Engineering Structures 30 (2008) 3513–3522 Contents lists available at ScienceDirect Engineering Structures journal homepage: www.elsevier.com/locate/engstruct Hybrid fluid-dynamic control devices to attenuate slender structures oscillations Ronaldo C. Battista a,∗ , Eliane M.L. Carvalho b , Roberto de Almeida Souza a a Instituto COPPE – Universidade Federal, Rio de Janeiro, Brazil b Universidade Federal Fluminense, Niterói, Brazil article info Article history: Received 24 November 2006 Received in revised form 25 December 2007 Accepted 26 May 2008 Available online 3 July 2008 Keywords: Structures Dynamic control Tuned fluid damper Wind induced oscillations abstract In the present work, a hybrid fluid-dynamic control system is proposed for the active/passive control of bending oscillations of tall and slender buildings under wind forces. The mathematical-numerical model of the hybrid system is developed from the classical tuned liquid column damper composed of one or more ‘‘U ’’ tubes filled with fluid. When in motion the control system generates hydraulic forces which counteract the inertia forces induced by the dynamic loadings acting on the structure. Some of the main design aspects, dynamic properties and the resulting performance of the proposed hybrid control system as compared to those of the traditional liquid columns and tuned mass dampers for passive control are presented and discussed with the aid of the results obtained by using both analytical and FEM models together with comparisons between the uncontrolled and controlled responses of the structure having attached the proposed hybrid fluid-dynamic devices. Two examples of a practical application are presented to demonstrate the feasibility and performance of the hybrid control device in attenuating the bending oscillation amplitudes of slender structures of tall buildings under wind forces. © 2008 Elsevier Ltd. All rights reserved. 1. Introduction Tall and slender building structures have, in general, low fre- quencies and damping ratios associated with their fundamental oscillation modes and, when subjected to dynamic loadings, they may experience large amplitudes of bending oscillation. To attenu- ate these oscillation amplitudes, alternative engineering solutions have been envisaged for each type of dynamic loading and for the physical and geometrical features of the structural system. These slender structures when subjected to strong winds can undergo significant oscillations, which may become unacceptable from the viewpoint of users comfort and structural serviceability as well as safety of the structure. The suppression of these oscillations has become an important design consideration in recent years. Many active and passive control devices such as the active and passive tuned mass dampers (AMD and TMD) [1,2], tuned liquid dampers (TLD) [3,4] and tuned liquid column dampers (TLCD) [5–7] have been proposed to mitigate excessive oscillations. The TLCD illustrated in Fig. 1 was first proposed by Sakai et al. [5], and is further explored in the present work. The TLCD dissipates the structural vibrations energy by a combined action ∗ Corresponding address: COPPE – Universidade Federal, Engenharia Civil, C. Postal 68506, CEP 21945-970 Rio de Janeiro, RJ, Brazil. Tel.: +55 21 2562 8477; fax: +55 21 2562 8484. E-mail address: battista@coc.ufrj.br (R.C. Battista). Fig. 1. Schematic of the TLCD. involving the motion of the liquid mass in the container, the restoring force on the liquid due to gravity, and the damping effect due to the to and fro flow of fluid through an orifice. The performance of the TLCD can generally be said to be dependent on the structural behaviour, damping and excitation as well as on the required level of reduction of vibrations. Once this system has a unidirectional action, it applies better to structures with a predominant top vibration direction. For other types of structures, a system composed of two TLCD in orthogonal direction has already been proposed and named double-tuned liquid column dampers (DTLCD) [6]. In the present work, a hybrid fluid-dynamic system (HTLCD) is proposed for the active/passive control of bending oscillations of tall and slender buildings under wind forces. The mathematical- numerical model of the hybrid system is developed [8] from its passive counterpart, which is a tuned liquid column damper made 0141-0296/$ – see front matter © 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.engstruct.2008.05.022