al. 1990; Sheikh and Khoury 1993; Yeh et al. 2002). Park and Pauley (1975(b)) have
argued that the available ultimate deformation is not necessarily the deformation that
corresponds to the maximum load capacity. They further said that "when survival without
collapse is the criterion, it is too conservative to define ultimate deformation as the
deformation corresponding to the maximum load-carrying capacity. It would seem
reasonable to recognize at least some of this deformation capacity after the maximum
load has been reached and to define and to define the available ultimate deformation as
that deformation when the load-carrying capacity has reduced by some arbitrary amount
after maximum load. For example, a 10 or 20% reduction in maximum load-carrying
capacity could be tolerated in many cases, but the exact amount would depend on the
particular case".
The yield displacement is defined as the displacement at the intersection of the
horizontal line representing the ideal lateral capacity, P,, (nominal capacity using the ACI
318 approach and a reduction factor of unity) and the straight line that passes through
zero and the point in the load-displacement curve at 75% of the ideal lateral capacity
(Priestley and Park 1987; Zahn et al. 1990; Sheikh and Khoury 1993). The definitions of
yield and ultimate displacements are depicted in Fig. 2-2.
Because FRP reinforced concrete exhibit different behavior than steel reinforced
concrete due to the absence of a yield point of the FRP reinforcement researchers have
attempted to produce ductility factors also called deformability factors that apply to FRP
reinforced concrete. There is the notion that FRP reinforced concrete structures have to
be treated in a different way in terms of ductility than what traditionally has been done
with steel reinforcement. Two basic methods have been proposed.