[42] Beam name CBC Beam Span L (mm) dimensions Height [h.sub.c]/width [b.sub.c] (mm) 28-day cylinder compressive strength [f.sub.c] (MPa) Concrete Modulus of elasticity [E.sub.c] (GPa)

Tension reinforcement area ([mm.sup.2])/yield strength [f.sub.yt] (MPa)/elastic modulus [E.sub.st] (GPa) Steel Compression reinforcement area ([mm.sup.2])/yield strength [f.sub.yc] (MPa)/elastic modulus [E.sub.sc] (GPa) Nominal thickness (n x ply -- thickness [t.sub.r])/width FRP [b.sub.frp] (mm) reinforcement Ultimate strength [f.sub.r] (MPa)/ -- elastic modulus [E.sub.r] (GPa) Applied moment at midspan (kN x m) Sobuz et al.

It occurs when the stress in the tension reinforcement reaches the representative strength values on the verge of its yield [f.sub.yk] or extreme fiber stress of compressed concrete - representative values of the compressive strength of [f.sub.ck], i.e., in the cross section reinforced concrete element begins to form so-called "plastic hinge" (starts the destruction).

At the same time, the relative deformation of the extreme fibers, compressed with concrete, reaches the value of [[epsilon].sub.cu] > [[epsilon].sub.c1], and tension reinforcement can work both before and on the border of yield: [[epsilon].sub.s] < [[epsilon].sub.s0], [[epsilon].sub.s0] [less than or equal to] [[epsilon].sub.s] [less than or equal to] [[epsilon].sub.suk].

The longitudinal reinforcement of the tested beams is two longitudinal bars of diameter 8 mm as

tension reinforcement and two bars of 8 mm as compression reinforcement (2[empty set]8 top and 4[empty set]8 bottom).

"The HCB consists of three parts: a shell made out of a fiberglass-reinforced polymer, a concrete arch within the shell, and

tension reinforcement tying the ends of the arch," say Van Nosdall, Moen, Cousins and Wollmann-Roberts.

Stresses in compression and tension zones corresponding to [[lambda].sub.sfrc.c] and [[lambda].sub.sfrc.t] strains related to

tension reinforcement stress [[sigma].sub.s1]:

The main factors influencing this action are shear span-to-depth ratio, compressive strength of concrete and area of tension reinforcement. According to Khuntia and Stojadinovic (2001), a cross-section plane before loading remains plane under load.

The effects of compressive strength, shear span-to-depth ratio and the percentage of longitudinal tension reinforcement ratio on the proposed cracking shear strength and ACI 318 Building Code equations are discussed as follows.

Neutral axis depth can be measured by test using the value of strain gauge attached to compression fiber and

tension reinforcements. Since strain gauge attached to extreme tensile and compression fiber failed before experiencing peak load, strain of compression and

tension reinforcement were used.

The

tension reinforcement ratio used was in the range of 0.46% to 3.39%.