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For the calculation of (semi)-rigid connections, the following characteristics of connection are introduced in Eurocode 3:
Moment Resistance
Rotational Stiffness
This design method allows us to determine a "Moment-rotation characteristic", which in turn allows us to represent the real connection by a rotational spring connection defined in the centre lines of column and connected beam in the point of their intersection (approximation to the real behaviour of the connection).
By using this method, the design of non-stiffened connections can be considered, which results in a reduction of the total cost of structural steelwork.
The principles for the design of these semi-rigid connections are satisfied when the detailed application rules given in the revised Annex J of Eurocode 3, Ref. [1] are followed. For the design of column bases, the application rules given in Annex L of Eurocode 3, Ref. [5] are followed.
The following types of connections are supported :
Beam-to-column connections : Bolted endplate + welded connections (knee, T, cross - with continuous beam or continuous column)
Beam-to-beam connections : Endplate type beam splice (plate-to-plate connection).
Column bases : Bolted base plate connection.
The types "beam-to-beam" and "column bases" are limited to symmetric and asymmetric I beams (including the elements with variable height) and RHS sections, both for major-axis bending configurations.
For the type " beam-to-column", the beam element is limited to symmetric and asymmetric I beams (including the elements with variable height) and RHS sections, both for major-axis bending configuration ; the column element is limited to symmetric I beams (including elements with variable height) in major-axis configuration, and to symmetric I beams in minor-axis bending configuration.
The following types of stiffeners are supported :
Beam-to-column connection:
Haunches : Welded from plate or made from a profile
Web doublers : Supplementary web plates
Backing plates : On the flanges
Stiffeners : Triangular + rectangular, positioned in beam or column
Column base connection:
Haunches : Welded from plate or made from a profile
Stiffeners : Triangular + rectangular positioned in column at haunches
Flange wideners
Shear iron
Note: The frame connection can be defined between two beams (e.g. column and beam) that must be perpendicular to each other in the "direction of connection". This on-the-spot-invented phrase will be best explained on a simple example.
Let us assume a column and a beam made of vertically oriented I-section.
In the side view, the two members are not perpendicular.
In the plan view, however, they ARE perpendicular to each other. And this is the "direction of connection".
Therefore, the connection can be defined here.
On the other hand, let us assume another column and a beam made of the same vertically oriented I-section. At first sight (in axonometric view) everything seems to be the same.
In the side view, the two members are perpendicular.
In the plan view, however, they are NOT perpendicular to each other. And this is the "direction of connection".
Therefore, the connection cannot be defined here.
The same can be said for curved beams. If the curvature of the beam does not break the condition of perpendicularity in the "direction of connection", the connection can be defined, see e.g. the picture below.
