APPLICATION OF TRANSLATIONAL TUNED-MASS DAMPERS ON THE SEVEN STOREY BUILDING TESTED WITHIN THE SOFIE PROJECT Guillaume Hervé poh’sie 1 , Giovanni Rinaldin 2 , Massimo Fragiacomo 3 , Claudio Amadio 4 , Ario Ceccotti 5 ABSTRACT The paper presents a numerical study conducted on a seven storey cross-laminated (X-lam) buildings equipped with translational Tuned Mass Dampers (TMD’s), as a technique for reducing the notoriously high drifts and maximum seismic accelerations of these types of structures. The building was modelled in the finite element software package Abaqus using 2D elastic shell elements and non-linear springs, which were implemented as an external user subroutine and properly calibrated to simulate the cyclic behavior of connectors in X-lam buildings. The used TMD device is linear, and placed on the top of the building. Time-history dynamic analyses were carried out under natural earthquake ground motions. Several comparisons between the response of the structure with and without TMD are presented, and the effectiveness and limits of these devices to improve the seismic performance of X-lam buildings are critically discussed. KEYWORDS: tuned mass dampers, non-linear springs, X-lam, dynamic analysis, seismic resistance 1 INTRODUCTION 123 The concept of Tuned Mass Damper (TMD) dates back to the last century, as it can already be recognized in the proposal made by Frahm (1909) with his undamped dynamic absorber [1]. A TMD consists of an additional mass, connected to the structure by means of an elastic element and a damper, able to dissipate energy. The TMD has been applied extensively to control wind-induced vibrations, whereas the use to control earthquake-induced effects is still the subject of research. The mass of the TMD affects significantly the response, as well as the 1 Guillaume Herve Poh’sie, PhD candidate, University of Trieste, Piazzale Europa 1, Trieste, TS, Italy. Email: pguillaumeherve@gmail.com 2 Giovanni Rinaldin, Post-doc Research Fellow, University of Sassari, Palazzo del Pou Salit, Piazza Duomo 6, Alghero, SS, Italy. Email: grinaldin@uniss.it 3 Massimo Fragiacomo, Associate Professor, University of Sassari, Palazzo del Pou Salit, Piazza Duomo 6, Alghero, SS, Italy. Email: fragiacomo@uniss.it 4 Claudio Amadio, Full Professor, University of Trieste, Piazzale Europa 1, Trieste, TS, Italy. Email: amadio@units.it 5 Ario Ceccotti, Director, Trees and Timber Institute of the National Research Council of Italy (CNR-IVALSA), Via Madonna del Piano 10, 50019 Sesto Fiorentino (FI) – Italy, ario@iuav.it possible friction along the sliding surface, which must be as small as possible to allow the initiation of motion even for small excitations (for example, vibrations in operating conditions, such as those induced by wind and frequent low intensity earthquake ground motions). A large number of TMD’s was installed on tall buildings, bridges, towers, chimneys, to control the response to wind actions, and the mass of the TMD is typically formed from blocks made of lead, steel or concrete. In this paper, the effectiveness of TMD installed on multi- storey wooden buildings against seismic actions is investigated. The results of the analysis performed with the mass ratio (TMD mass over building mass ratio) that provides the maximum benefit on the studied buildings are presented. All analyses conducted on the three- dimensional model of the building were carried out with the finite element program Abaqus (Simulia, 2012) [2]. The analysed building is part of the SOFIE project (CNR- IVALSA, 2008) [3], the purpose of which was to investigate the ability of cross-laminated (X-lam) buildings to resist earthquakes (see Figures 1 and 2). 2 TUNED MASS DAMPERS MODEl The proposed model of tuned mass damper is to control the first two vibration modes of the main structure. The TMD