An extensive experimental program of shaking table tests on reduced-scale structural models was carried out within the activities of the MANSIDE project, for the development of new seismic isolation and energy dissipation devices based on Shape Memory Alloys (SMAs). The aim of the experimental program was to compare the behaviour of structures endowed with innovative SMA-based devices to the behaviour of conventional structures and of structures endowed with currently used passive control systems.\ud This paper presents a comprehensive overview of the main results of the shaking table tests carried out on the models with and without special braces. Two dierent types of energy dissipating and recentring braces have been considered to enhance the seismic performances of the tested model. They are based on the hysteretic properties of steel elements and on the superelastic properties of SMAs, respectively.\ud The addition of passive control braces in the reinforced concrete frame resulted in signicant benefits on the overall seismic behaviour. The seismic intensity producing structural collapse was considerably raised, interstorey drifts and shear forces in columns were drastically reduced

SUMMARYThe paper presents a numerical investigation aimed at evaluating the improvements achievable through devices for passive seismic protection of buildings based on the use of shape memory alloys (SMA) in place of conventional steel or rubber devices. To get some generality in the results, di erent resisting reinforced concrete plane frames were analysed, either protected or not. 'New' and 'existing' buildings were considered depending on whether seismic provisions are adopted in the building design or not. Base isolation and energy dissipation were equally addressed for both conventional and innovative SMA-based devices. Fragility analyses were performed using speciÿc damage measures to account for comparisons among di erent damage types; the results were then used to estimate quantitatively the e ectiveness of the various protection systems. More speciÿcally, the assessment involved a direct comparison of the damage reduction provided by each protection system with respect to the severe degradation experienced by the corresponding non-protected frame. Structural damage, non-structural damage and damage to contents were used on purpose and included in a subsequent phase of cost analysis to evaluate the expected gains also in terms of economic beneÿts and life loss prevention. The results indicate that base isolation, when applicable, provides higher degrees of safety than energy dissipation does; moreover, the use of SMA-based devices generally brings about better performances, also in consideration of the reduced functional and maintenance requirements.

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A new technique for the identification of nonlinearity in multi-degree of freedom systems is presented. The technique is based on the joint application of the Gabor and the Hilbert transforms to the transient response of a system. The Gabor transform is used first to identify a time-variant matrix representing the spatial behaviour of the system. This matrix is then used to decouple the transient response into a set of uncoupled quasi-harmonic components. Finally the Hilbert transform is applied to identify the dissipative and restoring forces associated with each component which is equivalent to a single degree of freedom system. Numerical examples are supplied to help clarify the main advantages and the possible limitations of the method in the presence of strong nonlinearities and closely spaced frequencies.

Sensitivity and identifiability problems of the modal parameters in the presence of corrosion damage are studied. The first concerns the rate of change of the modal parameters against the damage increase. The second concerns the uncertainty intervals overlapping of the modal parameters between the sound and damaged states. To this end, different testing methods, different identification methods (time, frequency and time-frequency methods), different corrosion levels and different thermal condition (summer-winter) are considered. Prestressed concrete beams of identical geometry endowed with low to high reinforcement ratios are dynamically tested. The free decaying vibrations are used to identify the modal parameters: frequency, modal shapes and damping. The prestressing force is found to be not a variable of the problem. The damage levels range from very low to moderate. It is found that reliable damage identification is possible only for moderate damage. In spite of higher scatter, damping reveals a more stable and sensitive indicator than frequency. Modal shapes shows regular changes, but within the range of the uncertainty intervals.

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The problem of damage identification in presence of uncertainties is faced up in the framework of interval analysis. A method previously developed by the authors in the context of model updating and global minimization for dynamic problems is applied to identify the damage in framed structures. The inclusion property of the interval analysis is exploited to find the bounds of the physical solutions. Model parameters, experimental measures and modelling errors are considered as possible sources of uncertainty. The advantages of the interval approach are discussed through numerical simulations involving the different kind of uncertainties.