Limit State Method MCQ with answer and solution

Concept

Higher grade reinforcing steels have higher yield strength but lower percentage elongation and ductility compared to lower grade mild steel.

Step-by-step solution

1. Understand the relationship between steel grade and ductility: Ductility is inversely proportional to the characteristic yield strength of the steel. 2. Compare the given grades: Fe 250 (Mild Steel), Fe 415 (HYSD Steel), and Fe 500 (HYSD/TMT Steel). 3. Fe 250 has the lowest yield strength and the highest percentage elongation (minimum 20-22%), making it the most ductile.

Explanation

Ductility is the ability of a material to undergo significant plastic deformation before rupture. As the yield strength of steel increases (from Fe 250 to Fe 500/Fe 550), the carbon content and manufacturing processes generally reduce its percentage elongation (ductility). Therefore, mild steel (Fe 250) has the highest ductility among the commonly used reinforcing steels.

Why the other options are wrong

B: Fe 415 has a higher yield strength and lower percentage elongation than Fe 250. C: Fe 500 has the highest yield strength and lowest ductility among the three options. D: Ductility varies significantly across different grades of steel.

Shortcut

Lower grade of steel = Lower yield strength = Higher elongation = Higher ductility.

Common mistake

Confusing higher strength with higher ductility. Higher grade steels are stronger and stiffer, but less ductile.