Loads and material weights in structural design — pick the correct set of assumptions: • Unit weight of plain concrete ≈ 24 kN/m^3 (≈ 2400 kg/m^3) • Unit weight of reinforced concrete ≈ 25 kN/m^3 (≈ 2500 kg/m^3) • Dead load includes self-weight plus finishes and walls/partitions

Difficulty: Easy

Correct Answer: All of the above statements are correct

Explanation:


Introduction / Context:
Preliminary design and load calculations rely on standard unit weights and proper categorization of loads. Knowing typical densities for plain and reinforced concrete, and what constitutes dead load, is essential for accurate analysis and detailing.


Given Data / Assumptions:

  • Plain concrete unit weight taken as 24 kN/m^3 (≈ 2400 kg/m^3).
  • Reinforced concrete unit weight taken as 25 kN/m^3 (≈ 2500 kg/m^3).
  • Dead load includes self-weight of structural members plus finishes and walls/partitions that are permanently attached.


Concept / Approach:
Codes and handbooks provide standard material unit weights for load take-off. Dead load is the permanent, immovable load on the structure, including self-weight and permanent attachments such as floor finishes and masonry partitions.


Step-by-Step Solution:
Step 1: Compare stated unit weights with standard handbook values: 24 kN/m^3 for plain concrete and 25 kN/m^3 for RC are accepted norms.Step 2: Confirm definition of dead load: self-weight + finishes + walls/partitions meet the definition.Step 3: All three statements are consistent with common design assumptions, so “All of the above” is correct.


Verification / Alternative check:
Cross-check with standard structural design data tables; these values are widely used for preliminary and even detailed design where more accurate take-offs are unnecessary.


Why Other Options Are Wrong:
Only first/second/third: Each omits at least one true statement, so they are incomplete.
None: Incorrect because all listed statements are in line with accepted practice.


Common Pitfalls:

  • Using kg/m^3 and kN/m^3 interchangeably without converting (1 kN/m^3 ≈ 100 kg/m^3 for gravity ≈ 9.81 m/s^2).
  • Forgetting to include finishes and partitions in dead load, leading to underestimation.


Final Answer:
All of the above statements are correct

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