D11.A.6Design 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.
Parameter Name | Default Value | Design Scope | Description |
---|---|---|---|
CODE | - |
Must be specified as
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:
|
|
DFF | None | Analytical members only |
Deflection Length/ Maximum Allowable local deflection. See DFF, DJ1, and DJ2 Parameters See TR.40 Load Envelope for deflection checks using serviceability load envelopes. |
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 ):
|
|
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:
If not specified, |
|
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. | |
SGR | 0 | Steel Grade.
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
|
|
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 =
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 parametersDJ1
andDJ2
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
andDJ2
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 forDFF
.
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:
Parameter | Definition |
---|---|
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:
|
PBCRES Parameter
PBCRES {ZZ | YY} f1 r1 f2 r2 … f52 r52 (PMEMB pmember-list)
where:
Parameter | Definition |
---|---|
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:
|
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
ALL
list option may not be used for PMEMBERs.