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Member Specification dialog

Used to set and modify member (beam) specifications.

Opens when Beam is clicked on the Specifications - Whole Structure dialog.

This dialog contains multiple tabs, each of which is used to add a different member specification.

Release tab

Used to specify the end conditions of members by releasing specified degrees of freedom. Unless a release is specified, all members are rigidly connected the nodes (i.e., all degrees of freedom are restrained) except if the end is a cantilever end or supported.

Note: Refer to TR.22.1 Member Release Specification for additional information.
SettingDescription
Location

Specify either Start or End as the released joint Member Incidence of the member.

Release Type

Select either the Partial Moment Release or the Release option.

Partial Moment Release

Type a release Factor to define a partial release condition. The MP option is a means of specifying the same partial release for all the 3 moment degrees of freedom (MX, MY and MZ).

Alternately, use the MPX, MPY or MPZ options to apply different release factors in each direction.

Release

Click the Release radio button and check the boxes for the FX, FY, FZ, MX, MY or MZ directions to define the member release condition.  You may also specify a Spring Constant along the six degrees of freedom by using the KFX, KFY, ... KMZ edit boxes. For example, to define a Spring Constant in the local X direction, enter the Spring Constant in the KFX edit box.

Tension tab

Used to define tension-only members. These members are capable of carrying tensile forces only.

There are no additional parameters for this member specification.

Property Reduction Factors tab

Used to specify a set of reduction factors to be applied on the calculated section properties such as area, moments of inertia, and torsional constant.

Note: Refer to TR.20.10 Member Property Reduction Factors for additional information.
Select the method of how to specify member property reduction factors:
  • Global – specify the Reduction Factors to be used below, which will apply to any member regardless of material.
  • Code Specific – select the building code to use reduction factors specific to load cases per that code which are only applied to concrete members:
    • IS1893 2016
SettingDescription
Reduction Factors
Provide a set of reduction factors between which will be used in the stiffness analysis. These factors are directly multiplied to the following section properties:
  • Reduction Factor for Cross sectional Area (RAX)
    Note: For IS1893 2016 reduction factors, the RAX input field is inactive as this property reduction is not mandated by that code for concrete members.
  • Reduction Factor for Torsion Constant (RIX)
  • Reduction Factor for Moment of Inertia, major axis (RIY)
  • Reduction Factor for Moment of Inertia, minor axis (RIZ)
Notes:
  1. Reduction factors are considered for analysis only but not for design.
  2. Results using the reduced section properties are not available when using the member query feature.
Note: Automated stiffness reduction requires a STAAD.Pro Advanced license.

Cable tab

Used to define cable members. Select either the Tension or Length option to specify a member tension. Tension-only springs are capable of carrying tensile forces only. Thus, they are automatically inactivated for load cases that create compression in them. Compression-only springs are capable of carrying compressive forces only. Thus, they are automatically inactivated for load cases that create tension in them.

Note: Refer to TR.23.2 Member Cable Specification for more information.
SettingDescription
Initial TENSION

Use this option to specify the initial tension in the cable as a force.

SettingDescription
Average

The average tension in the cable is used (considered in advanced cable analysis only).

Start node

Tension is measured from the start node of the member (considered in advanced cable analysis only).

End node

Tension is measured from the end node of the member (considered in advanced cable analysis only).

Unstressed LENGTH

Use this option to specify the initial tension in the cable as a length for nonlinear cable analysis.

Factor in global X Fwx

Multiplying factors on self weight components applied in the global X direction.

Factor in global Y Fwy

Multiplying factors on self weight components applied in the global Y direction.

Tip: When Y is up, use a negative value to act as gravity.
Factor in global Z Fwz

Multiplying factors on self weight components applied in the global Z direction.

Tip: When Z is up, use a negative value to act as gravity.

Truss tab

Used to specify truss members. These members are capable of carrying axial forces only.

There are no additional parameters for this member specification.

Note: To specify tension in a truss member for a nonlinear cable analysis, you must edit the STAAD input file directly. Refer to TR.23.1 Member Truss Specification for additional details.

Compression tab

Used to define compression-only members. These members are capable of carrying compressive forces only.

There are no additional parameters for this member specification.

Offset tab

Used to rigidly offset a frame member end from a joint to model the offset conditions existing at the ends of frame members.

The actual beams and columns of a physical structure are represented by lines in the mathematical (computer) model. In the actual structure, a beam spans a distance which in the clear span between the faces of columns. But in the model, the line for the beam spans between the centerlines of the column. The half-depth portion of either column is considerably stiffer than the beam itself from the standpoint of bending. To take advantage of this additional stiffness, you may specify that the start and end faces of the beam are offset from the node by a distance equal to the half-column-depths.

Member offsets can be specified in other situations too. For example, consider:

  • when a bracing member does not meet the node which is defined in its incidence list
  • a girder and top slab in a bridge where the centerline of the girder is several inches below the centerline of the slab.

This facility is useful when you want to design the structural parameters of a member by considering the clear distance of the member between the supports (e.g., in the case shear forces or bending moments).

Refer to TR.25.1 Member Offset Specification for additional information on member offsets.

SettingDescription
Location

Specify either Start or End as the joint at which to specify an offset.

Direction

Select either the Local or Global axis system for assigning offset distances.

Offsets

Enter the offset distance from the joint in the three axis directions.

Inactive tab

Used to temporarily inactivate members for a specific analysis cycle. Inactivated members may be re-activated later for further processing.

Information on using this is available in EX. US-4 Inactive Members in a Braced Frame or EX. UK-4 Inactive Members in a Braced Frame . This option is also explained in TR.18 Inactive/Delete Specification.

There are no additional parameters for this member specification.

Fire Proofing tab

Used to automatically consider the weight of fire proofing material applied to structural steel.

Refer to TR.20.9 Applying Fireproofing on members for additional information on fireproofing.

SettingDescription
Fire Proofing Type

Two types of fireproofing configurations are currently supported:

  • BFP (Block Fireproofing):

    The fire-protection material forms a rectangular block around the steel section. The thickness specified is the minimum thickness which defines the outer block dimensions.

    BFP: Block Fireproofing

  • CFP (Contour Fireproofing):

    The fire-protection material forms a coating around the steel section. The thickness specified is a constant thickness around the section profile.

    CFP Contour Fireproofing
Thickness Thickness (dimension in the figures above) in length units
Density Density of fireproofing material in (force / length3) units

Imperfection tab

Used to define camber and drift specifications for selected members.

Note: Refer to TR.26.6 Member Imperfection Information for additional details.
SettingDescription
Imperfection type

Select if whether the imperfection is either Camber or Drift. Drift is usually for columns and camber for beams.

Local Direction

Specify if the camber or drift acts in either the member local Y or Z direction.

Value

Specify the value for the camber or drift, defined as a ratio of member length/offset. Default ratio value is 300.

Respect

(Camber option only) A dimensionless constant used to skip the camber imperfection calculation if the compressive load is small or EI is great or length is short. A combination of these terms, called ε, is calculated. If ε is less than the respect value given, then the imperfection calculation is skipped for that local direction, for that case, for that member. The imperfection calculation is also skipped for any member that is in tension.

ε y = Length × |  axial load  | E I z
ε z = Length × |  axial load  | E I y
Parent topic: Specifications - Whole Structure dialog
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