Presently, the maximum speed of Shinkansen trains reaches 300km/h. In this high-speed operation, one of the factors in estimating the quality of current collecting behavior is the stress of contact wire. There are various fittings clamped to the contact wire of overhead catenary equipment. These fittings dynamically become hard spots for pantograph collecting current. Above all, large magnitudes of contact wire stress have been marked at steady arm points. Though being under statics, in order to reveal the fundamental properties in the relation between constrain conditions of steady arms and a moving constant force, analytic calculations are carried out.