In steel fabrication using fillet welds, the permissible gap between flange plates and web plates should not exceed which maximum value?

Introduction / Context:
When connecting flange plates to web plates with fillet welds (e.g., built-up plate girders), the fit-up gap affects weld quality and load transfer. Excessive separation can reduce throat fusion, promote defects, and necessitate oversizing beyond what was designed. Hence codes and good practice set a maximum permissible gap for fillet-welded connections.

Given Data / Assumptions:

• Connection: fillet welds between web and flange plates.
• Quantity: maximum allowable gap between mating surfaces.
• Standard practice allows small separations with limits; beyond that, corrective measures are required.

Concept / Approach:
Fillet welds are sized based on required throat thickness. If the parts are separated, the effective throat is compromised. Up to a small limit (commonly taken as 1.5 mm), the joint may still be accepted or the weld size marginally increased; larger gaps call for additional measures such as backing bars, surfacing, or re-fitting to restore proper contact.

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