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Unformatted text preview: STRUCTURAL STRUCTURAL ANALYSIS ANALYSIS Method Of Joints Method Of Joints LEARNING OBJECTIVES LEARNING OBJECTIVES Be able to define a simple truss Be able to define a simple truss Be able to determine the forces in Be able to determine the forces in members of a simple truss using members of a simple truss using the method of joints the method of joints Be able to identify the zeroforce Be able to identify the zeroforce members members PREREQUISITE KNOWLEDGE PREREQUISITE KNOWLEDGE Units of measurement Units of measurement Trigonometry concepts Trigonometry concepts Rectangular component concepts Rectangular component concepts Equilibrium of forces in 2d Equilibrium of forces in 2d SIMPLE TRUSS A simple truss is a planar truss (2D truss) which begins as a triangular element and can be expanded by adding two members and a joint. For these trusses, the number of members (M) and the number of joints (J) are related by the equation M = 2(J) – 3 Check if the following truss is a simple truss EXAMPLE M = 11 & J = 7 M = 2(J) – 3 11= 2(7)3 11 = 11 SOLUTION Simple Truss ! ANALYSIS AND DESIGN Assumptions Two assumptions are made for the analysis of trusses: 1. All loads are applied at the joints. 2. The members are joined together by smooth pins. The two assumptions imply that the members act as twoforce members (pure axialforce member), either in tension or compression. Note: Compressive members are made thicker to prevent buckling. METHOD OF JOINTS The method of joints involves the analyses of forces in each truss member using 2D equilibrium equations at each joint (pin). Since the pin does not carry moment, the 2D equilibrium equations are: ∑ F = 0 and ∑ F = 0 Find the forces in members AB and BC EXAMPLE SOLUTION Use the method of joints and draw a free body diagram at B ∑ F x = 0; 500 – F BC...
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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.
 Fall '10
 Baladi

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