災害風險量化方法之研究：以模板支撐倒塌為例

Study on the Accident Risk Quantification: An Example of Formwork-Strut Collapse

「風險分析」起始於工業的發展，主要目的在於防止人員傷害與事業資產的損失。為能精確計算風險的大小，傳統的定量風險分析方法通常須配合充分的歷史統計資料作為評估事件發生機率與後果的參考，但對於某些風險事件其資料並不容易蒐集或是統計，使得定量風險分析並不易進行，但基於成本──效益與決策分析上的需要，發展一種基於主觀及宏觀的系統化量化分析工具有其必要性。本文提出一個結合影響圖與模糊理論的風險量化分析方法：首先根據影響圖的定義進行風險事件的關聯性分析，研判風險因子之間的相互影響關係以建立一個風險影響圖，接著利用專家的經驗由事件的現況建立模糊推論引擎與規則庫，用以進一步建構各個風險因子之間的影響關係；再透過模糊系統的運算求取風險發生的可能性，並轉換為機率，最後將機率與估計的損失相乘即可得到該風險事件的量化風險值。為了能夠藉由量化風險輔助決策支援的功能，本文接著進行風險因子的敏感度分析、不確定性分析，以了解各個因子在該階段對事件所具有的影響性，並作為因子改善的參考。在引入成本的概念之後，可以計算風險成本、安全投資成本與總成本之間的關係，同時進行成本──效益分析以求取最佳的安全投資方案。本文並以營造業之模板支撐倒塌為例，配合所提出之方法進行風險量化與成本──效益分析，以達到降低風險及提升安全性的目的。

Risk Analysis begins with the development of industry, and is used to prevent unexpected accidents losses. Risk quantification usually requires sufficient historic data and statistical methods to evaluate the probability and the consequence of events. Because the information of risk events is not easily collected in construction industry, the quantitative risk analysis is hardly possible. Developing a risk quantification tool based on the subjective judgment of experts is necessary for cost-benefit analysis and accident prevention strategy. This study proposes a risk quantification method, which combines influence diagram and fuzzy theory. At first, risk factors of a construction accident should be decomposed to hierarchically using concepts of influence diagram. Second, fuzzy inference rules are used to describe the relations among risk factors. After defuzzification, the possibility of accident risk could be obtained and further transformed to the probability by applying Onisawa’s formula. Finally, the quantitative risk can be estimated by the product of the probability and loss estimation. An example of formwork-shoring is shown in our study. Several analyses such as sensitivity and uncertainty are conducted through this approach, such that risk factors could be clearly identified and improved to reduce accident risk. In addition, cost-benefit analysis is accomplished by calculating risk costs, safety investments and total costs in order to determine optimized investment scheme.