Keywords: seismic retrofitting, performance based design, shear panels, low-yield steel, RC structures.

Among the new seismic design approaches, there are those based on the passive structural control systems. The main aim is to reduce the damage of the primary structure through the use of special devices acting as hysteretic and/or viscoelastic dampers. Many types of devices are based on the use of metallic yielding technology. Low yield steel shear panels could be very effective for this purpose because they allow the plastic deformation to be spread throughout the entire surface of the device rather than to be concentrated in a limited portion as it happens for many other systems [1]. Recently, a wide numerical and experimental research has been undertaken at the University of Naples Federico II in order to investigate the energy dissipation capacity of shear panels made of either low-yield steel (LYS) or pure aluminium and suitably reinforced by ribs to prevent shear buckling both in the elastic and plastic field [2].

On the other hand, low yield metal steel panels could be profitably used as new methodology for the seismic retrofitting of existing concrete structures [3]. Therefore in this paper, a preliminary design procedure is proposed, based on the performance design framework. This preliminary design procedure takes into account the characteristics of the original structure and requires a moderate level of engineering judgment with respect to the quantification of the displacement that would be acceptable for the original structure. The application of the preliminary design procedure gives the global characteristics of the required shear panels, i.e. the total stiffness, the total strength and the total displacement ductility. As, until now, there are no design charts available for the selection of the right panel configurations, the paper gives instructions on how to perform F.E. calculations in order to address this task. Therefore, on the basis of a FEM model, which has been set up by using the non-linear code ABAQUS, a numerical study is carried out, accounting for the effect of the main geometrical parameters (plate local slenderness and stiffness of applied ribs) on the shear capacity of the system. The numerical analyses are performed under both monotonic and cyclic loading procedures, aiming at determining the maximum strength and ductility of adopted shear panels. Besides, useful information on the hysteretic performance of shear panels is provided. Finally, the results obtained using non-linear F.E. modelling, are compared against the results obtained using more conventional modelling techniques, suitable for everyday engineering practice.

In order to demonstrate the procedure proposed in the paper an example of a real concrete frame structure is used. The obtained results are compared with respect to those obtained with the preliminary design procedure, proving the effectiveness of the proposed procedure (Figure 1).

1

Nakagawa, S., Kihara, H., Torii, S., Nakata, Y., Matsuoka, Y., Fujisawa K., Fukuda, K., "Hysteretic Behavior of Low Yield Strength Steel Panel Shear Walls: Experimental Investigation", in "Proc., 11th WCEE", Elsevier, CD-ROM, Paper No. 171, 1996.

2

De Matteis, G., Mazzolani, F.M., Panico S., "Pure Aluminium shear panels as dissipative control system for seismic protection of steel moment resisting frames", in "Proc., Behaviour of Steel Structures in Seismic Areas (STESSA 2003)", Balkema, The Netherlands, 609-614, 2003.

3

De Matteis, G., Mistakidis, E.S., "Seismic retrofitting of moment resisting frames using low yield steel panels as shear walls", in "Proc., Behaviour of Steel Structures in Seismic Areas (STESSA 2003)", Balkema, The Netherlands, 677-682, 2003.

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