Problem:

How to model a Sway Brace pipe support in AutoPIPE?

Solution:

Sway Brace has a rigid stiffness up to load limit of 1800lb, then stiffness changes to 1800lb/in. The full sway brace resistance load is exerted in the colde condition = free thermal movement * spring + preload

Note: There are 2 styles - Mechanical and hydraulic (viscous) sway brace. AutoPIPE models a mechanical.

Example:

The pipe moves 1.215" under thermal case T1 at node A01 (with inclined support removed), the sway brace load would exert a total 1800 lb/in x 1.215" plus 1800 lb preload = 3987 lbs in the Gravity case. When the pipe fully expands in the thermal T1 case there is zero resisting load in the operating condition

Sample model: Sway_Brace_6.dat

Insert a inclined support at A01, with 1800 lb /in spring rate

Insert > xtra data > concentrated force. Add 2 forces, +ve preload = 1800 in GR and –ve preload in T1 case i.e. gravity case force in same direction as thermal movment and force in T1 case in the opposite direction

Add a imposed displacement in the gravity case = the free thermal movement = 1.215”

Results show expected full preload = 3982lb exerted on anchor A00 by the sway brace. In the operating case – no load in seen in GT1 at both anchor A00 and A01 support

Note:

AutoPIPE  cannot simulate the arc or pendulum movement of a rigid strut. Typically good design practice limits angulation of struts or hangers to +/- 4 deg

One workaround is calculate the lateral restoring force for the angulation for each loading and apply this force at the pipe connection point.

See Also

Different Types of Supports

Bentley AutoPIPE