The J-factor (JF) is then calculated as the product of the load factor and the
deformability factor as follows:
JF = LF DF (2-5)
There is no general agreement as to the load or deformability point with which the
ultimate values are compared to calculate the strength and deformability factors needed to
determine the J-factor. Therefore, the results obtained using this method, are based on an
arbitrary selection of a starting point which makes them unreliable. Li and Wang 2002
also pointed out that the use of J-factor values seemed to contradict experimental results
that indicated higher ductility for specimens that had low J-factors. Another shortcoming
of this method is the fact that a large J-factor can be obtained even for a perfectly linear
load displacement diagram which goes against conventional ductility definition which is
the amount of plastic deformability of the structure.
PI
PU -------------------------------
Pu
P0 001
0 60001 6u f
Figure 2-4. Schematic for deformation method ductility factor