In case of a simply supported I-section beam of span L and loaded with a central load W, the length of elasto-plastic zone of the plastic hinge, is

• A. <img src="/_files/images/civil-engineering/theory-of-structures/97-21-185-1.png">
• B. <img src="/_files/images/civil-engineering/theory-of-structures/97-21-185-2.png">
• C. <img src="/_files/images/civil-engineering/theory-of-structures/97-21-185-3.png">
• D. <img src="/_files/images/civil-engineering/theory-of-structures/97-21-185-4.png">
• E. none of these.