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Frequently Asked Questions (FAQ)
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AnswerIf the position of the additional reinforcement is different from the position of the basic reinforcement, a jointly weighted centroidal axis is determined. This in turn has an influence on the SLS designs (e.g. hc, eff).
In the graphic, this is not possible for reasons of clarity. However, the RF-LAMINATE add-on module allows you to display the stresses point by point. This is deactivated by default because it quickly produces a huge amount of data for large structures.
If you also filter by the stress component that interests you, the output in the table becomes quickly clear and you can evaluate the distribution of stresses at a point via the layers there well.
The arrangement of shim plates in the column only increases the load-bearing capacity of a bolt row, for which failure mode 1 (complete flow of the flange without bolt failure) is governing. This is probably not the case in your example, that is, failure mode 2 is governing: In this case, the shims do not result in an increased connection resistance of the frame corner.
Further information on this topic can be found in the corresponding section of DIN EN 1993-1-8, which is the basis for the calculation in FRAME-JOINT Pro.
When using shim plates, the geometry specifications according to clause 188.8.131.52 of the standard mentioned above must also be observed.
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
The partial safety factor γM for reducing the modulus of elasticity is very likely activated in RFEM/RSTAB, 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, the option "Activate stiffness changes of RFEM/RSTAB" must be considered in the general data in the add-on module RF-STABILITY or RSBUCK, 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 (see also Figure 3) according to the following formula:
AnswerBoth DLT and NLT are considered to behave more like single-axis beam elements stressed primarily in bending. Although realistically there is a small amount of stiffness perpendicular to the span direction, this is neglected in beam design. This is in contrast to cross-laminated timber (CLT) which includes two-way stiffness in both the directions parallel and perpendicular to the span direction. Therefore, RF-LAMINATE is not the suitable add-on module to NLT or DLT design but rather used for CLT design.The best approach in RFEM is to model a standard stiffness surface with modified orthotropic elastic 2D material properties. For the material model details, the modulus of elasticity in the local y-axis direction (Ey) should be set to a very small number (i.e. 0.001). The shear modulus in the local yz-plane (Gyz) should also be set to this small value. This will replicate little to no stiffness in the direction perpendicular to the DLT or NLT span direction.The surface can then be applied in the RFEM model for the full analysis. Note, design is not possible for these elements directly in RFEM. Internal forces, stresses, deflections, etc. from the RFEM analysis can be exported to alternative programs (i.e. Excel) for further design according to the various standards.
The reason there is a difference in results between superimposing LCs in COs vs. RCs is because when you apply the loads at once in a CO you will receive a different load distribution throughout the entire structure compared to the RC where the results are what are being added together. This is based on FEA where adding all of the loading together is different compared to solving the LCs each individually and adding the results together. Can be compared to a different order of operations to put it simply. You can see the comparison in the two figures below. Figure 1 is the load cases added up in CO1 and figure 2 has the LCs added together in RC1.
The support spring is determined from the modulus of elasticity (E), the cross-sectional area of the wall (A) and the height of the wall (H) as follows:
Since the display of the spring for the linear meter is displayed, the unit kN/m² results, see Figure.
Because a net requires multiple cable segments to be modeled in a grid-type pattern, the cables are not one continuous member. This is not ideal for the RF-FORM-FINDING module as the cable prestress properties such as sag, target length, or force are best applied to a single cable segment. The program cannot easily apply these settings to a cable that is broken down into multiple segments along its length.
The best option to model the net in RFEM is to instead use a surface element. The material and stiffness properties of the surface are the equivalent properties to that of the net provided by the manufacturer. RF-FORM-FINDING can then be applied to the surface element such as a prestress force or stress.
AnswerIn version 5.23, the possibility of calculating the maximum deformation has been added, which finds the largest total deformation (in the case of nonlinear material also plastic deformation) for members, for surfaces and for solids. The calculation of the maximum deformation value is switched on by default. If you disable this option, the calculation should speed up.
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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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