Prof. Židonis has developed, and in this monograph introduces, an integral ZI method for theoretical calculation of each individual actual value of the stress-strain parameters (crack, the height of the compression and tension zones, the stress and strain of the layers of the structural member) at cross-sections of structural members subjected to bending moments and/or axial forces at any stage of loading directly considering the actual properties of the materials. The method helps resolve an extremely important and complicated problem, i.e that of theoretical computation of the actual position of the neutral axis. The ZI Method is applicable for calculating the values of the parameters of members with various cross-sections, of members that are differently reinforced, of members made of different materials, as well as that of layered structural members. Stress-strain functions can be described using different equations. For calculations, only the stress-strain diagrams of materials are needed.