STAAD 2.17.8 Design Parameters [PDF]

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Design Parameters

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Technical Reference Manual 2.17.8

Design Parameters

Design per AISC 360-05 (Unified) specifications is requested by using the CODE parameter. Other applicable parameters are summarized in the following Table. These parameters communicate design decisions from the engineer to the program and thus allow the user 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. Table 2.9 - AISC 360-05 Design Parameters Parameter Name CODE METHOD

Default Value

Description

AISC UNIFIED Used to designate this code. LRFD

Used to specify LRFD or ASD design methods.

KX

1.0

K value for flexural-torsional buckling.

KY

1.0

K value in local y-axis.

KZ

1.0

K value in local z-axis.

FYLD

250 MPa

Yield strength of steel.

FU

400 MPa

Ultimate strength of steel.

NSF

1.0

Net Section Factor for tension members.

SLF

1.0

Shear Lag Factor for determination of Net Effective Area of tension members.

MAIN

200

Allowable slenderness limit for compression members.

TMAIN

300

Allowable slenderness limit for tension members.

UNT

Member Length

Unsupported length of the top* flange for calculating flexural strength. Will be used only if compression is in the top flange.

UNB

Member Length

Unsupported length of the bottom* flange for calculating flexural strength. Will be used only if compression is in the bottom flange.

RATIO

1.0

DMAX

1000.0 mm

Maximum allowable depth for member selection.

DMIN

0.0 mm

Minimum allowable depth for member selection. Used in member selection. Refer to Section 5.47 for details.

PROFILE BEAM

Permissible ratio of actual load to allowable strength.

1.0

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

mk:@MSITStore:C:\SProV8i\STAAD\Help\Technical_Reference_2007.chm::/American_Steel_Design/... 6/11/2013

Design Parameters

Page 2 of 3 1.0 = design at ends and at every 1/12th point along member length. DFF

none "Deflection Length" / Maximum allowable (mandatory for local deflection deflection check)

DJ1

Start Joint of member

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

DJ2

End Joint of member

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

TRACK

0

Specifies the amount of detail included in design output 0 = Suppress all member capacities 1 = Print all member capacities

LX

Member Length

Length for flexural-torsional buckling

LY

Member Length

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

LZ

Member Length

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

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 on Table 2.1)

CB**

1.0

Coefficient Cb per Chapter F. If Cb is set to 0.0, it will be calculated by the program. Any other value will be directly used in the design.

STP

1.0

Section Type to determine Fr (compression residual stress in flange) 1.0 = Rolled section (Fr = 10 ksi) 2.0 = Welded section (Fr= 16.5 ksi)

AXIS

1

1 = Design single angles for bending based on principle axis. 2 = Design single angles for bending based on geometric axis.

* Top and Bottom represent the positive and negative side of the local Y axis (local Z axis if SET Z UP is used). ** Non-default values of CB must be re-entered before every subsequent CHECK CODE or SELECT mk:@MSITStore:C:\SProV8i\STAAD\Help\Technical_Reference_2007.chm::/American_Steel_Design/... 6/11/2013

Design Parameters

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command. Notes 1. For a description of the deflection check parameters DFF, DJ1, DJ2 see the Notes section of Table 2.1 of this manual. 2. NSF is the Net Section Factor as used in most of the Steel Design Codes of STAAD. It is defined as the Ratio of ‘Net cross section area’ / ‘Gross section area’ for tension member design. The default value is 1.0. For the AISC 360-05 code, it is described in section D.3.2. 3. SLF is the Shear Lag Factor, as used in Section D.3.3 of the AISC 360-05 code. This factor is used to determine the Effective Net Area by multiplying this factor with Net Area of the cross section. Please refer to Table D3.1 of the 360-05 code for a list of acceptable SLF values. In STAAD, the default value for SLF is 1.0. The Effective Net Area is used to determine the Tensile Strength for Tensile rupture in the Net Section, as per equation D.2.2. 4. To summarize, the “Gross Area” (Ag) is multiplied by NSF to get the “Net Area” (An) of the section. The “Net Area” (An) is again multiplied by SLF to get the “Effective Net Area” (Ae) of the section. Related Topics

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