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Mezzanine floors: Bracing

July 22, 2010

To brace or not to brace – is that the question?

Mezzanine floor bracing

Mezzanine floor bracing

It is always necessary to design mezzanine floors to accommodate a degree of dynamic and side loading, and bracing will always be required to resist any sideways loading.

Mezzanine floors are designed to be freestanding – that is they will remain in place even if the building in which they are located were to be removed. This allows them to be added or removed without needing to apply load to the building structure or involve a structural engineer in checking wall loadings.

Bracing can take a number of forms, a “panel or cross brace”, “knee brace” or “floor brace” and can be fabricated from flat, angle or tubular material.

The panel or cross brace comprises a pair of straps forming a cross, which are bolted to lugs at the top and bottom of an adjacent pair of columns. Panel bracing is very effective, but has the disadvantage of obstructing access between the columns where the brace is located.

Knee braces usually link a lug at the top of a column with a lug on a beam at an angle of 45 degrees. They are not as effective as panel braces, and locally reduce clear headroom and project below fire protection.

Floor braces are like an inverted knee brace, but usually are fixed to a lug at the top of a column, and fixed to the concrete floor slab at the bottom. Floor braces are inclined steeply from floor to column to minimise obstruction of the space between columns.

When no obstructions between the mezzanine floors columns are acceptable, bracing can be achieved by using heavier sections and designing structural bolted connections that can accommodate sideways loading. This is usually a more costly solution.

The removal of  a mezzanine floors braces following installation in order to facilitate access will at the very least apply sideways loads to the building fabric which could result in damage or invalidate insurances, and in the worst case where the mezzanine floor is unrestrained, could lead to collapse of the mezzanine floor and crushing of people below.

For further advice regarding the design of your mezzanine floors, call Llonsson Ltd on 01883 622068

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Llonsson Ltd

49 Court Farm Road,
CR6 9BL United Kingdom

T: 01883 622068 F: 01883 623280

Registered No: 2389444