CHALLENGES ON CLT STRUCTURES SEISMIC RESPONSE: TRADITIONAL SYSTEMS VS LOW-DAMAGE SYSTEMS Antonio SANDOLI 1 , Valentina TOMEI 2 , Barbara FERRACUTI 3 , Maria ZUCCONI 4 ABSTRACT In the last two decades the use of Cross Laminated Timber (CLT) panels is strongly increased in the field of low- rise timber constructions due to their easiness and quickness of construction, transportation, sustainability and good seismic response. In Europe CLT buildings are traditionally composed by arrangement of timber panels, connected one each other, and to the foundation, by means of mechanical timber-to-steel connections. The new frontiers of earthquake engineering require, in addition to human life safety, also the damage reduction after earthquake events. This requirement usually is not completely fulfilled by the traditional systems. To this aim, low-damage post-tensioned technologies for seismic resistance was introduced. PRES-LAM walls are hybrid systems constituted by rocking dissipative timber walls, whose main advantages are: (i) re-centering of walls during the seismic motion, (ii) added hysteretic dissipation, (iii) reparability of dissipaters. In this paper a review of state of the art is reported focusing the attention on the role of connections on traditional and hybrid systems and analysing their influence on the global seismic behaviour. Results of experimental tests carried out on entire walls or on subassembly of connections founded in literature are collected, compared and carefully analysed in order to highlight differences in terms of strength, stiffness, ductility and damage level exhibited by each system. Keywords: CLT systems; Connection systems; Dissipation systems; Low-damage system; PRES-LAM 1. INTRODUCTION In the last two decades the field of timber-based structures was strongly developed also in those countries not explicitly devoted to this kind of constructional technology. This development is principally due to the introduction of the engineered timber products (glue-lam elements, Cross- Laminated Timber CLT panels, Laminated Veneer Lumber LVL beams and panels, OSB panels, etc.) that gave the possibility to realize, in addition to the classics long-span roofs (trusses beams, domes, arches, etc.), also timber buildings for commercial and residential destinations in seismic-prone area. Moreover, the particular predisposition of the timber-based products and constructions towards the themes of life-cycle assessment, sustainability, and easiness of constructions has provided an important jump-forward in realizing this kind of structures. From structural point of view the timber buildings occupy a relevant position among the seismic resistant structures, due to their particular attitude to sustain high-intensity seismic loadings because of the light weight of the system, however some structural typologies could suffer a not negligible post- seismic damage. In particular, Rainer and Karacabely (2000) and Buchanan et al. (2011) analyzed the post-seismic damage observed after USA, New Zealand and Japan earthquakes in timber building highlighting a not negligible number of casualties occurred in mid-rise light-frame timber buildings, mainly due to soft-storey failure mechanisms. Moreover, the observed damage during the Kobe 1 PostDoc research fellow, University Niccolò Cusano, Rome, Italy, antonio.sandoli@unicusano.it 2 PostDoc research fellow, University Niccolò Cusano, Rome, Italy, valentina.tomei@unicusano.it 3 Associate Professor, University Niccolò Cusano, Rome, Italy, barbara.ferracuti@unicusano.it 4 Assistant Professor, University Niccolò Cusano, Rome, Italy, maria.zucconi@unicusano.it