Connections - Multi-Storey Buildings.

The most important aspect of structural steelwork for buildings is the design of the connections between individual frame components.

The selection of a component should be governed not only by its capability to support the applied load, but also by its ease of connection to other components.

Basically there are three types of connection, each defined by its structural behaviour: simple, continuous and semi-continuous (Fig. 2.31):

Connections: (a) simple; (b) continuous; (c) semi-continuous
Fig. 2.31 Connections: (a) simple; (b) continuous; (c) semi-continuous

(1) Simple connections transmit negligible bending moment across the joint: the connection is detailed to allow the beam end to rotate. The beam behaves as a simply supported beam.

(2) Continuous connections are designed to transmit shear force  and bending  moment across the joint. The connection should have sufficient stiffness or moment capacity as appropriate to justify analysis by either elastic or plastic analysis. Beam end moments are transmitted into the column itself and any beam framing into the column on the opposite side.

(3) Semi-continuous connections are designed to transmit the shear force and a proportion of the bending moment across the joint. The principle of these  connections is to provide a partial restraint to beam end-rotation without  introducing complicated fabrication to the joint. However, the design of such joints is complex, and so simple design procedures based upon experimental  evidence have been developed for wider application. The advantages of semi- continuous design are lighter beams without the corresponding increase in column size and joint complexity that would be the case with fully continuous connections.

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