Jawaharlal Nehru Technological University Hyderabad B.Tech III DESIGN OF STEEL STRUCTURES Previous Question Paper (January/February - 2021 - R16)

Bolted connections are widely used in steel construction due to their ease of assembly and reliability. The advantages include:

• Rapid assembly: Bolted connections can be installed quickly without the need for skilled labor or specialized equipment like welding sets.
• Immediate load capacity: Joints can carry design loads immediately upon tightening, unlike field welding which requires cooling time.
• Ease of inspection: The quality of a bolt and its tightness can be visually inspected or checked with a torque wrench.
• Structural modifications: Bolted joints allow for easy dismantling, relocation, or replacement of structural members.
• Safety: They do not produce fire hazards or toxic fumes, making them safer for site work.

The disadvantages include:

• Reduction in cross-section: Bolt holes reduce the net area of the connected members, requiring larger sections to compensate for the loss of strength.
• Vibration sensitivity: In structures subjected to heavy vibrations or dynamic loads, bolts may loosen over time unless locking devices are used.
• Cost: The cost of material (bolts, nuts, washers) and the labor involved in drilling or punching holes can be higher than welding.
• Stress concentration: Holes act as stress raisers, which can lead to fatigue issues in members subjected to cyclic loading.

Welded joints are classified based on the relative orientation of the members being joined and the type of weld used. The primary types are:

• Butt Welds (Groove Welds): Used to join members placed end-to-end or in the same plane. These are further classified based on the groove shape, such as square, V, U, J, or bevel grooves. They are highly efficient as they provide a continuous transition of stress.
• Fillet Welds: The most common type of weld, used for lap joints or T-joints where the weld is deposited in the corner formed by the two members. The cross-section is approximately triangular.
• Slot and Plug Welds: Used to connect two overlapping members by filling a hole (plug) or an elongated slot in one member with weld metal. These are typically used to supplement fillet welds or to prevent buckling in thin plates.
• Spot Welds: Primarily used in thin sheet metal construction, where the weld is made at a specific point by applying pressure and electric current.
• Seam Welds: A continuous series of spot welds used to create a leak-proof joint in thin plates.