Hiromitsu ITO

Study on externals evaluation and rust states of weathering steel bridges in Niigata

Eiji IWASAKI and Masatsugu NAGAI


Recently, the adoption of the unpainted weathering steel has increased in constructing the steel bridge to reduce the life cycle cost. In Japan the guideline of weathering steel application was established and according to the guideline, it is described that the applicable limit of weathering steel, which is maximum amount of marine salts density is less than 0.05mdd or in Niigata weathering steel is applicable in the area which is more than 20km from the coast.

In this study, aiming to search for the possibility of the expansion of weathering steel application, weathering steel bridges in the Niigata was investigated by Evaluation method based on external of rust.

The obtained result is described as follows:
1) In the bridge in the range from 10 to 20km in the distance of leaving the coast, the possibility that the unpainted weathering steel bridge can be adopted is high.
2) As for the upper and lower sides of the lower flange, the evaluation level is fall more than other parts.
3) It is difficult to forecast the progress of the rust in the future only from the evaluation level, and when externals are evaluated, is necessary to do the method of appreciable quantitatively of rust.
4) It is necessary painting and drain treatment at the end of girder.