考量環境脆弱度之橋梁震害影響評估與風險管理之研究-以大台北橋梁為例

Study on Environmental Vulnerability to Risk Management for Bridges Subjected to Earthquake

張永叡(Yung-Jui Chang)

指導教授 ： 曾惠斌

共同指導教授 ： 楊永斌

國立臺灣大學/工學院/土木工程學研究所/博士(2013年)

https://doi.org/10.6342/NTU.2013.01849

摘要

台灣位於環太平洋地震帶西側，地處菲律賓海板塊與歐亞板塊交界，島上斷層比比皆是，地震活動頻繁，災害威脅不斷。發生於1999年的921集集大地震(M7.3) 造成台灣中部廣大地區百年罕見的大災害，人民生命財產遭受重大損失，其中，因橋梁崩塌損壞，導致交通中斷超過20處， 嚴重影響災後救援及重建工作的進行，更是成為社會矚目的焦點。
台灣近十多年來，因地震受創的大地，更加破碎與鬆動，日趨極端化的颱風豪雨，更使山區產生大量的崩塌地，也使得土石流潛勢溪流倍增。在超大雨量的催化下引發大規模的土石流，導致橋梁受災而交通中斷， 使得此種災區形成孤島，民生危急的事件 ，一再的發生。 例如2001年7月桃芝颳風以降，台灣中南部山區的橋梁，一再遭受土石流沖毀 ;另一方面被大量土石淤高的河床 ，不僅改變了河相，也加劇了沖刷的力道， 水害也成了常見的橋梁災害。 因此，面對橋梁災害日趨複合性與多樣化，如何建立可靠的災害評估方法，釐定有效的防災因應對策，己成為橋梁災害防制的重要課題。另依據2012年世界銀行報告指出，2011年全球因天然災害的損失約美金3800億元，即使具有豊富抗災經驗的日本，在2011年東日本大震災中，也發生了史無前例之巨大的複合性大災難。 震災的歷史教訓告訴我們， 從單一面向來評估致災風險或釐定防災策略是不够周延的。
有鑑於此，本研究將以最重要的維生線—交通運輸系統中的関鍵工程「橋梁」的耐震性能為研究主題， 綜合考量橋梁的重要性、橋址的地震危害度，以及人文、社會、救災能力等環境因素， 將彼此之間的關係加以連結，建立一套災害風險評估模型，以量化的方式推求橋梁災害風險值，它可作為規劃橋梁維修補強策略的依據， 並可供作防救災對策之釐定， 以及救援資源合理化分配的參考。
本論文蒐集彙整歷史地震資料，以各橋梁之耐震評估所得之易損性曲線，加上各橋梁維修紀錄、重要度等相關資料， 以AHP層級分析法訂定各指標與權重， 求得橋梁脆弱度風險值；再以各橋址之地震危害度與淹水潛勢等資料，同以AHP層級分析法訂定各指標與權重， 求得區域之災害潛勢度風險值; 另以區域的重要設施、救災能力、社會經濟條件與人口特性指標等資料，用因子分析法萃取出共同因子，求取因子得點，可得到環境脆弱度風險值；最後將上述三項風險值統整出橋梁之綜合災害風險值，並加以排序，以作為風險管理的參考依據。
本研究以台北市及新北市共162座橋梁為資料庫，根據橋梁所在區域之災害風險總得分，微幅調整其易損性曲線，便可得到包含橋梁結構性能與地區特性的新易損性曲線，此可將評估結果更趨近實際現況。同時本論文也擇取6座橋梁進行案例分析， 以驗證本研究所提之橋梁災害風險評估方法之合理性及可靠度。
此外，本研究所建立之災害風險評估的模型與方法， 日後可將其功能擴充，讓使用者根據實務的需求，訂定合宜的影響指標及權重， 以獲致更真實的地震災害影響評估結果， 建立更符合實際需求之風險管理。

關鍵字

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

並列摘要

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.

並列關鍵字

damage assessment ； vulnerability ； fragility curves ； bridge maintenance management ； hazard evaluation system

參考文獻

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