According to IS:800 (1971), what is the minimum thickness requirement for a vertically stiffened web plate in a steel girder?

Introduction / Context:
Plate girders with vertical stiffeners require a minimum web thickness to prevent local buckling and to ensure stability. IS:800 (1971) provides this codal requirement.

Given Data / Assumptions:

• Standard: IS:800 (1971)
• Web plate is vertically stiffened
• d = clear depth of web between flanges

Concept / Approach:
The minimum thickness is derived from buckling and fabrication considerations. For vertically stiffened webs, the limit is expressed as t_w ≥ d/250.

Step-by-Step Solution:
Case: vertically stiffened girder webCodal limit: t_w ≥ d/250

Verification / Alternative check:
Other codes and design guides confirm that d/250 is standard for stiffened webs, while unstiffened webs have stricter limits.

Why Other Options Are Wrong:

• d/85: too conservative
• d/200, d/225: not as per IS:800

Common Pitfalls:
Confusing clear depth with overall depth; applying unstiffened criteria mistakenly.

Final Answer:
d/250