I have found two different formulae for calculating damage parameters (dc & dt) i.e.
dc = 1- (σ/σmax) (Paper-1)
dc = 1- Exp (-ac x εin)
Can anyone please tell me which formula is correct for finding damage parameters (dc & dt) for masonry modelling in Abaqus.
http://www.ikb.poznan.pl/fcee/2005.06/full/fcee_2005-06_053-069_identification_of_parameters_of_concrete.pdf