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CE 2010 Handout #16 Sections 6.1-6.2 (Exam #2)

Learning Objectives

 Define a truss.

 List and explain the assumptions necessary for truss analysis.

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

Review: Force Systems

 Concurrent

 Non-Concurrent

Trusses

 Carry considerably more ______________ than a beam.

 Consist of long, slender, 2-force members pinned together at (frictionless) joints forming

______________________.

 Little __________________ strength. Loads can only be applied in-plane

 Examples: roofs, towers, cranes, _______________

Assumptions

 Neglect member ____________ since it’s negligible compared to applied loads.

 Loads are ________________.

 Members are in tension or compression. Assume that all members are in ____________.

 Members in compression will have a _______________ value/sign.

 Loads are only applied to ______________. Therefore, the joints are in equilibrium.

 Method of Joints: _____________ and ______________ at each joint to find internal member

forces. Solve for _____ unknowns.

Strategy:

1. Find external reactions.

2. Start at a joint with 2 unknowns.

3. Move from joint to joint until all member forces are found.

4. Take advantage of symmetry!

CE 2010 Handout #16 Sections 6.1-6.2 (Exam #2)

Ex #1 The truss, used to support a balcony, is subjected to the loading shown. Approximate each joint as a pin and determine the force in each member. State whether the members are in tension or compression. Set P1 = 800 lb, P2 = 0.

Ex. #2 Determine the force in members DE, CD and CE of the truss using the method of joints, and state whether each member is in tension or compression.