Using the "Damper" member type, you can define a damping coefficient, a spring constant, and a mass. This member type extends the possibilities within the Time History Analysis.
With regard to viscoelasticity, the "Damper" member type is similar to the Kelvin-Voigt model, which consists of the damping element and an elastic spring (both connected in parallel).
The building model is calculated in two phases:
- Global 3D calculation of the global model, where the slabs are modeled as a rigid plane (diaphragm) or as a bending plate
- Local 2D calculation of the individual floors
After the calculation, the results of the columns and walls from the 3D calculation and the results of the slabs from the 2D calculation are combined in a single model. This means that there is no need to switch between the 3D model and the individual 2D models of the slabs. The user only works with one model, saves valuable time, and avoids possible errors in the manual data exchange between the 3D model and the individual 2D ceiling models.
The vertical surfaces in the model can be divided into shear walls and opening lintels. The program automatically generates internal result members from these wall objects, so they can be designed as members according to any standard in the Concrete Design add-on.
For a response spectrum analysis of building models, you can display the sensitivity coefficients for the horizontal directions by story.
These key figures allow you to interpret the sensitivity to stability effects.
The Steel Joints add-on provides you with the option to connect circular hollow sections using welds.
It is possible to connect the circular sections to each other or to planar structural components. The fillets of standard and thin-walled sections can also be connected with a weld.
Go to Explanatory VideoIn the "Steel Joints" add-on, you can consider preloaded bolts in all components during the calculation. You can easily activate the preloading using the check box in the bolt parameters, and it has an impact on the stress-strain analysis as well as the stiffness analysis.
Preloaded bolts are special bolts used in steel structures to generate a high clamping force between the connected structural components. This clamping force causes friction between the structural components, which allows for the transfer of forces.
Functionality
Preloaded bolts are tightened with a certain torque, causing them to stretch and generate a tensile force. This tensile force is transferred to the connected components and leads to a high clamping force. The clamping force prevents the connection from loosening and ensures safe force transmission.
Advantages
- High load-bearing capacity: Preloaded bolts can transfer large forces.
- Low deformation: They minimize the deformation of the connection.
- Fatigue strength: They are resistant to fatigue.
- Easy assembly: They are relatively easy to assemble and disassemble.
Analysis and Design
The calculation of preloaded bolts is performed in RFEM using the FE analysis model generated by the "Steel Joints" add-on. It takes into account the clamping force, friction between structural components, shear strength of bolts, and load-bearing capacity of the structural components. The design is carried out according to DIN EN 1993‑1‑8 (Eurocode 3) or the US standard ANSI/AISC 360‑16. You can save the created analysis model, including the results, and use it as an independent RFEM model.
Several modeling tools are available for elements in building models:
- Vertical line
- Column
- Wall
- Beam
- Rectangular floor
- Polygonal floor
- Rectangular floor opening
- Polygonal floor opening
This feature allows you to define the element on the ground plane (for example, with a background layer) with the associated multiple element creation in space.
You can import STEP files into RFEM 6. The data are directly converted into the native RFEM model data.
STEP is an interface standard initiated by ISO (ISO 10303). In the geometry description, all shapes relevant for RFEM (line, surface, and solid models) can be integrated by the CAD data models.
Note: This format is not to be confused with DSTV interfaces, which also use the file extension *.stp.
Use the "Import Support Reactions" Load Wizard in RFEM 6 and RSTAB 9 to easily transfer reaction forces from other models. The wizard allows you to connect all or several nodal and line loads of different models with each other in a few steps.
The load transfer from load cases and load combinations can be carried out automatically or manually. It's necessary that the models are saved in the same Dlubal Center project.
The "Import Support Reactions" load wizard supports the concept of positional statics and allows you to digitally connect the individual positions.
Go to Explanatory VideoThe initial stiffness Sj,ini is a crucial parameter for evaluating whether a connection can be characterized as rigid, semi-rigid, or pinned.
In the "Steel Joints" add-on, you can calculate the initial stiffness Sj,ini according to Eurocode (EN 1993‑1‑8, Section 5.2.2) and AISC (AISC 360-16, Cl. E3.4) with regard to the internal forces N, My, and/or Mz.
The optional automatic transfer of initial stiffnesses allows for a directly transfer as member hinge stiffnesses in RFEM. The entire structure is then recalculated and the resulting internal forces are automatically adopted as loads in the analysis and design of the connection models.
This automated iteration process eliminates the need for manual export and import of data, reducing the amount of work and minimizing potential sources of error.
Explanatory Video: Calculation of Initial Stiffness Sj,iniThis function provides you with the option to adopt reaction forces from other models as nodal and line loads.
The option not only transfers the reaction load as an action, but digitally couples the support load of the original model with the load size of the target object. The subsequent changes in the original model are automatically adopted in the target model.
This technology supports the concept of positional statics and allows you to digitally connect the individual positions of the same Dlubal Center project.
Go to Explanatory VideoDo you already know the editor for mesh refinement control? It is a great help for your work! Why? It's easy – it gives you the following options:
- Graphic visualization of the areas with mesh refinements
- Mesh refinement of zones
- Deactivating the standard 3D solid mesh refinement with transversion into the corresponding manual 3D mesh refinements.
These options help you to formulate a suitable rule for meshing the entire model, even for the models with unusual dimensions. Use the editor to efficiently define small model details on large buildings or detailed meshing areas in the coating area of the model. You will be amazed!
Converting members to surface models works without any major problems. Easily generate member local section reductions using the Generate Surfaces from Members function. Thus, you can convert the members into surface models.
Enter and model a soil solid directly in RFEM. You can combine the soil material models with all common RFEM add-ons.
This allows you to easily analyze the entire models with a complete representation of the soil-structure interaction.
All parameters required for the calculation are automatically determined from the material data that you have entered. The program then generates the stress-strain curves for each FE element.
Do you want to model and analyze the behavior of a soil solid? To ensure this, special suitable material models have been implemented in RFEM.
You can use the modified Mohr-Coulomb model with a linear-elastic ideal-plastic model or a nonlinear elastic model with an oedometric stress-strain relation. The limit criterion, which describes the transition from the elastic area to that of the plastic flow, is defined according to Mohr-Coulomb.
Did you know? In contrast to other material models, the stress-strain diagram for this material model is not antimetric to the origin. You can use this material model to simulate the behavior of steel fiber-reinforced concrete, for example. Find detailed information about modeling steel fiber-reinforced concrete in the technical article about Determining the material properties of steel-fiber-reinforced concrete.
In this material model, the isotropic stiffness is reduced with a scalar damage parameter. This damage parameter is determined from the stress curve defined in the Diagram. The direction of the principal stresses is not taken into account. Rather, the damage occurs in the direction of the equivalent strain, which also covers the third direction perpendicular to the plane. The tension and compression area of the stress tensor is treated separately. In this case, different damage parameters apply.
The "Reference element size" controls how the strain in the crack area is scaled to the length of the element. With the default value zero, no scaling is performed. Thus, the material behavior of the steel fiber concrete is modeled realistically.
Find more information about the theoretical background of the "Isotropic Damage" material model in the technical article describing the Nonlinear Material Model Damage.
- For a new connection model, you have to select a node in the RFEM model
- After selecting a node, the members connected to the node are automatically recognized and assigned
- In the window for assigning members, select the ones that will be assigned to the connection
- The members marked by us are displayed in the preview window on the right
- Connections can be modeled for multiple nodes in a structure.
- For member settings, select the ones to be supported
An improvement that will benefit your smooth workflow: You can now export your RFEM and RSTAB models in XML, SAF, and VTK (results from RWIND).
Do you want to modify surface stiffnesses? There are now two new types available for you:
- Multiplication factor of total stiffness
- Multiplication factors of partial stiffnesses, weights, and masses
Take your structural design one step further. RFEM 6 and RSTAB 9 support now a new file format for structural design, Structural Analysis Format (SAF). For this, both programs allow for the import as well as the export. SAF is a file format based on MS Excel, intended to facilitate the exchange of structural analysis models between different software applications.
You can be sure that costs are an important factor in the structural planning of any project. It is also essential to adhere to the provisions on emissions estimation. The two-part add-on Optimization & Costs/CO2 Emission Estimation makes it easier for you to find your way through the jungle of standards and options. It uses the artificial intelligence technology (AI) of the particle swarm optimization (PSO) to find the right parameters for parameterized models and blocks that guarantee the compliance with the usual optimization criteria. This add-on also estimates the model costs or CO2 emissions by specifying unit costs or emissions per material definition for the structural model. With this add-on, you are on the safe side.
- Calculation of stationary incompressible turbulent wind flow using the SimpleFOAM solver from the OpenFOAM® software package
- Numerical scheme according to the first and second order
- Turbulence models RAS k-ω and RAS k-ε
- Consideration of surface roughness depending on model zones
- Model design via VTP, STL, OBJ, and IFC files
- Operation via bidirectional interface of RFEM or RSTAB for importing model geometries with standard-based wind loads and exporting wind load cases with probe-based printout report tables
- Intuitive model changes via drag & drop and graphical adjustment assistance
- Generation of a shrink-wrap mesh envelope around the model geometry
- Consideration of environmental objects (buildings, terrain, and so on)
- Height-dependent description of the wind load (wind speed and turbulence intensity)
- Automatic meshing depending on a selected depth of detail
- Consideration of layer meshes near the model surfaces
- Parallelized calculation with optimal utilization of all processor cores of a computer
- Graphical output of the surface results on the model surfaces (surface pressure, Cp coefficients)
- Graphical output of the flow field and vector results (pressure field, velocity field, turbulence – k-ω field, and turbulence – k-ε field, velocity vectors) on Clipper/Slicer planes
- Display of 3D wind flow via animated streamline graphics
- Definition of point and line probes
- Multilingual user interface (German, English, Czech, Spanish, French, Italian, Polish, Portuguese, Russian, and Chinese)
- Calculations of several models in one batch process
- Generator for creating rotated models to simulate different wind directions
- Optional interruption and continuation of the calculation
- Individual color panel per result graphic
- Display of diagrams with separate output of results on both sides of a surface
- Output of the dimensionless wall distance y+ in the mesh inspector details for the simplified model mesh
- Determination of the shear stress on the model surface from the flow around the model
- Calculation with an alternative convergence criterion (you can select between the residual types pressure or flow resistance in the simulation parameters)
To model structures in RWIND Basic, you find a special application in RFEM and RSTAB. Here, you define the wind directions to be analyzed by means of related angular positions about the vertical model axis. At the same time, you define the elevation-dependent wind profile on the basis of a wind standard. In addition to these specifications, you can use the stored calculation parameters to determine your own load cases for a stationary calculation per each angular position.
As an alternative, you can also use the RWIND Basic program manually, without the interface application in RFEM or RSTAB. In this case, RWIND Basic models the structures and terrain environment directly from the imported VTP, STL, OBJ, and IFC files. You can define the height-dependent wind load and other fluid-mechanical data directly in RWIND Basic.
Do you have to calculate multiple load combinations in your models? Then several solvers (one per core) are initiated in parallel, each of which calculates a load combination. This ensures a better utilization of the cores and thus faster calculations.
Go to Explanatory VideoThe Dlubal Center ensures that your planning goes quickly and efficiently. Among other things, your projects and model files are managed here in a central location. Detailed information and graphics make it easier for you to assign all models and thus enable uncomplicated, clear processing of the project. Furthermore, your customer data including the licensed programs and add-ons is organized in the Dlubal Center.
More About Dlubal CenterDiscover the new functions of the snow and wind load wizards:
- Loading of hybrid models made of members and surfaces (RFEM only)
- Connection to the Geo-Zone Tool (depending on the global construction site definition)
- Switching off surface sides
Also in this case, RSTAB will certainly convince you. With the powerful calculation kernel, its optimized networking and support of multi-core processor technology, the Dlubal structural analysis program is far ahead. This allows you to calculate more linear load cases and load combinations using several processors in parallel without using additional memory. The stiffness matrix only has to be created once. Thus, it is possible for you to calculate even large systems with the fast and direct solver.
Do you have to calculate multiple load combinations in your models? The program initiates several solvers in parallel (one per core). Each solver then calculates a load combination for you. This leads to better utilization of the cores.
You can systematically follow the development of the deformation displayed in a diagram during the calculation, and thus precisely evaluate the convergence behavior.
If you are looking for models to practice on or as inspiration for your projects, you've come to the right place. We offer a vast number of structural analysis models to download, such as RFEM, RSTAB, or RWIND files.
Models to DownloadYou create your models in the graphical user interface typical for CAD programs. By right-clicking the graphical or navigator objects, you activate a shortcut menu that you can use to select and modify the objects.
The operation of the user interface is intuitive, as you will notice soon. Therefore, you can create the structural and loading objects in a minimum amount of time.
Go to Explanatory VideoAlways keep track of things: The project navigator manages your projects and models of the Dlubal applications in a central location. Have the models displayed clearly in a list form or with a preview image. Furthermore, the program shows you detailed information as a preview, such as file size, model data, modification date, and so on.
Are you looking for models for your design? Then you have come to the right place at the Dlubal Center. It contains an extensive database with partly parameterized models. These include, for example, trusses, glulam beams, tapered frames, or tower segments. You can import these models and, if necessary, modify them according to your individual requirements. Furthermore, you can save the models as a block for later use.