Difficulty: Easy
Correct Answer: 1650 kg/cm2
Explanation:
Introduction:Base plates under steel columns act as short cantilevers between the column footprint and the compression on concrete. The plate is designed in bending, so we must select the correct permissible bending stress for the steel plate material.
Given Data / Assumptions:
Concept / Approach:
In working-stress design, the permissible bending stress for mild steel plates is typically taken around two-thirds of the yield stress. For fy ≈ 2500 kg/cm2 (≈ 250 MPa), 0.66 * 2500 ≈ 1650 kg/cm2, which is commonly used for base plate bending checks.
Step-by-Step Solution:
1) Identify plate as bending element with maximum fiber stress = M * y / I.2) Select permissible bending stress for steel plate ≈ 1650 kg/cm2 in WSD terms.3) Check thickness so computed bending stress ≤ 1650 kg/cm2 under factored/working load as per method used.Verification / Alternative check:
Cross-check against codal tables for base plate design examples; values align with standard practice for mild steel under bending in working-stress format.
Why Other Options Are Wrong:
1500 kg/cm2 is conservative but not the common permissible; 1800 and 1890 kg/cm2 are higher than typical WSD value; 2100 kg/cm2 is overly high.
Common Pitfalls:
Confusing steel bending stress with concrete bearing stress, or mixing limit-state and working-stress numbers.
Final Answer:
1650 kg/cm2
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