A shear connection is a joint that allows the transfer of shear forces between two members. It is a connection with pure normal force load (tension joint), pure shear loading, or combination of normal and shear force. Shear connections are generally the most commonly used connections. They are typically used to connect beams with other beams or columns. Such connections transfer shear, with minimum rotational restraint, as opposed to moment connections. This can help reduce the reliance on moment connections, which are often more complex and costly.
Shear connectors are normally used in fabricated steel structures, such as railway bridges, deck slab, metro train platforms, etc...
Here are some types of the shear connections:
Angle Connection (Picture 1)
Single Plate Connection
Picture 1. Example of a single angle shear connection
One of the most common types of shear connections are the angle/plate connections, which either use an angle bracket or a plate to connect the flange of the parent to the web of the child member. Shear connections do not resist much moment forces as they are allowed some looseness to rotate. If the connections are permitted for rotation, the connections are to resist only shear forces. Therefore, they are designed as shear conenctions. It is one of the main differences between a shear and a moment connection. It is worth noting that welded shear connections resist higher moment loads than bolted ones.
Steps to Design
In this section, we will discuss about single plate (fin plate) shear connections (Picture 2). Fin plate connections are economical to fabricate and simple to erect. These connections are also popular, as they can be the quickest connections to erect and overcome the problem of shared bolts in two-sided connections.
Picture 2. Single plate shear connection
The behavior of single plate shear connections is affected by the support conditions, which are idealized as being either flexible or rigid. If the beam is supported by an ideal flexible support such as a beam, which is torsionally unrestrained, then the beam end rotation is entirely accommodated by rotation of the support. However if the beam is supported by a fully rigid support, such as the flange of a W-shape column, then the welded edge of the plate will remain firmly connected with the parent member when loaded by a gravity shear force and rotation is accommodated by deformation within the connection. In the ideal flexible connection, the inflection point is at the face of the supporting member; but in the ideal rigid connection the inflection point moves away from the face of the supporting member. Since “real” supports seldom behave exactly as flexible or rigid connections, redundant design procedures are necessary to provide a safe and efficient design. A typical single plate shear connection is composed of three parts: support, connector and beam. The support may be another beam or girder, a column flange, or a column web (Picture 3). The connector may be either bolted or welded to the support and to the beam. For example, a connector bolted to the support and welded to the beam forms a “bolted-welded” shear connection.
Picture 3. Single plate shear connection beam/column (left) and beam/beam (right)
In order to continue, we have to factor limit state considerations. The following list below are the 11 checks (AISC standards) necessary to design a single plate shear connection:
Bolt shear considering bolt eccentricity
Material bearing strength of the bolt group for both the plate and the beam web
Plate shear yielding
Plate shear fracture
Plate block shear
Plate flexural yielding due to bending using the plastic section modulus of the plate
Plate flexural fracture due to bending
Weld strength for plate to supporting member
Block shear for coped beams
Flexural yielding of the coped section of the beam
Rotational demand of connection for rigid connections only
To be able to pass mentioned criteria, we have to stick with general requirements for connecting plates, bolts, and welds.
The minimum bearing capacity is mandatory for all types of fractures of all connection components.
Some of the recommendations (which follows both Australian and American standards) that can be made to make it pass are the following:
Capacity of the bolt group connecting the fin plate to the web of the supported beam
The bearing capacity per bolt must be greater than the resultant force on the outermost bolt due to direct shear and moment.
Strength of the fin plate at the net section under bearing and shear
The shear capacity of the fin plate must be greater than the reaction at the end of the beam. The elastic modulus of the net section of the fin plate must be greater than the moment due to the end reaction and the projection of the fin plate.
Strength of the supported beam at the net section
The shear capacity of the supported beam must be greater than the reaction at the end of the beam. For long fin plates the resistance of the net section must be greater than the applied moment.
Strength of weld connecting fin plate to supporting column
The leg length of the fillet weld(s) must be greater than 0,8 times the thickness of the fin plate.
Local shear check of column web
The local shear capacity of the column web must be greater than half the sum of the beam end reactions either side of the column web.
Buckling resistance of long fin plates
The buckling resistance moment of the fin plate must be greater than the moment due to the end reaction and the projection of the fin plate.
The tension capacity of the fin plate and the beam web must be greater than the tie force. The bearing capacity of the beam web or fin plate must be greater than the tie force and the tying capacity of the column web must be greater than the tie force.
Shear Connection Design (Worked Example)
In this section, we will show an example of single plate shear connection, using SkyCiv Connection Design. The software will show the step-by-step calculations of a shear connection design:
Picture 4. Defining design code, category and type of the shear connection
By setting the design factors (member, bolt and weld factors), the next step in the design is with creating a connection assembly (Picture 5) to which the forces can be assigned (Picture 6) and the behaviour of the single plate shear connection can be simulated.
Picture 5.Design factors and connection assembly
Picture 6. Assigning the forces to a child member
After simulating the behaviour of single plate shear connection, the results (Picture 7) will be given in accordance with American Standard AISC 360-10 (14th Edition).
Picture 7. Results
The software will also produce a step-by-step guide of the connection shear design calculations for the user's reference. Click the 'Report' icon to view the design output.
For a detailed view of this worked example, feel free to download the detailed worked example of a shear connection design - produced by SkyCiv Connection.