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 crosssection consists of several unconnected partial sections, the sum of the moments of inertia is calculated without the parallel axis theorem components. The crosssection shown in Figure 01 consists of two angle sections that are not connected to each other.
Figure 01  CrossSection Consisting of Several Unconnected Partial Sections
The individual angle sections have the following moments of inertia:
I_{y,1,2} = 180.39 cm^{4} (referred to the centroidal axes y, z)
I_{z,1,2} = 65.05 cm^{4} (referred to the centroidal axes y, z)
The moments of inertia of the entire crosssection result in:
I_{y,1+2} = 2 ⋅ I_{y,1,2} = 2 ⋅ 180.39 = 360.78 cm^{4} (referred to the centroidal axes y, z)
I_{z,1+2} = 2 ⋅ I_{z,1,2} = 2 ⋅ 65.05 = 130.11 cm^{4} (referred to the centroidal axes y, z)
If the crosssection consists of several connected partial sections, the sum of the moments of inertia is calculated with the parallel axis theorem components. The crosssection shown in Figure 02 consists of two connected angle sections.
Figure 02  CrossSection Consisting of Several Connected Partial Sections
The individual angle sections have the following crosssection properties:
A_{1,2} = 16.25 cm²
y_{S,0,1,2} = ±2.30 cm (referred to the zero point)
z_{S,0,1,2} = 3.07 cm (referred to the zero point)
I_{y,1,2} = 180.39 cm^{4} (referred to the centroid axes y, z)
I_{z,1,2} = 65.05 cm^{4} (referred to the centroid axes y, z)
The crosssection properties of the entire crosssection result in:
y_{S,0,1+2} = 0.00 cm (referred to the zero point)
z_{S,0,1+2} = 3.07 cm (referred to the zero point)
I_{y,1+2} = 2 ⋅ I_{y,1,2} + 2 ⋅ A_{1,2} ⋅ (z_{S,0,1,2}  z_{S,0,1+2})²
I_{y,1+2} = 2 ⋅ 180.39 + 2 ⋅ 16.25 ⋅ (3.07  3.07)² = 360.78 cm^{4} (referred to the centroidal axes y, z)
I_{z,1+2} = 2 ⋅ I_{z,1,2} + 2 ⋅ A_{1,2} ⋅ (y_{S,0,1,2}  y_{S,0,1+2})²
I_{z,1+2} = 2 ⋅ 65.05 + 2 ⋅ 16.25 ⋅ (2.30  0.00)² = 301.46 cm^{4} (referred to the centroidal axes y, z)

Answer
Yes, it is possible to also perform punching shear designs for vertical walls.
Please note, however, that this feature was not available in the first versions of RF‑PUNCH Pro. For this, you will need RFEM 5.08 or later.

Answer
The thickness of membranes is usually very thin compared to the planar extension. Due to these extreme geometric conditions, the stiffness of membrane fabrics is usually related directly to a strip width, that is the line (compare with a line spring), without considering the thickness.In contrast, the general FEA software RFEM processes the material definitions (E, G, ν, and so on) and surface properties (shell, membrane, and so on) independently of each other. Thus, the pure definition of the material still does not clarify whether there is a rigid plate structure or a flexible membrane structure subjected to a tensile load. The final element specification is not clear until the surface properties are considered additionally for the simulation. Therefore, RFEM always requires the description of stiffness in the general unit syntax of force/surface, regardless of the geometric conditions of the structural component to be simulated.Thus, the linerelated membrane stiffness in the force/length syntax can be transferred to the force/surface syntax in RFEM by considering the reference thickness d:$\frac{\mathrm F}{\mathrm A}=\frac{\left({\displaystyle\frac{\mathrm F}{\mathrm L}}\right)}{\mathrm d}$whereF is the force,L is the length,d is the reference thickness,A is the surface.The stiffness transformed into the force/surface format in this way is thus related to the reference thickness and can convert the initially specified membrane stiffness in the force/length format in RFEM by specifying the reference thickness d as the membrane surface thickness. 
Answer
You can find this setting in the Display navigator.
Figure 01  Settings for Display of Axis System in Display Navigator

Answer
Yes, it is possible in Window "1.5 Punching Nodes."
Figure 01  Userdefined punching load
For example, this can be used if the determination of the punching load by using the smoothed or unsmoothed distribution of shear forces in the control perimeter is negatively affected by singularities.

Answer
The RF‑CONCRETE Columns addon module allows you to define a "creepproducing permanent load." You can find the corresponding tab in Window "1.1 General Data."
Figure 01  Window "1.1 General Data" with Tab "CreepProducing Permanent Load"
The reason for the entry is that RF‑CONCRETE Columns can apply this "creepproducing permanent load" for the automatic determination of the effective creep ratio according to EN 1992‑1‑1, 5.8.4.
In contrast, there is no explicit input option for this creepproducing permanent load in RF‑CONCRETE Members. In RF‑CONCRETE Members, the stability analysis of reinforced concrete columns by means of nonlinear design does not automatically reduce the effective creep ratio. You can find the background to the effective creep ratio applied in RF‑CONCRETE Members in Chapter 2.4.6 of the RFCONCRETE Members manual.
The same applies to the CONCRETE Columns or CONCRETE addon modules for RSTAB.

Answer
The design points in CRANEWAY have been adopted in compliance with the standard. In this case, the stresses are calculated for the following locations: Design Point 0
A periphery of the flange at the web edge or at the fillet start  Design Point 1
A flange at load application point (this can be checked as wheel spacing in Window 1.4)  Design Point 2
The flange edge
These points are not displayed in the resulting crosssection graphic in the CRANEWAY program. However, there is always a stress point at the design points 0 and 2 for which the result values can be directly displayed.  Design Point 0

Answer
In RWIND Simulation, each model surface in the wind flow is treated as a "smooth" wall. This definition results in a boundary layer in the areas around the flow close to the walls, which has an influence on the velocity profile perpendicular to the wall depending on the air viscosity. This boundary layer is created in RWIND Simulation according to the socalled "wall law." This law describes the velocity profile perpendicular to the wall and can be represented by the dimensionless variables u^{+} and y^{+}.Dimensionless variable u^{+}:$\mathrm u^+=\frac{\mathrm U}{{\mathrm u}_{\mathrm\tau}}$whereU is the velocity on the wall,uτ is the frictional velocity.Dimensionless variable y^{+}:$\mathrm y^+=\frac{{\mathrm u}_{\mathrm\tau}\cdot\mathrm y}{\mathrm\nu}$wherey is the wall distance,uτ is the frictional velocity,ν is the kinematic viscosity of the air.Using the friction velocity uτ:${\mathrm u}_{\mathrm\tau}=\sqrt{\frac{{\mathrm\tau}_{\mathrm w}}{\mathrm\rho}}$whereτw is the shear stress,ρ is the air density.By describing the boundary layer model in the viscous partial layer directly next to the wall$\mathrm u^+=\mathrm y^+$and in the subsequent logarithmic layer$\mathrm u^+=\frac1{\mathrm\kappa}\cdot\ln\;\mathrm y^++\mathrm C$you obtain the following velocity distribution,whereκ is the Kármán constant (κ = 0.41 for the simulation of a smooth wall),C is the constant (C = 5 for the simulation of a smooth wall).To ensure that the solution process is relatively fast and robust, the program specifies the corresponding boundary layer model directly in the first cell next to the model surface. The remaining part of the boundary layer results from the solution of the globally applied NavierStokes equations. 
Answer
Sometimes, it is not possible to print the graphics bigger as the lighting of the structure is controlled by a box in the background. Therefore, some space is lost in the printout report. 
Answer
The wind velocity profile in RWIND Simulation according to the ASCE 716 standard [1] is calculated based on Eq. 26.101. The coefficients and basic wind speed in this equation below are incorporated in the wind pressure equation.
Velocity wind pressure (imperial): q_{z} = 0.00256 K_{z} K_{zt} K_{d} K_{e} V^{2}We must reference this equation to calculate the inlet velocity relative to elevation for the RWIND Simulation CFD wind tunnel. To consider only velocity rather than pressure from this equation, the basic wind speed is multiplied by the squareroot of each coefficient. Notice the velocity variable in Eq. 26.101 is squared which requires the square root of the coefficients to be considered.$Inlet\;velocity\;=\;V\sqrt{K_e\;\cdot\;K_{d\;}\cdot\;K_z\;\cdot\;K_{zt}}$Because the ASCE 716 standard does not address wind CFD analysis and magnitude of the required inlet velocity, it is difficult to draw comparisons. Therefore, this is the closest estimate for calculating the RWIND Simulation inlet wind velocity per the code.
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.
Wind Simulation & Wind Load Generation
With the standalone 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.
Your support is by far the best
“Thank you for the valuable information.
I would like to pay a compliment to your support team. I am always impressed how quickly and professionally the questions are answered. I have used a lot of software with a support contract in the field of structural analysis, but your support is by far the best. ”