The structural analysis software RFEM 6 is the basis of a modular software system. The main program RFEM 6 is used to define structures, materials, and loads of planar and spatial structural systems consisting of plates, walls, shells, and members. The program also allows you to create combined structures as well as to model solid and contact elements.
RSTAB 9 is a powerful analysis and design software for 3D beam, frame, or truss structure calculations, reflecting the current state of the art and helping structural engineers meet requirements in modern civil engineering.
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In order to consider the support of the structure in the soil correctly, it is necessary to excavate the soil accordingly or to provide the solid with a corresponding opening.
For the CSA O86 and NDS, the Modification and Adjustment factors used in the Timber Design add-on in RFEM 6 can be manually adjusted. The factors are listed under the material properties.
To edit them manually, first open the material(s) being used for timber design and then set them to "User-Defined". Once this is done, navigate to the Timber Design tab where the Modification and Adjustment factors can be entered manually.
The Calculation for Torsion in the NDS Strength Configuration works together with the torsion limit set to ensure the safety of the member and structure. Below, you find a short explanation for each option:
Check torsional limit only:The ratio torsion check is compared to the torsion limit. If the ratio is smaller than the limit, then no further calculation is carried out. If the ratio is bigger than the torsion limit, an error will be shown in the design check. The error is then the most governing design check in the graphical and tabular results.
According to Timber Construction Manual:Torsion design is according to the Timber Construction Manual 4.6, and the result is a typical design ratio based on the calculation.
Ignore torsion:This setting is very similar to the first option. The ratio is compared from the torsion calculation to the torsion limit. If the ratio is smaller than the limit, then no further calculation is carried out. If the ratio is bigger than the limit, then a warning is shown in the design check. This warning will not be a governing design check in the results tables or graphics and serves only as a warning for safety considerations.
To neglect all torsion for the member design check, the limit value for torsion must be increased.
RFEM allows you to perform structural analysis and design of laminate and sandwich structures. The same applies to the cross-laminated timber. Stress and deflection analysis of laminate and sandwich surfaces is performed according to the laminate theory, taking into account the shear coupling.
Programs and Add-ons
RFEM is the main program that you can use to define the model and actions. You can model planar and spatial structures, consisting of plates, walls, shells, and members.
For the stress and deflection analysis, you need the Multilayer Surfaces add-on. It allows you to define and analyze layer structures.
Use the Timber Design add-on to also design the member supporting elements of the structure according to Eurocode 5 or ANSI/AWC NDS, for example.
Dynamic Analysis
If you need to perform a seismic or vibration analysis, the corresponding Dynamic Analysis add-ons are the perfect tools for determining natural frequencies and mode shapes, or for the analysis of external excitations.
In case of any questions about the Dlubal timber design solutions, our sales team will be happy to assist you.
Both RFEM and RSTAB are ideally suited for the structural analysis and design of timber structures.
Main Programs RFEM and RSTAB
The main programs RFEM and RSTAB are used to define the model with its properties and actions. In addition to spatial frame and truss structures, such as halls or space trusses, it is possible to model plate, wall, and shell structures with RFEM. Thus, RFEM is the more versatile variant—especially if you work in other areas, such as solid construction.
Available Standards
Add-ons for Timber Structures
Design add-ons supplement the functionality of the main programs. Use the Timber Design add-on to perform the ultimate and serviceability limit state design checks as well as the stability analysis and fire resistance design according to the standards listed above. In combination with the Torsional Warping (7 DOF) add-on, you can also perform lateral-torsional buckling analysis with up to seven degrees of freedom.
The special-solution Multilayer Surfaces add-on for RFEM is ideally suited for laminate surfaces made of cross-laminated timber (CLT).
The formula to determine the initial section depth di (CSA) or the equivalent square section dimension aeq (NDS) used for the slenderness ratio calculation is as follows:
In the dialog box of structural analysis settings, you can find the "Equilibrium for undeformed structure" checkbox under Options II (Image 01). If this is active, the structure is analyzed with the deformation reset to 0.
In the following, you can see an example of the result of the primary stress state determination; that is, the analysis of a soil massif subjected to its own weight. In Construction Stage 2, the "Equilibrium for undeformed structure" option is activated in the structural analysis settings, compared to Construction Stage 1 with the inactive option.The results are compared in Image 02.
It becomes clear that the stress state in the structures is the same, but when this option is activated, the deformations are reset to 0.
The specific soil material models have a variable stiffness that depends, among other things, on the prevailing stress level.
In the analysis of a single load case, this is only impressed on the structure and the soil. No stress level from other loads is taken into account, which might be necessary to obtain and use the correct soil stiffness from the soil material model.
The load case of a live load, for example, will result in different stiffnesses and thus deformations,if it is applied within a load combination on a structure that is already subjected to the soil weight as well as the structural weight and construction load,than it would result if setting it as the "first/single" load, which would be done in the analysis of the load case.
Therefore, it does not make sense to analyze the soil with the specific soil material models subjected to the individual loads / load cases if at least the always prevailing soil self-weight is not taken into account.
The main programs RFEM 6 and RSTAB 9 are distinguished by their clarity. The entire input in the program is set up in such a way that you always obtain a clear result for each calculation task. The design of objects is organized in a similar way. In the input, the program shows the necessary properties for each design object, including the corresponding loads, and outputs a clear result for this object after the analysis.
If you want to determine your own design results for the entire model for different load levels, the "Construction Stages Analysis (CSA)" add-on provides a solution. In addition to the basic simulation of the construction process (the object rise), the program also allows for parallel simulation of models with a constant number of objects. In this special case, the base model is internally juxtaposed several times, and can thus be transferred to the design with different loads.
To do this, proceed as follows:
To use numerical methods, such as FEM, in geotechnical engineering, it is reasonable to set the cohesion as not equal to zero. Therefore, a small cohesion between 0.5 and 1.0 kN/m² can be applied even for non-cohesive soils.