Truss Design Considerations 1 Truss Design Considerations Truss Design Considerations Design Implications Considering the Effects of Loading, Member Orientation and Support Truss Design Considerations 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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Truss Design Considerations - Structural Engineers · Truss Design Considerations 3 Theoretical zero force members that provide buckling resistance to top chord Truss Design Considerations
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Design Implications Considering the Effects of Loading, Member
Orientation and Support
Truss Design Considerations
Effect of tension vs. compression on member sizesPotential buckling failure modes and approaches to preventingPotential for stress reversalOverall lateral stability (lateral-torsionalbuckling)Member redundancy: Determinate vs. Indeterminate Trusses
Truss Design Considerations
Effect of tension vs. compression on member sizesPotential buckling failure modes and approaches to preventingPotential for stress reversalMember redundancy: Determinate vs. Indeterminate TrussesOverall lateral stability (lateral-torsionalbuckling)
Truss Pedestrian Bridge
Truss Design Considerations
2
Munich Airport Pedestrian Bridge
Truss Design Considerations
Effect of tension vs. compression on member sizesPotential buckling failure modes and approaches to preventingPotential for stress reversalMember redundancy: Determinate vs. Indeterminate TrussesOverall lateral stability (lateral-torsionalbuckling)
Illustrations: Daniel L. Schodek: Structures, fifth edition; Pearson Prentice-Hall, 2004
Truss Member Buckling Considerations(Schodek fig. 4.28)
Illustrations: Daniel L. Schodek: Structures, fifth edition; Pearson Prentice-Hall, 2004
Truss Member Buckling Considerations(Schodek fig. 4.29) Truss Pedestrian Bridge, Greece
Truss Design Considerations
3
Theoretical zero force members that provide buckling resistance to top chord
Truss Design Considerations
Effect of tension vs. compression on member sizesPotential buckling failure modes and approaches to preventingPotential for stress reversalMember redundancy: Determinate vs. Indeterminate TrussesOverall lateral stability (lateral-torsionalbuckling)
Illustrations: Daniel L. Schodek: Structures, fifth edition; Pearson Prentice-Hall, 2004 Variations in Truss Member Forces
(Schodek fig. 4.23)
Illustrations: Daniel L. Schodek: Structures, fifth edition; Pearson Prentice-Hall, 2004 Variations in Truss Member Forces
(Schodek fig. 4.23)
Truss Design Considerations
4
Truss Design Considerations
Effect of tension vs. compression on member sizesPotential for stress reversalPotential buckling failure modes and approaches to preventingOverall lateral stability (lateral-torsionalbuckling)Member redundancy: Determinate vs. Indeterminate Trusses
Illustrations: Daniel L. Schodek: Structures, fifth edition; Pearson Prentice-Hall, 2004
Truss Lateral Buckling(Schodek fig. 4.30)
Illustrations: Daniel L. Schodek: Structures, fifth edition; Pearson Prentice-Hall, 2004
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 sizesPotential for stress reversalPotential buckling failure modes and approaches to preventingOverall lateral stability (lateral-torsionalbuckling)Member redundancy: Determinate vs. Indeterminate Trusses
Truss Design Considerations
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Illustrations: Daniel L. Schodek: Structures, fifth edition; Pearson Prentice-Hall, 2004
Truss Stability & Determinacy(Schodek fig. 4.18)
Illustrations: Daniel L. Schodek: Structures, fifth edition; Pearson Prentice-Hall, 2004
Truss Stability & Determinacy(Schodek fig. 4.18)
Illustrations: Daniel L. Schodek: Structures, fifth edition; Pearson Prentice-Hall, 2004
Truss Stability & Determinacy(Schodek fig. 4.18)
Illustrations: Daniel L. Schodek: Structures, fifth edition; Pearson Prentice-Hall, 2004
Truss Stability &
Determinacy(Schodek fig. 4.05)
Truss Determinacy Formula
n = 2j – 3 → for determinacyn = Number of truss barsj = Number of joints
n > 2j -3 → indeterminaten < 2j -3 → unstable
Illustrations: Daniel L. Schodek: Structures, fifth edition; Pearson Prentice-Hall, 2004
n = 8, j = 62(6)-3=9 >8 ∴Unstable!
n = 9, j = 6 2(6)-3=9 =9 O.K.
n = 10, j = 62(6)-3=9 < 10 → indeterminate, but stable