RESISTANCE MECHANISM OF NON-SLIP-TYPE EXPOSED COLUMN-BASE UNDER TENSILE VARIALBE AXIAL-FORCE

An experimental study on non-slip-type exposed column bases proposed by the authors, subjected to both cyclic horizontal laodings and variable axial forces in the limits of compression was carried out to make bending moment characteristics of the column bases and to propose models of restoring force characteristics. In addition, the same experiments on conventional exposed column base were conducted to show the effectiveness of the proposed column bases. The following conclusions were drawn from the experimental results: 1) The restoring force characteristics of the non-slip-type column bases become linear-from-origin-type under variable axial forces, and the column bases sustain the self-centering performance reducing residual deformation of a building after an earthquake. 2) The energy absorption capability of the proposed column bases is higher than the conventional ones, and the energy absorption capacity is almost the same under between constant and variable axial forces. 3) The gap between the edge of the base plate and the foundation of the proposed column base under variable axial forces in tension and compression becomes smaller than the conventional one. 4) The gap between the base plate and the foundation of the proposed column base is not generated unless the axial force exceeds half of yield strength of all the anchor-bolts, therefore the bending resistance of the column base is not reduced by the shearing resistance of the anchor-bolt in the case of the lift-off of the column base.