# D11.A.6 Design Parameters

he design parameters outlined in the following table 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. New Zealand Steel Design Parameters
Parameter Name Default Value Design Scope Description
CODE -

Must be specified as NZS3404 1997 to invoke design per NZS 3404-1997.

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

ALM 1.0 Moment modification factor (refer cl. 5.6.1.1) If ALM is 0.0 or not specified, it is automatically calculated based cl.5.6.1.1; otherwise the input value is used.
BEAM 1.0 Design locations:
• 0 = design only for end moments and those at locations specified by SECTION command.
• 1 = Perform design for moments at twelfth points along the beam.
DFF None 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 1000.0 mm Maximum allowable depth (Applicable for member selection)
DMIN 0.0 mm Minimum required depth (Applicable for member selection)
DUCT 0 Seismic category of member ( sec. 12.2.5 ):
• 0 = Non-seismic (section 12 will not be checked)
• 1 = High ductile
• 2 = Limited ductile
• 3 = Nominal ductile
• 4 = Non-ductile
FU 500 MPa. Ultimate strength of steel. If not specified, ultimate strength is calculated from SGR as per SGR Parameter.
FYLD 248.0 MPa Yield strength of steel. If not specified, yield strength is calculated from SGR as per SGR Parameter.
GLD blank Gravity load case number. By default, no load case will be selected as gravity load case.
IST Refer to IST Parameter . Residual stress category:
• 1 - SR
• 2 - HR
• 3 - CF
• 4 - LW
• 5 - HW

If not specified, IST is evaluated depending upon shape. (See IST Parameter for details)

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/Z-axis. Used to calculate slenderness ratio. If specified, overrides the value calculated by program from restraint definition (PBCRES).
KZ 1.0
LHT 0 Physical members only Load height position as described in Table 5.6.3(2) of NZS3404:1997 0 = at Shear center 1 = At top flange (See LHT Parameter)
LX Member Length The distance between partial or full restraints which effectively prevent twist of the section about its centroid. (sec. 8.4.4.1.2)
LY Length for general column flexural buckling about the local Y/Z-axis. Used to calculate slenderness ratio. If specified, overrides the value calculated by program from restraint definition (PBCRES).
LZ
MAIN 180.0 A value less than or equal to 1.0 suppresses the slenderness ratio check. checks are not explicitly required per NZS3404. 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 PBRACE Parameter for details on the PBRACE parameter.
PBCRES None Refer to PBCRES Parameter for details on the PBCRES parameter.
RATIO 1.0 Permissible ratio of actual load effect to the design strength.
• 0 = Default (see note)
• 1 = AS 3679.1 - 350
• 2 = AS 3679.1 - 300 (default for standard rolled sections)
• 3 = AS 3679.1 - 250
• 4 = AS 1163 - C450
• 5 = AS 1163 - C350
• 6 = AS 1163 - C250 (default for tube sections)
• 7 = AS 3678 - 450
• 8 = AS 3678 - 400
• 9 = AS 3678 - 350
• 10 = AS 3678 - WR350
• 11 = AS 3678 - 300 (default for welded profiles and UPT)
Note: Refere to SGR Parameter
SKL 1.0 A load height factor given in Table 5.6.3(2). If not specified or specified as 0.0, will be automatically calculated.
SKR 1.0 A lateral rotation restraint factor given in Table 5.6.3(3). If not specified or specified as 0.0, will be automatically calculated.
SKT 1.0 A twist restraint factor given in Table 5.6.3(1). If not specified or specified as 0.0, will be automatically calculated.
TMAIN 400.0 A value less than or equal to 1.0 suppresses the slenderness ratio check. checks are not explicitly required per NZS3404. Any value greater than 1.0 is used as the limit for slenderness in tension.
TRACK 0 Output detail
• 0 = report only minimum design results
• 1 = report design strengths in addition to TRACK 0 output
• 2 = provide full details of design
TSP 0.0 Spacing between transverse stiffener provided in the web. If any value less than or equal to 0.0 is specified, clear depth of web will be used.
UNB Member Length Unsupported length in bending compression of the bottom and top flange respectively for calculating moment resistance. If not equal to member length, overrides the value calculated by program from restraint definition (PBRACE).
UNT Member Length

## DFF, DJ1, and DJ2 Parameters

(Analytical members only) Deflection calculations are not applicable to PMEMBERs.

Compute Delta = $( DX2 − DX1 ) 2 + ( DY2 − DY1 ) 2 + ( DZ2 − DZ1 ) 2$

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

• 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.

PARAMETERS
DFF 300. ALL
DJ1 1 ALL
DJ2 4 ALL

D = Maximum local deflection for members 1, 2, and 3.

• 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.
• 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.

## IST Parameter

IST parameter is used to specify the residual stress category referred in table 5.2 and 6.2.4.

If IST is specified, then that value is used. But if not specified then residual stress category automated from shape of the section according to Note 1 of table 5.2.

Profile Residual stress Category
Australian UB, UC, Angle, Channel, Tee, SHS, RHS, CHS HR-hot-rolled or hot-finished
Australian cold formed shapes CF-cold formed
Any other Australian shape HW-heavily welded longitudinally
Any shape from any country other than Australia

## 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 taken 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 taken to be 1.0 as the load acting at the top flange is contributing to stabilize against local torsional buckling.

## SGR Parameter

NZS3404 defines the values of steel grades that are used as either normal steel or high grade steel. The following table explains the material values used when either option is specified for a particular shape:

SGR Value Steel Grade Used Description
0 Default AS/NZS 3679.1 300 for rolled sections, AS 1163 C250 for hollow sections (Pipe, Tube, HSS), AS 3678 300 for welded sections (WB, WC, UPT, Tapered)
1 AS/NZS 3679.1 350
2 AS/NZS 3679.1 300
3 AS/NZS 3679.1 250
4 AS 1163 C450
5 AS 1163 C350
6 AS 1163 C250
7 AS 3678 450
8 AS 3678 400
9 AS 3678 350
10 AS 3678 WR350
11 AS 3678 300

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 yield 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.

A check is introduced to see if yield stress is less than 100 MPa or more than 450 MPa or not. If less than 100 MPa, a warning is issued but the yield stress will not be modified. If more than 450 MPa, then also a warning is issued and the yield stress is set to 450 MPa.

## Example of Member Design

The following example uses the Member design facility in STAAD.Pro. However, it is strongly recommended to use the Physical member design capabilities for NZS3404:

PARAMETER 1
CODE NZS3404 1997
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 2.0 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

## PBRACE Parameter

PBRACE {TOP | BOTTOM} f1 r1 f2 r2 … f52 r52 (PMEMB pmember-list)

where:

ParameterDescription
fn a fraction of the PMEMBER length where restraint condition is being specified. This value is any ratio between 0.0 and 1.0.
rn one of the possible restraint condition:
• U
• F
• P
• L
• FR
• PR
• C

## PBCRES Parameter

PBCRES {ZZ | YY} f1 r1 f2 r2 … f52 r52 (PMEMB pmember-list)

where:

ParameterDescription
fn a fraction of the PMEMBER length where restraint condition is being specified. This value is any ratio between 0.0 and 1.0.
rn one of the possible restraint condition:
• U
• T
• R
• TR

## Example of PMEMBER Design

PARAMETER 1
CODE NZS3404 1997
DMAX 0.4 PMEMBER 20 TO 25
DMIN 0.25 PMEMBER 20 TO 25
KX 0.75 PMEMBER 20 TO 25
KY 1.0 PMEMBER 20 TO 25
LX 4.5 PMEMBER 20 TO 25
LY 6.0 PMEMBER 20 TO 25
LHT 0.0 PMEMBER 20 TO 25
NSC 0.9 PMEMBER 20 TO 25
NSF 1.0 PMEMBER 20 TO 25
PBRACE BOTTOM 0.0 F 1.0 F PMEMBER 20 TO 25
PBRACE TOP 0.0 P 0.5 L 1.0 P PMEMBER 20 TO 25
PBCRES ZZ 0.0 TR 0.3 R 1.0 U
PBCRES YY 0.0 TR 1.0 U
SGR 0.0 PMEMBER 20 TO 25
TRACK 2.0 PMEMBER 20 TO 25
CHECK CODE PMEMBER 20 TO 25
Note: Parameters for PMEMBER design must be listed using member numbers. The ALL list option may not be used for PMEMBERs.