Abstract
Cracks inside steel plates were found under the retrofit welding of steel bridge piers. By Z-direction tension tests using cores from the piers, the analyses of chemical compositions, and direct microscopic observations, the cracks were proved to be lamellar tear cracks, which are due to old and bad property steels. Also, by paper researches on old documents, it is found that there are risks of lamellar tear for piers, which were constructed before 1973. Especially for steels having sulfur more than 0.01% and RAZ less than 15%, careful examinations must be than to use welding for retrofitting works. A basic plan for the examination is proposed in this paper.
