Abstract
In this paper, the inelastic dynamic response of steel space frames with tensile bracing members is studied by the method presented in the first paper. The method assumes that a column segment consists of uniaxially stressed fibers along its length. The dynamic response is computed by assuming an elasto-plastic type hysteresis behavior considering strain hardening in stress-strain relationship for the columns and in tension only for the diagonal bracing members. The responses of single-story, single-bay braced space frames subjected to simultaneous action of two horizontal components of sinusoidal ground acceleration are studied using lumped mass, rigid-floor idealization. The results of the analyses include the responses of the space frames with eccentricity between centers of mass and elastic resistance. In addition, it is shown that the analytical solution predict well the general cyclic force-deformation behavior of the experimental results of a braced frame given in Ref.9. Some of the significant aspecst of the results are summarized in the following : 1) The maximum responses of the space frames are less than those of the plane frames in the direction of the braced frames and greater than those in the orthogonal direction. 2) The torsional responses of the space frames are affected by the ratios of elastic stiffness and maximum strength in each horizontal direction and increase in the case of a great difference between elastic stiffness and maximum strength in two horizontal directions compared with little difference. 3) The torsional responses of the space frames with eccentricity subjected to sinusoidal gronud acceleration with no phase difference between two horizontal components are greater than those with a phase difference. 4) The magnitude of the total input energy into the space frames with the same maximum strength in two horizontal directions subjected to the identical ground acceleration scarcely depends on the rations of elastic stiffness in two horizontal directions and eccentricity between centers of mass and elastic resistance. The maximum response of a column of a space frame is, however, unable to be estimated by only the total input energy into the space frame.
