Study on Environmental Vulnerability to Risk Management for Bridges Subjected to Earthquake
Date Issued
2013
Date
2013
Author(s)
Chang, Yung-Jui
Abstract
Taiwan is located at the intersection of the Eurasian Plate and Philippines Sea Plate and belongs to the Circum-Pacific seismic zone, which is an area featuring numerous faults accompanied with severe seismic activity and natural hazards. In 1999, the 921 earthquake, also known as Jiji earthquake reached 7.3 on the Richter magnitude scale and caused serious damage and economic losses in the central area of Taiwan. More than 20 traffic disruptions due to bridge collapse delayed the rescue and reconstruction process and also brought the incident to the forefront of the public spotlight.
Over the past decade, the damaged land became loose and fragile, and global climate change accompanied with severe weather change from heavy rains and typhoons caused extensive collapse and an increase in the landslide potential. The landslides due to heavy rain have led to bridge damage and traffic interruptions, disaster areas became isolated and cot-off form life supply. In July 2001, Typhoon Toraji hit Taiwan, where several bridges in the mountain areas of central Taiwan were also destroyed by landslides. In addition, the silted up riverbed changed the river facies and sped up the scouring. Thus, flooding became one of the most common types of bridge damage. The subject of bridge damage has become much more complex these days, and how to build up a reliable natural hazard estimation system, as well as set up an effective prevention strategy has become the most important topic in bridge damage prevention. According to the annual report of World Bank in 2012, the economic loss due to global natural hazards in 2011 is 380 billion US dollars. Even Japan, with plentiful precaution and preparatory experience against natural calamities, had to face unprecedented complex disasters during the Great East Japan Earthquake in 2011. Through those experiences, we finally understand that a natural hazard estimation and prevention strategy should come into the overall consideration of transportation planning.
This research will be based on the most important life line – traffic transportation systems, and focus on the seismic resistance of bridges, as well as consider the importance of locating bridges and seismic hazards, and also the environmental factors; such as, humanities, society and rescue ability. By connections each of these factors building up a natural hazard estimation model, we can find out a risk assessment value based on quantified methods. This can become the foundation of bridge maintenance strategy and also can be references for the distribution of recue resources.
This study collects historical seismic data, fragility curves of bridges, repair and retrofit records, and other related information, and uses Analytic Hierarchy Process (AHP) to carry out the index and weights to find out the vulnerability of a bridge. Moreover, by using seismic hazard and flood potential information, we can also carry out the index and weights by AHP and find out the hazard potential for the area. Furthermore, this study takes the related information; such as, important local facilities, rescue ability, economic conditions and human characteristics, and uses Factor Analysis to find the common factors as well as the vulnerability of the area. Finally, the disaster risk value for a bridge can be determined and become a reference for risk management.
This research uses 162 bridges in Taipei and New Taipei City to form a database, and updates the fragility curve of the bridge according to the natural hazard score, which makes the estimation closer to the reality. This paper also takes into account 6 analysis cases to verify the proposed bridge hazard estimation method.
Finally, the realm of risk estimation method for natural hazards can also be expanded. According to the user requirements and carry out the suitable index and weights in order to find a better seismic risk estimation result and establish a more realistic risk manage system.
Subjects
災害風險值
脆弱度
易損性曲線
橋梁維護管理
災害評估系統
Type
thesis
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