There are six design checks grouped under the Bending category. These checks verify a member's capacity to resist bending moments and shear forces about the major and minor axes. Design checks for the deflection of the member are also included in this group.

When performing a bending check, you need to specify a number of properties relating to the unbraced length and the spacing of stiffeners on the member. When using the ASD code, the user may also specify a bending coefficient.

When checking or designing a member for bending, compression or combined bending and compression, a design constraint is automatically imposed by Steel Designer. This constraint verifies that the member satisfies the requirements of AIJ for the Width to Thickness Ratio (b/t) of Plate Elements.

To determine the critical buckling condition of a member, it is necessary to know the spacing of any bracing (if any) along the member. Purlins, girts or other structural elements that are not modelled in Multiframe could provide this bracing. Some bracing may only restrain lateral deflection in one direction. It is therefore necessary to enter unbraced lengths for both axes of the section, Lbx corresponding to the spacing of restraints preventing buckling about the x-x axis and Lby corresponding to the spacing of restraints preventing buckling about the y-y axis.

The initial values of Lbx and Lby are the length of the member.

The ASD code requires a bending coefficient Cb that is either calculated by the program according to the rules in the code, or may be specified by the user. If you leave Cb unchanged, Steel Designer will select a value for you, which will be displayed in Italics in the Design Details table in the Data window. This value is most commonly 1.0. If you type in a value, Steel Designer will always use this value and display it in non-italic (i.e. standard) text in the Design Details table.

When checking or designing a member for bending, you may need to specify the spacing of any stiffeners along the web of the member. This affects the member’s susceptibility to buckling due to bending. If there are no transverse stiffeners, you should leave the stiffener spacing set to zero.

To set the properties for bending

Ø  Select the required members in the Frame window

Ø  Choose Bending from the Design menu

Ø  Type in values for Lbx and Lby

Ø  If necessary enter a value for the bending coefficient Cb

Ø  Type in the stiffener spacing (s)