D5.A.6 Design Parameters
Design parameters communicate specific design decisions to the program. They are set to default values to begin with and may be altered to suite the particular structure.
Depending on the model being designed, you may have to change some or all of
the parameter default values. Some parameters are unit dependent and when altered, the n
setting must be compatible with the active unit
specification.
The follow table lists all the relevant EC3 parameters together with description and default values.
Parameter Name | Default Value | Description | ||||||
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CODE | - |
Must be specified as Design code to follow. See TR.48.1 Parameter Specifications. |
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ALH | 0.5 | The ratio of the distance of the point torque (from the start of the member) to the length of the member. The default value of 0.5 represents torque acting at the mid-span of a symmetrically loaded member. Values can range from 0 to 1. | ||||||
ALPHA | 1.0 | Used to input a user defined value for the α factor in equation 6.41 for combined bending and axial force checks. | ||||||
BEAM | 3 |
Parameter to control the number of sections to checked along the length of a beam:
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BETA | 1.0 | Used to input a user defined value for the β factor in equation 6.41 for combined bending and axial force checks. | ||||||
C1 | 1.132 | Corresponds to the C1 factor to be
used to calculate Elastic critical moment Mcr as per Clause
6.3.2.2 Note: This parameter is required for
the Dutch NA 2016.
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C2 | 0.459 | Corresponds to the C2 factor to be
used to calculate Elastic critical moment Mcr as per Clause
6.3.2.2 Note: This parameter is required for the Dutch
NA 2016.
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C3 | 0 | Corresponds to the C3 factor to be used to calculate Elastic critical moment Mcr as per Clause 6.3.2.2 | ||||||
CAN | 0 |
Member will be considered as a cantilever type member for deflection checks.
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CMM | 1.0 |
Indicates type of loading and support conditions on member. Used to calculate the C1, C2, and C3 factors to be used in the Mcr calculations. Can take a value from 1 to 8. Refer to Note 2 (below) for more information on its use. |
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CMN | 1.0 |
Indicates the level of End-Restraint.
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CMT | 1 |
Used to indicate the loading and support condition for torsion (ref. SCI publication P-057). Can take a value of 1-7. The values correspond to the various cases defined in section 6 and App. B of SCI-P-057. Refer to Note 4 (below) for more information |
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DFF | 360 |
Deflection Length/ Max.. allowable local deflection See Note 1d below. See TR.40 Load Envelope for deflection checks using serviceability load envelopes. |
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DJ1 | Start Jointof member | Joint No. denoting starting point for
calculation of Deflection Length. See Note 1 below. |
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DJ2 | End Joint of member | Joint No. denoting end point for calculation of
Deflection Length. See Note 1 below. |
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DMAX | 100.0 cm | Maximum allowable depth for the member. | ||||||
DMIN | 0 | Minimum required depth for the member. | ||||||
EFT | Member Length | The distance between the adjacent torsional
restraints. Effective length for torsion, lateral-torsional buckling check of
tapered members per Annex BB 3.2.2. A value of 0 defaults to the member length. |
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ELB | 0 |
Used to specify the method for combined axial load + bending checks
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ESTIFF | 0 |
(For use with the Dutch NA 2007 only; not applicable to the Dutch NA 2016) Method for checking columns forming part of (non)/buttressed framework:
Refer to D5.B.3.8 Clause 6.33 – Uniform members in bending and axialcompression for additional description on this parameter. |
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FAB | 3 |
Used to specify the fabrication class to be used to check for slender (Class 4) CHS/pipe sections (EN 1993-1-6:2007)
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FU | 0 | Ultimate tensile strength of steel. | ||||||
GM0 | 1.0 | Corresponds to the γm0 factor in EN 1993-1-1:2005 | ||||||
GM1 | 1.0 | Corresponds to the γm1 factor in EN 1993-1-1:2005 | ||||||
GM2 | 1.25 | Corresponds to the γm2 factor in EN 1993-1-1:2005 | ||||||
GST | 0 |
Used to specify the section type to be used for designing a General dialog from a user-provided table. The member will be considered as the specified type with the user-defined properties. Where design related checks on section geometry are required (e.g., depth/thickness ratio or width/thickness ratio), the values of B, D, TB, and TD are used as indicated and this is noted in the output file. The available options and corresponding required UPT general
section values are as below. If the required dimensions are not provided, a
warning is issued in the output file in the design results for the section
with the
Note: This parameter will be
ignored if it has been assigned to any section other than a UPT General
section.
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HGT | 0.0 | Distance from the top of the tapered web section to the
center of gravity of purlin.
Used for the lateral-torsional buckling calculations for web-tapered members. |
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KC | 1.0 |
Corresponds to the correction factor as per Table 6.6 of EN 1993-1-1:2005. Program will calculate kc automatically if this parameter is set to 0. Note: For the British, Singapore, & Polish NAs, kc will be calculated as given in the NA by default.
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KY | 1.0 | K factor in local y axis. Used to calculate the effective length for slenderness and buckling calculations. | ||||||
KZ | 1.0 | K factor in local z axis. Used to calculate the effective length for slenderness and buckling calculations. | ||||||
LEG | 0 |
Slenderness values for angles as determined from BS 5950-2000 Table 25. Valid range from 0 – 7 and 10-11. See Note 5 below. |
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LKP | Member length | (Applicable to the Dutch National Annex 2016 only) The unsupported tipping length between two clevises, between on clevis and one tipping support, or between two tipping supports. |
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LVV | Member length | Applicable for double angles measured between
interconnecting bolts for back-to-back struts or between end welds or end bolts
of adjacent battens (Table 25, BS 5950-2000). The default is the member's length. |
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LY | Member Length | Compression length in local y axis between
lateral restraints Slenderness ratio =
KY ×LY / RyyDistance between lateral restraints used for tapered I sections. Used for the lateral-torsional buckling calculations for web-tapered members. The default is the member's length. |
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LZ | Member Length | Compression length in local z axis between
lateral restraints Slenderness ratio =
KZ ×LZ / Rzz |
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MTH | 0 |
Used to select the clause to be used to calculate the LTB reduction factor, χLT. The available options and corresponding values are as below:
By default, the program will use Cl 6.3.2.3 for rolled & built-up I-sections and Cl. 6.3.2.2 for all other sections. If, however, the specified National Annex expands on Cl. 6.3.2.3 to include other section types (e.g., the UK NA), the program will use Cl. 6.3.2.3 by default for that particular section type. Refer to D5.B. European Codes - National Annexes to Eurocode 3 [EN1993-1-1:2005] for additional details on NA documents. |
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MU | 0 |
The ratio of the moment due to the transverse force to the
maximum moment M. To be used with Note: This parameter is only
applicable to the French NA & Belgian NA.
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NA | 0 |
Choice of National Annex to be used for EC3 design. Refer to D5.B. European Codes - National Annexes to Eurocode 3 [EN1993-1-1:2005] for values allowed for this parameter. (Refer to D5.A.1 General Description for more information) |
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NSF | 1.0 | Net tension factor for tension capacity calculation. | ||||||
PLG | 0 |
To be used to determine whether to include the additional interaction checks as per CL. NA.20(2) and NA.20(3) of the Polish National Annex. Note: This parameter is only
applicable to the Polish NA.
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PY | Yield Strength | The yield strength default value is set based on the default value of the SGR parameter. |
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RATIO | 1 | Permissible ratio of loading to capacity. | ||||||
SBLT | 0.0 |
Indicates if the section is rolled or built-up.
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SGR | 0 |
Steel grade as in Table 3.1: EN 1993-1-1: 2005:
Note: As EN 1993-1-1:2005 does not provide a buckling curve in table 6.2 for grade S 450 steel (in Table 3.1 of EN 1993-1-1:2005), the program will use the same buckling curves as for grade S 460 when calculating the buckling resistance as per clause 6.3.
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SRT | 0 |
(Applicable to the Dutch National Annex 2016 only)
Specify if the slenderness check for torsional stability and torsional
flexural stability are performed:
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STIFF | Member Length or depth of beam, whichever is lesser | Distance between transverse stiffener plates, used to prevent web shear buckling. If not specified or if a value of 0 is provided, the program will assume the web is unstiffened. | ||||||
TOM | 0 | Total torsion for design used for torsion checks. Can be used to override the total torsional moment to be used for member design. | ||||||
TORSION | 0 |
Method to be used for a specific member or group of members:
Note: For options 1 or 2, the program will perform the torsion related checked even if torsional moment is absent and will use a value of zero for the torsional moment.
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TRACK | 0 |
Specify level of detail in output.
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UNF | 1 | Unsupported length provided as a
fraction of actual member length used for lateral-torsional buckling
calculation. Note: If both
UNF
and UNL parameters are specified, the effective length used
is UNF ×UNL . |
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UNL | Member Length | Unsupported length for calculating allowable bending stress. Used for the lateral-torsional buckling calculation. Value should be in the current units of length. | ||||||
ZG | +Section Depth/2 |
Distance of transverse load from shear center. Used to calculate Mcr. Note: For Tee sections, ZG will have a default value of (+Flange thickness/2)
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Notes
-
CAN
,DJ1
, andDJ2
– Deflection-
When performing the deflection check, you can choose between two methods. The first method, defined by a value 0 for the
CAN
parameter, is based on the local displacement. Refer to TR.44 Printing Section Displacements for Members for details on local displacement..If the
CAN
parameter is set to 1, the check will be based on cantilever style deflection. Let (DX1, DY1, DZ1) represent the nodal displacements (in global axes) at the node defined by DJ1 (or in the absence of DJ1, the start node of the member). Similarly, (DX2, DY2, DZ2) represent the deflection values at DJ2 or the end node of the member.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.
Then, if CAN is specified a value 1, dff = L/Delta
Ratio due to deflection = DFF/dff
-
If
CAN
= 0, deflection length is defined as the length that is used for calculation of local deflections within a member. It may be noted that for most cases the “Deflection Length” will be equal to the length of the member. However, in some situations, the “Deflection Length” may be different. A straight line joiningDJ1
andDJ2
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. TheDeflection 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 andDJ2
should be 4. D = Maximum local deflection for members 1, 2, and 3.PARAMETERS DFF 300. ALL DJ1 1 ALL DJ2 4 ALL
-
If
DJ1
andDJ2
are not used, "Deflection Length" will default to the member length and local deflections will be measured from original member line. -
If a serviceability load envelope is specified under
LOAD LIST ENV
before a parameter block, the default value of DFF 360 is used for deflection calculations. If DFF 0 is specified for any member, then the deflection check is skipped for that member. -
The above parameters may be used in conjunction with other available parameters for steel design.
-
-
The values of
CMM
for various loading and support conditions are as given below:Table 2. Values for the CMM Parameter CMM
ValueLoading and Support Conditions 1 2 3 4 5 6 7 varying end moments and uniform loading
8 varying end moments and central point load
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Checking beam deflection
With the
IfTRACK
parameter set to 4, the members included in aBEAM CHECK
command will be checked for the local axis deflection rather than for the stress capacity using the currentLOAD LIST
.LOAD LIST ENV
is used, then serviceability envelope must be present to check for deflections. If only strength load cases are given inLOAD LIST ENV
, only strength checks will be performed andTRACK 4
is treated asTRACK 2
.Note: While both sets of code checks will be reported in the output file, only the last code check results are reported in the STAAD.Pro graphical interface. -
The values of
CMT
for various loading and support conditions are as given below:Table 3. Loading and Support Conditions represented by CMT
Parameter ValuesCMT
ValueDescription Diagram 1 (Default) : Concentrated Torque at Ends. Ends Torsion fixed and Warping fixed 2 Concentrated Torque along length of member. Ends Torsion fixed and Warping free 3 Concentrated Torque along length of member. Ends Torsion fixed and Warping fixed 4 Uniform Torque in member. Ends Torsion fixed and Warping free 5 Uniform Torque in member. Ends Torsion fixed and Warping fixed 6 Concentrated Torque in cantilever. End Torsion fixed and Warping fixed 7 Uniform Torque in cantilever. End Torsion fixed and Warping fixed Note: ForCMT
= 2 andCMT
= 3, you have the option of specifying the distance at which the concentrated torque acts, measured from the start of the member. This can be done by using theALH
design parameter. TheALH
parameter indicates the ratio of the distance of the point torque (from the start of the member) to the length of the member. This parameter will have a default value of 0.5 (i.e., the torque acts at the center of the span) and will accept values ranging from 0 to 1. -
LEG
– follows the requirements of BS5950 table 25. This table concerns the fastener restraint conditions for angles, double angles, tee sections, and channels for slenderness. The following values are available:Table 4. LEG
Parameter valuesClause Bolt Configuration Leg LEG
Parameter4.7.10.2
Single Angle
(a) - 2 bolts short leg 1 long leg 3 (b) - 1 bolts short leg 0 long leg 2 4.7.10.3 Double Angles (a) - 2 bolts short leg 3 long leg 7 (b) - 1 bolts short leg 2 long leg 6 (c) - 2 bolts long leg 1 short leg 5 (d) - 1 bolts long leg 0 short leg 4 4.7.10.4 Channels (a) - 2 or more rows of bolts 1 (b) - 1 row of bolts 0 4.7.10.5 Tee Sections (a) - 2 or more rows of bolts 1 (b) - 1 row of bolts 0 The slenderness of single and double angle, channel and tee sections are specified in BS 5950 table 25 depending on the connection provided at the end of the member. To define the appropriate connection, a
LEG
parameter should be assigned to the member.For single angles, the slenderness is calculated for the geometric axes, a-a and b-b as well as the weak v-v axis. The effective lengths of the geometric axes are defined as:The slenderness calculated for the v-v axis is then used to calculate the compression strength pc for the weaker principal axis (z-z for ST angles or y-y for RA specified angles). The maximum slenderness of the a-a and b-b axes is used to calculate the compression strength pc for the stronger principal axis.
Alternatively for single angles where the connection is not known or Table 25 is not appropriate, by setting the
LEG
parameter to either 10 or 11, the slenderness is calculated for the two principal axes y-y and z-z only. UseLEG 10
for the longer leg andLEG 11
for the shorter leg. TheLVV
parameter is not used.For double angles, the
LVV
parameter is available to comply with note 5 in table 25. In addition, if using double angles from user tables, (refer to TR.19.4 Double Angle) an eleventh value, rvv, should be supplied at the end of the ten existing values corresponding to the radius of gyration of the single angle making up the pair.