Welded connections are utilized because they are easy to design. They need fewer parts and materials and less fabrication and shop-handling work. A mix of field bolting and shop welding is frequently beneficial for steel form decks.
Welded Connections 101
Field Versus Welded Connection
Field connections can be established with high-strength bolts with connection angles that have been shop welded to a beam without the clearance issues that could occur with an all-bolted connection. Welded connections offer stiffness that might be advantageous if adequately considered in the design.
Because the end of a welded part at a junction cannot rotate concerning the other members there, welded trusses, for instance, deflect less than bolted trusses. The rotation there is essentially the same for column and beam if the end of a shaft is welded to a column.
However, one drawback of welding is that massive welds’ shrinkage must be considered. It is crucial in massive constructions where there would be an accumulative effect. Even a weld that appears decent could be useless if it is poorly done. A well-made, well-engineered weld is more durable than the base metal. Moreover, a weld that has been appropriately formed has the necessary penetration and is not fragile.
Done According to the AWS Criteria
When done in line with American Welding Society (AWS) criteria, common weld types with structural steel meant for welding can be described by note or symbol with the knowledge that a strong connection will be established. Manufacturers should only indicate the amount and size of welding necessary when creating a welded design.
Taking Several Considerations Into Account
Fit-up expenses for welding might be up to three times as expensive as welding itself. Therefore, while creating welded connections, manufacturers should take into account the labor involved in assembling the pieces so that the fabricator and the erector can solder them.
Different fillet weld, groove, plug, and slot welds are the most common types of welds used for structural steel. The fillet weld is the most commonly used type among the rest. It is the most cost-effective method for low loads because minimum material preparation is needed.
Groove welds are the most effective for big loads since it is simple to achieve because of the base metal’s maximum strength. Plug and slot welds are often only used in unique circumstances where fillet or groove welds are impractical.
A weld connection may employ more than one kind of weld. If so, the effective capacities of each type of weld used, independently determined concerning the group axis, are added to determine the connection’s permitted capacity.
Fillet Versus Groove Welds
Fillet welds might be utilized during shipment or assembly. In the finished structure, they are not given any power to carry stress. After final assembly or erection, these welds may, in some situations, need to be removed.
The general form of a fillet weld is that of an isosceles right triangle. The length of the leg determines the size of the weld. The thickness of the throat and the shortest distance between the root (where the legs intersect) and the weld face dictate the strength. The shorter of the two legs determines the nominal size of the weld if the lengths of the two legs are not equal.
Concave welds result in a more petite throat and hence less strength. To unite two surfaces roughly at right angles to one another, employ a fillet weld. To strengthen corner connections, fillet welds and groove welds can be combined. A corner of the edge to be linked may be raised to a skewed tee joint, and the included angle of the weld deposit may differ from perpendicular by up to 30°. The size of the root opening must extend the weld leg if the gap is more significant.
A groove is created between the edges of the two elements that need to be linked for a groove weld. Although they can also be used for tee and corner joints, these welds are typically employed to unite two plates lying in the same plane.
Standard groove weld types include square, single V, double V, single bevel, double bevel, single U, single U, single J, and double J, depending on the geometry of the edges to be welded. Flame cutting, arc-air gouging, or edge planning are all methods for shaping edges.
However, depending on the welding procedure, material up to 3/8 in thick may be groove-welded with square-cut edges. The groove welds should cover the entire width of the pieces linked. It is not permitted to have joints that are not entirely welded throughout the cross section or intermittent groove welds.
Learn More About Welded Connections and Form Deck
Complete-penetration and partial-penetration welds are additional categories for groove welds. The base metal and the weld material are melted throughout the joint’s depth in a complete-joint-penetration weld. This kind of weld is created by welding from both sides of the first-pass weld, which is chipped or gouged to sound metal before the back-pass weld is formed on the opposite side.
For the sake of stress calculations, the throat size of a complete-joint-penetration-groove weld is the full thickness of the thinner component welded, excluding weld reinforcement.
Contact our experts at Miami Metal Deck if you’re planning to use welded connection or form deck techniques in your next project.