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Various generic forms of connection may be used in steel frames. These include:
{{#image_template:image=File:Neo_Bankside-2.png|align=right|caption=[[NEO Bankside, London]]|wrap=true|width=250}}
*Beam-to-column flange connections that may be [[Moment_resisting_connections|moment-resisting]]
*Beam-to-beam web connections that are normally designed as [[Simple_connections|nominally pinned]]
*[[Simple_connections#Column splices|Column-to-column splices]]
*[[Simple_connections#Column bases|Column bases]] at foundations
*[[Simple_connections#Bracing connections|Bracing connections]].
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Connection detailing depends on the forces and moments to be transferred, and on the chosen member sizes. However, some common detailing rules apply, which are discussed below, in order to gain an appreciation of the form of connections in regular frames.

==Conventional connection types==
''Main articles: [[Braced frames]], [[Continuous frames]], [[Simple connections]], [[Moment resisting connections]]''
{{#image_template:image=File:Arch_fig63.png|caption=Example of a notched beam to beam fin plate connection for equal depth [[Steel_construction_products#Cellular beams|cellular beams]]|align=right|wrap=true|width=250}}
Partial depth end plates have an end plate welded only to the beam web. [[Simple_connections#Flexible end plate connections|Flush end plate connections]] that are [[Welding|welded]] to the flanges and web of the beam are commonly used as [[Simple_connections|nominally pinned connections]], although they do possess some bending resistance. Normally the end plate is 10 mm to 12 mm thick for use with M 20 bolts.  When used as [[Moment_resisting_connections|moment connections]], the end plate is thicker, typically 15 – 20 mm, and is extended above the top flange to allow for an additional row of bolts to located outside the flange. Fin plates are simple rectangular plates, typically 10 mm thick, welded to the supporting member. The supported beams are simply cut and drilled (and notched if the support is a beam).

For connections to [[Steel_construction_products#Structural hollow sections|Square Hollow sections]] (SHS), a form of expansion bolt connection may be used that forms a connection by expanding into the space behind the face of the section. However, the diameter of the expansion part of the bolts is up to twice that of the bolt diameter and so the spacing between the bolt holes has to be increased compared to normal bolts. Alternatively, proprietary 'blind' fixings may be used.
<gallery caption="Examples of common connection types" perrow=3 widths=200px heights=200px> 
Image:Arch_fig60.png|Connections to UC and SHS columns using [[Simple_connections#Flexible end plate connections|flush end plates]]
Image:Arch_fig61.png|Connections to UC and SHS columns using [[Simple_connections#Fin plates|fin plates]]
Image:Arch_fig62.png|Notched [[Simple_connections#Beam-to-beam and beam-to-column connections|beam to beam connection]] using [[Simple_connections#Flexible end plate connections|partial depth end plate]]
</gallery>

==Tubular connections==
{{#image_template:image=File:Arch_fig64.png|caption=Featured fin plate attachment to a tubular chord in a long span [[Trusses|truss]]|align=right|wrap=true|width=300}}
Connections between [[Steel_construction_products#Structural hollow sections|tubular sections]] are often exposed and may take various forms:
*Beam-to-column connections that are usually bolted
*In-line connections that may be bolted or [[Welding|welded]]. In-line connections often occur in long members that require splicing for [[Fabrication#Handling and transportation|transportation]].
*[[Steel_construction_products#Structural hollow sections|Tubular sections]] with [[Simple_connections#Fin plates|welded fins]]
*Inclined connections such as inclined bracing to horizontal chords. These are usually [[Welding|welded]].
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The chords and bracing in a [[Trusses|truss]] or lattice girder are often [[Welding|welded]].
{{#image_template:image=File:Arch_fig65.png|caption=Welded profiled connection between [[Steel_construction_products#Structural hollow sections|tubular sections]] in a [[Trusses#Warren truss|W-shaped roof truss]]|align=left|width=200}}
Where square [[Steel_construction_products#Structural hollow sections|hollow sections]] (SHS) are used then the ends of the SHS are cut to the required angle and [[Welding#Fillet welds|fillet welded]] to the face of the SHS chords. Where circular [[Steel_construction_products#Structural hollow sections|hollow sections]] (CHS) are used then the ends of the incoming CHS inclined members have to be cut to form the precise shape around the chords. This is known as [[Fabrication#Profiling of tubular sections|profiling]] which is a specialist process.

The figure shows the use of a shaped [[Simple_connections#Fin plates|fin plate]] to provide more visual appeal to an otherwise simple connection between the top chord and bracing of a deep [[Trusses|truss]].  
{{#image_template:image=File:Arch_fig66.png|caption=In-line connections between [[Steel_construction_products#Structural hollow sections|tubular sections]]|align=right|wrap=true|width=300}}
In-line connections are usually made by bolting, either by a flange plate with typically 4, 6 or 8 bolts (figure b), or a splice plate (figure c), or an end plate (figure d), which can be concealed behind a cover plate. Various examples of these connections are shown below.

A profiled cover plate may be provided so that the connection is not visible, as shown below.
<gallery caption="In-line connections between circular [[Steel_construction_products#Structural hollow sections|hollow sections]]" perrow=2 widths=250px heights=250px> 
Image:Arch_fig67.png
Image:Arch_fig68.png
</gallery>
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==Tie connections==
{{#image_template:image=File:Arch_fig71.png|caption=Multiple connections using [[Steel_construction_products#Stainless steel products|stainless steel]] tie rods|align=right|wrap=true|width=300}}
Connections between ties that act in tension take two forms:
*Couplers which require that the rods are threaded in opposite directions so that the coupler can be tightened.
*Pins which may be [[Welding|welded]] to the rods or provided with threads. The pin is normally connected to a [[Simple_connections#Fin plates|fin plate]] that is [[Welding|welded]] to another member.
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Rods and couplers are often stainless steel if exposed externally. Good examples of [[Steel_construction_products#Stainless steel products|stainless steel]] tie rods used in the external [[Facades_and_interfaces|façade]] of the Helsinki Sanomat building are shown. Where multiple connections between tie rods are required, special [[Steel_construction_products#Castings|castings]] or [[Fabrication|fabricated]] nodes are necessary.

Rods may be connected by various types of cast and formed nodes. The detail shown is supported from above by a threaded rod and the horizontal nodes allow for articulation in two directions.
<gallery caption="Connections using [[Steel_construction_products#Stainless steel products|stainless steel]] tie rods" perrow=2 mode=nolines widths=250px heights=400px> 
Image:Arch_fig69.png
Image:Arch_fig70.png
</gallery>
Sanomat Building, Helsinki
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==Further reading==
*[https://www.wiley.com/en-gb/Steel+Designers%27+Manual%2C+7th+Edition-p-9781119249863 Steel Designers' Manual 7th Edition.] Editors B Davison & G W Owens. The Steel Construction Institute 2012, Chapter 27, Joint design and simple connections
*Architectural Design in Steel – Trebilcock P and Lawson R M published by Spon, 2004
*[[Media:BCSA_35-03.pdf|Steel Buildings, BCSA No. 35/03]], Chapter 4, Multi-Storey Buildings

==Resources==
*[[Media:SCI_P167.pdf|SCI P167 Architectural Teaching Resource Studio Guide, 2000]]
*[[Media:SCI_EP35.pdf|Best Practice in Steel Construction: Commercial Buildings]]
*Steel Buildings in Europe - Multi-storey buildings:
**[[Media:SBE_MS1.pdf|Part 1: Architect’s guide]]
*[[Media:SCI_EP37.pdf|EP37 Best Practice in Steel Construction – Industrial Buildings, Guidance for architects, designers & constructors]]
*Steel Buildings in Europe - Single storey buildings:
**[[Media:SBE_SS1.pdf|Part 1: Architect’s guide]]
**[[Media:SBE_SS11.pdf|Part 11: Moment connections]]
*[[Media:SCI_P358.pdf|SCI P358 Joints in Steel Construction - Simple Joints to Eurocode 3, 2014]]
*[[Media:SCI_P398.pdf|SCI P398 Joints in Steel Construction - Moment-resisting Joints to Eurocode 3, 2013]]
*[https://www.tatasteelconstruction.com/static_files/Tata%20Steel/content/products/Structural%20Hollow%20Sections%20Hot%20Finish/Celsius%C2%AE%20355/Downloads/Design%20of%20SHS%20Welded_Joints_Brochure_07-2013.pdf Design of welded joints - Celsius®355 and Hybox®355, 2013, Tata Steel]

==See Also==
*[[Braced frames]]
*[[Continuous frames]]
*[[Simple connections]]
*[[Moment resisting connections]]

[[Category:Resources for Students]]

[[Category:Index of main articles]]