Steps for Method of Joint:
To find force in member of the truss by this method, the three Steps which are given below are followed.
Step-1: Calculate reaction at support.
Step-2: Make direction of force in the entire member; you make the entire member as tensile. If on solving problems, any value of force comes to negative this means the assumed direction is wrong, and that the force is compressive.
Step-3: Select a joint where two members are unknown to us.
1- First select that joint on which the three or less than three forces are acting. Then apply lami's theorem on that particular joint.
Step-4: Draw FBD of selected joint as whole truss is in equilibrium thus the selected joint will be in equilibrium and it should satisfy equilibrium conditions of coplanar concurrent force system.
∑V = 0 and ∑H = 0
Step-5: Now select the joint on which the 4 forces, 5 forces etc are acting. On that joint apply the resolution of forces method.
Note: If three forces act at joint and 2 of them are along the same straight line, then for the equilibrium of joint, the 3rd force should be equal to zero.