[EN] FAQ 000605 | In STEEL, it is possible to select the Sigma Delta stress in the details. What ...

The deformations of the FE nodes are always the first result of an FE calculation. It is possible to calculate strains, internal forces, and stresses based on these deformations and the stiffness of the elements.

The ASCE 7-22 Standard [1], Sect. 12.9.1.6 specifies when P-delta effects should be considered when running a modal response spectrum analysis for seismic design. In the NBC 2020 [2], Sent. 4.1.8.3.8.c gives only a short requirement that sway effects due to the interaction of gravity loads with the deformed structure should be considered. Therefore, there may be situations where second-order effects, also known as P-delta, must be considered when carrying out a seismic analysis.

This article presents the basic concepts in structural dynamics and their role in the seismic design of structures. Great emphasis is given to explaining the technical aspects in an understandable way, so that readers without deep technical knowledge can gain an insight into the subject.

• Cross-section optimization
• Transfer of optimized sections to RFEM/RSTAB
• Design of any thin-walled cross-section from SHAPE-THIN
• Representation of a stress diagram on a section
• Determination of normal, shear, and equivalent stresses
• Stress results of individual internal forces types
• Detailed representation of stresses in all stress points
• Determination of the largest Δσ for each stress point (for example, for fatigue design)
• Colored display of stresses and design ratios for a quick overview of the critical or oversized zones
• Parts lists and quantity surveying

• Determination of principal and basic stresses, membrane and shear stresses, as well as equivalent stresses and equivalent membrane stresses
• Stress analysis for structural surfaces including simple or complex shapes
• Equivalent stresses calculated according to different approaches:
  • Shape modification hypothesis (von Mises)
  • Shear stress hypothesis (Tresca)
  • Normal stress hypothesis (Rankine)
  • Principal strain hypothesis (Bach)
• Optional optimization of surface thicknesses and data transfer to RFEM
• Serviceability limit state design by checking surface displacements
• Detailed results of individual stress components and ratios in tables and graphics
• Filter function for surfaces, lines, and nodes in tables
• Transversal shear stresses according to Mindlin, Kirchhoff, or user-defined specifications
• Parts list of designed surfaces

In order to facilitate the data input, surfaces, members, sets of members, materials, surface thicknesses, and cross-sections are preset. It is possible to select the elements graphically using the [Select] function. The program provides access to the global material and cross-section libraries.

Load cases, load combinations, and result combinations can be combined in various design cases.

The combination of surface and member elements and separate designs allows you to model and analyze only critical parts, such as frame joints, using surface elements. The other parts of the model can be designed using member analyses.