抄録
The purpose of this study is to make it possible to predict the behavior, particularly the deformations, of steel frames subjected to lateral forces. The authors have previously proposed the extended slope-deflection method for elasto plastic frame systems in consideration of shear deformation of joint panels. In this paper, the assumptions of this method are discussed and the upper and lower bounds for the initial stiffness of steel frames in the elastic range are explained by using the energy method. The approximate expression for the stiffness of transversely loaded steel frames in the range of strain-hardening is made. Next, a series of tests of transversely loaded steel frames were carried out in order to examine the propriety of these methods. The specimens used in these experiments were constructed of rolled H-section members (JIS SS 41) : one group consists of four kinds of one story one bay portal frames and the other of two kinds of two story one bay frames. Comparing the test results with numerical calculation from the proposal theory, the following conclusions were obtained. 1) The initial stiffness of the test frames was between the upper and lower bounds calculated by the energy method. 2) The stiffness of the test frames in the strain-hardening stage were approximately satisfied with the following expression 1/(3n-2)・K_i, where, K_i : initial stiffness of a steel frame subjected to a lateral force, n : ratio of the strain at the initiation of strain of strain-hardening to the yield strain in a stress-strain curve. 3) According to the strength of the joint panels, the behavior of steel frames subjected to lateral forces only is varied.
