Issue in Plotting a Triangular reponse, what seems to be wrong?

I am plotting a tensile test plot of concrete. It suppose to look like a triangle. from 0 to max value f't and then come down to zero again. The left positive slope should be elastic modulus E and the right slope (negative slope) should be the same elastic modulus but divided by 10. I have already did the function but I see a step coming down in the triangle that should not be there. Can any one tell me what I am missing or doing wrong? Thank you.