This paper describes the investigation of damage conditions in existing steel structures due to self-strain stresses and estimation of influence of such damage conditions on earthquake resistant performance of the steel structures.In this study,the following four items are presented concretely.;a)investigation of damage conditions due to differential settlement in existing two steel fame structures with braces,b)estimation of influence of damages due to differential settlement on the earthquake resistant performance in the existing steel structure,c)estimation of influence of thermal stresses on the earthquake resistant performance in the existing steel structure,d)tests on the steel model fame of such structures with self-strain stresses,and on the brace-end details.The following findings were obtained from this study:
1)The great damage due to differential settlement in existing two steel fame structures with braces was found out.
2)The earthquake resistant performance of the steel fame structures with braces is affected strongly by the damage due to self-strain stresses (differential settlements and thermal stresses)
3)The structural performance of the braces is affected strongly by the braces-end details.