In transformed section analysis for reinforced concrete, the area considered in compression equals the concrete area in compression plus the reinforcement area converted using the modular ratio. What is this combined area called?

Difficulty: Easy

Correct Answer: equivalent section

Explanation:


Introduction / Context:
When analyzing composite concrete–steel sections under bending, we often 'transform' the steel into an equivalent area of concrete using the modular ratio m = Es/Ec. This permits the use of simple elastic beam theory on a homogeneous 'equivalent' section, enabling the calculation of neutral axis, stresses, and curvature without explicitly dealing with two materials in parallel.


Given Data / Assumptions:

  • Concrete is uncracked in compression.
  • Steel reinforcement in compression is converted to concrete area using modular ratio m.
  • Objective: name of the combined concrete+transformed steel area in compression.


Concept / Approach:
By multiplying the steel area by m, we obtain an area that, under the same strain, carries the same force as the original steel. Adding this to the concrete area gives the 'equivalent section' used for elastic analysis. The term 'cracked section' refers to tension-side concrete being ignored after cracking, which is not the same definition as requested here.


Step-by-Step Solution:

Determine modular ratio: m = Es/Ec.Transform steel in compression: A_s,comp(equiv) = m * A_s,comp.Add to concrete compression area: A_equiv = A_conc,comp + m * A_s,comp.


Verification / Alternative check:

Use A_equiv to locate the neutral axis and verify stresses with elastic formulas (M/I = σ/y = E/R).


Why Other Options Are Wrong:

Transferred section: not a standard term; 'transformed section' is used, but the combined area used in analysis is called the equivalent section.Cracked section: describes ignoring tension concrete, not the transformed compression area.None of these / elastic modular section: not the conventional nomenclature in RCC analysis.


Common Pitfalls:

Confusing 'transformed section method' with the name of the resulting area; the accepted label in exam literature is 'equivalent section'.


Final Answer:

equivalent section

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