FRP bar properties - Reinforced Concrete with FRP Bars: Mechanics and Design - page 55

Figure 3.19 Voids due to the presence of hollow glass fibers.
3.3.6 Bent bars
Only FRP bars that are made with thermosetting resin are allowed by ACI
440.6. For such bars, the bends can be made only while the resin is still in
its liquid state. ACI 440.6 defines the minimum values of inside bend radius
for GFRP and CFRP bent bars (Table 3.4). Minimum values of the strength
of bends have not yet been established.
3.4 PERFORMANCE OF FRP RC UNDER
FIRE CONDITIONS
The performance of an FRP RC member under fire strictly relies on the
temperature the embedded bars experience. When the surface of an FRP
bar embedded in the concrete exposed to fire approaches the glass transi-
tion temperature ( T g ) of the resin matrix, the resin begins to decompose and
eventually becomes unable to transfer the stresses from the concrete to the
fibers because of the loss of bond between the FRP bar and the surrounding
concrete. When the temperature of the bar exceeds T g , the individual fibers
can continue to carry the load if adequate bond is provided in the zones not
exposed to fire ( cold anchorage region ). The RC member collapse ultimately
occurs when the temperature of the fibers reaches their critical temperature .
The behavior of FRP bars under fire conditions is affected by several
parameters, namely fiber type, matrix type, bar diameter, fiber volume
fraction, manufacturing process, and surface treatment. Available research