Background Knowledge - Strengthening Design of Reinforced Concrete with FRP - page 11

0.003

c

d t

h

d t

A s

ε s

h

b

FIGURE 2.3 Typical rectangular section and strain profile at section failure.

0.85 fb cAf

c

β=

(2.2)

1 s y

Af
fb

sy
c

c =

(See Figure 2.3.) (2.3)

0.85

β

1

If

c
d t

> → 0.429 This is a Brittle Failure N. G.

Design problem:

C = T (2.4)

0.85 fb cAf

c 1 β=

(2.5)

s y

Af
fb

sy
c

c =

(See Figure 2.3.)

(2.6)

0.85

β

1

The value c is unknown and is to be substituted into the moment equation to solve
for the area of steel, A s ,

(while

c
d

< 0.429) .

t

2.2.3 m oment e quilibrium
To determine the moment-carrying capacity of the beam section in analysis problems
or the steel area in design problems, the moment-equilibrium equation is involved:

MAfd a
u

=φ −

(2.7)

s y

2

where

ac =β

=
=ρ

1

M

M
Mbdf

u

n

φ

2

(2.8)

(1 −

a
d

)

n y

2