Member : Design properties

These options are available for 1D members when the section material is steel. They define the properties relating to design from the interaction of the member with the rest of the structure.

End restraints

End restraints define how the end connections of the member affect the effective length calculations. These are applicable only to 1D members.

The description specifies the degrees of freedom that are restrained by the connection. Individual rotational and translational terms can be restrained but the most common connections can be selected directly. These are:

• Pinned – top flange laterally restrained. Nominal torsional restraint. No restraint against rotation
• Fixed – encastre
• Free – no restraint
• Full rotational – top flange laterally restrained. Nominal torsional restraint. Both flanges fully restrained against rotation on plan
• Partial rotational – top flange laterally restrained. Nominal torsional restraint. Both flanges partially restrained against rotation on plan
• Top flange lateral - top flange laterally restrained
• Custom – determine the detail of the particular connection. Note that inconsistent combinations of restraints will be automatically updated

Effective length calculation options

The options to determine effective lengths of 1D members are

• Automatically calculated – the effective lengths are calculated in each direction using the member's end restraints and any intermediate bracing points in accordance with the design specification.

• User-specified internal restraints – the effective lengths are calculated in each direction using the member's end restraints and manually specified internal restraints. The location of internal bracing points are determined by the framing geometry.

  • The Internal restraints along member span or All spans drop down provides a shortcut to set the restraint condition for all spans along the member. The Advanced option allows restraints along individual spans to be specified.
  • The Internal restraints at intermediate bracing points or All points drop down provides a shortcut to set the restraint condition for all bracing points along the member. The Advanced option allows restraints along at points to be specified.

• User-specified effective length - the effective lengths are manually defined, assuming one bending segment per member.

Note: GSA automatically detects and registers points and spans based on the nodes and elements along the member. When a Design task is executed, GSA automatically generates the member internal restraints to assign point and span restraints. If the All spans member restraint is set to advanced, the spans restraint conditions can be specified for individual spans. Likewise if the All points member restraint is set to advanced, the spans restraint conditions can be specified for individual positions along the member.

Destabilising load

This is the height at which the load is assumed to act which can have a destabilising effect on the member. By default this is relative to the shear centre, but can be relative to the top or bottom flanges.

Design variable overrides

These options allow selected variables in the design calculations to be overridden with fixed values. These options will be disabled if the chosen design code does not support the override.

Equivalent uniform moment factor for LTB

This option allows the user to override the automatically calculated factor to account for the shape of the moment diagram in lateral torsional buckling design equations. This override is applied for all bending segments in the member. This override is applied to the following variable for each design code:

Design Code	Variable name
AISC 360	$C_b$
AS 4100	$\alpha_m$
BS 5950	$m_{LT}$
CSA S16	$\omega_2$
EN 1993-1-1 and EN 1993-1-2	$C_1$
Hong Kong Code of Practice	$m_{LT}$
IS 800	$C_{mLT}$
SANS 10162-1	$\omega_2$

Moment amplification factor (strong/weak axis)

This option allows the user to override the the automatically calculated moment amplification factor to account for second order effects. If the code calculations do not include second order effects, the user can still specify an amplification factor to be applied in the calculations.