Civil Engineering PE Structural Analysis of Trusses 2

Question 1

A Pratt truss has vertical members under compression and diagonal members under tension when subjected to gravity loads. Which statement correctly describes the force distribution in a Pratt truss?

Accepted Answer

Diagonals are in tension and verticals are in compression

Answer

Diagonals are in compression and verticals are in tension

Answer

Both diagonals and verticals are in compression

Answer

Both diagonals and verticals are in tension

Question 2

Using the method of sections, a cut through a truss exposes three unknown member forces. To solve for all three unknowns, you need to apply which set of equilibrium equations?

Accepted Answer

ΣFx = 0, ΣFy = 0, and ΣM = 0 about a strategic point

Answer

ΣFx = 0 and ΣFy = 0 only

Answer

ΣM = 0 about three different points

Answer

ΣFx = 0 and ΣM = 0 about one point

Question 3

A truss panel point has two members meeting at 45° and 90° to the horizontal, with no external load applied. The member at 90° (vertical) carries zero force. What is the force in the 45° member?

Accepted Answer

Zero

Answer

Equal to the reaction force

Answer

Equal to the applied load divided by cos(45°)

Answer

Cannot be determined without additional information

Question 4

For a simply supported Pratt truss with span L and panel width d, how many panels does the truss have if the top chord members are all horizontal and there are 8 vertical members?

Accepted Answer

8

Answer

7

Answer

9

Answer

6

Question 5

A K-truss has members arranged in a K-pattern. Compared to a Pratt truss of the same span and load, the K-truss is typically used to:

Accepted Answer

Reduce the unsupported length of compression chord members

Answer

Increase the number of panel points for load application

Answer

Eliminate diagonal members to reduce weight

Answer

Allow for variable depth along the span

Question 6

In a Warren truss without vertical members, all interior members are diagonals. Under a midspan point load, the diagonal immediately to the left of midspan is in what state?

Accepted Answer

Compression

Answer

Tension

Answer

Zero force

Answer

Bending

Question 7

A truss is said to be 'determinate' when m + r = 2j. For a truss with 15 members and 3 reactions, how many joints must it have to be statically determinate?

Accepted Answer

9

Answer

12

Answer

6

Answer

18