Streetworks Foundations Design Report - Screw Piles & Frame to Support - 20m Atlas, Apollo, Orion, M-Range Streetworks Poles - Generic Design FLI document reference FLI 2023/89

Oct 24, 2026

Streetworks Foundations Design Report detailing the generic design of steel helical (screw) piles and steel grillage frames supporting proposed monopoles for 20m streetworks poles (Atlas, Apollo, Orion, M-Range). The document sets out loading assumptions using generic England parameters, explains pile-frame load transfer, and describes 3- and 4-pile frame capacities and layout constraints. It covers geotechnical design factors of safety, installation risks and mitigation, required site investigations, responsibilities, health and safety obligations, and appendices including drawings, calculations, installation logs, geotechnical reporting, and a design risk assessment.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages9

Reading Time23 min

AccessFree to download

Introduction

Description

Pile Frame Design

Screw Pile Design and Testing

Installation Risks and Mitigation

Health and Safety

Appendix A - Foundation Frame Drawings

Appendix B - Site Specific Design Calculations

Appendix C - Installation Logs

Appendix D - Geotechnical Report

Appendix E - Design Risk Assessment

Francis & Lewis International Ltd, Waterwells Drive, Waterwells Business Park, Gloucester, GL2 2AA, +44(0)1452 722200 [sales@fli.co.uk www.fli.co.uk](sales@fli.co.uk www.fli.co.uk) Streetworks Foundations Design Report Screw Piles & Frame to Support: 20m Atlas, Apollo, Orion, M-Range Streetworks Poles Generic Design FLI document reference: FLI 2023/89 | Site: | Generic Design | | | | --- | --- | --- | --- | | Structure: | 20m Streetworks Poles | | Revision: 06 | | | Document Reference: FLI 2023/89 | | By:
Tony Parker | Introduction This design document has been produced to cover the design of steel helical piles and steel grillage frames to support the proposed monopoles for a Generic Design. There are several risks to generic designs and recommended ways to reduce these as part of the design. Description The loading has been taken using generic site parameters for the middle of England. Loads as below: | Structure | OTM | Lateral load | Weight | | --- | --- | --- | --- | | 20m Atlas | 206kNm | 15.3kN | 38.2kN | | 20m Apollo | 174kNm | 13.2kN | 30.3kN | | 20m Orion | 203kNm | 15.2kN | 36.6kN | | M-Range | 204kNm | 15.1kN | 36.3kN | | 20m Orion V2 | 215kNm | 15.9kN | 36.7kN | Pile Frame Design The chosen structure will be supported by a steel grillage frame which in turn is supported by 3 or 4 No. Screw Piles. The loads from the structure are transferred to the pile sections through the steel grillage. If applicable, there may be some disruption of the existing site. This may include removal or relocation of existing cabinets, bases, and re-routing of services. Some of these items, including access for installation plant, can only be determined after the site survey which is to follow. The proposed layout is shown in the drawings below in appendix 1 and utilises FLI's bespoke 3 or 4 pile grillage frames. The frames and associated piles are vested under FLI’s design works and as such can only be produced by FLI. The 4 pile frames have a 2.0m PCD or a 2.83m PCD. These sizes can fit in many small Streetworks sites and feasibly be buried underground. The frames and associated connection will remain the same with each size of pile used. The 3 pile Streetworks frame works on a 2.0m PCD but was designed for tighter sites, and therefore there is a reduced capacity for the 3-pile frame. (Maximum capacity is shown on the drawing in Appendix A). | Site: | Generic Design | | | | --- | --- | --- | --- | | Structure: | 20m Streetworks Poles | | Revision: 06 | | | Document Reference: FLI 2023/89 | | By:
Tony Parker | The 3-pile T-frame is an innovative design developed for Streetworks poles enabling closer abutment of the installed pole to is boundary edge. This design includes adjustability in the PFC members which allow for variation in pile location. Screw Pile Design and Testing The Screw Piles are designed using the basic geotechnical engineering principles. Because it is a generic design the piles are designed to a basic factor of safety of 2.0 for weak ground of both Cohesive and Non-Cohesive. The non cohesive design case assumes SPT5 ground with a water level at 2 meters. The cohesive design case assumes a range of ground conditions increasing with depth from SPT5 as commonly seen. Due to the design using screw piles, it is recommended to attain a full site ground investigation first before installation to increase chances of successful installation. Even though the piles are tested after installation, it is possible the ground may be extremely soft, such as boggy peat, giving lack of capacity or the ground may be very hard, such and coarse gravel and rock, leading to refusal. If ground is too hard it is possible to mitigate this using a micro-pile design. This can reduce waste of site mobilisation costs and redesign or relocation. Installation Risks and Mitigation A summary of the risks to successful installation and mitigation measures are summarized on the attached log

FAQs

What structures and pole types are supported by the screw piles and frame system?

The design supports proposed monopoles for 20m streetworks poles including Atlas, Apollo, Orion, and M-Range, using a generic foundation approach.

How does the report describe load transfer from the pole structure to the foundations?

Loads are transferred through a steel grillage frame into 3 or 4 screw pile positions, with the grillage acting as the distributing element over the pile sections.

What installation risks does the report highlight and how are they mitigated?

The report emphasizes risks associated with site ground conditions and buried services. Mitigation includes completing a full site ground investigation, using trial holes during installation, scanning for buried services during the trial hole phase, and considering micro-pile mitigation if ground is too hard.

Oct 24, 2026

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