MIT Design Truss Analysis

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Truss AnalysisTruss Analysis

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Review: Member DesignReview: Member Design

! Compression elements have lower stresses due

to buckling

Pcr = 2EI/(kL)2

! When using graphic statics for truss analysis,

use clockwise convention to determine if an

element is in tension or compression.

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Truss LectureTruss Lecture

! Moments of forces for finding reactions

! Method of joints for analyzing trusses

! Graphical analysis for analyzing trusses

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Three Equations of EquilibriumThree Equations of Equilibrium

1. Sum of vertical forces must be zero

Fy = 0

2. Sum of horizontal forces must be zero

Fx = 0

3. Sum of moments must be zero

M = 0

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Moment EquilibriumMoment Equilibrium

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Moment of ForceMoment of Force

M = Fa

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Moment EquilibriumMoment Equilibrium

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Crane CounterweightCrane Counterweight

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Equilibrium of Ski Lift TowerEquilibrium of Ski Lift Tower

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Eiffel TowerEiffel Tower

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Cantilevered StreetlightCantilevered Streetlight

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Weight of LampWeight of Lamp

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Reactions at SupportsReactions at Supports

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TrussesTrusses

! Rotational Equilibrium Sum of the moments must equal zero.

Use to calculate reactions at

supports and to find internal forces

! Trusses are an efficient way to carry

loads with minimal material

! Look for examples of moment

equilibrium around you