Split Rings and Shear Plates
Split rings and shear plates are load transferring devices which rely on bolts or lag screws to restrain the joint assembly. They are more efficient structurally than bolts or lag screws used alone because they enlarge the wood area over which a load is distributed as shown in Figure 5.15 below.
Split rings and shear plates are used mainly to transfer loads in heavy timber or glulam members as in roof trusses. These connector units transfer shear either between the faces of two timber members or between a timber member and a metal side plate. They are not usually protectively coated and need be galvanized only if used with preservation treated wood or in wet service conditions.
It is important that the proper size of bolt be used with a connector since it is an integral part of the assembly. The bolt clamps the joint together so that the connector acts effectively.
Split ring and shear plate joints are fabricated using the special tools as shown in the photographs below. Care must be taken to ensure a good fit.
Figure 5.15: Stress Distribution for Bolted Joints with
and without Split Rings and Shear Plates
Split rings are manufactured in Imperial sizes in diameters of 63mm (2-1/2″) and 100mm (4″) from hot-rolled carbon steel for use with 13mm (1/2″) and 19mm (3/4″) diameter bolts respectively.
A single split ring insets into both the precut grooves in the wood surface being joined as shown in Figure 5.16 below. A tongue and groove split in the ring permits the ring to deform slightly under load so that all contact areas distribute load, and the special wedge shape on both sides of the ring eases insertion and ensures a tight fitting joint when the ring is fully seated in the grooves.
Figure 5.16: Split Ring Loading Arrangements
Shear Plates are manufactured in Imperial sizes in a diameter of 67mm (2-5/8″) in pressed steel for use with 19mm (3/4″) bolts or lagscrews, and in a diameter of 100mm (4″) in malleable iron for use with 19mm (3/4″) or 22mm (7/8″) bolts or lagscrews.
Grooves for shear plates must also be precision machined by special tools which recess the wood so that the shear plates sit flush with the surface.
Shear plates can be used singly to connect wood to steel, or be paired back to back to conect wood to wood as shown in Figure 5.17 below.
Typical wood-to-metal applications occur at purlin to beam, column to foundation, arch peak, and steel gusset connections.
Sttel side plates used in conjunction with bolts must be sized according to wood engineering standards to resist tensile and compressive forces as well as bucking at critical sections.
Figure: 5.17 Shear Plate Loading Arrangements