Anyone know the Garwood method which is used to determine the fracture energy of concrete (composite materials)?
Garwood method: with a load - load line displacement curve of an three point bending fracture test (or SENB), we have firstly:
J0=2U0/B(H-a0)
After, an iterative relation is used:
Jn=Jn-1(H-an)/(H-an-1)+2Un/B(H-an-1)
B,H : width and height of the beam respectively.
a : crack length
In fact, it's not clear the determination of the initial value Jo.
Please tell me references for this method.
Thank you very much for yours helps