Numerical modeling of a rocking and sliding cylindrical column under seismic excitation

This paper presents a finite element (FE) modeling approach for simulating the 3D response of a free-standing cylindrical column. The model is validated against experimental results, which involved testing of the cylindrical steel column under a set of 100 bidirectional ground motions. The specimen was free-standing and allowed to slide and rock in all directions. Both the tested specimen and the shake table platen were stiff enough to be modeled as rigid. The contact surface was modeled using Coulomb friction for the tangential behavior and stiff con-tact for the normal direction. Two energy dissipation mechanisms were modelled; friction and radiation damping. Since Rayleigh damping is not directly linked to the physical problem, it was set equal to zero. It has been proven that the response of a single column to an individual ground motion is a chaotic and unpredictable problem. Therefore, a statistical approach was utilized to compare the numerical to the experimental results, using the cumulative distribution function (CDF) for the main response quantities (i.e., maximum displacement at the top of the column and residual displacement), demonstrating satisfying agreement. The influence of the friction coefficient was assessed through an extensive sensitivity analysis using non-linear time-history analyses. Results proved that the statistics of the response only smoothly depend on the exact value of the friction coefficient even though the response to an individual ground motion seems chaotic.