In steel fabrication using fillet welds, the permissible gap between flange plates and web plates should not exceed which maximum value?
-
A0.5 mm
-
B0.75 mm
-
C1.0 mm
-
D1.25 mm
-
E1.5 mm
Answer
Correct Answer: 1.5 mm
Explanation
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.
Step-by-Step Solution:
Identify the interface: flange-to-web plate junction in a welded girder.Apply the fabrication tolerance for fit-up: maximum permitted gap = 1.5 mm.Select 1.5 mm from the options as the limiting value.Verification / Alternative check:
Workshop quality control typically flags larger separations for rework; WPS/PQR documents often note gap tolerances and remedies.Why Other Options Are Wrong:
0.5 / 0.75 / 1.0 / 1.25 mm: stricter than necessary; while acceptable, they are not the maximum permissible gap widely adopted for fillet welds in such joints.Common Pitfalls:
Assuming any visible gap is acceptable without adjusting weld size or procedure.Ignoring inspection criteria related to root opening and heat input, which affect weld integrity.Final Answer:
1.5 mm