Structural Analysis MCQ Questions & Answers | Civil Engineering

To determine the degree of static indeterminacy (Ds) for a rigid-jointed plane frame, use the formula: Ds = (3m + R) - (3j + A)

where:

m = number of members,
R = number of reaction components,
j = number of joints,
A = number of internal hinges (A = 0 in this case).

Given:

m = 15 (members),
R = 3 (reaction components),
j = 14 (joints),
A = 0 (no internal hinges).

Substitute these values into the formula:

Ds = (3 * 15 + 3) - (3 * 14 + 0)

Ds = (45 + 3) - (42)

Ds = 48 - 42 = 6

Thus, the degree of static indeterminacy is 6.

The nominal maximum size of the aggregates in heavily reinforced concrete members is determined to ensure proper compaction and minimal voids in the structure.

1. To avoid interference with the reinforcement, the size of the aggregate should be restricted to 5 mm less than the minimum clear distance between the main bars.

2. Similarly, to maintain adequate cover, the size of the aggregate should also be restricted to 5 mm less than the minimum cover to the reinforcement.

3. Therefore, the nominal maximum size of the aggregates should be the smaller of these two criteria to satisfy both conditions.

This ensures proper placement and compaction of the concrete mix around the reinforcement.

1. Wheel Load: When a train of wheel loads moves over a simply supported girder, the bending moment changes depending on the position of the wheel loads.

2. Influence Line: The influence line for bending moment indicates that the maximum bending moment occurs when the wheel load is at a specific point on the span.

3. Critical Position: For the maximum bending moment to occur, the critical position of the wheel load is generally at a distance from the support, calculated based on the span and the load distribution.

4. Conclusion: Hence, the maximum bending moment due to a train of wheel loads on a simply supported girder always occurs under a wheel load.

Therefore, the correct answer is Option B: Always occurs under a wheel load.