Stress measurements of the newly built Koubo dam gates were executed to obtain stress values in non-deteriorated condition for the future maintenance. While paying attention to the axial stress of arm near the trunnion pin, observed data are compared with ordinary design calculation values and FEM analysis values. Initial imperfection in the direction of the trunnion pin axis and shearing stiffness of the trunnion girder are quantitatively examined concerning the influence to the stress distribution of the arm. Furthermore, the influence on the load bearing ability of the unusual stress distribution caused by the imperfection is investigated by nonlinear FEM analyses considering future corrosion deterioration.
