A numerical model for sequential construction, repairing and strengthening of 2-D concrete frames

This paper presents a computationally efficient and accurate layer model for simulating, under serviceability conditions, the instantaneous and time-dependent static non-linear behaviour of 2-D reinforced and prestressed concrete building frames. Several types of situations can be considered: segmental construction, changes of material and cross-sectional properties, modifications in the joint and support conditions (including new shores) and addition or removal of new members and of external reinforcements. The proposed algorithm simulates damage, structural retrofit and construction or demolition. Cracking is described by a smeared model in which the tension-stiffening effect is considered in detail. The structural behaviour is described by a generalized matrix formulation where no initial assumption on the deformation shape is considered (since no shape functions are used). This formulation is accurate while computationally efficient for structures with many members (which generate models with a large number of degrees of freedom in standard finite element discretizations). The algorithm is validated by comparison with ad-hoc experiments and benchmark tests. Some applications are presented and relevant conclusions are derived from there.