In structural steel design, what is the maximum permissible size of a fillet weld placed on the square edge of a plate, considering proper fusion and avoidance of overwelding at the root?
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A1.5 mm less than the plate thickness
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BOne half of the plate thickness
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CEqual to the full plate thickness
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D1.5 mm more than the plate thickness
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ELimited to a maximum of 3 mm regardless of plate thickness
Answer
Correct Answer: 1.5 mm less than the plate thickness
Explanation
Introduction / Context:Fillet weld sizing on square plate edges must respect code rules to ensure sound fusion and to prevent lack-of-fusion defects at the root. Overly large fillets on square edges can trap slag and cause incomplete penetration, compromising connection performance.
Given Data / Assumptions:
- Square (unprepared) plate edge with fillet weld on the edge.
- Standard structural steel practice and code-based detailing rules.
- Objective: determine the upper bound of the leg size for such a fillet weld.
Concept / Approach:Codes and good practice limit the maximum leg size of a fillet weld on a square edge to slightly less than the plate thickness, typically by 1.5 mm. This provides a small root face to avoid overwelding and assists proper heat distribution for fusion without excessive melt-through or distortion.
Step-by-Step Solution:
Identify joint type: fillet weld on square edge (no edge preparation).Apply the maximum fillet size rule: maximum leg size = t_plate − 1.5 mm.Choose the option that states this limit explicitly.Verification / Alternative check:
Detailing guides from steel codes reflect the same limit to encourage proper root fusion.Why Other Options Are Wrong:
Half thickness or full thickness do not address root fusion concerns.More than plate thickness is geometrically and practically unsound.A fixed 3 mm limit is not general and fails for thicker plates.Common Pitfalls:
Ignoring edge condition; applying the rule meant for prepared edges to square edges.Final Answer:
1.5 mm less than the plate thickness