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D2.B.8 Design Parameters

The design parameters outlined in Table 1B.1 are used to control the design procedure. These parameters communicate design decisions from the engineer to the program and thus allow the engineer to control the design process to suit an application's specific needs. The design scope indicates whether design parameters are applicable for MEMBER Design, PMEMBER Design, or both.

The default parameter values have been selected such that they are frequently used numbers for conventional design. Depending on the particular design requirements, some or all of these parameter values may be changed to exactly model the physical structure. 

Table 1. Australian Steel Design Parameters
Parameter Name Default Value Design Scope Description
CODE -  

Must be specified as AUSTRALIAN to invoke design per AS 4100 - 1998.

Design code to follow. See TR.48.1 Parameter Specifications.

ALB 2.0  

Member section constant (refer cl. 6.3.3)

If ALB is 2.0, it is automatically calculated based on TABLE 6.3.3(1), 6.3.3(2); otherwise the input value is used.

ALM 0.0  

Moment modification factor (refer cl. 5.6.1.1)

If ALM is 0.0, it is automatically calculated based cl.5.6.1.1; otherwise the input value is used.

BEAM 0.0  

0.0  =  design only for end moments and those at locations specified by SECTION command.

1.0  =  Perform design for moments  at twelfth points along the beam.

DFF None (Mandatory for  deflection check) Analytical members only “Deflection Length”/ Maximum Allowable local deflection.
DJ1 Start Joint of member Analytical members only Joint No. denoting start point for calculation of “deflection length”
DJ2 End Joint of member Analytical members only Joint No. denoting end point for calculation of “deflection length”
DMAX 45.0 [in.]   Maximum allowable depth (Applicable for member selection)
DMIN 0.0 [in.]   Minimum required depth (Applicable for member selection)
FU 500.0 [MPa]   Ultimate strength of steel.
FYLD 250.0 [MPa]   Yield strength of steel.
IST 1  

Steel type -  1 - SR, 2 - HR, 3 - CF, 4 - LW, 5 - HW

Note: See p.47 of AS 4100-1998.
KT 1.0   Correction factor for distribution of forces (refer cl. 7.2)
KY 1.0   K value for general column flexural buckling about the local Y-axis. Used to calculate slenderness ratio.
KZ 1.0   K value for general column flexural buckling about the local Z-axis. Used to calculate slenderness ratio.
LHT 0 Physical members only

Load height position as described in Table 5.6.3(2) of AS 4100:1998

  • 0 = at Shear center
  • 1 = At top flange
LX see desc.   Unbraced length between torsional restraints. The default is the distance between partial or full restraints which effectively prevent twist of the section about its centroid as per Sec. 8.4.4.1.2.
LY Member Length   Length for general column flexural buckling about the local Y-axis. Used to calculate slenderness ratio.
LZ Member Length   Length for general column flexural buckling about the local Z-axis. Used to calculate slenderness ratio.
MAIN 0.0  

A value of either 0.0 or 1.0 suppresses the slenderness ratio check. checks are not explicitly required per AS 4100.

Any value greater than 1.0 is used as the limit for slenderness in compression.

NSC 1.0  

Net section factor for compression members = An / Ag

(refer cl. 6.2.1)

NSF 1.0   Net section factor for tension members.
PBRACE None Physical members only Refer to section 1B.11 for details on the PBRACE parameter.
PHI 0.9   Capacity reduction factor
RATIO 1.0   Permissible ratio of actual load effect to the design strength.
SGR 0  

Steel Grade. Refer to Note a below.

  • 0 = Default (see note below)
  • 1.0 = high strength grade steel
  • 2 = AS/NZS 3679.1 350
  • 3 = AS/NZS 3679.1 300
  • 4 = AS/NZS 1163 C450
  • 5 = AS/NZS 1163 C350
  • 6 = AS/NZS 1163 C250
  • 7 = AS/NZS 3678 450
  • 8 = AS/NZS 3678 400
  • 9 = AS/NZS 3678 350
  • 10 = AS/NZS 3678 WR350
  • 11 = AS/NZS 3678 300
  • 12 = AS 3597 500
  • 13 = AS 3597 600
  • 14 = AS 3597 700
SKL 1.0   A load height factor given in Table 5.6.3(2)
SKR 1.0   A lateral rotation restraint factor given in Table 5.6.3(3)
SKT 1.0   A twist restraint factor given in Table 5.6.3(1)
TRACK 0.0  

Output detail

  • 0.0 = report only minimum design results
  • 1.0 = report design strengths in addition to TRACK 0.0 output
  • 2.0 = provide full details of design
TSP Member web depth   Spacing of the transverse stiffeners.
UNB Member Length   Unsupported length in bending compression of the bottom flange for calculating moment resistance.
UNT Member Length   Unsupported length in bending compression of the top flange for calculating moment resistance.
Note: Once a parameter is specified, its value stays at that specified number until it is specified again. This is the way STAAD.Pro works for all codes.

D2.B.8.1 Notes

  1. DFF, DJ1, and DJ2 – Deflection calculations

    Compute  Delta = SQRT((DX2 - DX1)2 + (DY2 - DY1)2 + (DZ2 - DZ1)2)

    Compute Length = distance between DJ1 & DJ2 or, between start node and end node, as the case may be.

    Note: Deflection calculations are not applicable to PMEMBERs.
    1. A straight line joining DJ1 and DJ2 is used as the reference line from which local deflections are measured.

      For example, refer to the figure below where a beam has been modeled using four joints and three members. The "Deflection Length" for all three members will be equal to the total length of the beam in this case. The parameters DJ1 and DJ2 should be used to model this situation. Thus, for all three members here, DJ1 should be 1 and DJ2 should be 4.
      D = Maximum local deflection for members 1, 2, and 3.
      PARAMETERS
      DFF 300. ALL
      DJ1 1 ALL
      DJ2 4 ALL
    2. If DJ1 and DJ2 are not used, "Deflection Length"will default to the member length and local deflections will be measured from original member line.

    3. It is important to note that unless a DFF value is specified, STAAD.Pro will not perform a deflection check.  This is in accordance with the fact that there is no default value for DFF.

  2. LHT Parameter

    If the shear force is constant within the segment, longitudinal position of the load is assumed to be at the segment end.

    If there is any variation of the shear force and the load is acting downward determined from shear force variation and load height parameter indicates the load is acting on top flange (flange at the positive local y axis) and restraints at the end of the segment is not FU (FRU) or PU (PRU) Kl is assumed to be 1.4.

    If there is any variation of the shear force and the load is acting upward determined from shear force variation and load height parameter indicates the load is acting on top flange (flange at the positive local y axis) and restraints at the end of the segment is not FU (FRU) or PU (PRU) Kl is assumed to be 1.0 as the load acting at the top flange is contributing to stabilize against local torsional buckling.

  3. SGR Parameter

    Typically SGR 2-3 should be used for rolled profiles, SRG 4-6 should be used for hollow profiles and SRG 7-11 should be used for welded sections. When the default value (0) is used, the steel grade for different types of sections is selected by the program as follows:

    Table 2. Steel Grades used for the SGR Parameter
    Section Type Steel Grade Used
    WB, WC, Tee section cut from WB and WC, other welded and UPT sections AS 3678 300
    UB, UC, Tee section cut from UB and UC, EA, UA and all UPT sections UB, UC, Tee section cut from UB and UC, EA, UA and all other rolled sections AS 3679.1 300
    Pipe, Tube, CHS, RHS, SHS Pipe, Tube, CHS, RHS, SHS AS 1163 C250
    Note: If a value for the FYLD parameter has been specified, then that value will be used. Otherwise, the SGR value will be used to determine the yeild strength and tensile strength values for the steel. based on maximum thickness of the individual elements of the section. Only for shear capacity calculation web thickness is used. Similarly, Tensile Strength is determined either from FU parameter or from SGR parameter.
    CAUTION: A check is introduced to see if yield stress is more than 450 MPa or not. If it is, a warning is issued and the yield stress is set to 450 MPa.

D2.B.8.2 Example

The following example uses the member design facility in STAAD.Pro. However, it is strongly recommended to use the Physical member design capabilities for AS 4100:

PARAMETER 1
CODE AUSTRALIAN
ALB 0.0 MEMBER ALL
ALM 1.13 MEMBER ALL
BEAM 1.0 MEMBER ALL
DFF 250.0 MEMBER ALL
DMAX 0.4 MEMBER ALL
DMIN 0.25 MEMBER ALL
FU 400.0 MEMBER ALL
FYLD 310.0 MEMBER ALL
IST 2.0 MEMBER ALL
KT 0.85 MEMBER ALL
KX 0.75 MEMBER ALL
KY 1.0 MEMBER ALL
LX 4.5 MEMBER ALL
LY 6.0 MEMBER ALL
MAIN 1.0 MEMBER ALL

NSC 0.9 MEMBER ALL
NSF 1.0 MEMBER ALL
PHI 0.9 MEMBER ALL
RATIO 0.9 MEMBER ALL
SGR 1.0 MEMBER ALL
SKT 1.0 MEMBER ALL
SKL 1.0 MEMBER ALL
SKR 1.0 MEMBER ALL
TRACK 2.0 MEMBER ALL
UNB 3.4 MEMBER ALL
UNT 6.8 MEMBER ALL
CHECK CODE MEMBER ALL