Truss Design Considerations

Truss Design Considerations


Truss Design Considerations Design Implications Considering the Effects of Loading, Member Orientation and Support

Effect of tension vs. compression on member sizes Potential buckling failure modes and approaches to preventing Potential for stress reversal Overall lateral stability (lateral-torsional buckling) Member redundancy: Determinate vs. Indeterminate Trusses

Truss Design Considerations Effect of tension vs. compression on member sizes Potential buckling failure modes and approaches to preventing Potential for stress reversal Member redundancy: Determinate vs. Indeterminate Trusses Overall lateral stability (lateral-torsional buckling) Truss Pedestrian Bridge

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Munich Airport Pedestrian Bridge

Illustrations: Daniel L. Schodek: Structures, fifth edition; Pearson Prentice-Hall, 2004

Truss Design Considerations Effect of tension vs. compression on member sizes Potential buckling failure modes and approaches to preventing Potential for stress reversal Member redundancy: Determinate vs. Indeterminate Trusses Overall lateral stability (lateral-torsional buckling) Truss Member Buckling Considerations (Schodek fig. 4.28)


Truss Member Buckling Considerations (Schodek fig. 4.29)

Truss Pedestrian Bridge, Greece

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Theoretical zero force members that provide buckling resistance to top chord

Truss Design Considerations Effect of tension vs. compression on member sizes Potential buckling failure modes and approaches to preventing Potential for stress reversal Member redundancy: Determinate vs. Indeterminate Trusses Overall lateral stability (lateral-torsional buckling)


Variations in Truss Member Forces (Schodek fig. 4.23)


Variations in Truss Member Forces (Schodek fig. 4.23)

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Truss Design Considerations Effect of tension vs. compression on member sizes Potential for stress reversal Potential buckling failure modes and approaches to preventing Overall lateral stability (lateral-torsional buckling) Member redundancy: Determinate vs. Indeterminate Trusses Truss Lateral Buckling (Schodek fig. 4.30)


Methods of Providing Resistance to Truss Lateral Buckling (Schodek fig. 4.31)

Kansai International Airport, Japan, Renzo Piano

Truss Design Considerations Effect of tension vs. compression on member sizes Potential for stress reversal Potential buckling failure modes and approaches to preventing Overall lateral stability (lateral-torsional buckling) Member redundancy: Determinate vs. Indeterminate Trusses

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Truss Stability & Determinacy

Truss Stability & Determinacy

(Schodek fig. 4.18)

(Schodek fig. 4.18)



Truss Stability & Determinacy Truss Stability & Determinacy

(Schodek fig. 4.05)

(Schodek fig. 4.18)


Truss Determinacy Formula n = 2j – 3 → for determinacy

n = Number of truss bars j = Number of joints

n > 2j -3 → indeterminate n < 2j -3 → unstable

n = 9, j = 6 2(6)-3=9 =9 O.K. n = 11, j = 7 2(7)-3=11 =11 O.K.

n = 8, j = 6 2(6)-3=9 >8 ∴Unstable!

n = 10, j = 6 2(6)-3=9 < 10 → indeterminate, but stable

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Truss Connection Considerations (Onouye fig. 10.2)

Truss Assembly Details

Illustration Source: http://www.ce.berkeley.edu/~boza/courses/cee122/lectures/lecture2/connect-brace.jpg

Truss Connection Considerations

Connection Eccentricity Produces Moment — Pedestrian Bridge in Greece

Illustration Source: http://www.ce.berkeley.edu/~boza/courses/cee122/lectures/lecture2/connect-brace.jpg

Truss Connection Considerations

Knife-Plate Connections — Cutler Anderson Architects

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Grace Episcopal Church, Bainbridge Island, WA — Cutler Anderson Architects

Capitol Hill Library, Seattle, WA — Cutler Anderson Architects

Curvilinear façade supported by 3D linear truss framework: Band Shell, Millennium Park, Chicago, IL — Frank O. Gehry

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Truss Design Considerations

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