07 Rhs Trusses

7/27/2019 07 Rhs Trusses

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1Wardenier Tubular Structures Course

Examples

Hollow Section Trusses

Design Procedure


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Truss Design Procedure

Determine truss layout, span, depth, panel lengths, truss spacing by

usual methods.Keep connections to a minimum.

Determine loads at connections and on members.Simpli fy these

ini tially to equivalent loads at panel points.

Determine axial forces in al l membersby assuming that joints are

pinned and assume all member centre l ines are noding.

2.

3.

1.


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Axial load

Corrosion protection (sur face area)

Wall slenderness

Determine chord member sizes consider ing:4.


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5. Determine web member sizes consider ing:

Axial load

tweb< tchord

K= 0.75 for compression webs

6. Standardize the brace member sizes:e.g. to 2 or 3 sizes

Same width, diff erent th ickness? Inspection problem

Check availabil i ty!7. Layout connections:

Try gap connections first

Check connection geometry is within validity range

Check member sizes are within validity rangePay attention to eccentr ici ty limits

Consider fabr ication procedure


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8. Check connection eff iciencies(with charts)or resistances(with formulae or tables)Usual ly only a few connections need to be checked.

I f eff iciencies or resistances are not adequate, modif y the

connection layout(e.g. over lap instead of gap), or

Modify the members;Re-check connections.

9.


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Check effect of primary moments on chord design.Use proper load positions on members

Determine member bending moments assuming:

Pinned join ts everywhere or

Continuous chords with pin -ended webs

Design welded joints.F il let welding cheapest

(Note: Weld Design can be left to the fabr icator but not connection ver if ication)

10.

Check truss def lections under specif ied loads.11.

12.

For compression chord, also consider noding

eccentr icity moment.

Check member (axial and bending) interactions.



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Some Golden Rules to Avoid Connection Problems

General Tips

for

Designers


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Deflections of Trusses

Check Deflections Under Specif ied Loads

or Overlap

Joints

Gap Joints

or

braces


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Design Example of Design Guide 1


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CHS K joint


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Efficienc

CHS

K joint


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Effect Chord

Pre-stress


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Note: Gap of joint 2 is decreased to satisfy joint strength andthe eccentricity is taken into account for the member check


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Design Example of Design Guide 3


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RHS K joint


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Efficiency

RHS

K joint


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Effect Chord

stress


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Documents

07 Rhs Trusses