In the Geotechnical Analysis add-on, the Hoek-Brown material model is available. The model shows linear-elastic ideal-plastic material behavior. Its nonlinear strength criterion is the most common failure criterion for stone and rocks.
You can enter the material parameters using
Rock parameters directly, or alternatively via
GSI classification.
Detailed information about this material model and the definition of the input in RFEM can be found in the respective chapter Hoek-Brown Model of the online manual for the Geotechnical Analysis add-on.
Using the "Damper" member type, you can define a damping coefficient, a spring constant, and a mass. This member type extends the possibilities within the Time History Analysis.
With regard to viscoelasticity, the "Damper" member type is similar to the Kelvin-Voigt model, which consists of the damping element and an elastic spring (both connected in parallel).
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.
Within the "Plastic capacity design | Simplex Method" in RSECTION, the simultaneous variation of shear stresses over the cross-sectional area is performed in addition to the variation of axial stresses. This extended form of analysis allows you to use redistribution reserves, especially for the cross-sections subjected to shear loading, thus loading the cross-sections even more efficiently.
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
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.
Here, the weld design becomes child's play. Using the specially developed material model "Orthotropic | Plastic | Weld (Surfaces)", you can calculate all stress components plastically. The stress τperpendicular is also considered plastically.
Using this material model you can design welds closer to reality and more efficiently.
What are plastic hinges? Very simple – plastic hinges according to FEMA 356 help you to create pushover curves. These are nonlinear hinges with preset yield properties and acceptance criteria for steel members (Chapter 5 of FEMA 356).
Do you want to model and analyze the behavior of a soil solid? To ensure this, special suitable material models have been implemented in RFEM. You can use the modified Mohr-Coulomb model with a linear-elastic ideal-plastic model or a nonlinear elastic model with an oedometric stress-strain relation. The limit criterion, which describes the transition from the elastic area to that of the plastic flow, is defined according to Mohr-Coulomb.
The calculation of masonry is carried out in compliance with the nonlinear-plastic material law. If the load at any point is higher than the possible load to be resisted, redistribution takes place within the system. This have the simple purpose of restoring the equilibrium of forces. With the successful completion of the calculation, the stability analysis is provided.
Are you familiar with the Tsai-Wu material model? It combines plastic and orthotropic properties, which allows for special modeling of materials with anisotropic characteristics, such as fiber-reinforced plastics or timber.
If the material is plastified, the stresses remain constant. The redistribution is carried out according to the stiffnesses available in the individual directions. The elastic area corresponds to the Orthotropic | Linear Elastic (Solids) material model. For the plastic area, the yielding according to Tsai-Wu applies:
All strengths are defined positively. You can imagine the stress criterion as an elliptical surface within a six-dimensional space of stresses. If one of the three stress components is applied as a constant value, the surface can be projected onto a three-dimensional stress space.
If the value for fy(σ), according to the Tsai-Wu equation, plane stress condition, is smaller than 1, the stresses are in the elastic zone. The plastic area is reached as soon as fy (σ) = 1; values greater than 1 are not allowed. The model behavior is ideal-plastic, which means there is no stiffening.
Do you know exactly how the form-finding is performed? First, the form-finding process of the load cases with the load case category "Prestress" shifts the initial mesh geometry to an optimally balanced position by means of iterative calculation loops. For this task, the program uses the Updated Reference Strategy (URS) method by Prof. Bletzinger and Prof. Ramm. This technology is characterized by equilibrium shapes that, after the calculation, comply almost exactly with the initially specified form-finding boundary conditions (sag, force, and prestress).
In addition to the pure description of the expected forces or sags on the elements to be formed, the integral approach of the URS also enables a consideration of regular forces. In the overall process, this allows, for example, for a description of the self-weight or a pneumatic pressure by means of corresponding element loads.
All these options give the calculation kernel the potential to calculate anticlastic and synclastic forms that are in an equilibrium of forces for planar or rotationally symmetric geometries. In order to be able to realistically implement both types individually or together in one environment, the calculation provide you with two ways to describe the form-finding force vectors:
Tension method - description of the form-finding force vectors in space for planar geometries
Projection method - description of the form-finding force vectors on a projection plane with fixation of the horizontal position for conical geometries
Stress determination using an elastic-plastic material model
Design of masonry disc structures for compression and shear on the building model or single model
Automatic determination of stiffness of a wall-slab hinge
An extensive material database for almost all stone-mortar combinations available on the Austrian market (the product range is continuously being expanded, for other countries as well)
Automatic determination of material values according to Eurocode 6 (ÖN EN 1996‑X)
The program supports you: It determines the bolt forces on the basis of the FE analysis model and evaluates them automatically. The add-on performs the standard-compliant design of bolt resistance for failure cases, such as tension, shear, hole bearing, and punching, and clearly displays all required coefficients.
Do you want to perform weld design? The welds are modeled as elastic-plastic surface elements, and their stresses are read out from the FE analysis model. The plasticity criteria is set in the way that they represent failure according to AISC J2-4, J2-5 (strength of welds), and J2-2 (strength of base metal). The design can be performed with the partial safety factors of the selected National Annex of EN 1993‑1‑8.
The plates in the connection are designed plastically by comparing the existing plastic strain to the allowable plastic strain. The default setting is 5% according to EN 1993‑1‑5, Annex C, but can be adjusted by user-defined specifications, as well as 5% for AISC 360.
The standards already specify the approximation methods (for example, deformation calculation according to EN 1992‑1‑1, 7.4.3, or ACI 318‑19, 24.3.2.5) that you need for your deformation calculation. In this case, the so-called effective stiffnesses are calculated in the finite elements in accordance with the existing limit state with / without cracks. You can then use these effective stiffnesses to determine the deformations by means of another FEM calculation.
Consider a reinforced concrete cross-section for the calculation of the effective stiffnesses of the finite elements. Based on the internal forces determined for the serviceability limit state in RFEM, you can classify the reinforced concrete cross-section as "cracked" or "uncracked". Do you consider the effect of the concrete between the cracks? In this case, this is done by means of a distribution coefficient (for example, according to EN 1992‑1‑1, Eq. 7.19, or ACI 318‑19, 24.3.2.5). You can assume the material behavior for the concrete to be linear-elastic in the compression and tension zone until reaching the concrete tensile strength. This procedure is sufficiently precise for the serviceability limit state.
When determining the effective stiffnesses, you can take into accout the creep and shrinkage at the "cross-section level." You don't need to consider the influence of shrinkage and creep in statically indeterminate systems in this approximation method (for example, tensile forces from shrinkage strain in systems restrained on all sides are not determined and have to be considered separately). In summary, the deformation calculation is carried out in two steps:
Calculation of effective stiffnesses of the reinforced concrete cross-section assuming linear-elastic conditions
Calculation of the deformation using the effective stiffnesses with FEM
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
RSECTION calculates all relevant cross-section properties. This also includes the plastic limit internal forces. In the case of cross-sections consisting of different materials, RSECTION determines the ideal cross-section properties.
You have various options with RSECTION. For example, you can calculate the stresses from axial force, biaxial bending moments and shear forces, primary and secondary torsional moment, and warping bimoment for any cross-section shape. Determine the equivalent stresses according to the stress hypothesis by von Mises, Tresca, and Rankine.
Did you know? When unloading the structural component with a plastic material model, in contrast to the Isotropic | Nonlinear Elastic material model, the strain remains after it has been completely unloaded.
You can select three different definition types:
Standard (definition of the equivalent stress under which the material plastifies)
Bilinear (definition of the equivalent stress and strain hardening modulus)
Stress-strain diagram: definition of polygonal stress-strain diagram
If you release a structural component with a nonlinear elastic material again, the strain goes back on the same path. In contrast to the Isotropic|Plastic material model, there is no strain left when completely unloaded.
You can select three different definition types:
Standard (definition of the equivalent stress under which the material plastifies)
Bilinear (definition of the equivalent stress and strain hardening modulus)
Planning with members is also facilitated in the programs due to specific features. You can arrange members eccentrically, support them by elastic foundations, or define them as rigid links. Member sets allow you to easily apply the load on several members. In RFEM, you can also define eccentricities of surfaces. Here, you can transform nodal and linear loads into surface loads. If necessary, divide surfaces into surface components and members into surfaces.
There are many options available for simple input and modeling. Your model is entered as a 1D, 2D, or 3D model. Member types such as beams, trusses, or tension members make it easier for you to define member properties. In order to model surfaces, RFEM provides you with various types, such as Standard, Without Thickness, Rigid, Membrane, and Load Distribution. Furthermore, RFEM covers various material models, such as Isotropic | Linear Elastic, Orthotropic | Linear Elastic (Surfaces, Solids), or Isotropic | Timber | Linear Elastic (Members).
Display extended strains of members, surfaces, and solids (for example, the important principal strains, equivalent total strains, and so on) in the Project Navigator - Results in RFEM as well as in Table 4.0.
For example, you can display governing plastic strains when performing the plastic design of connections with surface elements.
The material model Orthotropic Masonry 2D is an elastoplastic model that additionally allows softening of the material, which can be different in the local x- and y-directions of a surface. The material model is suitable for (unreinforced) masonry walls with in-plane loads.
In RFEM, there is an option to couple surfaces with the stiffness types "Membrane" and "Membrane Orthotropic" with the material models "Isotropic Nonlinear Elastic 2D/3D" and "Isotropic Plastic 2D/3D" (add-on module RF-MAT NL is required).
This functionality enables simulation of the nonlinear strain behavior of ETFE foils, for example.
After starting the module, the joint group (rigid joints) is selected first, followed by joint category and joint type (rigid end plate connection or rigid splice plate connection). The nodes to be designed are then selected from the RFEM/RSTAB model. RF-/JOINTS Steel - Rigid automatically recognizes the joint members and determines from its location whether they are columns or beams. The user can intervene here.
If certain members are to be excluded from the calculation, they can be deactivated. Structurally similar connections can be designed for several nodes at the same time. Loads require selection of the governing load cases, load combinations, or result combinations. Alternatively, you can enter the cross‑section and load data manually. In the last input window, the connection is configured step by step.
The member type 'Dashpot' can be used for time history analyzes in RFEM/RSTAB with the add-on modules RF-/DYNAM Pro - Forced Vibrations and RF-/DYNAM Pro - Nonlinear Time History. This linear viscous damping element considers forces dependent on velocity.
With regard to viscoelasticity, the member type 'Dashpot' is similar to the Kelvin-Voigt model, which consists of the damping element and an elastic spring (both connected in parallel).
Hinged column, optionally with elastic restraint of head or footing
Bracket, optionally with elastic restraint of footing
Simple geometry input with illustrative graphics
Extensive material library
Allocation of framework to service classes and specification of service class categories
Detailed settings of the fire resistance design
Specification of limit deformation for the serviceability limit state design
Determination of design ratios, support forces, and deformations
For design according to EC 5 (EN 1995), the following National Annexes are available:
DIN EN 1995-1-1/NA:2013-08 (Germany)
NBN EN 1995-1-1/ANB:2012-07 (Belgium)
DK EN 1995-1-1/NA:2011-12 (Denmark)
SFS EN 1995-1-1/NA:2007-11 (Finland)
NF EN 1995-1-1/NA:2010-05 (France)
UNI EN 1995-1-1/NA:2010-09 (Italy)
NEN EN 1995-1-1/NB:2007-11 (Netherlands)
ÖNORM B 1995-1-1:2015-06 (Austria)
PN EN 1995-1-1/NA:2010-09 (Poland)
SS EN 1995-1-1 (Sweden)
STN EN 1995-1-1/NA:2008-12 (Slovakia)
SIST EN 1995-1-1/A101:2006-03 (Slovenia)
CSN EN 1995-1-1:2007-09 (Czech Republic)
BS EN 1995-1-1/NA:2009-10 (the United Kingdom)
Automatic generation of wind and snow loads
Multiple optional reductions according to the selected standard
Direct data export to MS Excel
Program languages: English, German, Czech, Italian, Spanish, French, Portuguese, Polish, Chinese, Dutch, and Russian
Verifiable printout report, including all required designs. Printout report available in many output languages; for example, English, German, French, Italian, Spanish, Russian, Czech, Polish, Portuguese, Chinese, and Dutch.
Direct import of stp files from various CAD programs
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