2.12 Parameters - Members

This window allows you to enter specifications for beams that are laterally supported by sheeting or purlins (see [3] clause 10.1 and 10.3).

The upper section lists the members selected for design together with the parameters affecting the lateral-torsional buckling analysis. The parameters are interactive with the specifications in the Settings - Member No. section below.

To the right of the Settings table, you can see information or options for selection in the form of a graphic facilitating the definition of boundary conditions. This graphic is aligned with the current parameter.

Below the Settings table, you find the check box Set input for members No. When you select it, the subsequent settings will be applied to All members or to selected members (enter the member numbers manually or select them graphically with ). This option is useful if you want to assign the same boundary conditions to several members.

In the Comment column, you can enter user-defined notes, for example, to describe the parameters of a member, which are relevant for lateral-torsional buckling.

This row shows the cross-section description for information. For a tapered member, the descriptions of the start and end cross-section are displayed.

To enter the shear panel parameters, select the check box in column A or the Settings table.

You can select the shear panel type in the drop-down list.

The application of a continuous lateral support is described in EN 1993-1-1 [1], Annex BB.2.1 and EN 1993-1-3 [3] clause 10.1.5.1.

To determine the shear panel stiffness of a trapezoidal sheeting (corrugated sheet), the following specifications are required (see Figure 2.40):

• Shear panel length l_S
• Beam spacing s
• Position of trapezoidal sheeting on section
• Trapezoidal sheeting description
• Fastening arrangement

You can enter the Shear panel length and the Beam spacing manually. You can also select them graphically with . This button becomes available as soon as the cursor is placed in one of these text boxes. Then, you can select two snap points in the RFEM/RSTAB work window, defining the shear panel or the beam spacing.

The Position on section of the trapezoidal sheeting can be considered in different ways by means of the list shown on the left. If the entered data is user-defined, the distance d is related to the centroid; the sign results from the orientation of the cross-section's z-axis.

To access the corrugated sheets library, click the  button that becomes available after clicking in the Trapezoidal sheeting description text box (see Figure 2.40). The cross-section library of RFEM or RSTAB appears (see Figure 2.42) where you can select the trapezoidal sheeting by double-click or with [OK]. Thus, the Shear panel coefficients K₁ and K₂ (according to the approval certificate) will be automatically entered in the Settings table. The basic width b of the trapezoidal sheeting indicated in the cross-section database has no influence on these coefficients.

The Fastening arrangement for the trapezoidal section affects the shear stiffness that the sheeting provides to the beam. If the trapezoidal sheeting is fastened only in every second rib, the shear stiffness to be applied is reduced by the factor 5.

To determine the provided shear panel stiffness, the following specifications are required:

• Shear panel length l_S
• Beam spacing s
• Position of bracing on section
• Post spacing b
• Number of bracings
• Section of diagonals
• Section of posts

You can enter the Shear panel length, the Beam spacing, and the Post spacing manually. You can also select them graphically with . This button becomes available as soon as the cursor is placed in one of these text boxes. Then, you can select two points in the RFEM/RSTAB work window, defining the shear panel or the spacings.

The bracing's Position on section can be considered in different ways by means of the list shown on the left. If the entered data is user-defined, the distance d is related to the centroid; the sign results from the orientation of the cross-section's z-axis.

The easiest way to define the cross-sectional areas of the diagonals and posts is to select the Section Description in the cross-section library of RFEM/RSTAB. You can access this library with the  button available at the end of the text box. Then, the CS-Area will be imported automatically. But you can also enter the value directly.

To determine the provided shear panel stiffness due to the trapezoidal sheeting and bracing, the following specifications are required:

• Shear panel length l_S
• Beam spacing s
• Position of shear panel on section
• Trapezoidal sheeting description
• Fastening arrangement
• Post spacing b
• Number of bracings
• Section of diagonals
• Section of posts

This way of defining the shear panel combines the parameters of the aforementioned options Trapezoidal sheeting and Bracing .

The value of the provided Shear panel stiffness S_prov can be entered also directly.

In addition, the shear panel's Position on section must be specified.

To enter the rotational restraint parameters, select the check box in column B or in the Settings table.

You can select the type of the rotational restraint in the drop-down list.

To determine the stiffness components from a corrugated sheet and the connection deformation, the following specifications are required (see Figure 2.46):

• Material and description of the corrugated sheet
• Method of determining C_D,A
• Beam spacing s
• Continuous beam effect

To access the corrugated sheets library, click the button that is displayed after clicking in the Component description text box (see Figure 2.44). The cross-section library of RFEM or RSTAB appears (see Figure 2.42) where you can select the corrugated sheet by double-clicking or with [OK]. The section parameters of Sheeting thickness t, Position of sheeting, effective Second moment of area for the downward loading direction, Distance of ribs b_R (corrugation width), and Width of the flange b_T are imported automatically.

When the continuous rotational restraint is set, you also have to consider the deformation of the connection. In the entry for Method of determining C_D,A, you can enter the spring stiffness C₁₀₀ for the individual load cases and combinations. It is also possible to determine it by the program according to [3] Table 10.3. To determine it automatically, use the  button that appears after clicking in the text box of the row C₁₀₀. A dialog box opens where you can select the appropriate coefficient.

When you click [OK], this value will be assigned to all load cases and combinations that are selected for design. If you want to assign the coefficient by load case, you have to open the Import of Coefficient dialog box via the C₁₀₀ text boxes of the individual load cases and combinations.

You can also define the Beam spacing manually or graphically with the button. In the work window of RFEM or RSTAB, click two nodes defining the distance between the beams.

The Continuous beam effect has an impact on the coefficient k of the rotational restraint C_D,C that can be controlled by the list of this table row (End panel: k = 2, Internal panel: k = 4).

To determine the stiffness component from single supports, for example purlins, the following specifications are required:

• Material and description of the cross-section
• Purlin spacing e
• Beam spacing s
• Continuous beam effect

The Material and the Cross-section description can each be selected in the library of RFEM or RSTAB that you access with the button. Activate the relevant text box by clicking in it.

You can enter the Purlin spacing and the Beam spacing manually or graphically with the  button. In the RFEM/RSTAB work window, click two nodes defining the distance between the purlins or horizontal beams.

The Continuous beam effect has an impact on the coefficient k of the rotational restraint C_D,C that can be controlled by the list of this table row (End panel: k = 2, Internal panel: k = 4).

You can also directly enter the value of the provided Total Rotational Spring Stiffness C_D.

According to [1] clause 6.2.3, section reductions due to holes must be considered in the tensile stress design. You can define the Net Cross-Sectional Area A_net separately for the Start and End of the member - fasteners are usually located at these two x-locations. The table also shows the gross cross-sectional area A.