NEF1205 - Session 9- Method of Joints & Zero Force Members PDF

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Summary

How to calculate different forces on truss using method of joints and zero force members...

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NEF1205 Session 9 – Method of Joints & Zero Forces Members – Tute Sheet Conceptual Questions

Which of the following statements is correct?

Q1.

a. Due to the nature of trusses, only two type of internal forces can exist within the members of the truss. These are; i. Compression and tension forces. ii. Compression and normal forces. iii. Normal and tension forces. iv. Friction and tension forces. b. What is a zero force member? i. It is a member which support no compressive loading (i.e., they do not carry any compressive forces). ii. It is a member which support no tensile loading (i.e., they do not carry any tensile forces). iii. It is a member which support no loading (i.e., they do not carry any force). iv. It is a member which support no shear loading (i.e., they do not carry any shear forces). c. Zero force members are necessary; i. To increase the stability of a truss during construction. ii. To provide added support if the loading is changed. iii. To increase the stability of a truss during construction and to provide added support if the loading is changed. iv. To make a structure statically determinate. d. Two members are considered collinear; i. If the angle between them is 90°. ii. If the angle between them is 180°. iii. If they are zero force members. iv. If they are coplanar. e. How many equilibrium equation can be written for a truss structure? i. The total number of equilibrium equations is 3 times the number of joints in the truss. ii. The total number of equilibrium equations is 2 times the number of joints in the truss. iii. The total number of equilibrium equations is the number of joints in the truss. iv. The total number of equilibrium equations is one and a half times the number of joints in the truss. f.

When analyzing a statically determinate truss, each joint must be in equilibrium and therefore; i. The sum of the forces acting on it is equal to zero and the sum of the moments acting on it is equal to zero. ii. The sum of the forces acting on it is equal to zero. iii. The sum of the moments acting on it is equal to zero. iv. The sum of the horizontal and vertical forces acting on it is equal to zero.

Problems & Exercises

Q1.

Identify the zero force (null) members and joints for the truss structures shown in the following figures.

a.

b.

Q2.

Determine the force in each member of the truss, and state if the members are in tension or compression.

Q3.

Determine the force in each member of the truss, and state if the members are in tension or compression. Set  = 30°.

Q4.

Identify the zero force (null) members and joints for the truss. Determine the force in each member of the truss, and state if the members are in tension or compression.

Q5.

Identify the zero force (null) members and joints for the truss. Determine the force in members a, b, and c of the truss and state if the members are in tension or compression.

References Hibbeler, R. C. (2011). Statics and Mechanics of Materials, in SI units . Pearson Education....