Creep behavior is associated with time-dependent, stress-induced changes in the strain and deformation of a structural member. Creep, along with shrinkage (decrease in direct strains over time) and aging (change in elastic modulus with age), are time-dependent material behaviors which may be applied to concrete objects using staged-construction analysis. Staged construction is a nonlinear-static application available to CSI Software with Ultimate Level. Additional information may be found in the CSI Analysis Reference Manual (Staged Construction, page 396). Staged construction is also necessary for modeling creep, shrinkage, and relaxation within tendons. Tendon elastic shortening, however, is automatically implemented with any software package.
Each of these time-dependent behaviors are specified according to CEB-FIP parameters (Comite Euro-International Du Beton, 1993). Creep formulation may follow full integration or an expedited Dirichlet series approximation (Ketchum, 1986). The CSI Analysis Reference Manual (Time-dependent Properties, page 85) presents further details.