The structure shown below is a truss which is
pinned to the floor at point A and also at point H. For this
structure:
A. Draw a Free Body Diagram showing all support forces and loads.
B. Determine the value of all the support forces acting on the
structure.
C. Determine the force in member FB by any method.
Unless otherwise indicated, all joints and support points are
assumed to be pinned or hinged joints.
Solution:
PARTS A & B:
STEP 1: 
Draw a free body
diagram showing and labeling all load forces and support
(reaction) forces, as well as any needed angles and dimensions.
STEP 2: Break any forces not already in x and y
direction into their x and y components.
STEP 3: Apply the equilibrium conditions.
Sum Fx = Ax + 8,000 lbs = 0
Sum Fy = Ay + Hy - 10,000 lbs =
0
Sum TA= Hy(4 ft) - (10,000 lbs)(4 ft) -
(8,000 lbs)(15 ft) = 0
Solving for the unknowns:
Hy = 40,000 lbs; Ax = -8,000 lbs; Ay
= -30,000 lbs
PART C - Now find internal force in member FB by section
method. Cut horizontally through members BC, FB, and FG. Analyze
lower section.
STEP 1: 
Draw a free body diagram of the lower section (see
diagram).
STEP 2: Resolve all forces into x and y
components (see diagram).
STEP 3: Apply equilibrium conditions:
Sum Fx = FB cos (51.3o) - 8,000 lbs = 0
Sum Fy = BC - 30,000 lbs + FB sin (51.3o) -
GF + 40,000 lbs = 0
Sum TB = (-8,000 lbs)(5 ft) - GF(4 ft) + (40,000
lbs)(4 ft) = 0
Solving for the unknowns: FB = 12,8000 lbs (t); GF = 30,000 lbs
(c); BC = 10,000 lbs (t)