**4.6 Damage classification**

From the load-deflection plots of steel-RC and GFRP-RC beams, as shown in **Figures 12**, **14**, and **16** the development of cracking patterns as shown in **Figures 11**, **13**, and **15**) in the two beams can be classified into three damage levels. Damage level I refers to the phase when the invisible cracking occurs. This damage zone is differentiated from the un-damaged state by the formation of

**Figure 13.**

*Typical crack patterns. (a) Damage level I. (b) Damage level II. (c) Damage level III.*

**Figure 14.** *Damage level classification.*

*Crack Classification in Steel-RC and GFRP-RC Beams with Varying Reinforcement Ratio Using… DOI: http://dx.doi.org/10.5772/intechopen.101305*

## **Figure 15.**

*Typical crack patterns. (a) Damage level I. (b) Damage level II. (c) Damage level III.*

**Figure 16.** *Damage level classification.*

visible hairline cracks and a distinct decrease in the stiffness of the beam is observed. *Damage level II* refers to the phase between the formation of hairline cracks and the stage of steel yielding in the case of the steel-RC beams and 1st dropin load in case of GFRP-RC beam and further leading to the formation of distributed flexural and shear cracks. *Damage level III* refers to the phase between the steel yielding and final failure caused due to concrete crushing in the SB beam. In the case of GB beams, this refers to the phase between 1st drop in load and the final

**Figure 17.** *Variation in AF Vs RA values at different levels of damages. (a) Damage level I. (b) Damage level II. (c) Damage level III.*

failure due to the crushing of compressive concrete. The formation of crack patterns at different levels of loading and the development of the different damage levels in steel-RC and GFRP-RC beams are shown in **Figures 11**–**16** respectively.
