Non-linear Analysis - The consistent stiffness method (CSM)
ShellDesign includes a specially developed procedure for performing non-linear FE-analyses of reinforced concrete structures, called the Consistent Stiffness Method (CSM). CSM works through a series of consecutive linear FE-analyses to include the effect of the highly non-linear behaviour of reinforced concrete.
Through use of the CSM, re-distribution of forces in the structure is allowed, resulting in an accurate prediction of the structural behaviour and more economical designs. Particularly, the response to imposed deformations, i.e. thermal loads, in terms of stress resultants, depends directly on the structural restraint and stiffness in the structure. As a consequence of cracking of concrete, stress resultants from a linear elastic FE-analysis for temperature loads are significantly reduced and an more accurate calculation can only be obtained from a non-linear analysis.
CSM is a practical and efficient nonlinear structural analysis carried out with ShellDesign in corporation with DNV-GL’s structural analysis program SESTRA.
Design flow when ShellDesign interacts with SESTRA in the iterative mode:
Demonstration of the effect of the CSM analyses:
Utilization of longitudinal reinforcement in the initial linear analyses (left) and the CSM analyses (right). Purple results represent utilization ratios above 1.0 (failure), pink results represent reinforcement in compression.