Civil Engineering PE Structural Analysis of Trusses 4

Question 1

In the analysis of a space (3D) truss, the determinacy condition is m + r = 3j. A space truss has 30 members, 6 reactions, and 12 joints. The truss is:

Accepted Answer

Statically determinate

Answer

Statically indeterminate to 1st degree

Answer

A mechanism

Answer

Statically indeterminate to 3rd degree

Question 2

The influence line for the force in a diagonal tension member of a Pratt truss shows that the member carries tension when the live load is placed:

Accepted Answer

In the panel where the member is located and extending to one support

Answer

Only directly over the member

Answer

Across the entire span

Answer

Only at the joint where the member terminates

Question 3

A composite truss has steel top and bottom chords with timber web members. Under gravity loading, which chord is in compression?

Accepted Answer

Top chord

Answer

Bottom chord

Answer

Both chords simultaneously

Answer

Neither chord; all compression goes to web members

Question 4

For the Cremona (graphical) method of truss analysis, forces are found by:

Accepted Answer

Drawing a force polygon (Maxwell diagram) where member forces close the polygon at each joint

Answer

Summing moments about strategic cut sections

Answer

Using stiffness matrices at each node

Answer

Applying virtual work to each member independently

Question 5

A truss bridge deck girder delivers concentrated loads only at panel points. This is a critical requirement because:

Accepted Answer

Loads applied between joints would cause bending in chord members, violating the two-force member assumption

Answer

Panel points are the strongest locations in the chord

Answer

Diagonal members cannot carry transverse loads

Answer

Bridge codes prohibit mid-panel loading

Question 6

In a Howe truss under gravity loading, the diagonal members are oriented such that they carry:

Accepted Answer

Compression

Answer

Tension

Answer

Zero force at midspan and tension at ends

Answer

Bending and shear

Question 7

A redundant (statically indeterminate) truss requires which additional condition beyond equilibrium to solve member forces?

Accepted Answer

Compatibility of deformations (force-deformation relationships)

Answer

A larger free-body diagram cut

Answer

Additional moment equations about more joints

Answer

Higher safety factors on all member forces