Ricerc@Sapienza

The high socio-economic impacts of moderate-to-strong earthquakes in terms of damage, dollars and downtime have highlighted the great divergence between societal expectations and the reality of modern building seismic performance. Community strongly requires raising the bar of the current seismic design philosophy, that conceives structures as ductile systems where inelasticity is concentrated within plastic hinge regions. Well complying with these methodologies many modern buildings have behaved as expected in recent earthquakes, however in many cases they were severely damaged. Therefore, the design target should be shifted towards low-damage design criteria, where the performance/damage of the entire building system can be controlled well under reparability threshold and towards operational limit states.
In light of these considerations, an EU-funded project, titled “(Towards the) Ultimate Earthquake proof Building System: development and testing of integrated low-damage technologies for structural and non-structural elements”, has been proposed and developed with the aim of promoting and supporting the wider implementation for such low-damage design philosophy and solutions for the whole building system, i.e. comprising both the structural skeleton and the non-structural envelopes/partitions . An experimental campaign consisting of 3D shaking table tests has been performed at the Laboratorio Nacional de Engenharia Civil (LNEC) in Lisbon on a half scaled 2-storeys timber-concrete low-damage building (PRESSS and Pres-Lam technologies) including either low-damage or high-performance non-structural elements. The structural skeleton is based on controlled rocking and dissipative frame and wall systems combining self-centering (post-tensioned cables/bars) and dissipative (Plug&Play dissipaters) capabilities, while different non-structural elements are attached to the structural system forming an integrated high-performance building.
In this paper focus is given to the structural skeleton and its detailing. The timber-concrete low-damage structural system is described from the design procedure to the experimental testing. The initial analytical studies implemented using a Direct Displacement Based Design (DDBD) approach are briefly mentioned. The seismic design of the specimen – both Frame and Wall directions - was developed following this methodology where the design actions of the structural members were found through an equilibrium approach. Then, the experimental results in terms of floor accelerations, displacements, drift ratios are compared to the numerical results, developed using a lumped plasticity approach and non-linear dynamic analyses in Ruaumoko 3D software. The efficiency of the implemented numerical modeling in capturing the structural behavior is thus proved.