# Structural Analysis Questions and Answers – Space Trusses

This set of Structural Analysis Questions and Answers focuses on “Space Trusses”.

1. What is the simplest element of a space truss?
a) triangle
b) tetrahedron
c) octahedron
d) pyramid

Explanation: Simplest element of a space truss is built on a basic triangle.

2. How many additional members are required to make a simple space truss from a basic tetrahedral element?
a) 1
b) 2
c) 3
d) 4

Explanation: Three additional members forming 1 extra joint are needed to form multi-connected tetrahedrons aka simple space truss.

3. How many equations are solved per joints while solving space trusses?
a) 1
b) 2
c) 3
d) 4

Explanation: 3 equations are solved per joint. Forces are conserved in all the three directions.
B= no. of bars of the truss
R= total no. of external support reaction
J= total no. of joints.

4. If B=6, R=6 and J= 4, then the truss is:-
a) statically determinate
b) statically indeterminate
c) stable
d) unstable

Explanation: B + R = 12 = 3*J. So, truss is statically determinate. Without further insight, we can’t predict stability.

5. If B=6, R=7 and J= 4, then the truss are:-
a) statically determinate
b) statically indeterminate
c) stable
d) unstable

Explanation: B + R = 13 > 3*J. So, truss is statically indeterminate. Without further insight, we can’t predict stability.

6. If B=6, R=5 and J= 4, then the truss is:-
a) statically determinate
b) statically indeterminate and stable
c) stable
d) unstable

Explanation: B + R = 11 < 3*J. So, the truss will be unstable.

7. The external stability of the space truss requires that the support reactions keep the truss in force equilibrium about all the axes.
State whether the above statement is true or false.
a) true
b) false

Explanation: They require moment equilibrium about all the axes as well.

8. What is the degree of freedom of space roller joint?
a) 0
b) 1
c) 2
d) 3

Explanation: It can move along a slot in the base plane.

9. According to assumptions, which type of joints are used in space truss?
a) pin joint
b) ball and socket joint
c) fixed joint
d) roller joint

Explanation: To treat every member of a space truss as axial- force members, every joint is assumed to be of ball & socket type.

10. How many reaction forces are involved in a short link type of joint?
a) 1
b) 2
c) 3
d) 4

Explanation: One force is unknown which acts in line with the link.

11. How many reaction forces are involved in a roller type of joint?
a) 1
b) 2
c) 3
d) 4

Explanation: One unknown force acts perpendicular to the plane of roller.

Sanfoundry Global Education & Learning Series – Structural Analysis.

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