Abstract
In steel frames, the fracture of welded parts must be prevented when the frames are subjected to large lateral displacement during the strong earthquakes. On this point of view, it is very important to clarify the magnitude of the strain in the beam flange near the connection under earthquakes. In this paper are investigated the relations between the ductility factor of the beam flange near the connection based on strain (e_b) and the ductility factor of the frame based on lateral displacement (μ), using the numerical method. As the result the simple and available e_b-μ equations are presented. The results are shown as follows. (1) e_b-μ relations can be estimated rationally by analyzing the two relations i. e. e_b-ξ_b relation and ξ_b-μ relation, where ξ_b is the ductility factor of the beam-end based on rotational angle. (2) e_b-μ relations under monotonically increasing lateral displacement are expressed in terms of the parameters on material (stress-strain) properties and of the ratio of the beam's bending component to the total lateral displacement in the elastic region. (3) e_b-μ relations under cyclic lateral displacement are much affected by the cyclic displacement history. Nevertheless, the following two values can be easily evaluated in engineering practice, using the monotonic e_b-μ relations. The one is the maximun value of e_b for the maximum ductility factor of the frame, and the other is the amplitude of e_b under cyclic lateral displacement with constant amplitude.
