For example if we have two unknown vertical forces

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Unformatted text preview: example, if we have two unknown vertical forces and one unknown horizontal force, then solve for the horizontal force first using ∑ FX = 0. 3. If the answer for an unknown comes out as negative number then the direction of the unknown force is opposite to that drawn on the FBD. APPLICATIONS For a given load on the platform, how can we determine the forces at joint A and the force in the link (cylinder) BC? A steel beam is used to support roof joists. How can we determine the support reactions at each end of the beam? TWO-FORCE MEMBERS The solution of some equilibrium problems can be simplified if we can recognize members that are subjected to forces at only two points (e.g., at points A and B). Applying the equations of equilibrium to such member one can determine the resultant forces at A and B. These resultants must be equal in magnitude and act in the opposite directions along the line joining points A and B. EXAMPLE Two-force Members In the above figures, since the directions of the resultant forces at A and B are known (along the line joining points A and B), all AB members can be considered two-force members if their weights are neglected. This...
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This note was uploaded on 10/31/2010 for the course CEE CE 221 taught by Professor Baladi during the Fall '10 term at Michigan State University.

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