Modeling and seismic response of structures with concrete rocking columns and viscous dampers

The maximum acceleration response of a simple yielding structure is proportional to its structural strength. Therefore, in order to reduce accelerations, the overall strength of the structure should be decreased while controlling possible resulting increases of displacements with supplemental damping. The use of "rocking columns", a type of double hinged gravity column, is suggested to reduce the strength of part of the lateral resisting system. A simplified analytical model of the columns represented by a moment-curvature relationship and a stiffness matrix, verified through experiments, is developed and implemented in the structural analysis program IDARC2D. The experimental study done on rocking concrete columns is briefly presented to show their global behavior and adjust the simplified model. For dynamic analysis, nonlinear stress zone approach and hysteretic models are also developed. A numerical study is conducted to demonstrate that story acceleration responses can be reduced compared to conventional structures, while the increased displacements are controlled using supplemental viscous dampers. A 1/3 scaled model structure, previously tested at the University at Buffalo, is used to evaluate the global seismic behavior of weakening alternatives modified using rocking columns and added viscous dampers.