Offsite manufacturing for construction, or offsite for short, has been around for a while in the roads sector but its full potential is now starting to be realised. . That potential is an ability to reduce impact on customers, improve safety during construction, and reduce cost and time in delivery.
Increasing application of offsite
While bridges and gantries have long been manufactured offsite and then lifted into place, other elements such as bridge abutments are now using the same process.
This sees standardised products created to solve a range of geotechnical problems. In the process, these products remove wet trades and reduce time on site process – an important consideration as it both reduces disruption for customers and cuts the amount of time operatives spend next to traffic.
The growing list of road components manufactured offsite includes control units for gantries, substations, and even foundations for substations that come with standardised service ports. There are even companies looking at offsite for ground-bearing slab systems for roads. These might be manufactured in a centralised facility or in temporary ‘flying factories’ close to site that move along as the project progresses.
Following the example of buildings
Can roads projects make as much use of offsite as the buildings sector, which has led the way in offsite? Well, by their nature roads project are very different. For one thing, ground conditions can change dramatically over the course of a road. So, elements that have to transfer loads to the ground would have to be designed differently in different places. A range of standard solutions and products may be the answer, or, initially, a traditional designed interface with the ground and a standardised foundation on top.
Other elements and associated buildings and infrastructure such as service stations and breakdown vehicle locations lend themselves readily to offsite manufacture. There are even systems being tested that standardise elements of the road build-up and running surfaces. These are manufactured remotely and then finished on site, vastly reducing the amount of work at the construction site and marrying the benefits of offsite and in situ in a type of hybrid solution.
Adopt from the outset
At WSP, we start by looking at the objectives of a project and identifying how offsite could benefit them – using our own tools to evaluate which elements might be appropriate for offsite. It’s important to do this early in the design stage because it feeds into everything, including material choice, sizes, weights and tolerances.
Offsite also goes hand in hand with emerging and rapid advances in digital design. WSP is looking at how BIM and the digital twin can enable standardised designs to be manufactured offsite and installed quickly and easily. A digital twin can assist in fully understanding the site context – essential given the diverse geotechnical conditions over a length of highway, supporting better decision making about the application of offsite components and methods. BIM, combined with visualisation technologies such as virtual and augmented reality (VR/AR) can support digital rehearsal – which enables construction teams to practise an installation in minute detail to ensure everything goes smoothly when it comes to the real thing.
Outcomes can’t be ignored
Whatever the drivers for adopting offsite – customer, safety, cost, schedule, quality or technical challenges, the opportunities it brings are tantalising. The buildings sector has harnessed some of these benefits with schools now being delivered in less than a single academic year on sites with almost no construction noise to disrupt teaching. With the expanding use of offsite across multiple sectors, its flexibility and benefits offer massive opportunities. The development of offsite components I’ve discussed here are the tip of the iceberg when it comes to the opportunities in the highways and roads sector.
WSP Author:
Richard Anderson, Technical Director, WSP
