C

0

-0。15 -0。10 -0。05 0。00 0。05 0。10 0。15

Top displacement [m]

Figure 3。 Pushover curves for the assessment of the ‘as-built’ structure   capacity。

The simplified assumption of shear span LV = 0。5L during the horizontal loading process was adopted in modeling the structure [12]。 Given that the original detailed construction drawings were known and the comprehensive material testing was performed, a knowledge level equal to 3, KL3, was assumed (according to the Ordinance 3431 [11]) corresponding to a confidence factor (i。e。 CF) of 1。 As a consequence of this knowledge level, the average strength values for materials were

assumed in the analysis。

4。2。 Theoretical capacity vs demand

The significant damage limit state (LSSD), which corresponds, according to Ordinance 3431 [11], to attainment of the 0。758u in one of the plastic hinges, was investigated to assess the structural capacity。

On the basis of such a limit state, pushover analyses on the ‘as-built’ structure were performed in the longitudinal direction (positive and negative X directions, named PX and NX , respectively) and in transverse direction (positive and negative Y directions, named PY and NY , respectively) (see Figure 3)。 The theoretical results in terms of maximum base shear, Fmax, top displacement, dmax, and absolute inter-story displacement are summarized in Table III。

Seismic demand was computed with reference to the Ordinance 3431 [11] design spectrum (soil

type c, 5% damping) which provides a pseudo-acceleration spectrum compatible with that obtained

by the experimental ground motion record, Montenegro Herceg Novi (see Figure 4)。 Although the ‘as-built’ structure was tested under a maximum PGA level of 0。20g, theoretical analysis was also performed for a seismic level of 0。30g to evaluate the theoretical structural performance under a larger seismic action intensity。 Seismic demand was calculated by combining the pushover analysis of an equivalent multi-degree-of-freedom (MDOF) model with the response spectrum of an equivalent single-degree-of-freedom (SDOF) system。 The results in terms of maximum top

Table III。 Summary of the results in terms of capacity and demand for the ‘as-built’ and the FRP-retrofitted structure。

‘As-built’ structure FRP-retrofitted structure

Capacity Demand Capacity Demand

Push Limit 0。20g 0。30g 0。20g 0。30g

direction state Level Fmax  (kN) dmax  (m)   IS displ。  (m) dmax  (m)   dmax  (m) Fmax  (kN) dmax  (m)   IS displ。 (m)   dmax  (m)   dmax   (m)

PX LSSD 1 232 0。0690 0。0124 0。0623