Methodology and Findings
This study systematically collected and analyzed approximately 320 drawings representing structures lacking seismic design. By classifying them based on structure types and uses, the research focused on seismic performance evaluation for a diverse range of buildings, including a detached masonry house (MA-1) and reinforced concrete rigid frame living facilities (RC-1, RC-2, RW-1, RW-2).
Seismic Performance Evaluation Results
Detached Masonry House (MA-1)
- First Evaluation: The second floor is safe for human life in both X and Y directions, while the first floor is at a collapse risk.
- Second Evaluation: The second floor is at a collapse prevention level in the X direction and safe in the Y direction, with the first floor posing a collapse risk in the X direction and achieving collapse prevention in the Y direction.
- Third Evaluation: The X direction exhibits a plastic hinge collapse risk and inter-floor displacement safety, while the Y direction is safe for human life in the plastic hinge and immediately habitable in the inter-floor displacement.
Reinforced Concrete Rigid Frame Building (RC-1)
- First Evaluation: The structural seismic index indicates instability for all floors except the fourth floor.
- Second Evaluation: All floors, excluding the fourth, demonstrate instability with a structural seismic index below 0.6.
- Third Evaluation: The X direction is safe for human life in the plastic hinge and collapse prevention in inter-floor displacement, while the Y direction poses a collapse risk in the plastic hinge and achieves collapse prevention in inter-floor displacement.
Implications and Recommendations
The seismic vulnerabilities identified in the evaluated structures highlight the pressing need for comprehensive seismic design criteria and evaluation standards for a broader range of buildings. The findings underscore the potential risks posed by buildings without seismic design considerations, emphasizing the critical importance of seismic performance evaluation and reinforcement.
In conclusion, seismic resilience is a global imperative, and localized efforts must expand to encompass a wider spectrum of structures. The seismic vulnerabilities identified in this study call for immediate action in revisiting and broadening the scope of seismic design criteria to ensure the safety and stability of buildings, ultimately minimizing the impact of earthquakes on both property and human lives.