FRP

thickness

FRP volumetric ratio Ultimate strain Neutral axis depth

Ultimate curvature Ultimate rotation Ultimate rotation absolute increase

FRP type tf (mm) qfrp = 2tf(b + d)/bd nccu (2) xc (mm) $u (rad/mm × 105) 8u (rad) Aabs。  (%)

Original — — 3。50 80。9 4。325 0。0125 0

1 GFRP ply 0。480 0。00768 7。30 72。07 10。129 0。0248 98

2 GFRP plies 0。960 0。01536 8。87 70。81 12。527 0。0298 138

3 GFRP plies 1。440 0。02304 10。08 70。12 14。376 0。0337 169

1 CFRP ply 0。166 0。00266 7。12 72。26 9。854 0。0242 93

2 CFRP plies 0。332 0。00531 8。62 70。98 12。145 0。0290 131

3 CFRP plies 0。498 0。00797 9。77 70。28 13。902 0。0327 161

Curvature (rad/mmx105)

Figure 6。 Moment–curvature for original, GFRP and CFRP upgraded C3 column cross-section。

left-hand side of the diagram with respect to CFRP confinement。 Figure 6 shows that both GFRP and CFRP confinements cause a negligible increase in the cross-section ultimate moment (from a value of Mu = 51。14 kN m in the original configuration to Mu = 51。48 kN m in the retrofitted one, whether for GFRP or CFRP confinement)。 In contrast, theoretical calculations clearly show that, with reference to the glass and carbon fibers selected, the curvature increase and the related

ultimate rotation increase (see Table IV) are very significant but are not substantially affected by the two different kinds of laminates。

Once it had been established that both materials were able to increase almost equally the ultimate concrete axial strain, hence both the ultimate curvature and ultimate rotation, given that in the case of interior application in buildings, durability performance is not the driving design criterion, the choice of the fibers to be utilized was essentially governed by costs。 Comparing the application costs per m2, it was calculated that by using uniaxial glass fibers with unit weight of 900 g/m2, instead of uniaxial carbon fibers with unit weight of 300 g/m2, the costs were reduced by about 30%。 This was the reason for selecting glass laminates。