Challenge 1

STRESS-STRAIN CURVE FOR CONCRETE

There are three types of curves present in the stress-strain curve

(1) Idealised curve for concrete which represents characteristic strength of concrete.

(2) curve based on apparent concrete strength which is 0.67fck or 67% of characteristic strength value.

(3) design curve of concrete which is 0.67fck/1.5=0.446fck. here 1.5 is the factor of safety.

(3) The first half of the stress-strain curve is a parabolic rectangular curve. the value of stress increases as the value of strain increases. it creates a parabolic curve till the strain value reaches 0.002.

(4) The second half of the stress-strain curve is a linear curve. As strain goes on increasing stress remains constant till a strain value of 0.0035.

(5) we use a factor of safety in order to ensure the safety of structure against collapse as we learned earlier that it is only a 5% chance that our working load will increase.