These details are to be used for conditions where a double span gives an advantage over single span i.e. deflection governing.
Typical applications are wall and brickwork restraints, window cill or header rails where deflection due to horizontal wind is to be limited to a specific deflection ratio: e.g. brickwork restraint commonly limited to a ratio of span/300 as shown in the load tables.
If a deflection limit greater than span/300 is required, then calculate the capacity for this by multiplying the capacity given in the table by 300/the required limit e.g. required capacity for span/500 = 300/500 x table capacity for span
It is not permissible to use this method to calculate capacities for deflection limits less than span/300.
For brickwork restraints, it is assumed that the wall will support the C-section on the weak axis.
Download our purlin technical manual in the downloads section below for more information.
Dimension ‘X’ in sliding anchor fixing plate to suit standard 18mm diameter holes in Metsec rail
Slotted ties to suit brick coursing.
For cases where the wall will not be built until after the rail erection, or where the wall is not to be built up so that it supports both the inner and outer flanges of the C-section on the Y axis, Metsec side rail support and diagonal tie systems are required.
For window cill support rails where the weight of the window is to be supported by the rail, see the side rail support system for this condition.
This arrangement can be used where stringent deflection limits are applied. i.e. glazing supports, brickwork restraints etc.
The maximum double span section length is 15m, therefore the maximum column centres are 7.5m.
The C-section sleeve range includes one thickness per height of profile, as shown on the table below.
|Ref No||Thickness mm||Weight kg|
Unless otherwise stated, all required holes are 18mm diameter for M16 bolts and are normally pierced in pairs on standard gauge lines. For ‘General detailing’ notes see General Detailing Information.