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CE 2010 Handout #17 Sections 6.3-6.4 (Exam #2)

Learning Objectives

 Identify zero force members

 Calculate internal forces in truss members using the method of sections.

Zero Force Members Ex. #1 & #2 For the given loading, determine the zero force members in the truss shown.

Method of Sections Analysis

 If an entire truss is in equilibrium, then if it is cut into two sections, each section is also in

equilibrium.

 Method can be used to solve for three unknown member forces. Available equations:

_________________ __________________ ____________________ Method of Sections Strategy

 Locate a section cut to obtain desired member forces. Try to avoid cutting through more than 3

members.

 Find external reactions using the whole truss (if necessary).

 Make section cut and choose the side with the least number of forces.

 Use equations of equilibrium to solve for up to 3 unknown internal forces.

 M = 0 can be used more than once if desired. Choose its location wisely to avoid having more

than 1 unknown force in your equation. Hint: you can M about a point not on your section.

CE 2010 Handout #17 Sections 6.3-6.4 (Exam #2)

Ex. #3 The truss shown serves to support the

deck of a bridge. Find the force in members

EF, FI, and HI. State whether each member is

in tension or compression.

Ex #4 The roof truss supports the vertical loading

shown. Determine the force in members BC, CK

and KJ and state if these members are in tension

or compression.