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Frequently Asked Questions (FAQ)
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Basically, the buckling load is determined as follows when activating the option to transfer the most unfavorable value of the axial force for a non-constant distribution:
Critical Load Factor * most unfavorable value of the axial force = buckling load
However, the most unfavorable value refers to the member part, not to the entire member. The value of the most unfavorable axial force of the entire member is only assumed as the most unfavorable value if "1" is selected for "Internal member division for", see Figure 1.
Otherwise, the mean value is first determined internally from the most unfavorable values of the respective member divisions. The following diagram shows the most unfavorable value for two member parts from the normal force distribution in the following figure:
(60 kN + 30 kN)/2 = 45 kN
Thus, the following buckling load results for the first buckling mode in this example:
2.429 * 45 kN = 109,3 kN
It is very likely that the partial safety factor γM for the reduction of the modulus of elasticity is activated in RFEM, but is not considered in the manual calculation.
γM can be viewed and, if necessary, adjusted within the "Edit Material" dialog box, see Figure 1.
Furthermore, in the RF-STABILITY or RSBUCK add-on module, the option "Activate stiffness changes of RFEM" must be considered in the general data, see Figure 2.
With an effective length of 35.405 m, an area moment of inertia of 8356 cm 4 , a modulus of elasticity of 21000 kN/cm² and a partial safety factor of 1.1 as a divisor, the following buckling load results according to the following formula:
In order to consider the failure of certain members when using RF‑/DYNAM Pro - Equivalent Loads, proceed as follows:
1) Deactivating the corresponding members for the eigenvalue determination within the corresponding load case, see Image 01 (add-on module, tab Natural Vibration Cases, Calculation Parameters) and Image 02 (main program, Calculation Parameters, Deactivate and select).
2) Determining dynamic load cases from RF‑/DYNAM Pro by using the calculation, then deactivating the corresponding member in the main program within the global calculation parameters of the dynamic load cases, see Image 03.
You have probably defined a shear panel and a rotational restraint for your design case in the RF‑/STEEL EC3 add-on module, but have not yet defined all specifications for the rotational restraint.
In Window 1.13, scroll down under Settings. For the rotational restraint, the "spacing of beams" is still defined as s = 0 m. Adjust the value accordingly.
The automatic increment of a reinforcement for the deformation analysis is not possible. As soon as the deformation calculation is based on the stiffness determination, it is not constructive to develop an algorithm that, for example, increases the reinforcement at the point of the maximum deformation. Such a procedure would not result in the deformation being reduced.
Therefore, the reinforcement must be increased manually.
AnswerPlease check if the structure tears due to pure load. It is possible that the increase in deformations is mainly caused by creep and shrinkage, which are not active at time 0. In the nonlinear calculation, shrinkage is considered as a strain load, which can cause additional stresses.
In principle, the program always tries to perform a plastic design for cross-section classes 1 and 2. However, if torsion is additionally contained, the design can only be performed elastically. This is due to the interaction conditions according to EN 1993-1-1 clause 6.2.9, which do not include any torsional component.
For this reason, the "Cross-Section Design and Torsion" setting is available in the details of the add-on module. By adjusting the limit shear stress for the cross-section designs, you can also neglect the torsion under your own responsibility.
AnswerThe RF-PIPING add-on module is available for modeling pipelines. This add-on module is an extension of RFEM. The functions of the piping module are activated when the piping analysis is activated in the General Data dialog box, Options tab.
The material file needs to be saved separately within RF-LAMINATE and then shared with another user if they would like to access the user-defined compositions or custom layups. The additional user will then need to open the .jyr file that was shared within RF-LAMINATE directly.
Image 01 - Saving laminate composition layers
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Wind Simulation & Wind Load Generation
With the stand-alone program RWIND Simulation, wind flows around simple or complex structures can be simulated by means of a digital wind tunnel.
The generated wind loads acting on these objects can be imported to RFEM or RSTAB.
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