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TECHNICAL PAPER

M1 M2 M3 M4 M1 M2 M3 M4
0 0 24 kN
24 kN
1 1 60 kN
60 kN
2 2 84 kN
3 4 84 kN 3 4 116 kN
Deflection (mm) 5 6 100 kN Deflection (mm) 5 6 136 kN

160 kN

7 114 kN 7
184 kN
8 8
196 kN
9
9
10 10
Figure 9(a): Deflection profile along center line of overhang [M-line in Figure 9(b): Deflection profile along center line of overhang [M-line in
Figure 5(a)] in the unstrengthened state Figure 5(a)] in the NSM FRP-strengthened state

It is noteworthy that removal of loose concrete after testing It should be noted that position 2 [see Figure 5(a)] represents a
showed that bond between the NSM FRP and concrete was location above the outer stem of the box-girder and therefore
largely maintained except in the area of diagonal cracking in represents the end of the overhang. In all cases, it is seen that
the concrete [Figure 8(b)] in a manner similar to that of the there is virtually no discernable deflection past this point. In
as-built specimen but at a significantly higher load due to the both cases (center line and edge), the addition of the NSM FRP
strengthening action of the NSM FRP strips. The maximum strips results in a decrease in deflection at comparable loads as
strain value recorded in the CFRP strips at ultimate capacity was measured by the two potentiometers closest to the overhang
3846 microstrain indicating that the FRP itself was not close to
rupture. edge [points 3 and 4 in Figure 5(a)] with the deflections in the
strengthened case as shown in Figure 10(b), as an example
It is of interest to compare deflection profiles as measured being between 68% and 78% of those in the unstrengthened
by the linear potentiometers between the as-built and case in Figure 10(a). The effectiveness of the NSM FRP strips is
strengthened specimens. Figures 9(a) and (b) compare profiles further highlighted by the fact that the deflection away from the
along the center line of the specimen denoted by line M in the edge is lower in the strengthened case even at the higher load
layout in Figure 5(a), while Figures 10(a) and (b) compare profiles levels.
along line A in the layout in Figure 5(a) which is adjacent to an
outer edge of the specimen.

A1 A2 A3 A4 A1 A2 A3 A4
0 0
24 kN 24 kN
1 1
60 kN
2 60 kN 2
84 kN
3 84 kN 3 116 kN
Deflection (mm) 4 5 102 kN Deflection (mm) 4 5 136 kN

114 kN
160 kN
6
7 6 7
8 8
184 kN
9 9
196 kN
10 10
Figure 10(a): Deflection profile along a line of linear potentiometers Figure 10(b): Deflection profile along a line of linear potentiometers adjacent
adjacent to the edge of the unstrengthened test specimen to the edge of the test specimen in the NSM FRP-strengthened state

16 THE INDIAN CONCRETE JOURNAL | JUNE 2021