Spatial thin-walled reinforced concrete structures taking into account physical nonlinearity in SCAD software. Rod finite element

This paper considers a spatial frame bar finite element for modeling reinforced concrete beams and columns. Both concrete and reinforcement are described by the equations of the deformation theory of plasticity and the theory of plastic flow. Degradation of concrete during cracking is modeled by the descending branch of the sigma - epsilon diagram (the deformation theory of plasticity), as well as the compression of the yield surface and its displacement in the space of principal stresses (the plastic flow theory). The longitudinal reinforcement is considered discretely. It is assumed that there is no reinforcement slipping in concrete. The paper provides the results of the studies that reveal the causes of computational instability related to the presence of a descending branch of the s - e diagram for concrete, and proposes ways to overcome it. The reliability of the obtained results is confirmed by comparing them with the results of experimental studies performed by other researchers, as well as with the results of numerical solutions obtained by the particle method. This paper also provides an example of the nonlinear analysis of the fragment of a multi-storey building from the SCAD Soft collection of problems (www.scadsoft.com).