ROTATION CAPACITY OF STEEL MEMBERS
The purpose of this research theme is to give a contribution on the topic of the behaviour of Steel Moment Resisting Frames under seismic actions, and in particular on the members behaviour.
Starting from the assumption that in modern design practice it is generally accepted that steel is an excellent material for seismic-resistant structures because of its strength, ductility and capability to withstand substantial inelastic deformations, an experimental campaign on steel beams has been made. The principal scope of the work has been the revision of the classification criteria of steel members actually adopted by seismic codes and the introduction of a new criterion which takes into account the principal factors that influence the structural response.
A wide experimental campaign of monotonic and cyclic tests has been carried out to investigate the different parameters that influences the ductility and the overstrength of steel members: the material strength, different slenderness ratios and cyclic actions. Indeed, a wide range of cross sections has been tested, such as I sections, rectangular hollow sections (RHS) and square hollow sections (SHS). The cantilever beam scheme was adopted because it is representative of the behaviour of the beams of a MRF under seismic actions, and to take also in account the moment gradient. The size and the numbers of cycles has been programmed according to AISC protocol. During the tests different parameters has been monitored, such as the applied displacements, the applied forces and the displacements of different components, trough a total measurement device set composed of 6 LVDT, 2 inclinometers and 2 strain gages.
The processing of the experimental results allows to classify the tested profiles applying different classification criteria proposed by the technical codes EC3, NTC 08, OPCM 3274. From the comparison between the different classification criteria comes out that the classification criteria of EC3 is the less conservative, because according to it all the sections appear to be in the 1st class. Referring to the other two classification criteria it comes out a non coincidence of results, because the criterion adopted by NTC 08 is based on the definition of rotation capacity R, instead the OPCM 3274 is based on the definition of the overstrength factor s.
- COST ACTION C26 “Urban Habitat Constructions Under Catastrophic Events”, European Science Foundation, WG2 “Earthquake resistance”, 2006-2010.
- “Capacità rotazionale e criteri di classificazione delle membrature” RELUIS-DPC project, Line 5 (Sviluppo di Approcci Innovativi per il Progetto di Strutture in Acciaio e Composte Acciaio-Calcestruzzo), 2005-2008.
- “L’influenza della modellazione dei collegamenti sulla risposta sismo-resistente dei telai di acciaio” Research Program of National Interest (PRIN): “L’influenza dei collegamenti sul comportamento sismo-resistente delle strutture”, 1999-2001.