Simulation of three-dimensional seismic building response including nonlinearity and semiactive control

The seismic response of a three-dimensional framed structure with yielding of the girders and controlled by a semiactive magnetorheological damper system is numerically simulated. The simplifying assumptions of the numerical model are outlined, and the techniques used to reduce the number of degrees of freedom are explained and derived. An algorithm for a nonlinear beam element is developed and implemented in a nonlinear finite element code that has been developed in conjunction with the present study.; This nonlinear finite element code is general purpose. It has the advantage of being implemented in MATLAB using object-oriented techniques, designed with a modular framework, and perhaps most importantly, released under the GNU General Public License that ensures that the source code is available to all users for modification and redistribution.; Semiactive MHF, LQR, and robust H_∞ control strategies are used to develop the control laws for the magnetorheological damper system. The results from these semiactive strategies are compared to those for the uncontrolled structure and to those for a structure using a passive mode magnetorheological damper system. The comparisons are made in order to judge the effectiveness of the semiactive strategies. Six seismic time histories are used as the structural excitation. Evaluation criteria are defined and used to judge the effectiveness of the control system with respect to structural response, yielding, and control effort. The effects of eccentricity of the three-dimensional model are examined, and observations are made about the use of story drift as a structural control benchmark. The lack of stiction in the magnetorheological damper model is investigated and the efficacy of semiactive control as compared to equivalent passive and active strategies is discussed.; It is found that the magnetorheological dampers are effective in reducing the response of the structure and the reduction achieved is similar to that from a comparable fully-active control device. However, the semiactive control strategies were not significantly more effective than the passive mode magnetorheological damper. Eccentricity was found to cause no significant change in the effectiveness of structural control and stiction effects do not seem to be significant.