Stress-strain curve for concrete | Design of reinforced concrete structures

Stress-strain curve for concrete 

• fck = characteristics strength of concrete
• there are big difference between strength of concrete of cube and strength of concrete structure.
• Strength of concrete less in structure instead of concrete cube.
• Civil engineering branch is best branch for any student of engineering.
• because of we do not maintain quality control at curing of concrete in structure rather in cubes.
• that's why we use 0.67 factor add for difference of strength.

            Design strength = 0.67 fck / Ɣm 

                                        = 0.67 fck / 1.5

                                        = 0.446 fck

• when strain value of concrete 0.2%(0.002) then load value increase but stress constant.
• when strain value of concrete 0.35% (0.0035) , it's mean concrete break at that point.
• Modulus of elasticity of concrete = Ec =5000 √fck

         Figure of stress-strain curve for concrete