In addition to our technical support (e.g. via chat), you’ll find resources on our website that may help you with your design using Dlubal Software.
Frequently Asked Questions (FAQ)
Search FAQ
Further Information
Customer Support 24/7

Answer
If the holes are subject to a regular grid, they may be defined by the composite cross sections (Figure 1).Otherwise it is still possible to reduce the cross section in the properties as a whole (Fig. 2).Thus, a flat reduction of the stiffness of the cross section is made. Unfortunately, it is not possible to distinguish between reductions in the compression and tension of the cross section. 
Answer
The design of wood joints with pinshaped fasteners is currently limited to steelwood joints according to Chapter 8.2.3. Pure woodwood compounds on shear under consideration of the Johansen theory are therefore currently not possible. Direct woodwood connections by means of fullthread screws are possible with the module RF / JOINTS wood  wood to wood with which main secondary beam connections can be calculated. 
Answer
There are basically two options here:
 The use of rod eccentricities, see technical contribution Consideration of rod and surface eccentricities
 In the case of, for example, differently defined rod end joints in combination with different dimensions of offsets, the use of couplings or rigid rods may help, see Figure 1

Answer
Unfortunately, it is not possible to perform the calculation with and without push group in a file. For each state a separate file must be created. 
Answer
In the current regulations, connection means or connections are always detected in one plane only. The reason for this is that the evidence of shear etc. can only be analyzed in the 2D plane. The verification of the bearing evidence, for example, is not possible for offplane failure.Since in a threedimensional calculation also internal forces in v _{y} and v _{z} can occur, it has been proven in practice to allow a small proportion of internal forces in the secondary direction and not fully exploit the connection. However, if the proportion of the lateral force in the secondary direction becomes too high, a detailed investigation with an FE simulation may be necessary. 
Answer
The auxiliary values λ1 and λ2 are required to determine the effective lengths.
These two values are used to determine an α value from Figure 6.19 of EN 199318, which is then used to calculate the effective lengths (for noncircular flow lines) of the Tstub flanges.
The maximum value for λ1 is 0.9 and the maximum value for λ2 is 1.4 > see Figure 6.11 of EN 199318
Based on your geometry, however, the result is, for example, a λ2 of> 1.4 for the end plate
α can only be calculated with the maximum value of 1.4. 
Answer
Connection moments are not calculated in RF/STEEL EC3. 
Answer
The total rotational spring comprises of several individual rotational springs, which are given in [1] as Equation 10.11.
In the case of a noncontinuous rotational restraint by purlins, RF‑/STEEL EC3 takes into account the rotational stiffness due to the connection stiffness C_{D,A}, the rotational stiffness C_{D,C} due to the bending stiffness of the available purlins, and also the rotational stiffness C_{D,B} due to the section deformation, if activated.
Since the execution of the connection is unknown, the infinite value is set by default. The spring stiffnesses are considered as a reciprocal value 1/C, thus giving 'infinitely' the result of spring stiffness = 0. If you know the rotational spring stiffness of the connection, you can specify this value manually.
The rotational stiffness C_{D,C} due to the bending stiffness is determined according to the following formula:
$\begin{array}{l}{\mathrm c}_{\mathrm D,\mathrm C}\;=\;{\mathrm C}_{\mathrm D,\mathrm C}\;/\;\mathrm e\\{\mathrm C}_{\mathrm D,\mathrm C}\;=\frac{\mathrm k\;\cdot\;\mathrm E\;\cdot\;\mathrm I}{\mathrm s}\end{array}$
where
E is the modulus of elasticity
k is the coefficient for position (inner span, outer span)
I is the moment of inertia I_{y}
s is the distance of the beams
e is the distance of the purlinsThe rotational stiffness C_{D,B} due to the bending stiffness is determined according to the following formula:
$\begin{array}{l}{\mathrm c}_{\mathrm D,\mathrm B}\;=\;{\mathrm C}_{\mathrm D,\mathrm B}\;/\;\mathrm e\\{\mathrm C}_{\mathrm D,\mathrm B}\;=\sqrt{\mathrm E\;\cdot\;\mathrm t_{\mathrm w}^3\;\cdot\;\mathrm G\;\cdot\;{\mathrm I}_{\mathrm T,\mathrm G}\;/\;(\mathrm h{\mathrm t}_{\mathrm f})}\\{\mathrm I}_{\mathrm T,\mathrm G}\;=\mathrm b\;\cdot\;\mathrm t_{\mathrm f}^3\;/\;3\end{array}$
where
E is the modulus of elasticity
t_{w} is the web thickness of the truss or the supported component
G is the G modulus
h is the height of the truss or the supported component
t_{f} is the flange thickness of the truss
b is the truss width
e is the distance of the purlinsThe attached example includes two design cases.
Case 1 was designed without taking into account the crosssection deformation. The total rotational spring stiffness is
C_{D} = C_{D,C }= 4,729 kNm/mCase 2 was designed while taking into account the crosssection deformation. The total rotational spring stiffness is
C_{D} = 72.02 kNm/mSingle spring C_{D,B} = 73.14 kNm/m
Single spring C_{D,C} = 4,729 kNm/mTotal spring:
$\begin{array}{l}\frac1{{\mathrm C}_{\mathrm D}}=\frac1{{\mathrm C}_{\mathrm D,\mathrm B}}+\frac1{{\mathrm C}_{\mathrm D,\mathrm C}}\;=\;\frac1{73.14}+\frac1{4,729}\\{\mathrm C}_{\mathrm D}\;=72.02\;\mathrm{kNm}/\mathrm m\end{array}$

Answer
The easiest way to find the internal forces at these nodes is to print the pictures of members into the printout report.
If this solution is not an option, you can also find the values in the result table 4.1 in the printout report. Since the extreme values are only activated by default, it is still necessary to activate nodal values in the selection.
It is usually not reasonable to include the internal forces of all member in the printout report. Therefore, you can only select the members that are relevant to you.

Answer
RFJOINTS performs an idealized design of a steel connection according to the standard, which cannot be easily compared with an exact FE calculation.
Thus, the following conditions must be met:
 Consideration or exclusion of friction/compression/tension within the contact solid (tab "Solid") as well as for the bolts modeled subsequently
 Consideration of internal forces and deformations within the subsequently modeled end plates or similar, which causes redistribution of bolt forces in the FE calculation (in contrast to the idealized design in RF‑JOINTS)
This can be corrected by rigid connection objects, for example (an end plate as a rigid surface).  Uniform load introduction into the FE model, for example, by using rigid members or rigid surfaces as described in the article "FEM Modeling Approaches of Rigid Connections"
Contact us
Did you find your question?
If not, contact us via our free email, chat, or forum support, or send us your question via the online form.
First Steps
We provide hints and tips to help you get started with the main programs RFEM and RSTAB.
Your support is by far the best
“Thank you very much for the useful information.
I would like to pay a compliment to your support team. I am always impressed how quickly and professionally the questions are answered. In the industry of structural analysis, I use several software including service contract, but your support is by far the best.”