Advance Design comes with a new FEM engine implemented for a 2nd order analysis with 7 degrees of freedom (DOF). The feature enables the design of a broad variety of cross-sections shapes, even mono-symmetric or asymmetric shapes, which are widely used in building design but are not covered by code rules.
Advanced Stability functionality helps structural engineers obtain more economic structures, by using thin-walled profiles, which are required more and more often in day-to-day project-related activities.
Source: Stability problems for the buckling of columns and beams - “Steel Structures Design using FEM”, Rolf Kindmann / Matthias Kraus
Advanced Stability feature automatically calculates 2nd order effects on the steel elements. The functionality is available starting with Advance Design 2019.
This enhanced solver will perform a thorough analysis of individual members during the steel design sequence, considering the following:
Based on these results, cross-section design is performed by computing:
Normal stress σx is based on normal force Nx, bending moments My and Mz as well as warping moment Mw
Shear stress τ is based on shear forces Vy and Vz as well as torsional moment Mx (Mx = Mxp + Mxs)
Von Mises stress σVM is based on normal stress and shear stress
The obtained values are then compared to the limit stresses:
The internal forces and moments resulted from the effects of deformed geometry of the structure can be determined using a 2nd order theory that takes into account this influence, according to EN1993-1-1 (§5.2.1). 2nd order effects are also known as P-Δ (non-linear) effects and occur in every structure where elements are axially loaded with compression forces. P-Δ effects are associated with the magnitude of the applied axial compression (P) and displacement (Δ).
Usually, there are no analytical solutions for flexural-torsional problems that include nonlinear deformations. Therefore, a FEM approach is used in order to determine approximate solutions for the differential equations.
The impact from 2nd order effects on a structure must be assessed for every designed structure, since they increase the deflections, moments and forces beyond those calculated by 1st order analysis. In many cases, by calculating the elements according to 2nd order analysis, lighter structures can be designed by using thin-walled steel profiles.
Warping is a deformation that occurs under uniform torsion and causes the section to no longer remain plane. This phenomenon has significant effect on open cross sections such as I, H or channels. For these type of sections, warping results cannot be neglected.
Source: Design of steel beams in torsion – SCI Publication P385
In thin-walled closed cross sections (the most appropriate type of cross section to resist torsion), uniform torsion is predominant. Therefore, in the analysis of thin-walled closed cross sections subjected to torsion, the warping torsion (Mxs) is normally neglected.
Torsional moment is the internal twisting moment about the beam’s longitudinal axis and it is usually considered in two components: St. Venant torsional moment and warping torsional moment. Warping moment is the bending moment in a flange acting as a result of restraint of warping. The moments in the two flanges are equal and of opposite sign.
In members with thin-walled open cross sections (such as I or H sections), inside of which only the uniform torsion component appears, it is necessary that the supports do not prevent warping and the torsional moment is constant. Otherwise, if the torsional moment is variable or warping is restrained at some cross sections (usual situation), the member is under non-uniform torsion.
Due to the fact that the cross sections also rotate around the longitudinal axis (especially next to the free end), there also appears uniform torsion. Thus, in this case, the resistance to torsion is given by the sum of both effects (M = Mxp + Mxs), the warping torsion component, Mxs, being significantly larger than the uniform torsion component, Mxp, in sections near the built-in end.
Advance Stability, a brand-new design method of Graitec Advance Design, enables the design of any shape of cross-sections included in the Advance Design library, even mono symmetric or asymmetric shapes which are widely used in building practice but are not covered by code rules. With Advance Design, you can let imagination flow inside your structures, without sacrificing the safety provided by this proven design method.
 Rolf Kindmann, Matthias Kraus, Steel Structures Design using FEM
 Eurocode 3: Design of steel structures – Part 1-1 : General rules and rules for buildings
Read more about different functionalities of Advance Design in the following articles: