A Simply Supported Reinforced Concrete Beam -

Three stages before collapse:1. Un-cracked Concrete stage2. Cracked Concrete (tension zone) - Elastic Stage3. Cracked Concrete (tension zone) - Ultimate Strength Stage

Typical Stress-Strain Curves for Concrete and Reinforcing Steel

1. Un-cracked Concrete stage

1. Un-cracked Concrete stage

1. Un-cracked Concrete Stage

fcft = fcStress-Strain Diagram for Concreteft < frM < Mcr fc = ft

2. Cracked Concrete (Tension Zone) - Elastic Stage

ft > frM > Mcr fc = 0.45fc'fs =0.5 fy

3. Cracked Concrete (Tension Zone) - Ultimate Strength Stage

ft > >frM > >Mcr fs = fyfc = entire stress block until compression failure