Dynamic Tests on a Steel Frame Equipped with Hysteretic and Visco-Re-Centring Energy Dissipating Bracing Systems

Abstract An extensive program of dynamic experimental tests, named JetPacs (Joint Experimental Testing on Passive and semiActive Control Systems), has been carried out at the Structural Laboratory of the University of Basilicata considering a 1:1.5 scaled three-dimensional steel frame, derived from a 2-storey, 1-bay prototype building. The JetPacs Project was developed within the RELUIS 2005-08 project, founded by Italian Dept. of Civil Protection. This work refers to the experimental tests on the model equipped with two different EDB systems based on Hysteretic Dampers (HD) and visco-re-centering devices (SMA+VD). The devices were designed with the purpose of limiting the inter-storey drifts so that the frame yielding is surely prevented. The visco-re-centering device was obtained by coupling Viscous Dampers (VD), with re-centering device based on shape memory alloy (SMA) wires, while the Hysteretic Damper was constituted by low-carbon U-shaped steel plates. The main objective of this paper is to compare the seismic response of the structure with SMA+VD and HD EDB's in order to calibrate a new performance based design procedure for the evaluation of the mechanical characteristics of SMA+VD devices. In this paper, the experimental results of the shaking table tests, in terms of comparison of both design solutions which lead to a comparable level of protection for the framed structure, are shown. The results obtained by numerical nonlinear time history analysis (NTHA) of both design solutions are also showed and compared with experimental ones

From the Cure of the Simple Structural Analysis to the Control of the Final Technological Quality - The Conservation of "Santa Maria Degli Angeli Orphanage" in Castelgrande (Potenza, Italy)

The conservation work carried out on the “Santa Maria degli Angeli” Orphanage in Castelgrande (Potenza, Italy) following the earthquakes of 1980 and 1981 is a good example of the need to evolve and refine the concept of seismic consolidation and upgrade of monumental heritage; this, considering not only the needs of the current structural calculation, but also those related to the design of durability and overall technological quality. Built from 1878 around the original nucleus of a chapel, the seminary, then an orphanage, kindergarten, nursery school, sewing workshop and school, and summer mountain colony, constitute a precise landmark in the landscape of the ancient town of Castelgrande. Severely damaged by the earthquakes, it was declared unfit for use and evicted, and is still abandoned today.Immediately afterwards, radical refurbishment works were carried out on it, with the creation of sub-foundations, injections and tackles with reinforced concrete slabs for the load-bearing walls, replacement of the floors in steel beams and bricks with reinforced concrete floors, replacement of the wooden roofs with others of the same configuration, but in steel beams and clay tables, with a reinforced concrete slab above. The workings were not completed due to lack of funds and those performed so far show today serious pathologies (in particular the corrosion of the reinforcement of the joist of the floors and of the steel beams) as result of the lack of attention to fundamentals of materials science and of durability. Based on the current legislation and calculation methods, the research verified the seismic vulnerability of the building and proposed the necessary corrective actions: in particular, the replacement of the roofs with others, lighter and more durable, made of laminated, conditioned local Quercus cerris wood. A new destination has been proposed, linked to the presence of the Astronomical Observatory, and its upgrade to nZEB has been designed, in respect of its monumental features

Retrofit di edifici in c.a. tramite isolamento alla base

Con le nuove Norme Tecniche per le Costruzioni, emanate con D.M. 14 gennaio 2008, è stato introdotto un capitolo interamente dedicato alla progettazione delle strutture con isolamento sismico. Il testo delle norme, oltre a contenere i criteri per la progettazione di nuovi edifici, prevede anche la possibilità di utilizzare la tecnica dell’isolamento per interventi di retrofit di strutture esistenti. Se si considera che le strutture isolate, in genere, non subiscono danni significativi neanche in caso di terremoti violenti, l’applicazione dell’isolamento a strutture esistenti può consentire di realizzare, quando si presentino le corrette condizioni di applicazione, interventi economicamente accettabili, se non addirittura convenienti rispetto alle tecniche di rinforzo classiche, per effetto della ridotta esigenza di manutenzione post terremoto. Nel presente lavoro vengono illustrati i risultati sperimentali di diverse prove condotte su modelli sperimentali di strutture esistenti in c.a., nell’ambito di progetti di ricerca nazionali ed internazionali, finalizzate alla verifica dell’efficacia di tale strategia di protezione sismica, anche in termini di retrofit di strutture esistenti. Particolare attenzione viene data, inoltre, all’analisi delle procedure di progetto/verifica degli edifici con isolamento sismico previste dalle recenti NTC08 e relativa Circolare esplicativa e, allo scopo di illustrare i principali aspetti progettuali e costruttivi dell’adeguamento di edifici intelaiati in c.a. mediante isolamento sismico, viene, infine, riportata la procedura di progetto applicata ad un esempio di edificio esistente, con richiami ai relativi paragrafi delle norme