Overlap of Batten Plates in Welded Connections

Introduction:
Welded connections are used in steel structures to join members. Batten plates are used to reinforce welded connections. The overlap of batten plates with the main members is an important factor in the design of welded connections. In this context, the question asks about the minimum overlap of batten plates with the main members.

Answer:
The correct answer is option 'B', i.e., 5t. The following points explain this answer in detail:

- Batten plates are used to provide additional strength to welded connections by increasing the effective thickness of the joint. They are usually made of the same material as the main members and are welded to them.
- The overlap of batten plates with the main members is essential to ensure that the load is transferred from the batten plate to the main member through the weld. If the overlap is inadequate, the weld may fail due to a shear force or tensile stress.
- The overlap of batten plates is usually expressed as a multiple of the thickness of the batten plate (t). The most common values are 2t, 3t, 4t, 5t, 6t, 7t, and 8t. The recommended value depends on the type and size of the members, the design loads and the welding procedure.
- According to the Indian Standard Code of Practice for Structural Steel (IS 800:2007), the minimum overlap of batten plates should be 5t for fillet welds and 6t for butt welds. This is based on experimental studies and is considered to be a safe and practical value for most practical situations.
- The 5t overlap for fillet welds means that the batten plate should extend at least 5 times its thickness beyond the end of the main member. For example, if the batten plate is 10 mm thick, the overlap should be at least 50 mm. Similarly, for butt welds, the overlap should be at least 6 times the thickness of the batten plate.
- It should be noted that the overlap of batten plates is not the only factor that affects the strength of welded connections. Other factors such as the size and shape of the weld, the quality of the weld, the type of loading, and the material properties also play a crucial role.
- In conclusion, the overlap of batten plates with the main members in welded connections should be at least 5 times the thickness of the batten plate for fillet welds and 6 times for butt welds, according to the IS 800:2007. However, the designer should consider all the relevant factors and consult the relevant codes and standards before finalizing the design.