The problem statement related to modification of structural design model, when stiffness parameters of the structural members undergo changes, was considered. Some data was outlined from the design practice concerning design cases that occur during erection and maintenance of buildings and structures, when stiffness parameters of some structural members undergo changes. A physical mechanism that controls changing of these parameters was described for some of the design cases. Likewise, attention was paid to the design cases when changing of stiffness parameters has no relation to changing of actual stress-and-strain state and when such change occurs. Appropriate analysis methods were described.