Detail of Beam Connection | Simple Framing Connection | Semi-Rigid Framing Connection | Rigid Frame Connection

Detail of Beam Connection | Bolt Beam Framed Connection | Welded Beam Framed Connection 

Detail of Beam Connection

Beams are connected to main beams or into the columns.

The design of these connections is more important -since the failure of connection is more catastrophic than the failure of the beam section.

In this chapter different types of a beam, connections are explained

As discussed in  IS: 800-1984 recognizes the following three types of steel framework construction, depending upon the type End Moment ration

  • Simple Framing (curve I)
  • Semi-Rigid Framing (curve III),
  • Rigid Frame Construction (curve II)
    • The typical moment-rotation curves for the three types of framing (or connections) are shown in Fig.

Simple Framing Connection

Simple framing is the one where rotational restraint at the ends of the members is as little as practicable, and in consequence, the structure may, for the purpose of design, be assumed as pin-connected.

For beams, simple framing provides only shear transfer at the ends.

The design of simply supported beams under the working stress method uses this type of connection, while simple framing is not used in plastic design.

One may consider the framing Simple if the original angle between intersecting pieces may change up to 80% of the amount it would theoretically change if frictionless hinged connections could be used

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Semi-Rigid Framing Connection

Rigid frame construction is the one where full continuity is provided at the connections so that original angles between the intersecting members are held virtually constant, i.e., with rotational restraint of the order of 90% or more of that necessary to prevent any angle change.

Such connections give the greatest rigidity and economy in the weight of steel used when applied in appropriate cases.

Such connections are used under both the working stress and plastic design methods.

Rigid Frame Connection

Semi-rigid framing is the one where rotational restraint is between 20 and 90% of that necessary to prevent any relative angle change.

The semi-rigid connections develop less than the full moment capacity of the connected members.

With semi-rigid framing, the moment transmitted across the joint is neither zero (or a small amount) as in simple framing, nor is it the full continuity moment as assumed in the elastic rigid-frame analysis.

Because of the difficulty of evaluating the degree of restraint, semi-rigid connections are not used in plastic design and are rarey used in working stress design.

Actual connections are neither completely rigid nor completely flexible, and can be classified on the basis of the ratio of the moment developed by the connections to the full moment capacity of the connected member, expressed as a percentage.

As stated above, the approximate percentages for simple connections are from 0 to 20, for a semi-rigid connection from 20 to 80, and for a rigid connection from 80 to 90. The percentage of a particular connection must be determined by actual tests.

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Type of Steel Beam Connection

Riveted Beam Connection 

Bolt Beam Connection 

Welded Beam Connection  


Riveted Beam Connection 

  • Simple Beam Connections for Riveted

      • Riveted Framed Connection
      • Riveted Seated Connection
        • Riveted Unstiffened Seated connection
        • Riveted Stiffened Seated connection 
  • Moment Riveted Resistant or Rigid Connection

Simple Beam Connections for Riveted

Riveted Framed Connection

  • A framed connection is the one when a beam is connected to a girder or a stanchion by means of two angles placed on the two sides of the web of the beam, as shown below fig. no-1

Framed Connections

Riveted Framed connection Fig No-1

  • When the beams intersect and are attached to other beams so that flanges of both are at the same elevation, as shown below fig. no-2 (a), (b), the beams framing-in have their flanges coped or cutaway.

Riveted Framed connection at the s

Beam Framing

angle level  Fig No -2

  • The loss of section is primarily loss of flange that carries little shear so that normally rope results in little loss of strength.
  • In framed connections, an angle shelf is sometimes used to support the connecting beam during the erection, simply to facilitate the process (as shown below fig. no-1), though the angle shelf is not an integral part of the connection and may be removed after the connection process is over. 3

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Riveted Seated Connection

  • When a beam is connected to the flange (or the web) of a steel stanchion, the width of the flange (or the depth of the web) may be insufficient to accommodate the connecting angles.
  • In that case, framed beam connections are not suitable, and seated beam connections are preferred.
  • In its simplest form, a seated connection is the one in which a horizontal angle with its horizontal leg at its top is used to receive the beam on it, as shown in as per below fig; in such as a case it is called unstiffened seat connection.

Seated Connection 

Seated Connection

  • In addition to the seat angle, a web cleat is provided when the beam is connected to a beam (as per above fig ) while a flange cleat is used when the beam is connected to a stanchion.
  • The angle cleats (i.e. web cleat or flange cleat) are essential parts of seated connections because they keep the beam stable in a vertical position and prevent it from lateral buckling.
  • When the reaction to be transferred by the beam is so large that the scat angle cannot support it, then the horizontal leg of the seat angle is stiffened by means of one or two stiffener angles, as shown in as per below fig.

StiffeSeated Connection

  • The stiffener angles should be tightly fitted under the seating angle and suitable packing should be provided, as shown in as per above fig.
  • Seated connections require more space in the vertical direction, and due to this, they are not commonly used for connecting the beam to a beam.
  • Seated connections are more suitable for connecting the beam to either the flange or to the web of a steel stanchion.
  • Similarly, a framed connection is not suitable for connecting a beam to the web of a column because of the space limitation on either side of the beam.

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Moment Resistant or Rigid for Riveted Connection

Up to this stage, we have discussed simple connections that transfer shear only, and permit full rotation of the beam.

Some times, it may be required to transmit moments also, in addition to shears, such as in building frames.

As discussed earlier, there are two types of constructions which permit the transfer of moments, either fully or partially:

    • Rigid construction and 
    • Semi-rigid construction.

In both the above types of construction, the connections or joints are so designed that they permit the transfer of moment in addition to shear.

Based on the magnitude of the moment to be transferred, these may be two types of connections :

    • Small moment resistance connections
    • Large movement resistance connections  

Clip Angle

Small moment resistance connections

Breaker Section

Large movement resistance connections  

Bolt Beam Connection

Simple Beam Connections

    • Bolt Framed Connection
    • Bolt Seated Connection
      • Bolt  Unstiffened Seated Connection
      • Bolt  Stiffened Seated Connection 

Moment Resistant or Rigid for Bolt Connection

Simple Beam Connections

Bolt Framed Connections

  • When the end shear to be transferred is less, it is possible to connect the beam to the main beam or to the column using cleat angles, as shown in also show fig. (a) and (b).


Framed Connections

Framed Connections

  • If the flanges of the beam to be connected are at the same level, the flanges of the connecting beam are cut, as shown below fig,

Framed Connections

Framed Connections if flanges are at the same level

  • This will not pose any structural problem since at the end of simply supported beams moment is zero, and shear strength depends mainly on the strength of the web.

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  • Bolt Unstiffened Seated Connection

    • When shear force are larger, the depth of the cleat angle required for framed connection may be more than what can be provided at the available space.
    • In such cases of the seat, angles are connected to this column over which beam rests.
    • At top cleat, angles are provided to prevent the lateral displacement of the beam after positioning it over seat angle also shows in below fig. a typical such connection.

Unstiffened Seated Connection

  • Bolt Stiffened Seated Connection

    • If shear force to be transferred at the beam is still large, the seat angle may fail.
    • To strengthen it, a stiffener angle can be provided, as shown in as per below fig. Such connections are known as a stiffened seated connection.

Stiffened Seated Connection

Stiffened Seated Connection

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Moment Resistant or Rigid Connection for Bolt

    • Clip-Angle or Split Beam Connection
    • Bracket Connection
  • Clip Angle Connection

    • This type of connection may be used at the end of the moment to be transferred in the end is small as per below fig. shows a typical clip angle connection.

Clip angle connection

Clip angle connection

End Moment ration

Split Beam Connection

  • Bracket Connection

    • If the moment to be transferred through this connection is large such connections are used as per below fig. shows a typical bracket connection.

Bracket connection

Bracket connection

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Welded Beam Connection  

Simple Welded Beam Connections

  • Beams may be connected to the supporting beam or to the supporting column by welding.
  • In fact, welded connections are used more commonly instead of bolted connections.
  • The end of the beam may be designed to transfer the only shear to the supporting structure by
    • Framed connection
    • Unstiffened seated connection
    • Stiffened seated connection.
  • The ends of the beam may be designed to transfer shear as well as moment by welded connection.
  • Such connections are known as moment resistant connection.
  • In this chapter, the design of all such connections is explained

Moment Welded Resistant or Rigid Connection

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Simple Welded Beam Connections

Welded Framed Connection

The direct fillet or butt welds explained in need accurate lengths and edge finishes, which may be quite difficult to achieve.

Instead of these connections, framed connections may be adopted, which are flexible.

The following two types of framed connections are possible.

  • Double Plated Framed Connections
    • Instead of two plates may be used for the connection beam and the supporting member to get more flexibility in the connection.
    • The plate to are connected to the web of the beam by shop welding.
  • Double Angle Framed Connections
    • Instead of two angles may be used for the connection beam and the supporting member to get more flexibility in the connection.
    • The angles to are connected to the web of the beam by shop welding.

Double Plated Welded Framed Connections

Double Angle Framed Connections

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Welded Unstiffened Seated Connection

  • When the end reaction to be transferred is low, welde unstiffened seat connection can be used.
  • The beam is placed over a seat welded and angle

Welded Stiffened Seated Connection.

Welded Stiffened Seated Connection.

Welded Stiffened Seated Connection

  • As per a typical stiffened seat connection. The seat used can be a split two-plate, or I beam forming a T-section.
  • The seat plate thickness isn’t less than the thickness of the flange of the beam, and the thickness of the stiffening plate is not less than the thickness of the web of the beam.
  • Seat plate and stiffening plates are welded, as shown below, Fig (a).
  • The width of the seat plate is kept equal to the width of the flange of the beam. The same size plate can be used as a stiffening plate.
  • Weld looks like a T-section, as shown below, fig. (b).

Stiffened Seated Connection

  • In multistory braced frames, simple, or Type PR connections of beams to columns are often made using beam seats.
  • These may be made with heavy angles or, if loads are large, a stiffened seat may be used. The stiffened seat is usually made by welding two plates in the form of a tee.

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