The damage on the rectangular column C6 was less significant even though crushing of concrete and cracks at the interface with beams were observed (see Negro et al。 [1])。

The experimental outcomes in terms of total absorbed energy, maximum base shear and top

displacement along with the maximum inter-story displacement for directions X and Y are sum- marized in Table I: the maximum base shear was reached along direction Y (276 kN) rather than X (195 kN)。 This was consistent with the arrangement of the wall-type column C6 placed with its strong axis in direction Y 。 In contrast, much larger top displacements were reached in direction X (0。1057 m) rather than Y where a maximum top displacement of 0。1031 m was achieved。 On the basis of the damages detected on the structure, Table I shows that the maximum inter-story drifts were reached at the second story (0。0570 m in X and 0。0472 m in Y )。

4。 POST-TEST ASSESSMENT OF THE ‘AS-BUILT’ STRUCTURE

Numerical analysis is performed with the aim of reproducing a typical design process that can be adopted by a structural engineer to assess an existing building。 The purpose was mainly to use a typical rehabilitation design methodology and verify its outcome by a qualitative comparison with the experiment; the analysis was not aimed at verifying the analytical model against the

experimental results。 Thus, a finite element analysis program, SAP2000 [8], very commonly used by structural engineering practitioners, was utilized to run the numerical analyses。 An assessment

procedure based on a pushover analysis was adopted; indeed, this method was considered more appropriate to a practitioner’s approach。

4。1。 Lumped plasticity model of the structure

A post-test assessment of structural global capacity was performed by nonlinear static pushover analysis on the ‘as-built’ structure。 Pushover analyses in the longitudinal and transverse directions were performed by subjecting the structure to a monotonically increasing pattern of lateral forces proportional to the 1st and 2nd modes of vibration (in directions X and Y , respectively) and mass distribution。 Lateral loads were applied at the location of the center of masses in the model。 Center of mass at each story, mass values, modal displacements of each center of mass in directions X and Y , along with the corresponding normalized lateral loads, are summarized in Table II。

In the analytical model slabs were omitted and their contribution to beam stiffness and strength was considered, assuming a T cross-section for the beams with the effective flange width equal to the rectangular beam width (250 mm) plus 7% of the clear span of the beam on either side of the web [9]。 This assumption provides flange width values between the conservative flange

width indicated in Eurocode 8 [7] for design purposes and the width recommended for gravity

load design。 Moreover, to take into account the effect of the slabs, a rigid diaphragm was assumed

at each story of the model。 For a comprehensive study of the seismic response of existing RC buildings, shear failure of members should be taken into consideration; however, in the present case it was not considered because shear demand was significantly lower than both beam and

Table II。 Geometrical characteristics, mass times modal displacement and normalized lateral loads for directions  X  and Y 。

Mass × modal Normalized Mass × modal Normalized displacement lateral displacement lateral

Center of (1st mode)