The modal relevance factor (MRF) can help you to assess to which extent specific elements participate in a specific mode shape. The calculation is based on the relative elastic deformation energy of each individual member.
The MRF can be used to distinguish between local and global mode shapes. If multiple individual members show significant MRF (for example, > 20%), the instability of the entire structure or a substructure is very likely. On the other hand, if the sum of all MRFs for an eigenmode is around 100%, a local stability phenomenon (for example, buckling of a single bar) can be expected.
Furthermore, the MRF can be used to determine critical loads and equivalent buckling lengths of certain members (for example, for stability design). Mode shapes for which a specific member has small MRF values (for example, < 20%) can be neglected in this context.
The MRF is displayed by mode shape in the result table under Stability Analysis → Results by Members → Effective Lengths and Critical Loads.
Did you use the eigenvalue solver of the add-on to determine the critical load factor within the stability analysis? In this case, you can then display the governing mode shape of the object to be designed as a result.
Did you use the eigenvalue solver of the add-on to determine the critical load factor within the stability analysis? If so, you can then display the governing mode shape of the object to be designed as a result. The eigenvalue solver is available here for the lateral-torsional buckling analysis, depending on the design standard used.
The structural analysis programs RFEM/RSTAB offer you a wide range of automated functions that make your dayily work easier. One of them is the automatic generation of load and result combinations for the accidental design situation of fire design. The members to be designed with the corresponding internal forces are imported directly from RFEM/RSTAB. You don't need to do anything else. The program has also already stored all information about the material and cross-section for you.
By assigning a fire resistance configuration to the members to be designed, you define the parameters relevant for the fire resistance design. Here you can manually specify the critical steel temperature at the design time. Or let the program to determine the temperature determined automatically for a specified fire duration. You can select from various fire temperature curves and fire protection measures. It is also possible to make further detailed settings, such as the definition of the fire exposure on all sides or three sides
Perform the fire resistance design with a reduced load-bearing capacity according to the component temperature determined automatically right at the design time. You can determine this automatically according to various temperature curves in the program (a standard temperature-time curve, an external fire curve, a hydrocarbon curve). For other types of temperature determination, it is also possible for you to manually specify the temperature to be applied in the design. You can determine this, for example, according to the parametric temperature-time curve from DIN EN 1991‑1‑2 or from a fire protection report.
Did you use the eigenvalue solver of the add-on to determine the critical load factor for the stability analysis? Verz well, you can then display the governing mode shape of the object to be designed as a result. The eigenvalue solver is available for the lateral-torsional buckling analysis, depending on the design standard used. You can also use the internal eigenvalue solver for the general method according to EN 1993‑1‑1, 6.3.4.
In this case, you calculate the critical load factor for all analyzed load combinations and the selected number of mode shapes for the connection model. Compare the smallest critical load factor with the limit value 15 from the standard EN 1993‑1‑1, Clause 5. Furthermore, you can make user-defined adjustment of the limit value. As a result of the stability analysis, the program displays the corresponding mode shapes graphically.
For the stability analysis, RFEM uses the adapted surface model to specifically recognize the local buckling shapes. You can also save and use the model of the stability analysis, including the results, as a separate model file.
Compared to the RF‑/TIMBER Pro add-on module (RFEM 5 / RSTAB 8), the following new features have been added to the Timber Design add-on for RFEM 6 / RSTAB 9:
In addition to Eurocode 5, other international standards are integrated (SIA 265, ANSI/AWC NDS, CSA O86, GB 50005)
Design of compression perpendicular to grain (support pressure)
Implementation of eigenvalue solver for determining the critical moment for lateral-torsional buckling (EC 5 only)
Definition of different effective lengths for design at normal temperature and fire resistance design
Evaluation of stresses via unit stresses (FEA)
Optimized stability analyses for tapered members
Unification of the materials for all national annexes (only one "EN" standard is now available in the material library for a better overview)
Display of cross-section weakenings directly in the rendering
Output of the used design check formulas (including a reference to the used equation from the standard)
Compared to the RF-/STEEL Warping Torsion add-on module (RFEM 5 / RSTAB 8), the following new features have been added to the Torsional Warping (7 DOF) add-on for RFEM 6 / RSTAB 9:
Complete integration into the environment of RFEM 6 and RSTAB 9
7th degree of freedom is directly taken into account in the calculation of members in RFEM/RSTAB on the entire system
No more need to define support conditions or spring stiffnesses for calculation on the simplified equivalent system
Combination with other add-ons is possible, for example for the calculation of critical loads for torsional buckling and lateral-torsional buckling with stability analysis
No restriction to thin-walled steel sections (it is also possible to calculate ideal overturning moments for beams with massive timber sections, for example)
Have you carried out the design successfully? The results of the deformation analysis are now listed in clearly arranged output tables or detailed dialog boxes with info text. The program shows you all intermediate values in a comprehensible manner. Graphical representation of design ratios and deformation in RFEM allows you for a quick overview of critical areas.
Due to the results output of the design checks with all intermediate results, you can follow the calculation to the smallest detail. The complete integration of results in the RFEM printout report ensures that you obtain verifiable structural design.
Import of relevant information and results from RFEM
Integrated, editable material and section library
Sensible and complete presetting of input parameters
Punching design on columns (all section shapes), wall ends, and wall corners
Automatic recognition of the punching node position from an RFEM model
Detection of curves or splines as a boundary of the control perimeter
Automatic consideration of all slab openings defined in the RFEM model
Construction and graphical display of the control perimeter
Optional design with unsmoothed shear stress along the control perimeter that corresponds to the actual shear stress distribution in the FE model
Determination of the load increment factor β via full-plastic shear distribution as constant factors according to EN 1992‑1‑1, Sect. 6.4.3 (3), based on EN 1992‑1‑1, Fig. 6.21N, or by a user‑defined specification
Numerical and graphical display of results (3D, 2D, and in sections)
Punching design of the slab without punching reinforcement
Qualitative determination of the required punching reinforcement
Design and analysis of the longitudinal reinforcement
Complete integration of results in an RFEM printout report
You have two options in RFEM. On the one hand, you can determine the punching load from a single load (from column/loading/nodal support) and the smoothed or unsmoothed shear force distribution along the control perimeter. On the other hand, you can specify them as user-defined.
Calculate the design ratio of the punching shear resistance without punching reinforcement as a design criterion and the program will deliver you the corresponding result. In the case of exceeding the punching shear resistance without punching reinforcement, the program determines the required punching reinforcement as well as the required longitudinal reinforcement for you.
Consideration of 7 local deformation directions (ux, uy, uz, φx, φy, φz, ω) or 8 internal forces (N, Vu, Vv, Mt,pri, Mt,sec, Mu, Mv, Mω) when calculating member elements
Usable in combination with a structural analysis according to linear static, second-order, and large deformation analysis (imperfections can also be taken into account)
In combination with the Stability Analysis add-on, allows you to determine critical load factors and mode shapes of stability problems such as torsional buckling and lateral-torsional buckling
Consideration of end plates and transverse stiffeners as warping springs when calculating I-sections with automatic determination and graphical display of the warping spring stiffness
Graphical display of the cross-section warping of members in the deformation
This feature helps you with the load application. You can have the required loading applied incrementally. This option is particularly suitable for your calculations according to the large deformation analysis. Furthermore, you can easily perform post‑critical analyses in RFEM.
RFEM 6 offers you a wide range of helpful and efficient functions for working with load combinations. You can add the load cases included in load combinations together and then calculate them in consideration of the corresponding factors (partial safety and combination factors, coefficients regarding consequence classes, and so on). Generate the load combinations automatically in compliance with the combination expressions of the standard. You can perform the calculation according to the linear static analysis, second-order analysis, or large deformation analysis, as well as for post-critical analysis. Optionally, you can define whether the internal forces should be related to the deformed or non-deformed structure.
Footfall Analysis links with RFEM, using the model geometry from there, thus the user is not required to create a second model specifically for footfall analysis
Allows the user to analyze any type of structure for footfall analysis, irrespective of the shape, material, or use
Quick and accurate predictions of resonant and impulsive (transient) responses
Cumulative measurement of vibration levels – VDV analysis
Intuitive output enabling the engineer to advise improvements of critical areas in a cost-effective way
Pass/fail limit check in accordance with BS 6472 and ISO 10137
Selection of excitation forces: CCIP-016, SCI P354, AISC DG11 for floors and stairs
Frequency weighting curves (BS 6841)
Quick investigation for full model or specific areas
Vibration Dose Analysis (VDV)
Adjusting the minimum and maximum walking frequencies as well as the walker’s weight
User input damping values
Varying the number of footfalls for resonant response, user input or software calculated
Environmental response limit based on BS 6472 and ISO 10137
The determination of the critical buckling moment is carried out in RF-/STEEL AISC by using the eigenvalue solver which allows an exact determination of the critical buckling load.
The eigenvalue solver shows a display window of the eigenvalue graphics, which enables checking of the boundary conditions.
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.
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.
Import of materials, cross-sections, and internal forces from RFEM/RSTAB
Steel design of thin‑walled cross‑sections according to EN 1993‑1‑1:2005 and EN 1993‑1‑5:2006
Automatic classification of cross-sections according to EN 1993-1-1:2005 + AC:2009, Cl. 5.5.2, and EN 1993-1-5:2006, Cl. 4.4 (cross-section class 4), with optional determination of effective widths according to Annex E for stresses under fy
Integration of parameters for the following National Annexes:
DIN EN 1993-1-1/NA:2015-08 (Germany)
ÖNORM B 1993-1-1:2007-02 (Austria)
NBN EN 1993-1-1/ANB:2010-12 (Belgium)
BDS EN 1993-1-1/NA:2008 (Bulgaria)
DS/EN 1993-1-1 DK NA:2015 (Denmark)
SFS EN 1993-1-1/NA:2005 (Finland)
NF EN 1993-1-1/NA:2007-05 (France)
ELOT EN 1993-1-1 (Greece)
UNI EN 1993-1-1/NA:2008 (Italy)
LST EN 1993-1-1/NA:2009-04 (Lithuania)
UNI EN 1993-1-1/NA:2011-02 (Italy)
MS EN 1993-1-1/NA:2010 (Malaysia)
NEN EN 1993-1-1/NA:2011-12 (Netherlands)
NS EN 1993-1-1/NA:2008-02 (Norway)
PN EN 1993-1-1/NA:2006-06 (Poland)
NP EN 1993-1-1/NA:2010-03 (Portugal)
SR EN 1993-1-1/NB:2008-04 (Romania)
SS EN 1993-1-1/NA:2011-04 (Sweden)
SS EN 1993-1-1/NA:2010 (Singapore)
STN EN 1993-1-1/NA:2007-12 (Slovakia)
SIST EN 1993-1-1/A101:2006-03 (Slovenia)
UNE EN 1993-1-1/NA:2013-02 (Spain)
CSN EN 1993-1-1/NA:2007-05 (Czech Republic)
BS EN 1993-1-1/NA:2008-12 (the United Kingdom)
CYS EN 1993-1-1/NA:2009-03 (Cyprus)
In addition to the National Annexes (NA) listed above, you can also define a specific NA, applying user‑defined limit values and parameters.
Automatic calculation of all required factors for the design value of flexural buckling resistance Nb,Rd
Automatic determination of the ideal elastic critical moment Mcr for each member or set of members on every x-location according to the Eigenvalue Method or by comparing moment diagrams. You only have to define the lateral intermediate supports.
Design of tapered members, unsymmetric sections or sets of members according to the General Method as described in EN 1993-1-1, Cl. 6.3.4
In the case of the General Method according to Cl. 6.3.4, optional application of "European lateral-torsional buckling curve" according to Naumes, Strohmann, Ungermann, Sedlacek (Stahlbau 77 [2008], pp. 748‑761)
Rotational restraints can be taken into account (trapezoidal sheeting and purlins)
Optional consideration of shear panels (for example, trapezoidal sheeting and bracing)
RF-/STEEL Warping Torsion module extension (license required) for stability analysis according to the second-order analysis as stress analysis including consideration of the 7th degree of freedom (warping)
Module extension RF-/STEEL Plasticity (license required) for plastic analysis of cross‑sections according to Partial Internal Forces Method (PIFM) and Simplex Method for general cross‑sections (in connection with the RF‑/STEEL Warping Torsion module extension, it is possible to perform the plastic design according to the second‑order analysis)
Module extension RF-/STEEL Cold-Formed Sections (license required) for ultimate and serviceability limit state designs for cold-formed steel members according to the EN 1993-1-3 and EN 1993-1-5 standards
ULS design: Selection of fundamental or accidental design situations for each load case, load combination, or result combination
SLS design: Selection of characteristic, frequent, or quasi-permanent design situations for each load case, load combination, or result combination
Tension analysis with definable net cross-section areas for member start and end
Weld designs of welded cross-sections
Optional calculation of warp spring for nodal support on sets of members
Graphic of design ratios on cross-section and in RFEM/RSTAB model
Determination of governing internal forces
Filter options for graphical results in RFEM/RSTAB
Representation of design ratios and cross‑section classes in the rendered view
Color scales in result windows
Automatic cross-section optimization
Transfer of optimized cross-sections to RFEM/RSTAB
Parts lists and quantity surveying
Direct data export to MS Excel
Verifiable printout report
Possibility to include the temperature curve in the report
When performing the design of tension, compression, bending, and shear loading, the module compares the design values of the maximum load capacity to the design values of the actions.
If the components are subjected to both bending and compression, the program performs an interaction. In RF-/STEEL EC3, you can determine the factors according to Method 1 (Annex A) or Method 2 (Annex B).
The flexural buckling design requires neither the slenderness nor the elastic critical buckling load of the governing buckling case. The module automatically calculates all required factors for the bending stress design value. RF-/STEEL EC3 determines the elastic critical moment for lateral-torsional buckling for each member on every x-location of the cross-section. If required, you only need to specify lateral intermediate supports of the individual members/sets of members, definable in one of the input windows.
If members are selected for the fire resistance design in RF-/STEEL EC3, there is another input window available where you can enter additional parameters, such as: a coating or cladding type. Global settings cover the required time of fire resistance, temperature curve, and other coefficients. The printout report lists all intermediate results and the final result of the fire resistance design. Furthermore, it is possible to print the temperature curve in the report.
First, it is necessary to decide whether to perform design according to ASD or LRFD. Then, you can enter the load cases, load combinations, and result combinations to be designed. Load combinations according to ASCE 7 can be generated either manually or automatically in RFEM/RSTAB.
In the next steps, you can adjust presettings of lateral intermediate supports, effective lengths, and other standard-specific design parameters, such as the modification factor Cb for lateral-torsional buckling or the shear lag factor. In the case of continuous members, it is possible to define individual support conditions and eccentricities of each intermediate node of single members. A special FEA tool determines critical loads and moments required for the stability analysis.
In connection with RFEM/RSTAB, it is possible to apply the Direct Analysis Method taking into account the influence of the general calculation according to the second-order analysis. In this way, you avoid using special enlargement factors.
Design of members and sets of members for tension, compression, bending, shear, combined internal forces, and torsion
Stability analysis of buckling and lateral-torsional buckling
Automatic determination of critical buckling loads and critical buckling moments for general load applications and support conditions by means of a special FEA program (eigenvalue analysis) integrated in the module
Alternative analytical calculation of the critical buckling moment for standard situations
Optional application of discrete lateral supports to beams and continuous members
Automatic cross-section classification (compact, noncompact, and slender)
Serviceability limit state design (deflection)
Cross-section optimization
A wide range of available cross-sections, such as rolled I-sections; channel sections; T-sections; angles; rectangular and circular hollow sections; round bars; symmetrical and asymmetrical, parametric I-, T-, and angle sections; double angles
Clearly arranged input and result windows
Detailed result documentation including references to design equations of the used standard
Various filter and sorting options of results, including result lists by member, cross-sections, and x-location, or by load case, load combination, and result combination
Result table of member slenderness and governing internal forces