In this study, the corrosion damage investigation and field loading test of a pratt truss bridge which was constructed 97 years ago were carried out for clarifying the acting live-load stress of main structure members and deflection behaviors. The maximum reduction rate of cross-section area was confirmed in the joint part between sway bracing and the vertical member. From the consideration of current traffic restriction, 2 dump trucks with 80kN weight used as loading condition. As the test results, the acting compressive force of vertical member with severest corrosion damage was estimated about 1/3 of buckling load. Also, it could not confirm the serious effects due to corrosion damages and repairs to load bearing capacity under current traffic restriction.
