A strict approach to the study of effective elastic moduli of an isotropic
medium containing a set of flat parallel cracks is proposed. The idea of th
e approach is to use a generalized periodic structural model and to reduce
model boundary-value problems formulated based on it to a system of linear
algebraic equations. Integrating the stress field over a structure cell yie
lds exact finite expressions for all the components of the effective elasti
city tensor. The numerical results illustrating the effect of the crack arr
angement on the effective stiffness of a cracked body are presented and com
pared with known approximate theories.