analytical study (see Jeong and Elnashai [6]), this record was selected among many different earthquake scenarios because: (1) the analysis of inter-story drift time histories (that provides

more accurate results than static pushover analysis in the case of irregular buildings) showed that it could induce no pronounced peaks in terms of inter-story drifts especially in the earlier part of the response, thus allowing the collection of considerable experimental results before subjecting the structure to the maximum demand; (2) this record is Eurocode 8 [7] spectrum compatible。

As the retrofit phase was intended to consist of a ‘light’ intervention, the appropriate intensity of

PGA was chosen in order to obtain a level of damage in the first round of tests significant but not so severe as to be beyond repair。 Thus, it was decided to run the test in the ‘as-built’ configuration

Table I。 Experimental  outcomes。

Test Total absorbed energy (kJ) Max base shear (kN) Max top displ。 (m)

Level Max I –S displ。 (m)

‘As-built’ 0。20g 44。00 195 0。1057 1 0。0246

2 0。0570

3 0。0358

X -direction FRP retrofit 0。20g 42。20 211 0。1088 1 0。0320

2 0。0554

3 0。0343

FRP retrofit 0。30g 83。36 196 0。2053 1 0。0594

2 0。1060

3 0。0635

‘As-built’ 0。20g 65。00 276 0。1031 1 0。0306

2 0。0472

3 0。0326

Y -direction FRP retrofit 0。20g 68。66 287 0。1125 1 0。0397

2 0。0476

3 0。0311

FRP retrofit 0。30g 104。38 281 0。1266 1 0。0423

2 0。0559

3 0。0507

with a scaled PGA level of 0。20g。 The results of the first test showed that the major damage concerned the ends of the square columns with crushing of concrete at all stories。 The level of damage was more significant at the second story。 For each floor, the most damaged members were the columns, where torsional effects produced inclined cracks on the compressive sides。 During tests, significant cracks opened on the tensile side of the columns at the beam–column interface。