Technical data: Frangible Safety Post – 114mm Diameter
The Frangible Safety Post is a novel glass and carbon fibre reinforced, composite, cylindrical post that is intended for the installation of vertical traffic signs and other devices installed adjacent to the roadway. This post is not recommended for use where an access panel is cut into it. The product is strong and stiff and is of uniform diameter and wall thickness. The post has the following dimensions and physical characteristics:
- Outside diameter: 114.3 mm
- Wall thickness: 5.0 mm
- Unit weight: 3.2 kg / metre
- Standard colour: Mouse grey RAL 7005
Typical installation of an FSP post
Except where noted, properties were determined by physical measurement. Test methods and physical properties have been verified by an independent chartered engineer. The declared values below are minimums for each characteristic.
- Max bending moment, Mu: 17 kNm
- Stiffness for bending, EI: 94.6 kNm2
- Max moment for torsion*, Tu: 10.6 kNm
- Stiffness for torsion, GIu: 29.9 kNm2
- Shear capacity*, V: 89.6 kN
- Shear capacity (measured**), V:>21.4 kN
* calculated value
** test equipment unable to safely apply greater force
The structural characteristics of the Frangible Safety Post, above, are used to calculate the sign carrying capacity given the load requirements of BS EN 12899-1 or BS EN 1991-1-4. These calculations may be done using proprietary or off the shelf software packages that have included the structural details of this product.
Testing / Approvals
The Frangible Safety Post – Series 114mm has been tested using BS EN 12767:2019.
The performance classification for this post is:
- Diameter: 114mm
- Speed: 50,70,100
- Energy : NE
- Occ Safety: B
- Backfill: S
- Collapse: SE
- Direction: MD
- Roof Indent: 0
Tested spacing between posts – 750mm separation
Tested minimum mounting height – 1.5m
General Performance Considerations
The intended use of the Frangible Safety Post is for the mounting of appropriately sized, vertical traffic signs and other roadside devices. Other uses (i.e. where access holes are created low on the pole) have not been investigated and are not recommended. It is the responsibility of the road authority to specify Frangible Safety Posts in locations appropriate for NE rated products.
When specifying / installing signs on multiple posts equal loading of each post is recommended to maximise wind load carrying capacity for that installation. When multiple Frangible Safety Posts are used for a sign the may be installed as close as 750mm apart.
Mounting another sign on installed posts
A post and foundation suitable to support a particular sign may not be sufficient to carry another in that location. Any substitution of signs or unplanned additions of supplemental plates to an existing installation should only be done after confirming that the post / foundation are not taken beyond its maximum wind load design capacity.
Post uses standard fixings
Effect of vehicle impact
Frangible Safety Posts tend to collapse when hit by a car. Depending on the speed of impact the sign may fall with the post (very slow impact) or slide off post and fall behind the car that hit it and near the post installation spot (medium or high speed impact). In the unlikely event that a post is bumped by a vehicle but not knocked down it may still be damaged and be unable to continue to carry the sign. Replacement of any Frangible Safety Post which has been involved in a vehicle impact is recommended.
When damaged by a vehicle, the Frangible post fragments generated may have some ragged edges and fibrous residue.