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The national parameters of EN 1992‑1‑1 for each country can be exported from RF‑/CONCRETE, RF‑/CONCRETE Columns, and RF‑/FOUNDATION Pro. To do this, there are interfaces with MS Excel, OpenOffice, and CSV. By exporting the national parameters, you can edit them in (for example) MS Excel, and display possible differences between the individual National Annexes clearly (see the image).
Various optimizations are available with program version x.06.1103. The RF-/FOUNDATION Pro add-on module has also been subjected to further development.
With RFEM version 5.06, member stiffnesses can be influenced by methods that are aligned with US steel construction standard ANSI/AISC 360-10. According to this standard, reduction factor τb must be considered for the determination of internal forces in all members of which the flexural resistance contributes to the model's stability. This coefficient depends on the axial force in the member: The larger the axial force, the larger τb is.
The RF-PUNCH Pro add-on module allows you to perform punching shear design of slabs and foundation plates (floor slabs) on wall ends and wall corners.
For structural components consisting of slabs, it is necessary to perform shear design on the locations with concentrated load introduction, applying the punching shear design rules according to Sect. 6.4 of EN 1992‑1‑1 [1]. The concentrated load introduction is present on the individual locations; for example, by columns, concentrated load, or nodal supports. In addition, the end of linear load introduction on slabs is also regarded as concentrated load introduction. For example, this includes wall ends, wall corners, and ends or corners of line loads and line supports. You can perform the punching shear design for floor slabs or foundations, considering the existing available plate topology about the designed node of punching shear. The punching shear design according to EN 1992‑1‑1 checks that the acting shear force vEd does not exceed the resistance vRd.
As an alternative to the conventional automatic arrangement of surface reinforcement in RF-CONCRETE Surfaces, it is also possible to set it according to the individual requirements. This is advantageous for the creation of reinforcement drawings, for example, as the reinforcement areas can be clearly defined and dimensioned.
The RF‑PUNCH Pro add‑on module allows you to perform the punching shear design of floor slabs and foundation plates according to EN 1992‑1‑1. In the case of a floor slab, the basic control perimeter is applied according to 6.4.2 (1), EN 1992‑1‑1 [1] at a distance of 2d from the loaded area.
Downstand beams or T-beams are often used in reinforced concrete structures. In contrast to the previous representation and calculation options where, for example, a downstand beam was considered as a fixed support and the determined support reaction was applied to a separate member structure using a T-beam section, the ultimate structural FEA software like RFEM allow you to consider the structure as a whole and thus achieve a more precise analysis.
In the AISC 360 – 14th Ed. C2.2, the direct analysis method requires initial imperfections to be taken into consideration. The important imperfection of recognition is column out-of-plumbness. According to C2.2a, the direct modeling of imperfections is one method to account for the effect of initial imperfections. However, in many situations, the expected displacements may not be known or easily predicted.
Requirements for the design of structural stability are given in the AISC 360 – 14th Ed. Chapter C. In particular, the direct analysis method provisions, previously located in Appendix 7 of the AISC 360 – 13th Ed., are described in detail. This method is considered an alternative to the effective length method, which in turn eliminates the need for effective length (K) factors other than 1.0.
Generally, avoiding cracking in concrete structures is neither possible nor necessary. However, cracking must be limited in a way so that the proper use, appearance, and durability of the structure are not affected. Therefore, limiting the crack width does not mean preventing from the crack formation, but restricting the crack width to harmless values.
In the case of combined FEM structures (surface and member elements) as well as folded plate structures, it is possible to attribute a beam structure for the design on a member to a fictitious T-beam cross-section, whose geometry depends on the effective width. When using the "Rib" member type in RFEM, the stiffness is represented by a slab component (surface element) and a web component (member element). This approach has some design specifics that are explained in this article.
Heat loss due to external components without thermal decoupling of the internal components is enormous. For this reason, external structural components are thermally separated from the building envelope using a special built-in component. For the connection of a balcony slab with a reinforced concrete floor, Schöck Isokorb® or HALFEN HIT Insulated Connection can be used, for example. For the design of such built-in components, the respective technical approval must be taken into account. The following article shows an example of considering Schöck Isokorb® in the FEM calculation.
In the construction process, it is often necessary to fabricate the concrete elements in sections. A classic example of this production in sections is the use of prefabricated downstand beams, in which the slab is completed in the onsite concrete construction. By creating a new concrete area, interfaces may arise between the already hardened concrete and the fresh concrete. The transfer of the longitudinal shear forces arising between the partial cross-sections must be considered in the design.
The RF-PUNCH Pro add-on module allows you to perform punching shear designs according to EN 1992‑1‑1 [1]. In addition to the design checks of single columns, wall ends and wall corners can be analyzed in RF‑PUNCH Pro. At this point, I would also like to reference a previous article about RF‑PUNCH Pro, which explains how to determine punching load on wall ends and wall corners.
According to Clause 7.3.2 (2), standard DIN EN 1992-1-1 requires: "In profiled cross‑sections like T‑beams and box girders, the minimum reinforcement should be determined for the individual parts of the section (webs, flanges)." In the case of a floor beam with a T‑section, the minimum reinforcement should be determined for both flanges and the web if the corresponding partial cross‑sections are in the tension area. Image 01 shows the division into partial cross-sections.
If an aluminum member section is comprised of slender elements, failure can occur due to the local buckling of the flanges or webs before the member can reach full strength. In the add-on module RF-/ALUMINUM ADM, there are now three options for determining the nominal flexural strength for the limit state of local buckling, Mnlb, from Section F.3 in the 2015 Aluminum Design Manual. The three options include sections F.3.1 Weighted Average Method, F.3.2 Direct Strength Method, and F.3.3 Limiting Element Method.
RFEM and the RF-CONCRETE add-on modules provide various options for the deformation analysis of a T-beam in the cracked state (state II). This technical article describes the calculation methods (C) and modeling options (M). Both the calculation methods and the modeling options are not limited to T-beams, but will only be explained using this system as an example.
In the case of a large amount of reinforcement, it might be useful to grade the longitudinal reinforcement of a beam, which means: curtailment. The grading corresponds to the tensile force distribution. Using RF-CONCRETE Members and CONCRETE, you can specify the curtailment of the reinforcement, which is considered in the automatically proposed reinforcement for the longitudinal reinforcement. When determining this reinforcement proposal, it is necessary to ensure that the envelope of the acting tensile force can be absorbed.
After running an analysis in RF-/STEEL AISC, the mode shapes for sets of members can be viewed graphically in a separate window. Select the relevant set of members in the result window and click the [Mode Shapes] button.
When designing reinforced concrete components according to EN 1992‑1‑1 [1], nonlinear methods of determining internal forces for the ultimate and serviceability limit states are possible. In this case, the internal forces and deformations are determined with respect to their nonlinear behaviour. The analysis of stresses and strains in cracked state usually provides the deflections, which clearly exceed the linearly determined values.
In order to ensure the effects of panels, which should act as tensile or compression chords, it is necessary to connect them to the web in a shear-resistant manner. This connection is obtained in a similar way as the shear transfer in the joint between concreting sections by using the interaction between compressive struts and ties. In order to ensure the shear resistance, it must be verified that the compressive strut resistance is given and the tie force can be absorbed by the transverse reinforcement.
The Steel Joist Institute (SJI) previously developed Virtual Joist tables to estimate the section properties for Open Web Steel Joists. These Virtual Joist sections are characterized as equivalent wide-flange beams which closely approximate the joist chord area, effective moment of inertia, and weight. Virtual Joists are also available in the RFEM and RSTAB cross-section database.
Since the ultimate limit state of beams in the area of openings is affected, particular attention should be paid to this. In general, small openings can be sufficiently covered by adapting the beam structure to the openings. For big openings, it is necessary to consider and model the area separately.
With RF-PUNCH Pro, the punching shear design can be performed according to 6.4, EN 1992-1-1. In the following example, the design according to DIN EN 1992-1-1 will be presented first with automatic design of the inner and outer perimeters and then on the basis of the inner perimeters defined by the user on a simple example.
The secondary reinforcement according to DIN EN 1992-1-1 9.2.1 is used to ensure the desired structural behavior. It should avoid failure without prior notification. The minimum reinforcement has to be arranged independently of the size of the actual loading.
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 design of a torsional loaded beam according to AISC Design Guide 9 will be shown, based on a verification example. The design will be performed with the RF‑STEEL AISC add-on module and the RF‑STEEL Warping Torsion module extension with 7 degrees of freedom.
Effective lengths for columns can be determined automatically with RF-/CONCRETE Columns. This article describes which entries are necessary and how the calculation of the effective lengths is performed.
RFEM offers different options for the graphical display of results that have been determined in RF-CONCRETE Surfaces. This article gives an overview of these options.