Effective stiffness for modeling reinforced concrete structures in soil-structure interaction calculation

In design engineering practice, soil-structure interaction calculations normally take into account the elastic behavior of structures and the effective stiffness of their elements. The effective stiffness is calculated using special reduction coefficients. This approach is only just, as the nonlinear behavior of reinforced concrete is largely limited by ultimate deformations of the structure and its particular elements. At the same time, above-limit settlement and tilt of ferro-concrete structures will be inevitably accompanied by more pronounced inelastic behavior, as well as major deviations in the results of elastic and nonlinear behavior calculations of ferroconcrete structures. This necessitates the soil-structure interaction calculation which would account of the physically nonlinear behavior of surface structures. The article gives an example of nonlinear analysis of stressed-deformed state of a structure experiencing above-limit deformations. The results of nonlinear analysis are compared to those obtained with use of elastic approach, where the behavior of ferroconcrete has been calculated with the use of various reduction coefficients-standard and authors' revised-that take into account the physical nonlinearity of ferroconcrete. The comparison has revealed a number of drawbacks in the prescribed standard values and has validated the expediency of the revised reduction coefficient.