Strengthening of Columns for Confinement - Strengthening Design of Reinforced Concrete with FRP - page 185

Load Step ∆GP

Resultant Moment

FIGURE 7.12 Radial loading concept.

2. Calculate ff

lf / and check the ratio to decide which model is used (eccen-
tric model based on Lam and Teng equations or eccentric model based on
Mander equations), as seen in Figure 7.10.

3. Define eccentricity e , which specifies the radial path of loading on the inter-
action diagram, as seen in Figure 7.12.

4. Define loading step ΔGP as a small portion of the maximum load and com-
pute the axial force at the geometric centroid:

GP

(7.6 4)

GP = GP +

new old

5. Calculate moment GM about the geometric centroid:

GM
GP

e = andGM = × e P (7.65)

6. Transfer moment to the updated inelastic centroid and calculate the new
transferred moment TM, as seen in Figure 7.13:

(7.6 6)

TM =+ − GM GP( Y Gc )

The advantage of transferring the moment to the position of the inelastic
centroid is to eliminate the coupling effect between the force and moment,
since EAM = 0 about the inelastic centroid (Rasheed and Dinno 1994):

ε
φ

GP
TM

EA 0
0

0

=

(7.67)

I