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Traditionally, concrete beams were supported on columns using integral corbels. Apart from being difficult and costly to form in the column, they reduce headroom locally and spoil the appearance. Using BSF connectors eliminates the need for corbels, leaving a smooth soffit. Round, or odd-shaped columns present no problems. For heavy loads from beams into columns, walls or other beams, the BSF system should be used. They consist of three-part telescopic connectors, but are otherwise similar in application principle to the range of telescopic stair connectors. They are designed for heavy-duty beam supports, with capacities from 225–1100 kN. By using pairs of connectors, loads up to 1400 kN can be catered for.

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Standard product features


Steel (grade S355, minimum).

Concrete strength class (minimum):


Reaction to fire:

Class A1, according to EN 13501-1.

NBS Specification

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This product is associated with the following NBS Create clause:
45-75-42/390 Carbon steel shear load connector

Product specification

An important note about specifying



Invisible Connections Ltd


+44 (0)1844 266000

Product reference

[BSF 225]
Capacity: 225 kN.
[BSF 300]
Capacity: 300 kN.
[BSF 450]
Capacity: 450 kN.
[BSF 700]
Capacity: 700 kN.
[BSF 1100]
Capacity: 1100 kN.

Steel finish


Manufacturer details

Unit 6 Thame Forty,
Jane Morbey Road,
Oxfordshire, OX9 3RR
Tel +44 (0)1844 266000
Fax +44 (0)1844 390167
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