Multi-performance evaluation of traditional and low-damage non-structural components

Non-structural components include all the building elements not part of the main loadbearing system of a structure or an industrial facility. These components are designed to provide specific performance, such as controlling the passage of heat or resisting to fire, while the seismic behaviour is typically neglected in the design process. Nevertheless, the response of these elements can significantly affect the building functionality after earthquakes, even for low-intensity events, and their poor performance can result in substantial economic losses and business interruption. Consequently, the non-structural damage has a severe impact on the post-earthquake building recovery in addition to the potential risk to life safety. As either the earthquake engineering community or the public demand a higher level of earthquake protection, improving the seismic performance of structural systems is not enough and the expectation of advanced seismic behaviour for non-structural components is demanded. The need for reduction of non-structural seismic risk is thus being recognized fundamental in the decision-making process and in the performance-based seismic design the attention is nowadays focusing on both the harmonization of structural/non-structural performance and the development of damage-control or low-damage non-structural systems. Considering the previous background, this Thesis mainly aims to: 1) provide evidence on the convenience of implementing innovative low-damage technologies for non-structural components, 2) highlight the importance of including the study of the seismic performance of new or retrofitted elements within an integrated multi-performance design approach. The Thesis initially provides an overview of the damage states/mechanisms evolving during earthquake shakings in different typologies of non-structural elements, i.e. architectural elements, building services and contents. Fragility curves developed from past experimental research are also collected; in fact, determining which parameters mainly influence the failure modes and when a damage condition is achieved can help in the proposal of new solutions. Then, a literature review can be found on the innovative damage-mitigation technologies developed during the last decades for both structural and non-structural components. These solutions can be combined to define an integrated high-performance earthquake-proof building system. The Thesis also describes the experimental investigations (1D shake-table testing) carried out on a new earthquake-resistant solution proposed with the aim of reducing the seismic demand on non-structural systems anchored to concrete structures, i.e. supplemental damping is added to post-installed fasteners. The test results confirm the beneficial effects of this solution to seismically protect the non-structural elements for expansion or chemical fasteners in both un-cracked and cracked concrete. The convenience of implementing low-damage systems is thus investigated through numerical and experimental studies. Cost/performance-based evaluations of multi-storey buildings comprising different traditional vs. low-damage structural systems (frames, walls) and non-structural elements (facades, partitions, ceilings) are performed to highlight that these solutions are able to withstand earthquake shakings with negligible damage, consequently reducing the expected losses in terms of repair costs and downtime. The high performance of such types of technologies, and particularly of the integrated system, is also proved through 3D shake-table tests of a 1:2 scale two storey-two bay building, consisting of a low-damage timber-concrete structural skeleton and high performance or damage-control non-structural components/envelopes. The experimental campaign is fully described from the design of the specimen and of its structural/non-structural detailing, to the construction and assembly phases, to the test setup. Preliminary experimental results are provided, focusing on the seismic demand/performance of all the tested non-structural components. Finally, the importance of implementing a multi-performance design approach for nonstructural components is presented in the last part of the Thesis. An integrated seismic & energy cost/performance investigation of traditional vs. low-energy and/or low-damage façade systems is initially carried out, to highlight that the dynamic behaviour of these systems must be studied to better design the non-structural detailing. Furthermore, a multi-criteria decision analysis, including all the non-structural performance (structural, architectural, long-term) and the initial cost as criteria/sub-criteria, is proposed and developed in order to drive decisions on non-structural systems, i.e. defining the best solution/detailing among alternatives.