Keywords: dissipative systems, pure aluminium, seismic control, shear panels, steel frames, FEM model.

The protection of buildings against seismic damage is based on inserting into the primary framed structure special devices acting as hysteretic and/or viscoelastic dampers. Shear panels really represent a convenient system for passive seismic protection of framed buildings for low and high intensity earthquakes thanks to their remarkable lateral stiffness, limited elastic strength, high hardening and large ductility. Their dissipative action is based on the metallic yielding technology and if they are provided with appropriate stiffeners, they can also give rise to a large energy dissipation capacity related to the large portion of panel where shear plastic deformations take place before the local and global buckling phenomena occur.

Recently, a wide experimental and numerical programme has been undertaken at the University of Naples "Federico II" in order to investigate the energy dissipation capacity of aluminium alloy shear panels, subjected to heat treatment to improve the ductility properties and to reduce the residual stresses and suitably reinforced by ribs to prevent shear buckling both in the elastic and plastic field. As applied material, the pure aluminium (EN-AW 1050A) has been chosen because of its very low strength, large ductility, low specific weight and availability on the market.

Experimental cyclic tests on 1000x1500 mm aluminium shear panels, characterised by different stiffeners configuration, have been carried out. To simulate the monotonic and hysteretic behaviour of the systems, according to the experimental tests, a sophisticated FEM model has been set up. Such a model has been calibrated according to the main behavioural phenomena (plate local buckling, rib buckling and panel global buckling) evidenced during the tests. Also, all specimen imperfections have been taken into account.

The comparison between experimental and numerical results shows that the proposed model is reliable enough to well interpret a number of important behavioural phenomena, such as local shear plastic buckling, rib buckling, global shear buckling of the panel and interactive instabilities. Also the developed deformed shapes are in good agreement with the ones seen in the experimental tests. Therefore, the numerical results appear to be adequate both in terms of shear stress-shear strain curve and in terms of the main global features of the system (energy dissipation capacity, global secant stiffness and equivalent damping ratio).

On the other hand, it has been noted that the proposed model is not able to well interpret the very early stages of the loading process, but this could be due to the fact that the effect of the residual stresses is not considered due to the lack of experimental data. Further improvement to the numerical model in this direction is desirable.

1

S. Panico, G. De Matteis and F.M. Mazzolani, "Numerical investigation on pure aluminium shear panels", Proc. of the XIX Convegno C.T.A., 2, 459-470, Genova, Italy, 2003.

2

G. De Matteis, F. Addelio and F.M. Mazzolani, "Sul dimensionamento dei pannelli di alluminio puro per la protezione sismica di telai di acciaio", Proc. of the 11th National Congress Anidis "L'Ingegneria Sismica in Italia", Genova, Italy, 2004.

3

G. De Matteis, F.M. Mazzolani and S. Panico, "Numerical analysis of pure aluminium stiffened shear panels for design optimisation", Proc. of IV International Conference CIMS '04 (Coupled Instabilities in Metal Structures), Rome, Italy, 2004.

4

G. De Matteis, A. Formisano, F.M. Mazzolani and S. Panico, "Design of Low-Yield Metal Shear Panels for Energy Dissipation", Proc. of Cost C12 Conference, Innsbruck, January 2005.

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