staad 2.14.10 design parameters

Technical Reference Manual

2.14.10 Design Parameters

Design per LRFD specifications is requested by using the CODE parameter. Other applicable parameters are summarized in Table 2.5. 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 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.

The parameters DMAX and DMIN are applicable for member selection only.

Table 2.5 - AISC LRFD (2nd and 3rd Ed.) Design Parameters

Parameter Name

Default Value

Description

KX 1.0 K value for flexural-torsional buckling.

KY 1.0 K value in the local y-axis. Usually this is the minor axis.

KZ 1.0 K value in the local z-axis. Usually this is the major axis.

LX Member Length

Length used for flexural-torsional buckling.

LY Member Length

Length to calculate the slenderness ratio for buckling about the local y-axis.

LZ Member Length

Length to calculate the slenderness ratio for buckling about the local z-axis.

FYLD 36.0 ksi Yield strength of steel.

STP 1 Section type to determine Fr (compressive

residual stress in flange) per 3rd Ed. LRFD spec., p 16.1-97.

1 = Rolled section (Fr = 10 ksi)

2 = Welded section (Fr = 16.5 ksi)

FU 60.0 ksi Ultimate tensile strength of steel.

NSF 1.0 Net section factor for tension members.

UNT Member Length

Unsupported length (Lh) of the top* flange for

calculating flexural strength. Will be used only if flexural compression is on the top flange.

UNB Member Length

Unsupported length (Lh) of the bottom* flange

for calculating flexural strength. Will be used only if flexural compression is on the bottom flange.

STIFF Member Length or depth,

Spacing of stiffeners for beams for shear design.

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whichever is greater

CB** 1.0 Coefficient Cb per Chapter F of AISC LRFD. If Cb is set to 0.0, it will be calculated by the program. Any of value will be used directly in design.

TRACK 0.0 Specified the level of detail included in the output.

0.0 = Suppress all design strengths

1.0 = Print all design strengths

2.0 = Print expanded design output

DMAX 45.0 in. Maximum allowable section depth.

DMIN 0.0 in. Minimum allowable section depth

DFF None (Mandatory for deflection

check)

"Deflection Length" / Maximum allowable local deflection

DJ1 Start Joint of Member

Joint No. denoting starting point for calculation of "Deflection Length" (see note 1 of Table 2.1)

DJ2 End Joint of Member

Joint No. denoting end point for calculation of "Deflection Length" (see note 1 of Table 2.1)

CAN 0 0 = deflection check based on the principle that maximum deflection occurs within the span between DJ1 and DJ2.

1 = deflection check based on the principle that maximum deflection is of the cantilever type (see note 2 of Table 2.1)

RATIO 1.0 Permissible ratio of actual load effect to design strength.

BEAM 1.0 0.0 = design at ends and those locations specified by the SECTION command.

1.0 = design at ends and at every 1/12th point along member length.

PROFILE Used in member selection. See Section 5.47 for details.

AXIS 1 1 = Design single angles for bending about their principle axis.

2 = Design single angles for bending about their geometric axis.

FLX 1 1 = Single angle member is not fully braced against lateral torsional buckling.

2 = Single angle member is fully braced against lateral torsional buckling.

3 = Single angle member is braced against lateral torsional buckling at the point of



*Top and Bottom represent the positive and negative side of the local Y axis (local Z axis if SET Z UP is used).

For a description of the deflection check parameters DFF, DJ1, DJ2 and CAN, see the Notes section of Table 2.1 of this manual.

The STIFF parameter represents the term “a” as defined in Section F2, page 6-113 of the LRFD 2nd edition manual.

** Non-default values of CB must be re-entered before every subsequent CHECK CODE or SELECT command.

Related Topics

maximum moment.

MAIN 0.0 0.0 = check for slenderness

1.0 = suppress slenderness check

Any value greater than 1 = Allowable KL/r in compression.

TMAIN 300 Any value greater than 1 = Allowable KL/r in tension.



staad 2.14.10 design parameters

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