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.
Do you always know where the wind is blowing from? From the direction of innovation, of course! With RWIND 2, you have a program at your side that uses a digital wind tunnel for the numerical simulation of wind flows. The program simulates these flows around any building geometry and determines the wind loads on the surfaces.
Are you looking for an overview of snow load zones, wind zones, and seismic zones? Then you are in the right place. Use the Geo-Zone Tool to determine quickly and efficiently snow loads, wind speeds, and seismic data according to ASCE 7‑16 and other international standards.
Would you like to try out the capabilities of the Dlubal Software programs? You have the opportunity to do so! The free 90-day full version allows you to thoroughly test all our programs.
Accuracy of RWIND Results and Ratio of Accuracy Versus Cost
The RWIND program was designed to quickly and easily calculate wind flow around buildings in order to obtain pressure values on their surfaces and generate load forces. In order to meet this main goal, a number of compromises had to be made, such as allowing the use of a simplified model or a relatively coarse computational mesh. It is obvious that these simplifications affect the accuracy of the results. Increasing the accuracy of the results using a finer mesh and other user settings in RWIND is possible, but this process may not be easy and requires sufficient experience with CFD simulations. An important question here is what is the acceptable ratio of effort and cost to the improvement in accuracy achieved. We recommend reading the CFD Project Accuracy vs. Effort article which deals with this issue in detail.
RWIND Error E315
When increasing the mesh density, memory and performance requirements do not grow linearly, but with the 3rd to 4th power (we have three spatial dimensions and also a reduction of the time step is necessary). This not only leads to a significant slowdown of the calculation, but also various problems can start to appear, which are usually related to the fact that the program approaches its limits or the limits of the hardware used. These problems also include error E315 which indicates a general failure inside the OpenFOAM© calculation modules – such as memory allocation failure, loss of numerical precision, and so on. The specific reasons for the failure can be different. More detailed information can be found from the relevant Log File.
RWIND Customer Support and its Limits
Dlubal customer support always tries to help RWIND users who encounter any problems. However, numerical simulations of wind flow can be very complex and results cannot generally be guaranteed. This is due to the fact that there is still no mathematical proof of the existence and uniqueness of the solution of the Navier-Stokes equations that describe this flow and which RWIND solves numerically using the finite volume method. Although the calculation converges to the correct solution in most cases, a failure of the calculation cannot be excluded. In the event that a calculation failure occurs in a large and complex project, assistance can be very time-consuming. If you are interested in additional extended assistance, please Contact Our Sales Team.
The stresses of a surface can be displayed via the COM interface. First, you need the interface for the model (IModel) and then the interface for the calculation (ICalculation2). Using this interface, you can get the interface for the results (IResults2):
Sub stresses_surfaces_example()Dim iApp As RFEM5.ApplicationDim iModel As RFEM5.modelSet iModel = GetObject(, "RFEM5.Model")On Error GoTo EIf Not iModel Is Nothing Then ' get interface from model Set iApp = iModel.GetApplication iApp.LockLicense ' get interface from calculation Dim iCalc As RFEM5.ICalculation2 Set iCalc = iModel.GetCalculation ' get interface from results from loadcase 1 Dim iRes As RFEM5.IResults2 Set iRes = iCalc.GetResultsInFeNodes(LoadCaseType, 1) ' get equivalent stresses Dim str_equ() As RFEM5.SurfaceEquivalentStresses str_equ = iRes.GetSurfaceEquivalentStresses(1, AtNo, VonMisesHypothesis) End IfE:If Err.Number <> 0 Then MsgBox Err.Number & " " & Err.descriptionEnd IfIf Not iApp Is Nothing Then iApp.UnlockLicenseEnd If
The GetSurfaceEquivalentStresses function requires the specification of the calculation hypothesis. In this case, the results of the von Mises stress are displayed. Please note that the COM interface uses SI units so the stress is transferred in N/m².
Finite elements with plastic material are divided into 10 layers. Initially, a normal elastic analysis is performed in the first iteration. Then, the stress in each element is calculated according to the set strength hypothesis in each individual layer. If the limit stress in one of the layers is exceeded, the stiffness of this layer is reduced. Based on the reduced stiffnesses of the 10 layers, an overall stiffness is determined for each element. Using this new stiffness, it is possible to start a new iteration of the calculation.
It is iterated as long as the changes are only small.
The total stress is converted into the stresses of the individual layers using the laminate analysis. This analysis is also applied for the conversion between the stiffnesses of the layers and the total stiffness.
Four different strength hypotheses can be used as the limit stress:
The selection of the failure hypothesis is shown in Image 01.
The von Mises hypothesis is preset, as it is the most frequently used strength hypothesis.