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Parameters for design and check

National Annex parameters

The parameters defined by the National Annex can be reviewed and modified in the Manager for National Annexes.

Partial safety factors

g_M solid timber

g_M glued laminated timber

g_M accidental combinations

Shear parameters

k_cr shear modification factor

Tensile stress alternative for Double tapered or Curved beams

Eq.(6.54) or Eq.(6.55) Used in determination of the greatest tensile stress perpendicular to the grain in the apex zone of a double tapered or curved beam.

More information about the parameters can be found in the appropriate Theoretical Background manual and in the EN 1995 code itself.

How to adjust the National Annex parameters

1. Open the Manager for National Annexes (through the Project Data dialogue or using the National Annex flag in the bottom right corner of the SCIA Engineer application window.
2. Select the required National Annex in the top part of the dialogue.
3. In the bottom part of the dialogue, select the EN 1995 section and click the three-dot button ().
4. Review and/or modify the parameters.
5. If required, use the button at the bottom to read the default NA parameters.
6. Confirm with OK.

Design and check parameters

Ultimate limit state

Environmental influences

Service class

Structures shall be assigned to one of the service classes defined in the code.

Material properties

Modification factor k_mod

Modification factor for duration of load and moisture content.

Apply depth factor k_h

For rectangular sections the effect of the member depth can taken into account for solid and glued laminated timber.

Compression perpendicular to the grain

Ignore check

Setting to ignore the compression perpendicular to the grain check

Contact length

Length of supports for check for compression perpendicular to the grain.

Curved beams

Lamination thickness t

Thickness of the laminations of a glued, laminated cross-section.

Default sway types

These default sway types are used for all members, unless the user changes them in the settings made for particular members. The sway type is used for calculating the buckling ratios.

Y-Y

If ON, the members are sway for buckling about the Y-Y axis. If OFF, the members are non-sway for buckling about the Y-Y axis.

Z-Z

If ON, the members are sway for buckling about the Z-Z axis. If OFF, the members are non-sway for buckling about the Z-Z axis.

Buckling length ratios k_y, k_z

Max k ratio

The calculated value of k is limited and must not exceed the given value

Max. slenderness

If the slenderness of the checked member exceeds this value, the program prints a warning in the output report.

2nd order buckling ratios

a) According to input: The buckling data are considered in the 2nd order analysis by values as they were defined.
b) All non-sway: The whole structure is considered as non-sway.

General settings

Section check only

If this option is checked, only the section check is carried out. No stability check is performed.

Flexural buckling accounted for by 2nd order calculation

When this option is selected, there is no flexural buckling check performed as the second order calculation has accounted for this effect already.
Note: The reduction factor is set to 1 to account for this effect.

Serviceability limit state

Material properties

Deformation factor kdef

Deformation modification factor as defined in table 3.2 of the code.

Increase kdef according to 3.2(4)

Allows for increase of k_def factor for timber which is installed at or near its fibre saturation point.

Relative deformations

Limiting values for deflections

The table defines the limit deformation values for various structural elements.

Buckling defaults

The default buckling parameters are used whenever a new 1D member is input into the project. By default, the new member takes these default parameters. If required, you may later alter these default values and assign specific values to the particular member ("Timber Member Data").

Buckling systems relation

zz

System length for buckling around the local zz axis (weak axis). This is usually the length between the points braced in the direction of the local yy axis.

yz

System length for torsional buckling. This is the length between the restraints for torsion.

lt

System length for lateral-torsional buckling. This is usually the length between the points braced in yy direction (= length between the lateral restraints).
The buckling lengths for the calculation are always of the following form :
l = L * k
where
l = effective buckling length for calculation
L = system length
k = k factor

Relative deformation systems relation

ky factor

a) Calculate: The value of the ky factor is calculated by the program.
b) Factor: The user defines the value of the factor.
c) Length: The user inputs the buckling length directly.

kz factor

ditto for kz factor

Influence of load position

This field is relevant for lateral-torsional buckling check. It provides for consideration of destabilising loads in moment factors for LTB.
Destabilising loads are loads that act above the level of the beam’s shear centre and are free to move sideways with the beam as it buckles (and produce a disturbing effect)

For a member with variable height, the value of ky ratio has no meaning. Buckling properties are calculated using the critical Euler force for this member. However, the user can choose to define a not-calculated buckling ratio which is used in each intermediate point of the member.

For a theoretical explanation about the calculation of buckling ratios ky and kz, see Steel Code Check Theoretical Background, Calculation of buckling ratios.

How to adjust the timber design and check parameters

1. Open the Setup Manager using tree Timber > Timber Setup.
2. Review and/or modify the parameters.
3. If required, use the buttons at the bottom to read the default parameter-values.
4. Confirm with OK.

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