Semiactive Friction Connections for Seismic Control of Multi-Storey Buildings

This document describes an investigation of the efficiency of friction-based passive and semiactive systems for control of the seismic response of multi-storey buildings, and the mechanisms behind their performance. Passive and semiactive systems are novel strategies used to reduce the seismic demand in structural systems by increasing the energy dissipation capacity and altering the dynamic properties of the building. The investigation is conducted by the means of simulations of the non-linear response of low- and medium-rise frames to a variety of seismic excitations with different frequency content, using a computer program especially designed for this purpose. The efficiency of existing passive and four semiactive control systems, as it was demonstrated by the simulations, is closely related to pre-defined control parameters, which limit their effectiveness. In order to investigate the possibility of improving the performance of the existing control systems, two new algorithms are also developed in this research, exploring decentralised and partially decentralised architectures. The novelty of these new algorithms is the use of variable gain factors that determine the required control forces either: (i) based on the relation between the real-time response of the structure and pre-defined values of target deformation, which in this investigation are related to the elastic limits of deformation in the frame (decentralised system); or (ii) by proportionally determining the control forces into a novel strategy of maintaining a constant inter-storey drift along the height of the building (partially decentralised system). The performance of the new control systems on four multi-storey frames is compared to that of existing passive and semiactive systems. The results indicate an improved performance in the two new systems, in comparison to existing strategies, in terms of enhanced adaptability, by not compromising the levels of response reduction, but using lower levels of control forces.