Class 3 Review

Class 3 Review - Evaluate the appropriate expression(2-D or 3-D truss For the 2-D case 2*Number of Joints – Number of Links – 3 = 2*J – L –

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ENGR 111 - Track A 1 Truss Class 03
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ENGR 111 - Track A 2 How are trusses built? Links and Joints Trusses are built by joining bars (links) to form a lattice-like structure. The joints transmit forces from one link to another but are incapable of  transmitting torques. This is one link! This is one  link! Links  (a.k.a.  bars) Joints
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ENGR 111 - Track A 3 Calculating minimum number of links Q: How do I find out how many links are necessary  to create stable trusses? 2-D:  No. of Links Needed = 2*No. of Joints -3 3-D:  No. of Links Needed = 3*No. of Joints -6
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ENGR 111 - Track A 4 How to determine stability of a truss Now you can determine whether your truss is unstable (underconstrained, links missing) trusses: a truss that can slide and  rotate as a whole.  stable (correct number of links) overconstrained (too many links). 
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Unformatted text preview: Evaluate the appropriate expression (2-D or 3-D truss). For the 2-D case: 2*Number of Joints – Number of Links – 3 = ? 2*J – L – 3 = ? For the 3-D case: 3*Number of Joints – Number of Links – 6 = ? 3*J – L – 6 = ? If positive, the truss is unstable, you need to add links. If zero, the truss is stable, good job! If negative, the truss is over constrained, you could remove some links. ENGR 111 - Track A 5 Cross-bracing Q: How do I stabilize an unstable truss? Stabilize an “underconstrained” or wobbly truss by adding diagonals or “cross-braces” Convert all quadrilaterals to triangles: Design guideline: “add short cross-braces” (B) is better than (C) (A) Unstable (B) Short brace (C) Long brace...
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This note was uploaded on 04/27/2009 for the course ENGR 111 taught by Professor Walker during the Spring '07 term at Texas A&M.

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Class 3 Review - Evaluate the appropriate expression(2-D or 3-D truss For the 2-D case 2*Number of Joints – Number of Links – 3 = 2*J – L –

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