Steel Section Design and Connections Tutorial - Kxcad.net

T2.2.13 Rafter Torsional Restraints
Ensure you are in Search for Next Brief Mode
Click on the outer left hand rafter
Select Appendix-G : Stability Checks from the Integrated Design menu
To determine the position of the torsional restraints required in the rafter, we
first check the stability over the first two portions (2 @ 1.4 m = 2.8 m length
starting @ 0 m).
If this fails then provide a torsional restraint at 1.4 m and check the stability over
the second and third portions (1 @ 1.4 + 1 @ 1.8 = 3.2 m length starting @ 1.4
m).
If this also fails then provide a second torsional restraint at 2.8 m and check the
stability over the third and forth portions (2 @ 1.8 = 3.6 m length starting @ 2.8
m).
Click on the torsional restraint tab
Enter the value of 2.8 in Portion
1
This portion is unstable, so we
provide our first torsional restraint
@ 1.4 m
Enter a value of 1.4 in the ‘Start
at’ just before Portion 1 the Input
Data
This portion is still unstable, so we
provide our second torsional
restraint @ 2.8 m
Enter a value of 2.8 in the ‘Start
at’ just before Portion 1 the Input
Data
Enter a value of 3.6 in Portion 1
This provides torsional restraints at 2.8 and 3.6 m. Let us check other rafters by
copying and applying this design brief.
Change to Copy Current Brief Mode
Select rafter members 2, 3, 4, 5, and 6 to copy theAppendix-G brief including
the torsional restraints information to all other rafter members
Click on Search for Next Brief Mode
Important Note:
Although the length of portion 1 is defined as 3.6 m, it will automatically check a
portion between the torsional restraint at 2.8 and the point of contraflexure in
each rafter.
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