The National Building Code of Canada (NBC) 2020 Article 4.1.8.7 provides a clear procedure for earthquake methods of analysis. The more advanced method, the Dynamic Analysis Procedure in Article 4.1.8.12, should be used for all structure types except those that meet the criteria set forth in 4.1.8.7. The more simplistic method, the Equivalent Static Force Procedure (ESFP) in Article 4.1.8.11, can be used for all other structures.
In RFEM 6, the results for the FE mesh nodes are determined using the finite element method. For the distribution of internal forces, deformations, and stresses to be continuous, these nodal values are smoothed through an interpolation process. This article will introduce and compare the different types of smoothing that you can use for this purpose.
In computational fluid dynamics (CFD), complex surfaces that are not completely solid can be modeled using porous or permeability media. In the actual world, examples of such things include windbreak fabric structures, wire meshes, perforated facades and claddings, louvers, tube banks (stacks of horizontal cylinders), and so on.
In the RFEM 6 and RSTAB 9 programs, it is possible to group objects based on different criteria. Hence, objects that meet the defined criteria can be selected and edited at the same time. This is possible with the “Object Selection” tool, which is comparable to “Special Selection” in RFEM 5. This article will show you how to group objects with “Object Selection" as a new guide object of RFEM 6 or RSTAB 9.
Given that realistic determination of the soil conditions significantly influences the quality of the structural analysis of buildings, the Geotechnical Analysis add-on is offered in RFEM 6 to determine the soil body to be analyzed.
The way to provide data obtained from field tests in the add-on and use the properties from soil samples to determine the soil massifs of interest was discussed in Knowledge Base article “Creation of the Soil Body from Soil Samples in RFEM 6”. This article, on the other hand, will discuss the procedure to calculate settlements and soil pressures for a reinforced concrete building.
The quality of the structural analysis of buildings is significantly improved when the soil conditions are considered as realistically as possible. In RFEM 6, you can realistically determine the soil body to be analyzed with the help of the Geotechnical Analysis add-on. This add-on can be activated in the model’s Base Data as shown in Image 01.
An FE mesh quality display is available in RFEM as a tool for structural analyses of two-dimensional components. It leads to the execution of an internal check of the generated finite elements for defined criteria.
RFEM and RSTAB save the input data, the FE mesh, the results, the printout reports, and the 3D gITF model preview, including all visual objects, in one file.
For solids, there is another option for the FE mesh setting. You can arrange a layered FE mesh in addition to a holistic FE mesh refinement. For this option, you can perform a defined division of the solid with finite elements between two parallel surfaces. This option is particularly suitable for very large solid geometries with a low height.
Supports can be copied and moved using drag & drop, even if the "Move/Copy" function is not available in the shortcut menu. This applies to all kinds of supports: nodal supports, line supports, and surface supports. These can easily be assigned to further nodes, lines, or surfaces.
In RF-/FOUNDATION Pro, a graphical display of the result details is available. To see them, go to Window 2.2 Governing Design Criteria after the calculation. In the interactive graphic of this window, individual design-relevant values can be displayed for each design performed.
The "Mapped Mesh Preferred" option has an influence on the mesh generation of surfaces with curved and folded outlines. The program tries to align the FE mesh with the boundary lines of the surfaces.
In the "Material Model - Isotropic Nonlinear Elastic" window, you can select the yield laws according to the von Mises, Tresca, Drucker-Prager, and Mohr-Coulomb yield rules. This makes it possible to describe the elasto-plastic material behavior. The yield function depends on the principal stresses or the invariants of a stress tensor. The criteria apply to 2D and 3D material models.
Concrete on its own is characterized by its compressive strength. An important part of reinforced concrete is reinforcing steel, which contributes to both the compressive and the tension resistance of the concrete. Welded wire fabric is generally located in the tension areas of the beams or surface elements (hollow core ceiling, wall, shell) to transfer the tensile forces induced by external loading.
In RF‑CONCRETE Surfaces, the design of the surface reinforcement is done by means of a freely definable reinforcement mesh. In RF‑CONCRETE Surfaces, you can display the reinforcement direction by activating the reinforcement arrow that represents it.
In RFEM and RSTAB, it is possible to define nonlinear properties of member releases. In addition to the activity diagrams and force-deformation relationship, you also have the simple option of using signs or limit values of the internal forces as criteria for the effectiveness of the release. This way, you can specify which internal forces should be transferred at the member end.
In Part 1, the selection of the design criteria for dimensioning the reinforcement for the serviceability limit state design in RF‑CONCRETE Members and CONCRETE was explained. Now, we go into detail for the function "Find economical reinforcement for crack width design".
The RF-CONCRETE Members and CONCRETE add-on modules provide the option for "Dimensioning of Longitudinal Reinforcement for Serviceability Limit State". You can select the design criteria for the calculation of the longitudinal reinforcement.
The National Building Code of Canada (NBC) 2015 Article 4.1.8.7 provides a clear procedure for earthquake methods of analysis. The more advanced method, the Dynamic Analysis Procedure in Article 4.1.8.12, should be used for all structure types except those that meet the criteria set forth in 4.1.8.7. The more simplistic method, the Equivalent Static Force Procedure (ESFP) in Article 4.1.8.11, can be used for all other structures.
This article describes how a flat slab is generated as a 2D model in RFEM and the loading is applied according to Eurocode 1. The load cases are combined according to Eurocode 0 and calculated linearly. In the RF-CONCRETE Surfaces add-on module, the bending design of the slab is performed while taking into account the standard requirements of Eurocode 2. The reinforcement is complemented by a rebar reinforcement for areas that are not covered by the mesh basic reinforcement.
The product range of Dlubal Software contains various modules for design of steel and timber connections. The RF-/JOINTS Steel – Column Base add-on module allows you to analyse footings of hinged or restrained steel column bases. The fastener selection, foundation geometry, and material quality are crucial for the cost-effective and safe design of the column base.
If a bending load of a brittle beam element (an unreinforced concrete beam) is increased by means of the bending capacity, the structure responds by breaking the cross-section and the member is separated into two segments. At the time of the failure, the broken part suddenly loses its potential to transfer the bending moment. Due to the segmentation, the critical part also fails to transfer the other force types, such as axial forces.
In RFEM, you can generate surfaces from members (for example, to perform an accurate FE simulation on a member). Specific parameters such as automatic FE mesh refinement or rigid surfaces can be defined prior to the generation.
If intersections created in RFEM 4 are opened in an RFEM 5 file, the file management of intersections remains in the old format for compatibility reasons. Thus, the individual partial surfaces of the intersection can be activated or deactivated using only the "Integrated/Components" tab, all partial surfaces can only have the same thickness, and it is impossible to use the separate FE mesh refinement for the individual surface components.
For a structural analysis printout in the usual DIN A4 page format, the default settings of 1,000 x 1,000 pixels graphic quality are completely sufficient. However, if the printout should be on a larger page format, you can increase the print quality to a maximum of 5,000 x 5,000 pixels in the Graphic Printout options, or specify a user‑defined value.
The DXF interface in RFEM now exports a 3DFACE element in the DXF file for each FE mesh cell of the exported structure. The 3DFACE element is detected by AutoCAD during import, for example, and can be displayed as a surface in the graphic. Different visual styles help display the 3DFACE surfaces in a desired view.
The form-finding process in RF-FORM-FINDING displaces the corner nodes of FE elements of a membrane surface in space until the defined surface stress is in equilibrium with the boundary conditions. This displacement is independent of the element geometry. In the case of elements with four corner nodes, the free displacement may cause spatial drilling in the element plane and thus exceed the validity limits of the calculation; therefore, triangular elements are generally recommended for form‑finding systems. Triangular elements remain independent of the corner node displacement and stay within the calculation limitations.
If nonlinearities are used in a model (for example, contact solids), an error message may appear at the end of the calculation due to the locally unfulfilled convergence criteria. The reason for this is that the convergence of the global iteration conditions governs in the calculation.