Transforming delivery of major infrastructure projects using Modern Methods of Construction

United Kingdom | Monday, 14 August 2023
Reading Time : 8 minutes

In today's challenging construction environment, clients face mounting pressure, and project delivery is closely scrutinised. Buzzwords like "better, faster, greener" capture ambitious aims, while delivering value for money is a given. Clients now seek wider societal goals, such as catalysing growth, generating employment, and benefiting the community through social value.

Post COP 27, sustainability, net zero, and carbon reduction are still top priorities, though tension can arise between these various needs and the others mentioned above. Fortunately, Modern Methods of Construction (MMC) offer solutions. The UK Government Construction Playbook defines MMC as a wide array of offsite manufacturing and onsite techniques, encouraging innovative alternatives to traditional methods. By adopting MMC, productivity, efficiency, and quality can be significantly improved, transforming the delivery of major infrastructure projects right from the design and planning stages.

Design for offsite construction

Moving fabrication from site to a factory-type environment offers numerous benefits. The controlled setting enhances product quality and reduces wastage. The repetitive nature of production also boosts efficiency, requiring fewer labour hours for the end-product. The welfare of the workforce can be improved, for example, fabrication jigs can be set at an ergonomically optimised working height. Then there are the advantages that come with working in one location compared with itinerant site work.

Project outcomes can also be improved. With pre-fabrication undertaken in advance, and construction becoming assembly, then time on site can be reduced. A shorter construction programme makes less impact on existing transport networks and reduces risk profile, for example, by minimising susceptibility to adverse weather conditions.

Offsite construction using full-height precast units on the A34 Perry Barr project

Design for offsite construction can help to realise these benefits by considering offsite from the concept stage, rather than attempting to convert a traditional design to offsite at a later stage. This was done by WSP on the A34 Perry Barr scheme, where a precast abutment scheme was tailored to infill a new bridge deck within a roundabout where storage space was limited.

Major transport projects with many linear metres of asset types offer opportunities to prefabricate regular elements, such as parapets or duct banks. For major assets, such as long viaducts, it is possible to replicate the benefits of offsite construction by deploying an onsite 'pop-up' factory or using launching/sliding or off-line techniques to concentrate the fabrication works in a controlled environment, provided the design is optimised to suit the use of repeated elements.

Design for manufacture and assembly

Design for manufacture and assembly develops and extends the offsite approach. This can involve, for example, designing for transport constraints, such that modules are sized to fit on a standard HGV trailer rather than requiring special escort, thereby reducing the impact of vehicle movements on the community.

Taking the approach further, a product-led design, or platform approach, involves designing to suit the product constraints, rather than tailoring the work in situ to suit the design. This product-led approach can provide efficiency, lower risk and reduce defects in manufacture and assembly since teams are working repeatedly with the same units. The potential for increased material quantities can be offset to some extent by controlled customisation, similar in concept to the 'design to order' approach seen in other areas of manufacturing.

WSP deployed design for manufacture and assembly techniques on the HS2 Enabling Works Contract. On behalf of HS2 enabling works contractor LMJV (Laing O'Rourke and J. Murphy & Sons Joint Venture), we worked collaboratively as part of a design joint venture with Ramboll. WSP provided design input to a modular abutment system developed with Laing O'Rourke, which saved one month of construction time in the bridge programme for the M42 crossing.

To maximise benefits from design for manufacture and assembly, it’s important to engage design, construction, and manufacturing teams early. This relies on early procurement decisions to identify relevant parties in the supply chain and enable design discussions. Procurement agreement is also needed where early selection of a particular product-set restricts later opportunities for competitive tendering but offers wider project benefits. Project set-ups, such as alliance working or integrated delivery teams, can help achieve these outcomes. Furthermore, long-term contracts, or delivery of a phased series of lots with the same team, allow for feedback-driven improvements over time.

Product-led design using a modular system on the HS2 M42 crossing copyright HS2 Ltd

Digital Delivery

Building Information Modelling (BIM) is a commonly cited means of achieving digital delivery, resulting in a digital twin – a realistic digital representation of the asset. Applying BIM should enable handover of the asset from construction into operations with full asset information. The benefits of BIM during design and construction are well-rehearsed, providing a single source of truth, improved coordination eliminating clashes on site, and allowing review of the virtual construction sequence.

The wider aspects of digital delivery can serve as enablers for offsite construction and design for manufacture and assembly. Design using smart objects, taken from a digital products catalogue, can facilitate product-led design and provide the data required for manufacture as well as reducing the modelling time. Configurator tools can be used to fit product sets to design requirements; WSP worked on a configurator for single-span integral bridges for National Highways.

Design automation can enable rapid engineering and optioneering. It can also enable optimisation against multiple constraints, for example, finding an optimum design balance between carbon and cost. In future, harmonisation, rationalisation and digitalisation of standards and specifications could allow for automated configuration and compliance management. This is an area WSP has been active in, supporting National Highways in its development of the Technical Standards Enterprise System.