Abstract
1. Introduction
We have proposed a hysteretic damper of tubular shaped steel in order to adapt to anchor bolts of exposed bases in steel moment frames. The damper is expected to deform stably over a large plastic deformation range in the axial direction after local buckling occurs. In the previous research, cyclic loading tests of exposed bases with the dampers have been conducted. The test results reveal the technical viability, however there is a problem that the deformation capacity decrease caused by insufficient of the shear stiffness and strength. The present paper describes the loading tests for exposed-type column base with the dampers using different shear resisting mechanisms. Moreover, the evaluation method of the deformation capacity is proposed.
2. Loading tests
The number of specimens is six. The parameters are sizes of the tubular dampers and shear resisting mechanisms. force are employed as the shear resisting mechanisms. The specimens are loaded cyclically with incremental deformation amplitude under constant axial force.
The test results show that the deformation capacity of the specimen with the concrete floor slab is higher than any other with the shear key. This is because the concrete floor slab can bring the highest shear stiffness In case of the specimen with carrying high compressive force, shear stiffness deteriorated because the grout under the base plate collapsed.
3. Evaluation of deformation capacity
The test results confirmed that the bending shear deformation of the dampers correlate highly with the shear stiffness of the resisting mechanism. In order to evaluate the deformation capacity of the tubular dampers, an influence factor to consider the bending shear deformation is introduced. The method to evaluate the deformation capacity with the regression formula for the factor is proposed.
4. Conclusion
The main conclusions are summarized as follows: 1) In the case of the specimens with concrete floor slab for shear resisting, the deformation capacity was the highest among the specimens in the loading tests. 2) The method to evaluate the deformation capacity with the empirical formula is proposed.
