Semi-active Pneumatic Devices for Control of MDOF Structures

A preliminary study of a semi-active control system with pneumatic devices, aimed to improve the response of multi-degree of freedom structures to earthquakes, is presented. The devices are attached at various levels of a structural frame. The aim of the design is to find a combination of forces that are produced by the devices, in order to obtain optimal structural response. The mechanical response of the devices is regulated by air pressure, which is varied in each device at every time step in such a way that the forces in the devices will be close as possible to those, obtained by the optimization procedure. Linear auto-regressive model with exogenous input is used to predict the displacements and the velocities of the frame in order to overcome the time delay in the control system. The control forces are calculated at every time step, using the instantaneous optimal control algorithm, according to the values of the displacements and of the velocities that are predicted for the next time step, for each story of the structure. Numerical analysis of a seven story structure with pneumatic devices was carried out. It shows a significant improvement of the structural response when the proposed control system is applied, compared to that of an uncontrolled structure and of a structure with semi-active controlled electrorheological dampers.