Partial factors according to SANS 10163-1
Design of timber structures according to SANS 10163-1 is based on limit state theory. Following safety factors are used during the design:
Resistance factor φ
Resistance factor is applied in accordance with chapter 13.1.1. The software uses following values:
Verification of | Factor φ |
Timber, Anchorage of nail plates | 0.68 |
Strength of nail plates | 0.68 |
This factor cannot be modified by the user.
Partial material factor for load duration γm1
Partial material factor for load duration γm1 is applied in accordance with 13.1.2.1. The factor is calculated using formula
\gamma_{m1}=\frac {C_{fD} \cdot W_{DU}+C_{fI} \cdot W_{IU}+C_{fW} \cdot W_{WU}}{W_{DU}+W_{IU}+W_{WU}}
where: | WDU |
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WIU |
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WWU |
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CfD |
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CfI |
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CfW |
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The factored load effects are calculated as sums of horizontal parts of loads. The combination factors in accordance with chapter 7.3 of SANS 10160-1 are taken into account. The load coefficients Cf are defined in accordance with Table 3.
The maximum value of γm1 is 1.0.
Partial material factor for load sharing γm2
Partial material factor for load sharing γm2 is applied in accordance with 13.1.2.2. The value of this factor can be changed in "Truss properties", tab "Standard". Permitted range is <0,87;1,00>. The conditions described in 13.1.2.2 shall be fulfilled in this case.
Partial factor for stressed volume γm3
The partial material factor for stressed volume γm3 is applied in accordance with 13.1.2.3. Following formulas are used.
Girders:
\gamma_{m3}=0,87+0,015L
Other trusses:
\gamma_{m3}=0,85+0,03L
where is: | L |
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Girders are recognized automatically in Truss 3D. Standalone application Truss 2D use the appropriate formula according to the check box "Girder" in the "Truss properties".
This factor cannot be modified by the user.
Partial factor for moisture content γm4
Partial material factor for moisture content γm4 is applied in accordance with 13.1.2.4. The default value is 1.0 (normal moisture content less than or equal to 170g/kg).
Moisture content | Factor γm4 |
Normal (≤ 170g/kg) | 1.00 |
Exceeding 170g/kg but not exceeding 200g/kg | 1.00 |
Exceeding 200g/kg | 1.33 |
At time of construction between 170g/kg and 250g/kg and after that, falling to 170g/kg | 1.33* |
At time of construction exceeding 250g/kg and after that, falling to 170g/kg | 1.33* |
Fluctuating over a range exceeding 100g/kg | 1.33* |
* Note: Default value. The value can be changed to 1.00 by unchecking the setting "Moisture content could exceed 200g/kg".
Partial factor for pressure treatment γm5
Partial material factor for pressure treatment γm5 is applied in accordance with 13.1.2.5. This factor is 1.0 as a default. If the setting "Treated" is switched on in "Truss properties", the factor will be taken as 1.11.
Factor for load duration d1
This factor is used in the calculation of deflection for serviceability load states. The factor is applied in accordance with chapter 12.1.
d_1=\frac {W_{DS}+W_{IS}+W_{WS}}{C_{dD} \cdot W_{DS}+C_{dI} \cdot W_{IS}+C_{dW} \cdot W_{WS}}
where: | WDS |
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WIS |
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WWS |
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CdD |
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CdI |
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CdW |
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The serviceability load effects are calculated as sums of horizontal parts of loads. The combination factors in accordance with chapter 8.3 of SANS 10160-1 are taken into account.
These values of the deflection coefficients Cd are used (in accordance with 12.1.2):
Load | Coefficient Cd |
Self-weight, permanent, medium-term | 0.7 |
Short-term incl. wind load | 1.0 |
Factor for moisture content d2
This factor is used in the calculation of deflection for serviceability load states. The factor is applied in accordance with chapter 12.2. The values are based on the Table 1. The appropriate value is selected according to the setting "Moisture content" in "Truss properties".