Experimental Study on Deformability of Steel Column Base Connections

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This study could be divided into two main groups. One was undertaken to examine the mechanical behavior of the frames each connected to different types of column bases, and the other was those of the exposed portions of anchor bolts subjected to combined tension and shear. From this study, the followings were clarified.*Mechanical behavior of frames each connected to different types of column bases In the frames connected to all types of column bases, the strength and rigidity of the frames became large and the area of the hysteresis loops becomes large, as the axial compression increases.The inflection points of the frames having exposed type or encased type column bases lower as the lateral force acting on them increases ; however, such lowering does not occur in the frames whose column bases are sufficiently embedded in foundation beams.The apparent points of end fixation of the encased type column bases and the embedded type column bases are located at the mid-height of the encasement and at a point 1.3 times the tube dimension below the top of the foundation beams respectively.*Mechanical characteristics of exposed portion of anchor bolts under combined tension and shear When subjected to shear, the ultimate capacity of anchor bolts placed through a grout layer shows slight decrease and such bolts show great deformation because of mortar separation compared with normal structural bolts.Where shear plane is located within the threads of the anchor bolts subjected to repeated loading, their capacities decrease and their displacements increase more substantially than in the case where they are subjected to monotonic loadings.The ultimate capacity under combined tesion and shear given by Equation shown in Recommendations for the Design and Fabrication of Tubular Structures in Steel is generally rather on the safe side under