Trusses Method of Joints

1. Trusses Method of Joints Engr . Saeed A Maitlo Lecturer Institute Of Biomedical Technology ,LUMHS Jmashoro.

2. What is a truss. A truss is an assembly of linear members connected together to form a triangle or triangles that convert all external forces into axial compression or tension in its members. • A rigid framework, as of wooden beams or metal bars, designed to support a structure, such as a roof.

3. Method of Joints • If a truss is in equilibrium, then each of its joints must also be in equilibrium • The method of joints consists of satisfying the equilibrium conditions for the forces exerted “on the pin” at each joint of the truss

4. Method of Joints • If a truss is in equilibrium, then each of its joints must be in equilibrium. • The method of joints consists of satisfying the equilibrium equations for forces acting on each joint. ∑ Fx= 0 ∑Fy= 0

5. Method of Joints • Recall, that the line of action of a force acting on a joint is determined by the geometry of the truss member. • The line of action is formed by connecting the two ends of each member with a straight line. • Since direction of the force is known, the remaining unknown is the magnitude of the force. Joint A Joint B Tension Force Joint B Joint A Compression Force

6. Method of Joints Upper Cord members Verticals Diagonals Lower Cord Members

7. Method of Joints Gusset Plate Weld Idealized joint – members connected by a frictionless pin

8. Method of Joints Upper chord in compression Lower chord in tension This is a Pratt truss

9. Upper chord in compression Lower chord in tension This is a Howe truss