Tower Strengthening
FLI tower strengthening solutions for aged structures provide a cost-effective means of extending tower service life by bypassing corroded stubs, restoring structural stability and preventing foundation-related failure. FLI’s tower strengthening systems improve safety, minimise downtime and enable existing assets to remain in service.
Tower Failure & Hidden Corrosion
The photograph shows a tower that collapsed following failure of the base stubs at the plunge point, while the tower structure itself remains free from corrosion.
The video illustrates the risks associated with hidden corrosion in older towers, particularly at the interface between the tower and its foundation. In this instance, there are again no visible external signs of corrosion.
FLI’s bypass systems provide strengthening solutions for a wide range of ageing structures, ensuring network safety without the need for full tower replacement.
Learn more about our screw pile foundation solutions.
Off-the-shelf solutions for all networks.
Swann A2 ButterFLI (low capacity)
Swann B2-3 ButterFLI (medium capacity)
30H ButterFLI (medium capacity)
TT30 ButterFLI (medium capacity)
TT40 ButterFLI (medium capacity)
Swann B3 ButterFLI (high capacity)
Satturn FLI Heart
AD703 FLI Heart (high capacity)
Eve Type 9 FLI Heart (high capacity)
Swann Type 4 FLI Star
Swann Type 4 FLI Spade
DC415 FLI Oval
DC410 FLI Oval
ATT850 FLI Angle
ButterFLI: light, medium & high capacity.
ButterFLI plates restore full capacity to corroded tower foundation connections, supporting tower leg capacities of up to 750 kN ULS. The system bypasses the corroded stub by interfacing with the lowest tower flange and can be adapted to suit any CHS leg and flange configuration without the need for additional stiffening plates.
The plates are lightweight and designed for hand carrying and installation, eliminating the requirement for plant. Load is transferred into the existing concrete foundation through post-fixed anchors and high-strength grout.
Patent pending.
ButterFLI is a proven tower strengthening solution for ageing structures affected by foundation corrosion.
Low Capacity
Restores full capacity to corroded foundation connection of tower legs up to 400kN ULS.
Bypasses corroded stub by interfacing with the lowest tower flange.
Medium Capacity
Up to 600kN ULS. Can be modified for any CHS leg and flange without stiffening plates.A three-plate “Split-Wing” design is used for larger leg diameters and higher forces whilst still enabling hand installation.
High Capacity
Up to 750kN ULS or alternately used for towers with low strength concrete foundations.
FLI Heart
For sites with low edge distances or congested conditions where space is limited, anchor layouts have been reduced to a 320 mm PCD to accommodate edge distance constraints and existing concrete reinforcement.
The Medium Capacity Heart is a single-plate solution providing capacity up to 550 kN ULS. The High Capacity Heart uses a three-plate configuration, delivering capacity up to 750 kN ULS. Both solutions are suitable for strengthening ageing structures where edge distance limitations or concrete conditions restrict alternative approaches.
Patent pending.
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FLI Oval
This new product has been designed to suit the Dynamic Concepts DC415. It is a two-plate solution featuring two M36 Fischer anchors per leg with a 720 mm anchor embedment.
Patent pending.
FLI Star
Developed for the Swann Type 4, the FLI Star can be modified to suit any CHS leg and flange configuration, with or without stiffening plates. It is designed for towers supported on grout with stiffened flanges or HD studs.
The system transfers loads using bearing face pressure and modified pressure surfaces to resist shear forces. As with all FLI bypass solutions, the components are hand-carriable and can be installed by hand, with no requirement for tower outage.
Medium Capacity:
Restores full capacity to corroded foundation connections of tower legs up to 600 kN ULS.
High Capacity:
Provides capacity up to 760 kN ULS.
Patent pending.
FLI Spade
Restores full capacity to corroded tower foundation connections, supporting tower leg capacities of up to 583 kN ULS.
The system is used where corroded drainage flanges have caused movement at the tower base. It can be modified to suit any CHS leg and flange configuration, with or without stiffening plates. The connection is made directly to the tower leg, bypassing the entire base detail.
The solution comprises two clamping plates and two arms, all of which can be hand installed. Load is transferred into the existing foundation via four post-fixed anchors and high-strength grout.
Patent pending.
FLI Angle
Restores full capacity to corroded tower foundation connections, supporting tower leg capacities of up to 300 kN ULS.
Developed for the ATT850, the FLI Angle can be adapted to suit any angle tower leg, bypassing corroded stubs and interfacing with the lowest tower splice.
The two-part solution is designed for hand installation. Loads are transferred into the existing concrete foundation through three post-fixed anchors and high-strength grout.
The system is intended for ageing angle towers affected by corrosion at the base connection.
Patent pending.
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FLI Wheel - Monopole bypass interface
Corroded holding-down bolts are bridged using an interface that allows a new monopole to be installed on the existing foundations.
Patent pending.
ButterFLI: Concrete Break Out Kit
Addresses tower bases that have previously been strengthened by overpour.
The system provides a template for cutting the concrete to accommodate the ButterFLI solution and includes cover plates to safely close the remaining slot.
Patent pending.
ButterFLI: Installation Day 1
Tower legs are drilled to remove any trapped water.
The stub is drilled in preparation for grouting.
Grout is injected inside the stub to displace trapped water and stabilise corrosion.
The stub is wire brushed and painted.
Using a template, anchor holes are drilled, then scabbled and cleaned.Anchor bolts are installed using epoxy resin with the ButterFLI plates in position.
ButterFLI: Installation Day 2
Anchor bolts are tested to verify capacity and then torqued to the specified values. ButterFLI plates are grouted using reusable, curved steel grout boxes, enabling rapid installation and a clean, consistent finish.
These solutions provide a safe and effective method of strengthening ageing structures while minimising disruption and downtime.
