The equivalent loads determined in RF-TENDON due to prestress are transferred in RFEM as member loads or as line loads. A member load is used for member types with their own stiffness; a line load is used for member types without their own stiffness. In order to understand which values of the concentrated loads are to be transferred from RF‑TENDON to RFEM, you should use the following display settings: ~ Reference of the loads to the global coordinate system (GCS), ~ Load display: "Point"
With the latest version of CONCRETE and RF-CONCRETE Members, it is possible to perform shear design for the connection of compression and tension flanges on a T-beam web.
As of version X.04.0096, RF‑/TIMBER Pro also allows you to design other material categories such as softwood, hardwood, and glulam timber as a member in compliance with EN 1995‑1‑1. The design spectrum has been expanded for the material categories LVL, Plywood, OSB, Particleboard, and Fiberboard. In order to facilitate the selection in the materials library, there is another function for targeted filtering by plate or wall stress.
RF-LAMINATE allows free definition of materials. Thus, you can combine any compositions of different materials. The combination of concrete and timber is possible as well. However, the rigid composite must be provided when defining such a composition. In RF-LAMINATE, you can consider full shear coupling or no shear coupling at all.
The RF‑FORM‑FINDING add‑on module can be activated in the "Edit Model - General Data" window, "Options" tab. By activating the module, a new RF‑FORM‑FINDING load case is created and an additional menu appears in the main program, allowing for the definition of prestress conditions for membrane and cable elements.
The shear resistance design value of a joint depends mainly on the formation or the roughness of the connection. When determining the ultimate limit state, this is considered by the factors µ (friction) and c (adhesion percentage of the contact area of the composite concrete).
RFEM 5.04.xx allows for graphical visualization of normal and shear stress of members (this feature is available only if the RF‑STEEL add‑on module is licensed).
In January 2015, DIN Committee NA 005‑08‑23 Steel Bridges applied the introduction of a modification in equation 10.5 of DIN EN 1993‑1‑5. This involves the interaction of longitudinal and transverse pressure in a buckling analysis. Now, the interaction equation provides for auxiliary factor V, which is calculated from the reduction factors of the longitudinal and transverse stresses.
For structural reasons, shear connections usually include fin plates or flange angles. Main and secondary beams arranged on the top edge require notching or long fin plates. Hinged end plate connections are often welded to the web.
In addition to bending, torsional, longitudinal, and strain loads, you can define and analyze the internal pressure of members with circular hollow cross‑sections in RFEM and RSTAB. The following perimeter and axial stresses resulting from the internal pressure load are analyzed using Barlow's formula and transferred to design modules in order to superimpose the remaining stresses due to internal forces.
In RFEM, you can save the results of individual load increments during the calculation and display them graphically. Thus, you can graphically display and check the reaction diagram of different load levels for nonlinear supports.
Damage equivalent factors depend on the respective components to be designed in RF‑/STEEL Fatigue Members, and they are explained in the corresponding standards. The following list shows an overview of the standards describing the calculation of the damage equivalent factors in detail.
In order to represent the stiffness of the entire structure correctly, you can consider shear coupling between the ceiling and the downstand beam using the line release. This way, you can define a spring constant, thus avoiding the replacement system by using coupling members. The spring constant results from the shift modulus of the fastener, which can be determined according to EN 1995-1-1 or ANSI/AWC NDS, for example.
Result combinations exported from RF‑/DYNAM Pro – Equivalent Loads are generated by superimposing the results from the individual modal responses. For this, the SRSS rule can be used as "equivalent linear combination". When result combinations are used in RF‑/STEEL, two options are available for calculating stresses. In the first option, the results from the result combinations are used directly. This is done line by line, for each maximum and minimum controlling internal force. In the second option, stresses are determined from the individual load cases. The quadratic superposition rule is then performed again in RF-/STEEL.
Using the [To Display…] button, you can specify the amount of reinforcement to be displayed in the results of the required reinforcement in Window 2.2 of RF‑CONCRETE and CONCRETE. In addition to the default setting, you can display the resulting reinforcement amount as (for example) the sum of the longitudinal and longitudinal torsion reinforcement, or the sum of the torsion and shear reinforcement. You can also reduce the number of preset results, of course.
To stabilize the components bearing stability risks, a shear panel and/or a rotational restraint can be defined in RF‑/STEEL EC3. Optionally, trapezoidal sheets, bracings, or individual purlins can be taken into account.
The form-finding process in RFEM seeks an equilibrium state where the defined prestress of membranes and the prestress or length changes of cable elements with boundary reactions are in equilibrium. For this, the program provides the option to define an isotropic or an orthotropic prestress state for membranes.
In RF-STEEL Surfaces, it is possible to display the stresses relevant for the design of welds, for example, according to EN 1993‑1‑8, Figure 4.5. When evaluating the stress components, the local xyz-axis system of the surfaces must be considered.
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.
The buckling analysis of plates with stiffeners is a special task for engineers. For this, EN 1993-1-5 provides three calculation methods: Effective Cross-Section Method, [1], Sect. 4-7; Reduced Stress Method, [1], Sect. 10; Finite Element Methods of Analysis (FEM), [1], Annex C.
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.
The RF-FORM-FINDING add-on module determines equilibrium shapes of membrane and cable elements in RFEM. In this calculation process, the program searches for such geometric position where the surface stress/prestress of membranes and cables is in equilibrium with natural and geometric boundary conditions. This process is called form-finding (hereinafter referred to as FF). The FF calculation can be activated in RFEM globally in the "General Data" of a model, "Options" tab. After selecting the corresponding option, a new load case or a calculation process called RF-FORM-FINDING is created in RFEM. An additional FF parameter is available for defining surface stress and prestress when entering cables and membranes. By activating the FF option, the program always starts the form-finding process before the pure structural calculation of internal forces, deformation, eigenvalues, etc., and generates a corresponding prestressed model for further analysis.
Silos are used as large containers for storage of bulk materials such as agricultural products or source materials as well as intermediates of industrial production. The structural engineering of such structures requires a precise knowledge of the stresses due to particulate solids in the building structure. The standard EN 1991‑4 "Actions on Silos and Tanks" [1] provides the general principles and requirements for determining these actions.
The design of cross-sections usually requires many different cross-section properties. In RFEM and RSTAB, all required properties of standardized cross-sections are available in the cross-section library and can be used directly for the calculation. If the cross-sections are not standardized, SHAPE-THIN allows you to use these cross-sections, too. You can simply enter the geometry to determine all required cross-section properties. The following example shows the calculation of a shear area on a practical example.
Click the [Details] button in RF-GLASS to select the results to be displayed. In order to get a better overview for the result evaluation, you can select the individual stress graphics (principal stresses, stresses oriented to axes, shear stresses) as well as various result windows. This way, you can show only the results you require.
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.
Some compound beam structures, such as stacked containers or retracted telescopic bars, transfer the forces in the connection between the components by friction. The load-bearing capacity of such a connection depends on the effective axial force perpendicular to the friction plane and on the friction coefficients between both friction surfaces. For example, the more the friction surfaces are compressed, the more horizontal shear force can be transferred by the friction surfaces (static friction).
For stress calculations, some standards use the "wall thickness analysis". We get the wall thickness by subtracting corrosion, abrasion allowance, manufacturing allowances (threading, grooving, and so on), and mill tolerances from the nominal wall thickness. All necessary values can be entered in the "Piping Cross‑Section" dialog box, "Stress Analysis Parameters" tab.
For the serviceability limit state design according to Section 6.6 of Eurocode EN 1997‑1, settlement has to be calculated for spread foundations. RF-/FOUNDATION Pro allows you to perform the settlement calculation for a single foundation. For this, you can chose between an elastic and a solid foundation. By defining a soil profile, it is possible to consider several soil layers under the foundation base. The results of the settlement, foundation tilting, and vertical soil contact stress distribution are displayed graphically and in tables to provide a quick and clear overview of the calculation performed. In addition to the design of the foundation settlement in RF-/FOUNDATION Pro, the structural analysis determines the representative spring constants for the support and can be exported to the structural model of RFEM or RSTAB.