Module 2 :
Analysis of Statically Determinate Structures
Lecture
9 :
Example for Trusses
Looking at joint C :
CF is a zero-force member and
Equilibrium of joint E :
and
Equilibrium of joint F :
and
Equilibrium of joint H :
Sign convention: Tension +ve, compression –ve.
Note that we have not obtained the support reactions before finding the member forces. It was not necessary for this specific problem. Find out these reactions at supports G and H and check if joint equilibrium is satisfied at these two joints with the member forces that we have found already.
CF is a zero-force member and 
and 
and 
