Steel Connections Load Transfer

Steel Connections The way steel connections are designed is crucial for the structure to be able to hold the load of the steel's weight. There are a multitude of different configurations and metal type uses for transferring loads in connection. It really depends on the elements of the connection, "nature, and magnitude of the forces (and moments), available equipment, fabrication and erection considerations, costs," and more (Alduri, 2012).

Thus, there are a wide variety of connection types that are designed to help hold the load of the structure and prevent deformation of the steel connections from occurring, which would ultimately threaten the structure as a whole. Unfortunately, "connections to steel poles are often overlooked in the design process," therefore it is crucial for a better understanding of how steel connections bear loads in order to ensure the strongest connections and finished product (Design of Steel Transmission Pole Structures Standards Committee, 2011, p 32).

This makes it crucial for construction projects to take in account the various types of steel connections based on the unique nature of individual projects. Connections can be bolted together by bolts and rivets or welded. There are minimum requirements for edge distances and bolt spacing for bolted connections, where the bolts and rivets have to be a certain width and distance apart from one another. Bolts cannot be used in the flanges, but only in the webs of the steel poles.

Bolts only transmit sheer force and do not bend. The most effective bolted connection for holding high loads is the High Strength Friction Grip (Institute for Steel Development & Growth, 2012). Moreover, bolted connections are much easier to replace or inspect compared to welded connections, which makes them a better choice for long-term structures. On the other hand, moment connections transmit both shear and movement, and are typically seen in most welded designs.

According to the research, in a bolted design, "tension in one plate is equilibrated by the bearing stress between the bolt and the hole in the plate" (Institute for Steel Development & Growth, 2012). This helps mobilize the bearing stress because of the clearance between the bolt and the plate when the plates slip.

(Institute for Steel Development & Growth, 2012) Welded connections are very efficient in the field and "have the advantage that no holes need to be drilled in the member and consequently have higher efficiencies" because the steel is not made vulnerable by drilling (Institute for Steel Development & Growth, 2012). Welded connections, however, are vulnerable to cracking under heavy loads. Rivets must create a 2-inch minimum connection between plates, while bolts must be in series of four bolts in a single connection plate (Alduri, 2012).

Rivets are still used today, but are slowly being replaced more and more by bolted connections, as they last longer (Institute for Steel Development & Growth, 2012). Rivets have the lowest strength of all three connection types, and thus are not as strong as bolted connections. Moreover, rivets cost more and are less effective overall. There are mathematical formulas that are necessary to calculate the proper load put on steel connections.

If stress exceeds a certain amount, the steel connections will ultimately falter, causing the potential to generate serious damage to the overall structure and potentially even collapse (Steel Construction, 2014). For the purpose of understanding how much load is appropriate for connections, fabricators must use the following formulas for bearing and bolted steel connections. (Design of Steel Transmission Pole Structures Standards Committee, 2011, p 13) (Design of Steel Transmission Pole Structures Standards Committee, 2011, p 13) There are a wide number of connections designs that incorporate bolts, rivets, and welds.

Beam to Beam Connections Beam to beam connections are typically bolted in. They require between three to four pairs of bolts at each connection point that attach the beams vertically (Alduri, 2012). (Alduri, 2012) Beam to Column Connections When connecting beams to columns, developers have to be very careful to allow for joint flexibility. Otherwise, the joints will begin to bend at dangerous angles under the pressure of the force. In bolted connections, there needs to be bending allowed in order to transfer the tensile force (Alduri, 2012).

This angled connection allows for better transferring of the load weight, making it stronger design than if there were no angle bending at all. When using rigid joints, it is crucial that "stiffner plates are used to shore up the column flanges against the forces transmitted by the beam flanges," (Alduri, 2012). These stiffners may.