Systematic Interpretation of Rust Evaluation Methods for Weathering Steels

Additions to Contingency Plan for Enhancing Secureness of Weathering Steel Structures

“…To modify corrosion loss to occur for nickel containing advanced weathering steels [2][3][4][5][6][7][8][9][10][11], one may use so called weathering alloy index V [8] which can be calculated by,…”

“…However, psychological risks cannot be completely erased due to the uncertainty of events such as unpredictable environmental change during long term service that might initiate supposedly impermissible breakage of upper deck which might cause water leakage from superstructures, human error in planning and/or designing stage, etc. To cope with such risks, one must carry out corrosion monitoring using, say, above mentioned methods [4,5,6]. Although anomalous state is detected at early stage, it is neither failure nor end-of-life for the weathering steel structure.…”

“…However, experienced persons stated that the rust state could be monitored just by visual examination. Requested by Japan Association of Bridge Engineers, the Japan Iron & Steel Federation carried out a collective investigation to articulate the experienced person's intelligence, resulting in the five-step ranking visual inspection method [5] as shown in Fig. 4, in which the principle is based on a simple idea of using a visual comparative test method as explained in Ref.…”

“…[6]. In this visual inspection method, weathering steel with rust categorized in Rating-5 at the 9th year is predicted to lose its thickness at a rate of less than 0.4mm per side for 100 years, Rating-4 and Rating-3: less than 0.5mm, Rating-2: less than 2mm, Rating-1: more than 1mm to less than 50mm according to the exposed test piece analyses [5]. According to Ref.…”

“…developed a computerized corrosion prediction system [2,3], which is now used as a corrosion recognition and control tool during the planning and designing stages of weathering steel structures [4]. Visual as well as instrumental rust monitoring methods and their criteria have been already established as reported elsewhere [4,5]. Also, an example of secure management system for weathering steel bridges is proposed as listed in Refs [6,7].…”