Explanation Method adopted: Method of section. Assumptions: Consider the state of member as the tension where the force is pulling the member and as compression where the force is pushing the member. Consider the force indicating the right side as positive and left side as negative in horizontal components of forces. Consider the force indicating upward is taken as positive and downward as negative in vertical components of forces. Consider clockwise moment as negative and anti-clock wise moment as positive wherever applicable. Apply the Equation of equilibrium wherever applicable. If only two non-collinear members form a truss joint and no external load or support reaction are applied to the joint, the two members must be zero-force members. If three members form a truss joint for which two of the members are collinear, and the third member is a zero-force member provided no external force or support reaction is applied to the joint. Joint H : Show the free-body diagram of the joint B as in Figure 1. Using Figure 1, Zero-force members: Three members AB , BC , and BN forming a truss joint B for which two of the members AB and BC are collinear, and the third member BN is a zero-force member. Since, no external force or support reaction is applied to the joint B . Thus, the zero force members at joint B is B N _ . Joint N : Show the free-body diagram of the joint N as in Figure 2. Using Figure 2, Zero-force members: The force in the member BN is zero. Three members AN , NM , and NC forming a truss joint N for which two of the members AN and NM are collinear, and the third member NC is a zero-force member. Since, no external force or support reaction is applied to the joint N . Thus, the zero force members at joint N is N C _ . Joint D : Show the free-body diagram of the joint D as in Figure 3. Using Figure 3, Zero-force members: Three members CD , DE , and DO forming a truss joint D for which two of the members CD and DE are collinear, and the third member DO is a zero-force member. Since, no external force or support reaction is applied to the joint D . Thus, the zero force members at joint D is D O _ . Joint O : Show the free-body diagram of the joint O as in Figure 4. Using Figure 4, Zero-force members: The force in the member OD is zero. Three members MO , OE , and CO forming a truss joint O for which two of the members MO and OE are collinear, and the third member CO is a zero-force member. Since, no external force or support reaction is applied to the joint O . Thus, the zero force members at joint O is C O _ . Joint L : Show the free-body diagram of the joint L as in Figure 5. Using Figure 5, Zero-force members: Three members ML , LK , and LE forming a truss joint L for which two of the members ML and LK are collinear, and the third member LE is a zero-force member. Since, no external force or support reaction is applied to the joint L . Thus, the zero force members at joint L is L E _ . Joint H : Show the free-body diagram of the joint H as in Figure 6. Using Figure 6, Zero-force members: Three members GH , HI , and HJ forming a truss joint H for which two of the members GH and HI are collinear, and the third member HJ is a zero-force member. Since, no external force or support reaction is applied to the joint H . Thus, the zero force members at joint H is H J _ . Joint J : Show the free-body diagram of the joint J as in Figure 7. Using Figure 7, Zero-force members: The force in the member HJ is zero. Three members JK , JI, and GJ forming a truss joint J for which two of the members JK and JI are collinear, and the third member GJ is a zero-force member. Since, no external force or support reaction is applied to the joint J . Thus, the zero force members at joint J is G J _ . Entire truss: Show the free body diagram of entire truss as in Figure 8. Using Figure 8, Reactions: Moment about point A : Determine the vertical reaction at point I by taking moment about point A . ∑ M A = 0 I y ( 16 ) − 2 ( 12 ) − 3 ( 10 ) − 5 ( 8 ) − 2 ( 4 ) = 0 (I) Along the vertical direction: Determine the vertical reaction at point A by resolving the vertical component of forces