In order to be able to carry out a pushover analysis, it is necessary to transform the determined capacity curve into a simplified form. The N2 method is described in Eurocode EN 1998. This article should help to explain what a bilinearization according to the N2 method involves.
KB 001829 | Determination of Bilinearization for Pushover Curve (N2 Method)
The design of cold-formed steel members according to the AISI S100-16 / CSA S136-16 is available in RFEM 6. Design can be accessed by selecting “AISC 360” or “CSA S16” as the standard in the Steel Design Add-on. “AISI S100” or “CSA S136” is then automatically selected for the cold-formed design.
RFEM applies the Direct Strength Method (DSM) to calculate the elastic buckling load of the member. The Direct Strength Method offers two types of solutions, numerical (Finite Strip Method) and analytical (Specification). The FSM signature curve and buckling shapes can be viewed under Sections.
In SHAPE-THIN 8, the effective cross-section of stiffened buckling panels can be calculated according to EN 1993-1-5, Cl. 4.5.
The critical buckling stress is calculated according to EN 1993-1-5, Annex A.1 for buckling panels with at least 3 longitudinal stiffeners, or according to EN 1993-1-5, Annex A.2 for buckling panels with one or two stiffeners in the compression zone. The design for torsional buckling safety is also performed.
The pushover analysis is managed by a newly introduced analysis type in the load combinations. Here, you have access to the selection of the horizontal load distribution and direction, the selection of a constant load, the selection of the desired response spectrum for the determination of the target displacement, and the pushover analysis settings tailored to the pushover analysis.
In the pushover analysis settings, you can modify the increment of the increasing horizontal load and specify the stopping condition for the analysis. Furthermore, it is possible to easily adjust the precision for the iterative determination of the target displacement.
- Consideration of nonlinear component behavior using plastic standard hinges for steel (FEMA 356, EN 1998‑3) and nonlinear material behavior (masonry, steel - bilinear, user-defined working curves)
- Direct import of masses from load cases or combinations for the application of constant vertical loads
- User-defined specifications for the consideration of horizontal loads (standardized to a mode shape or uniformly distributed over the height of the masses)
- Determination of a pushover curve with selectable limit criterion of the calculation (a collapse or limit deformation)
- Transformation of the pushover curve into the capacity spectrum (ADRS format, single degree of freedom system)
- Bilinearization of the capacity spectrum according to EN 1998‑1:2010 + A1:2013
- Transformation of the applied response spectrum into the required spectrum (ADRS format)
- Determination of target displacement according to EC 8 (the N2 method according to Fajfar 2000)
- Graphical comparison of the capacity and required spectrum
- Graphical evaluation of the acceptance criteria of predefined plastic hinges
- Result display of the values used in the iterative calculation of the target displacement
- Access to all results of the structural analysis in the individual load levels