臺灣四面環海、季風強烈，許多沿海鋼橋坐落於腐蝕環境較嚴重的地方，腐蝕是許多鋼橋在檢測時主要劣化原因，造成鋼橋支承端或支承上部主要構件斷面損失，影響端部承載能力，隨服務年限增長，會使結構安全性與使用性能逐漸下降。為了瞭解氯鹽環境下，鋼橋腐蝕後承載能力殘存率，本研究提出一套可以從腐蝕環境之大氣條件與海岸條件推估鋼橋剩餘承載能力之分析流程。
本研究引用日本學者小漥幸惠的氯鹽預測公式，選擇臺灣三個區域進行分析，並結合金屬腐蝕速率公式計算出鋼材腐蝕深度。針對鋼橋支承端部與端部腹板進行有限元素軟體分析，在不同腐蝕型態、腐蝕高度、腐蝕寬度與剩餘厚度下，了解承載能力下降程度，提出三種承載能力評估公式，包含簡易評估公式與詳細評估公式。最後，簡易評估公式可與環境資料及金屬腐蝕速率公式結合，建立一套從大氣腐蝕條件推估鋼橋端部剩餘承載能力的分析流程，了解鋼橋隨時間劣化對支承部位承載能力的影響。

In Taiwan, many steel bridges are located in severe chloride environment which causes corrosion at the girder end. Corrosion is the main reason for the deterioration of many steel bridges during inspection, resulting in thickness loss and affect the load-carrying capacity of bearing part. With the increase of service years, the structural safety and serviceability will decline. In order to understand the residual rate of bearing capacity of steel bridges after corrosion in chloride environment, this study proposes a set of analytical procedures for estimating the remaining bearing capacity of steel bridges from the atmospheric conditions and coastal conditions of the corrosive environment.
In this study, a calculation model for airborne chloride ion from Kokubo is used to calculate atmospheric chloride concentration and three regions in Taiwan were selected for analysis. The corrosion depth of steel was calculated based on equation from ISO 9225. By using finite element analysis, ABAQUS, the capacity of the corroded bridges can be evaluated under different corrosion patterns, corrosion heights, corrosion widths and remaining thicknesses. Three bearing capacity evaluation equations are proposed, including simple evaluation equation and detailed evaluation equation. Additionally, combined the simple evaluation equation with the environmental data and the metal corrosion rate equation, this study will establish an analysis process for estimating the residual bearing capacity of the steel bridge bearing part from the atmospheric corrosion conditions.

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