Steel Free Hybrid Reinforcement System for Concrete Bridge Decks ...

where K 3 is a different empirical constant. Studies by both Ehsani and Gao
recommend a K 3 value of 2850.
In consideration of these recommendations, the ACI Report specifies the
development length for FRP reinforcement is to be, conservatively,
d
b
f
fu
l
bf
=
(2.7)
2700
In SI units,
d
b
f
fu
l
bf
=
(2.8)
18.5
with units of mm and MPa.
2.2 CANADIAN AND US STEEL-FREE DECK SLABS AND OTHER STRUCTURES
Several types of nonferrous hybrid reinforcement systems can be engineered for
concrete bridge decks, some of which are illustrated in Fig. 2.4. Combinations of these
systems also offer viable design alternates for nonferrous bridge deck reinforcing systems.
The tied-arch approach used in Canada is illustrated in Fig. 2.4a. The tied-arch behavior of
the deck slab is not very much unlike arch action (shaded region in Fig. 2.4b) in conventional
reinforced concrete beams after sufficient flexural cracking has occurred. The arch action
becomes effective only after the deck slab cracks due to flexural tensile stresses. A layered
hybrid composite system where the deck slab comprises of precast prestressed panels or
precast stay-in-place forms on the bottom, topped with cast-in-place concrete containing FRP
rebar is shown in Fig. 2.4c. A hybrid reinforcement system using both continuous FRP
reinforcing bars and fiber reinforced concrete matrix shown in Fig. 2.4d represents the type
of hybrid reinforcing system being studied in an ongoing project at the University of
Missouri.
The Salmon River Bridge in Nova Scotia, Canada is the first known steel-free
concrete bridge deck and was built in 1995 (Bakht and Mufti, 1996). This design shown in
Fig. 2.4a uses a deck slab reinforced only with short discontinuous polypropylene fibers (Vf
= 0.55%). Steel straps provided outside the deck slab tie the top flanges of the steel girders
supporting the deck. The tied arch behavior is engineered through the use of shear studs
(providing composite action between the deck slab and the steel girders) and steel straps.
Fibers in the deck slab provide resistance to early-age plastic shrinkage cracking and
28