防波堤可靠度評估模式之研究

The Model for Evaluating Reliability of Breakwaters

波高的隨機分佈是構成海洋結構物可靠度分析及在其規劃設計各種近離岸工程使用上的最主要考量之一，其分佈特性隨著不同的地域環境，不同的潮汐海流，不同的季節氣候，不同的風場狀況......等會有各種不同的頻率分佈。海洋結構物所受的外在荷種力與結構體內阻抗力均視為隨機變數，由各地區觀測所得的資料，俾以用數學式描述以上二力的隨機分佈函數。結構體之可靠度可由荷種力及阻抗力所推導。常用之常態分佈僅僅概念性地分析波浪，無法利用正確波浪分佈推導防波堤之可靠度，其原因為上述二力之各種長時期之觀測數據不易正確求得，以至可靠度之分析受極大之限制。港灣工程中防波堤位置之規劃或工程設計，常需要有當地的基本海象資料，如潮汐、海流、波浪、降水、漂沙、風......等。然而各種海象的不確定性會造成防波堤規劃或設計的不確定性，進而影響到未來興建完竣後之安全可靠度。因此，如能量化海象資料的不確定性，將可有效地評估防波堤在規劃、設計、施工及維護管理的參考，作為港灣工程師之參考。

Breakwaters are the most important port structure. They protect the port from the wave force caused by the wind or storms. However, the uncertainties of the wave pressure, friction coefficient, wave height, influence the safety of the deep breakwaters. It also affects the safety of the entire port. Based upon the mean-value-first-order-second-moment technique, a model of wave pressure on breakwaters is developed which incorporates the random wave pressure or the friction coefficient properties as well as the uncertainty of the wave force. The results show that the reliability of the sliding analysis of the east outer breakwaters in Keelung harbor are between 99.60% to 99.7% from 1983 to 1990. And the reliability of the overturning analysis is also above 99.5% from 1983 to 1990. In a similar manner the reliability of the sliding and overturning in the storm were also analyzed and results are given.