ShellDesign is a design tool and post processor for reinforced concrete shell structures subjected to stresses in and out of plane. ShellDesign is owned, developed and supported by Dr.techn.Olav Olsen AS. The program is based on extensive development and project experience accumulated through a large number of offshore concrete projects over the years and is an extension of the design tool CONCODE. ShellDesign has since 2006 been used on several projects and has shown to be applicable for small and large concrete structures, both offshore and inshore.
ShellDesign performs sectional design calculations (code checks) according to several design standards. The implemented design standards are:
- DNV-OS-C502 Offshore Concrete Structures
- NS 3473.E Concrete structures - Design and detailing rules 6th edition
- NS-EN 1992-1-1:2004+NA:2008: Design of Concrete Structures - General Rules and Rules for Buildings (Eurocode 2)
For the sectional calculations, information about section geometry, loading, reinforcement and material properties are required. Geometry and loading can either be given as user input directly, or extracted from the results of a finite element (FE) analysis. Extraction of FE-results from ABAQUS or DNV-GL’s structural analysis program SESTRA is currently supported. Compatibility with other FE-programs can be implemented upon request.
Design flow based on results from a FE analysis:
Results from ShellDesign are presented in tables and in 3D graphics, in the form of utilization ratios of concrete and reinforcement, shear capacities, crack widths and other relevant design results. 3D graphics is presented in DNV GL’s post-processor, Xtract (licensed by DNV GL).
The common practice is to use the conventional design method where the design calculations are based on results from linear elastic structural FE analyses. This allows for use of the principle of superposition, which is convenient when there are a lot of loads that must be combined to several load combinations. The design calculations accounts for the nonlinear behaviour of reinforced concrete due to cracking etc. when establishing the response of the cross-section.
Finalized fish tank and the analysis model:
ShellDesign has also the capability to include the non-linear material behaviour of reinforced concrete into the structural FE analysis (nonlinear FE-analysis). The method is based on an iterative analysis/design process in interaction with DNV-GL’s SESTRA and is named the Consistent Stiffness Method (CSM).
“The Modified Compression-Field Theory (MCFT)” has lately been implemented in ShellDesign. MCFT includes a full tri-axial material model in the program and enables a more consistent and rational design for shear where the shortcomings in the simplified design rules for transverse shear in the design codes are eliminated.