Engr Help

Example - Analysis of Trusses using the Method of Joints (continued)

Next construct a FBD of the members at joint A and express the equations of

equilibrium. Assume all truss members are in tension.

Σ F_y = 0 gives - 1600 + F_AB (1/√2) = 0 or F_AB = 1600 (√2)

Σ F_x = 0 gives F_AE - 800 + 1600 (√2) (1/√2) or F_AE = - 800

So the force in member AE is 800 N in compression.

Next contruct a FBD at joint C. Note forces in members BC and CD can be

determined without first finding the support reactions.

For equilibrium Σ Fx = 0 - F_BC (1/√2) + 800 = 0 F_BC = 800(√2) N

and Σ Fy = 0 - 800(√2) (1/√2) – F_CD = 0 F_CD = - 800 N