In the Timber Design add-on for RFEM, you can design members as well as surfaces according to Eurocode 5, SIA 265 (Swiss standard), CSA O86 (Canadian standard), or ANSI/AWC NDS (American standard); for example, cross-laminated timber, glued-laminated timber, softwood, mass timber, and so on.
Go to Explanatory VideoFor timber surfaces with the "Constant" thickness type, the crack factor kcr and thus the negative influence of cracks on the shear capacity is taken into account.
As you probably know, the design checks for the selected members are carried out, taking into account the defined charring time. All necessary reduction factors and coefficients are stored accordingly in the program and are taken into account when determining the load-bearing capacity. That saves you a lot of work.
The effective lengths for the equivalent member design are taken directly from the strength entries. You do not have to enter them again.
After completing the design, the program presents the fire resistance design checks clearly and with all result details. This allows you to follow the results completely transparently. The results also contain all the required parameters, so you can determine the component temperature at the design time.
In addition to all these features, the program allows you to integrate all result tables and graphics, including the ultimate and serviceability limit state results,into the global printout report of RFEM/RSTAB as a part of the steel design results.
In RFEM and RSTAB, you can design members with the "Laminated Veneer Lumber" material type. The following manufacturers are available:
- Pollmeier (Baubuche)
- Metsä (Kerto LVL)
- STEICO
- Stora Enso
In the ultimate configuration, you can consider strength coefficients for increasing the strengths. The coefficients reducing the strengths are automatically taken into account regardless of this. Try it now!
Go to Explanatory VideoYou can graphically evaluate result sections for the timber surface design. This can be done in the RFEM graphic as well as in the result history window. The sections can be placed at any location in order to evaluate the design results in detail.
- Design of tension, compression, bending, shear, torsion, and combined internal forces
- Consideration of a notch
- Design of compression perpendicular to the grain on the end and intermediate supports with (EC 5) and without reinforcement elements (fully threaded screws)
- Optional shear force reduction at the support (see the Product Feature)
- Design of curved and tapered members
- Consideration of higher strengths for similar components that are close together (factor ksys according to EN 1995‑1‑1, 6.6(1)-(3))
- Option to increase shear resistance for softwood timber according to DIN EN 1995‑1‑1:NA NDP to 6.1.7(2)
- Stability analyses for flexural buckling, torsional buckling, and flexural-torsional buckling under compression
- Import of the effective lengths from the calculation using the Structure Stability add-on
- Graphical input and check of the defined nodal supports and effective lengths for stability analysis
- Determination of the equivalent member lengths for tapered members
- Consideration of Lateral-Torsional Bracing Position
- Lateral-torsional buckling analysis of the structural components subjected to moment loading
- Depending on the standard, a choice between user-defined input of Mcr, analytical method from the standard, and use of internal eigenvalue solver
- Consideration of a shear panel and a rotational restraint when using the eigenvalue solver
- Graphical display of a mode shape if the eigenvalue solver was used
- Stability analysis of structural components with the combined compression and bending stress, depending on the design standard
- Comprehensible calculation of all necessary coefficients, such as the factors for considering moment distribution or interaction factors
- Alternative consideration of all effects for the stability analysis when determining internal forces in RFEM/RSTAB (second-order analysis, imperfections, stiffness reduction, possibly in combination with the Torsional Warping (7 DOF) add-on)
Among others, the following cross-laminated timber manufacturers are available in the layer structure library:
- Binderholz (USA)
- KLH (USA, CAN)
- Kalesnikoff (USA, CAN)
- Nordic Structures (USA, CAN)
- Mercer Mass Timber
- SmartLam
- Sterling Structural
- Superstructures listed in Lignatec Edition 32 "Cross-Laminated Timber of Swiss Production"
By importing a structure from the layer structure library, all relevant parameters are adopted automatically. The library is continually updated.
Your options in timber design are diverse. You can consider cut-to-grain angles, transverse tension stresses, and volume-dependent radii of curvature for tapered and curved members. To design the area of the grain cut, the strength is adjusted accordingly in the case of bending tension or bending pressure. In order to also allow you to perform a stability analysis with the equivalent member method, the height to determine the effective and lateral-torsional buckling lengths is set at a distance of 0.65 × h to the actual design point.
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)
A library for cross-laminated timber panels is implemented in RFEM, from which you can import the manufacturer's layer structures (for example, Binderholz, KLH, Piveteaubois, Södra, Züblin Timber, Schilliger, Stora Enso). In addition to the layer thicknesses and materials, there is also the information about stiffness reductions and the narrow side bonding.
Go to Explanatory VideoDo 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
Here you have a free choice. You can perform the support pressure design at any point for the loading in the y- and z-directions of a cross-section. You are free to differentiate between inner and outer supports. A factor kc,90 for the pressure perpendicular to the grain can be user-defined (for example, 1.75 for glued-laminated timber). If allowed, the support length is increased automatically according to the standard specifications. This allows you to achieve a more efficient design with minimum effort.
RFEM/RSTAB also provides a range of functions for the case of a fire. The program allows for 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. Also, all information about the material and cross-section is stored. You don't need to do anything else.
You only define the parameters relevant for the fire resistance design by assigning a fire resistance configuration to the members and surfaces to be designed. Moreover, you can also make further detailed settings, such as the definition of the fire exposure on one side up to all sides.
Compared to the RF-FORM-FINDING add-on module (RFEM 5), the following new features have been added to the Form-Finding add-on for RFEM 6:
- Specification of all form-finding load boundary conditions in one load case
- Storage of form-finding results as initial state for further model analysis
- Automatic assignment of the form-finding initial state via combination wizards to all load situations of a design situation
- Additional form-finding geometry boundary conditions for members (unstressed length, maximum vertical sag, low-point vertical sag)
- Additional form-finding load boundary conditions for members (maximum force in member, minimum force in member, horizontal tension component, tension at i-end, tension at j-end, minimum tension at i-end, minimum tension at j-end)
- Material types "Fabric" and "Foil" in material library
- Parallel form-findings in one model
- Simulation of sequentially building form-finding states in connection with the Construction Stages Analysis (CSA) add-on
Did you know? In the Design Supports, you can now define fully threaded screws as transversal compression stiffening elements for the "Compression Perpendicular to Grain" design. In this case, the pressing-in and buckling of the bolts is analyzed.
Moreover, the design shear resistance is checked in the plane of the screw tip. The angle of dispersal can be considered as linear under 45° or nonlinear (according to Bejtka, I. (2005). Verstärkung von Bauteilen aus holz mit vollgewindeschrauben. KIT Scientific Publishing.).
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.
Use the member cross-section reductions to consider the start, internal, or end notches of a beam. The beam reduction is thus taken into account in the calculation of the load-bearing capacity. However, this does not apply to the stiffness.
Is there torsion? In this case, you can decide how to perform the design. You have the following options:
- Allow further design if shear stress due to torsion does not exceed limit value
- Design according to Timber Construction Manual, 4.6
- Ignoring torsion
Dlubal Software just makes everything a little easier. The performed design checks of the design standard are displayed in a clear way. A design criterion is determined for each design check. Furthermore, the program deliver the design details displayed in a structured way, including the initial values, the intermediate results, and the final results. An information window in the design details shows you the calculation process with the applied formulas, standard sources, and results in great detail.
Once you activate the Form-Finding add-on in the Base Data, a form-finding effect is assigned to the load cases with the load case category "Prestress" in conjunction with the form-finding loads from the member, surface, and solid load catalog. This is a prestress load case. It thus mutates into a form-finding analysis for the entire model with all member, surface, and solid elements defined in it. You reach the form-finding of the relevant member and membrane elements amid the overall model by using special form-finding loads and regular load definitions. These form-finding loads describe the expected state of deformation or force after the form-finding in the elements. The regular loads describe the external loading of the entire system.
The Ponding load type allows you to simulate rain actions on multi-curved surfaces, taking into account the displacements according to the large deformation analysis.
This numerical rainfall process examines the assigned surface geometry and determines which rainfall portions drain away and which rainfall portions accumulate in puddles (water pockets) on the surface. The puddle size then results in a corresponding vertical load for the structural analysis.
For example, you can use this feature in the analysis of approximately horizontal membrane roof geometries subjected to rain loading.
Go to Explanatory VideoWhat happens when there is a downwind? The topside lateral-torsional bracing is not applied to reduce the effective lengths and lateral-torsional buckling lengths.
The form-finding process gives you a structural model with active forces in the "prestress load case" This load case shows the displacement from the initial input position to the form-found geometry in the deformation results. In the force or stress-based results (member and surface internal forces, solid stresses, gas pressures, and so on), it clarifies the state for maintaining the found form. For the analysis of the shape geometry, the program offers you a two-dimensional contour line plot with the output of the absolute height and an inclination plot for the visualization of the slope situation.
Now, a further calculation and structural analysis of the entire model is performed. For this purpose, the program transfers the form-found geometry including the element-wise strains into a universally applicable initial state. You can now use it in the load cases and load combinations.
There is often no fire resistance design for the lateral supports of a structure. Would you like to handle this differently in your project? In order to consider this in the calculation, you can define other equivalent member lengths for the fire situation.
If your design is successful, the relaxed part of your work follows. Because the program does many processes for you. For example, the performed design checks are displayed in a table. It shows you all the result details. Due to the clearly presented design formulas, you will be able to understand the results without any problems. There is no "black box" effect here.
The design checks are carried out at all governing locations of the members and displayed graphically as a result diagram. Furthermore, detailed graphics, such as the stress distribution on a cross-section or the governing mode shape, are available for you in the result output.
All input and result data are part of the RFEM/RSTAB printout report. You can select the report contents and extent specifically for the individual design checks.
- Calculation of deflections and comparison with the normative or manually adjusted limit values
- Consideration of a precamber for the deflection analysis
- Different limit values are possible, depending on the design situation type
- Manual adjustment of reference lengths and segmentation by direction
- Calculation of deflections related to the initial structure or to the deformed structure
- Automatic consideration of time-dependent deformations by increasing the load with the creep factor (can also be user-defined on the stiffness side)
- Simplified vibration design
- Graphical result display integrated in RFEM/RSTAB; for example, the design ratio of a limit value, the deformation, or the sag
- Complete integration of the results into the RFEM/RSTAB printout report
Did you know? You can individually define the reference lengths to be considered in the calculation of the deflection limit value and the segments to be checked, depending on the direction. For this, define design supports at the intermediate nodes of a member and assign them to the respective direction for the deformation analysis. In the resulting segments, you can also define a precamber for each direction and segment.
For the design according to Eurocode 5, the parameters of the National Annexes (NA) are integrated for the following countries:
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DIN EN 1995-1-1/NA:2014-07 (Germany)
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ÖNORM EN 1995-1-1/NA:2019-06 (Austria)
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SN EN 1995-1-1/NA:2015-03 (Switzerland)
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BDS EN 1995-1-1/NA:20157-06 (Bulgaria)
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BS EN 1995-1-1/NA:2019-09 (United Kingdom)
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CEN EN 1995-1-1/2014-05 (European Union)
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CYS EN 1995-1-1/NA:2019-06 (Cyprus)
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CZE EN 1995-1-1/NA:2015-05 (Czech Republic)
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DS EN 1995-1-1/NA:2019-09 (Denmark)
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ELOT EN 1995-1-1/NA:2010-01 (Greece)
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EVS EN 1995-1-1/NA:2015-11 (Estonia)
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HRN EN 1995-1-1/NA:2015-03 (Croatia)
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I S. EN 1995-1-1/NA:2014-05 (Ireland)
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ILNAS EN 1995-1-1/NA:2020-3 (Luxembourg)
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IST EN 1995-1-1/NA:2014-09 (Iceland)
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LST EN 1995-1-1/NA:2014-06 (Lithuania)
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LVS EN 1995-1-1/NA:2014-12 (Latvia)
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MSZ EN 1995-1-1/NA:2015-06 (Hungary)
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NBN EN 1995-1-1/NA:2014-06 (Belgium)
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NEN EN 1995-1-1/NA:2014-06 (Netherlands)
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NF EN 1995-1-1/NA:2020-04 (France)
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NP EN 1995-1-1/NA:2014-09 (Portugal)
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NS EN 1995-1-1/NA:2014-08 (Norway)
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PN EN 1995-1-1/NA:2014-07 (Poland)
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SFS EN 1995-1-1/NA:2016-12 (Finland)
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SIST EN 1995-1-1/NA:2018-01 (Slovenia)
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SR EN 1995-1-1/NA:2014-12 (Romania)
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SS EN 1995-1-1/NA:2018-02 (Singapore)
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SS EN 1995-1-1/NA:2014-05 (Sweden)
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STN EN 1995-1-1/NA:2019-12 (Slovakia)
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TKP EN 1995-1-1/NA:2019-09 (Belarus)
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UNE EN 1995-1-1/NA:2016-04 (Spain)
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UNI EN 1995-1-1/NA:2016-11 (Italy)
You can enter the structural system and calculate the internal forces in the programs RFEM and RSTAB. You have full access to the extensive material and cross-section libraries.
Timber Design is completely integrated into the main programs. At the same time, it automatically takes into account the structure and the available calculation results. You can assign further entries for the timber design, such as effective lengths, cross-section reductions, or design parameters, to the objects to be designed. You can easily select the elements graphically using the [Select] function at many places of the program.