Temporary Works

Euston Station, London, UK

Project Brief

LSY Engineering Consultants Ltd was appointed to provide temporary works design and structural engineering support for the removal and realignment of an existing gas main anchorage connection at Euston Station as part of the HS2 enabling works programme.

Our involvement was focused on the construction phase, where we reviewed the existing gas main arrangement, assessed the associated structural risks, and developed temporary works solutions to facilitate the contractor’s proposed sequence of works.

The temporary works design was developed to allow the pipe realignment to be undertaken safely and efficiently while maintaining adequate support and restraint to the existing pipework throughout the construction process.

Challenges

The principal challenge was developing a detailed understanding of the proposed construction methodology and identifying the structural implications associated with each stage of the pipework modification works.

The scheme involved cutting out and realigning sections of existing gas infrastructure while maintaining stability of the system throughout the works. This required careful assessment of temporary loading conditions, pipe restraint requirements, and the interaction between existing and new infrastructure.

Close coordination was required with the gas and pipework engineers to understand the operational requirements, connection details, and behaviour of the various pipe systems involved. The project included a combination of existing cast iron pipework and new polyethylene (PE) gas mains, each with different structural and installation requirements.

A further challenge involved developing temporary support arrangements that would maintain the stability of the pipework during the realignment works while providing sufficient flexibility for the contractor to undertake the installation sequence safely and efficiently.

The project therefore required a detailed understanding of both the permanent gas infrastructure and the proposed construction methodology to ensure the temporary works solution remained practical, buildable, and fully coordinated with the wider project team.

Process

LSY undertook a detailed review of the existing gas main arrangement, available site information, ground conditions, and the proposed pipe realignment sequence to establish the structural requirements for the temporary works.

Working closely with the gas and pipework engineers, we assessed the anticipated forces generated during the staged construction process and developed a temporary support and anchorage solution capable of safely resisting these loads.

Detailed structural calculations were undertaken to design a reinforced concrete anchorage system capable of transferring the pipe forces safely into the ground. The temporary works solution incorporated:

A 1250mm × 1250mm × 400mm reinforced concrete anchorage base.
High-strength concrete to achieve the required early-age strength.
A 152 × 152 × 23 UC S355 steel anchorage section.
Approximately 300mm embedment of the steel section into the reinforced concrete base.

Particular attention was given to ensuring the temporary works design remained compatible with the existing and proposed pipework arrangements, including:

Existing 15-inch cast iron gas main.
Proposed 250mm polyethylene (PE) gas main.
Existing and proposed valve assemblies.
Flanged pipe connections.
Temporary and permanent anchorage requirements.

The support system was designed to accommodate the staged construction sequence while maintaining the stability of the pipework during cutting, connection, and realignment operations.

To facilitate construction, LSY produced detailed temporary works drawings clearly identifying:

Anchorage steelwork.
Connection details.
Construction sequencing considerations.
Installation requirements.
Reinforcement arrangements.
Reinforced concrete anchorage details.

Outcome

The temporary works solution was implemented successfully, enabling the gas main realignment works to proceed safely and efficiently within the HS2 construction programme.

The project demonstrated the importance of developing a thorough understanding of the permanent works design and maintaining close coordination between structural, mechanical, and gas engineering disciplines throughout the construction phase.

By designing a practical and adaptable anchorage solution, LSY enabled the contractor to undertake the pipe modification works with confidence while maintaining structural stability and operational safety throughout the process.

The successful delivery of the project strengthened our relationship with the client and led to further appointments on gas infrastructure, temporary works, and major infrastructure projects across London and the wider UK.

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Balfour Place, London, UK

LSY Engineering Consultants was appointed to provide temporary works design services for the structural refurbishment of a six-storey listed property with basement accommodation in Mayfair, London. The project involved the removal of several loadbearing structural walls at basement level and the formation of new openings through existing vault structures as part of the wider redevelopment works. LSY's commission was to develop temporary works solutions that would safely support the existing structure during the demolition and alteration phases. Our scope included the design of needling and propping systems to facilitate the removal of basement walls, together with roof support and back-propping arrangements to maintain structural stability throughout the top-down demolition sequence. Challenges The project presented several significant engineering challenges. The property was a listed building located within a sensitive Central London environment, where historic bomb damage from the Second World War had the potential to affect existing ground conditions and foundation arrangements. As a result, excavation works required careful planning and execution to minimise risk. In addition, the existing foundation details at basement level were unknown. This uncertainty necessitated a programme of trial hole investigations to establish the form and condition of the foundations before both temporary and permanent works designs could be finalised. The constrained nature of the site, combined with the requirement to maintain structural stability throughout the demolition process, demanded a highly coordinated temporary works strategy. Process The basement walls scheduled for removal were approximately 440mm thick and supported loads from five storeys above together with the roof structure. The upper floors comprised a combination of traditional timber floor construction and filler joist floors. The permanent works proposal included a steel box-frame structure spanning approximately 5m. To facilitate its installation, LSY designed a temporary needling and propping system supported on temporary foundations capable of carrying the significant vertical loads from the existing structure above. A similar engineering solution was adopted at the front of the property, where the existing basement bay window structure was to be removed as part of the redevelopment works. Due to programme constraints, the building was required to be demolished using a top-down construction methodology. To support this sequence, LSY designed a comprehensive temporary propping arrangement that utilised existing internal steel beams at each floor level. This approach provided structural support during the progressive demolition of the upper floors from roof level down to ground floor. Outcome The temporary works strategy proved highly successful and enabled the contractor to maintain the planned construction programme. By utilising existing steel beams within the structure, LSY eliminated the need to extend temporary props continuously down to basement level. This significantly reduced the number of props required throughout the building and removed the need for extensive temporary foundations at each floor. As a result, large areas of the structure remained unobstructed, allowing other trades to continue working efficiently during the demolition process. Within the basement, the needling and propping systems were specifically developed to incorporate surplus materials already available to the contractor. This innovative approach avoided the procurement of additional temporary works equipment, generating substantial cost savings while reducing installation time and improving overall project efficiency. Through careful planning, detailed structural assessment, and close collaboration with the project team, LSY delivered safe, practical, and cost-effective temporary works solutions that successfully supported the refurbishment of this prestigious Mayfair property.

King’s College School, Wimbledon, London, UK

Weedon Street Bridge, Sheffield, UK

LSY Engineering Consultants Ltd was appointed by Cadent Gas Ltd, to provide structural engineering services for works associated with Weedon Street Bridge in Sheffield. The project involved the removal of two 24-inch gas mains attached to the east and west elevations of the existing bridge structure. Each pipeline extended approximately 70 metres across the River Don and required careful planning and execution due to the age of the bridge, the scale of the pipework, and the operational constraints of the site. Our appointment included: An initial structural condition survey and reporting. Structural assessment of the proposed temporary works and scaffold arrangements. A post-completion structural inspection to verify that the removal works had not adversely affected the bridge.

Dover Town Hall, UK

LSY Engineering Consultants Ltd were appointed to provide temporary works design and structural engineering support for the refurbishment of Maison Dieu House, a Grade I listed building forming part of Dover Town Hall. The project required careful planning and close technical coordination to maintain the safety and stability of the historic masonry arch structures during construction activities.

Weedon Street Bridge, Sheffield, UK