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.
Do you often spend too long calculating cross-sections? Dlubal Software and the RSECTION stand-alone program facilitate your work by determining section properties of various cross-sections and performing a subsequent stress analysis.
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When designing cross-laminated timber (CLT) panels, the calculated moment capacities in the major strength direction (β = 0°) should be multiplied by 0.85 for conservatism according to the American National Standard Institute ANSI/APA PRG 320.
This value is known as the conservatism factor, Ccon in the Timber Design add-on and can be adjusted under the Strength Configuration for NDS.
If you want to specify your own design results for a structural component of one design situation type for different configurations, the "Construction Stages Analysis (CSA)" add-on provides a solution. Among other things, this add-on allows you to perform a parallel simulation of a model 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 differently set design configurations.
For the conversion, you can proceed as follows:
According to AISC Section E5, the effects of eccentricity on single-angle members can be neglected when the following conditions are met:
Under the Strength Configuration, activate the "Use effective slenderness ratio acc. to E5" option. Choose between planar or space truss, then select whether the leg is connected though the longer or shorter leg.
After solving the calculation, the result is presented under Design Check EE2900. In cases where section E5 requirements are not met, RFEM proceeds with evaluating the member for combined axial load and flexure according to Chapter F and H.
In the serviceability limit state design 1b), the deformation wfin is calculated from the deformation components wcreep and winst. The creep deformation wcreep includes the deformation coefficient kdef. This depends on the material used and on the service class.
The deformation coefficient kdef is preset with the value of 0.6. It does not change automatically with regard to the respective service class. If it is necessary to use a different kdef value for the serviceability limit state design, you can adjust the settings of the National Annex accordingly. Pay attention to which structural component corresponds to the worst (highest) service class.
The most likely cause of the different results is that you have probably not set the same smoothing of the surface internal forces.
This can be set separately in RFEM 6 and in the add-on.
If the smoothing is the same in both settings, the stresses are also the same.
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.
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.
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.
According to EN 1993‑1‑1, 6.3.4 (1), the General Method allows for the lateral-torsional and torsional-flexural buckling analysis of individual structural components which are subjected to loading in their principal plane and include any single-symmetric cross-section, a variable height, and any boundary conditions, as well as the analysis of entire planar structures or partial structures consisting of such components. Therefore, the design of structural components with an asymmetric cross‑section is not possible using the General Method. Steel Design reports a failed design and shows the corresponding error message.
The stability analysis may be performed as section design according to EN 1993‑1‑1, 5.2.2 (7) a, provided that a spatial calculation according to the second-order analysis is performed with the global and local imperfections applied. In order to model the lateral-torsional buckling, it is necessary to determine the internal forces according to the geometrically nonlinear torsional buckling analysis with regard to warping torsion. Then, it is only necessary to perform the section design, as all stability effects are covered by the calculation. Therefore, this design method is applicable to all cross‑sections subjected to any loading.Considering cross-section warping as an additional degree of freedom is possible with the Torsional Warping add-on.