While designing rectangular base plates per legacy steel code provisions (IS:800-1982), the permissible bending stress constant fbct to be used in thickness calculations is taken as:

Introduction / Context:
Base plates transfer concentrated column loads to concrete pedestals or foundations. Thickness design treats the plate as a slab on elastic or bearing medium, limiting plate bending stresses to an allowable value. In older working-stress formats (IS:800-1982), a permissible bending stress constant fbct is used for sizing.

Given Data / Assumptions:

• Legacy code basis: working-stress design for structural steel.
• Typical mild steel yield stress considered ≈ 2500 kg/cm2 (≈ 250 MPa).
• Permissible bending stress taken as a fraction of yield.

Concept / Approach:

In working-stress design, the permissible bending stress is typically around 0.66 * fy for mild steel. Converting ≈ 0.66 * 2500 kg/cm2 gives ≈ 1650 kg/cm2, which is the standard constant employed in plate thickness formulae of that era.

Step-by-Step Solution:

Verification / Alternative check:

Handbooks accompanying IS:800-1982 list identical working-stress limits for bending in plates. Though modern limit-state design uses factored actions and partial safety factors, legacy multiple-choice questions still reference this constant.

Why Other Options Are Wrong:

• 1500 and 1800/1890/2000 kg/cm2: Do not match the standard permissible bending constant derived from 0.66 * fy for mild steel in the old code framework.

Common Pitfalls:

• Mixing modern limit-state values with working-stress allowable stresses.
• Using concrete bearing stress values instead of steel bending for plate sizing.

Final Answer:

1650 kg/cm2