Peter Hitchcock

Vibration Control of a Wind-Excited Benchmark Tall Building with Complex Lateral-Torsional Modes of Vibration

This paper describes a proposed wind-excited benchmark tall building incorporating three-dimensional lateral-torsional modes of vibration, which is typical of a significant number of modern tall buildings. A series of wind tunnel pressure tests were conducted on a 1:400 scale model to determine the translational and torsional wind forces acting on the benchmark building. A finite element model was also constructed and mass, damping, and stiffness matrices were subsequently formulated as an evaluation model for numerical analysis. The evaluation model was further simplified to a state reduced-order system (ROS) using the state order reduction method. A numerical vibration control example was conducted to demonstrate the suppression of the wind-induced three-dimensional lateral-torsional motions using a bi-directional tuned mass damper (TMD) incorporating two magnetorheological (MR) dampers, one in each orthogonal direction, to act as a semi-active control system, referred to as a smart tuned mass damper (STMD). The optimal control forces generated by the MR dampers were obtained through the linear quadratic regulator (LQR) to minimize the storey accelerations. The formulation details, methodology and numerical simulation results are outlined in this paper.

Damping Enhancements Of A 5 Storey Benchmark Building Using Liquid Column Vibration Absorbers

This paper examines the response reduction capabilities of a passive fluid damper device known as the liquid column vibration absorber (LCVA), when installed on a 5 storey benchmark building structure requiring control. The 5 storey benchmark building, is a scaled model of 3.6 metres maximum height, that is excited at its base level on a shake table. The benchmark frame is one in a series of recognised benchmark buildings for research into control, as adopted by the hternational Association for Structural Control (IASC). The behaviour of the LCVA, unlike prior studies, has been examined utilising computational fluid dynamics (CFD) software, solving for the Navier Stokes equations. The dynamic behaviour of the structure is examined by utilisng capabilities of structural finite element software, adopting the Newmark time integration method of solution. In order to study the interaction of fluid and structure for vibration control conditions, two series of tests were conducted. The first examined the effective damping added to the structure by using the LCVA, under free vibration conditions. A comparison was made to uncontrolled free vibration of the structure, and the effective damping was evaluated based on the RMS response reduction achieved. The structure was then implemented with an appropriate single LCVA, and re-excited with a specified wind load. The wind load was simulated as an equivalent base acceleration. The resulting reduction in wind response was then examined. Using this approach, the potential of using the LCVA as a vibration control device is illustrated. Furthermore, the use of a coupled CFD structural analysis to understand the overall behaviour is demonstrated.