stress strain curve problem

hey all 

i am  try to find the the concrete stress strain curve according to paper with i attached (i highlight the main equation with red)

Mainly there is 3 parts, the first part is linear and the second part is curve according to the equation.

My question the two parts don't meet at the same point so this will create the graph the i did in excel

So could any one help me or tell me if this affect the result in ABAQUS