For those seeking to make BIM a reality, Richard Fletcher, Managing Director at Trimble explains how Trimble’s Tekla Structures software was piloted for 3D rebar modelling on the Highways England M1 J19 Improvement Scheme.
Discover how the software was trialled alongside traditional 2D detailing, how this forward-thinking design team worked together, the benefits of a BIM approach and lessons learnt. The whole process was a first for everyone involved.
Designed to relieve bottleneck congestion, increase journey reliability and road safety and, separate local traffic from long distance traffic, the aim of Highways England’s M1 J19 Improvement Scheme is to improve junction 19 of the M1 motorway, related sections of the M6 motorway and, the A14 trunk road.
Highways England awarded main contractor Skanska UK the design and construction of a new four-level M1 Junction 19 near Rugby in the Midlands under the Early Contractor Involvement (ECI) initiative.
Although not contracted as a BIM project, Skanska and the design and sub contracting team identified the opportunity to develop its collaboration skills, trialling and implementing BIM processes and software. The team presented a business case to the project board seeking approval to adopt BIM on the basis of potential benefits, including cost savings.
About the structures
The project involved the construction of six bridges including gantries, culverts and minor retaining walls. In this instance, the focus is on two structures, S8 and C14. S8 comprising a 13.7m-wide skewed precast concrete beam deck, with full height abutment walls and piled foundations, and a single span of 14.1m. It carries the new M1-A14 southbound link over a proposed local road. C14 was a 3.15m square cantilever gantry footing with piled foundations.
S8 structure (left), C14 square cantilever gantry footing with piled foundations (right)
The BIM pilot project
Knowing the strength in Tekla Structures rebar detailing and bridge modelling capabilities, a Skanska BIM manager recommended its use. BIM Projects Manager Maurice Hill, from BRC - the UK’s largest steel reinforcement fabricator for concrete -explains:
The initial plan was to run a ‘shadow’ BIM project alongside the on site works, to allow us to assess the current technology and procedures. The structures were previously modelled by Jacobs to a level where we could determine that the software packages could communicate through The Industry Foundation Classes (IFC) exchanges.
As part of the construction deliverables, Jacobs’ team in Leeds had modelled all six major structures, forming part of the federated model; 3D reinforcement models were not produced, as the modelling software used was not considered sufficient for complex bridges. Instead, 2D reinforcement drawings were produced for construction. Given this was not strictly a BIM process, Jacobs sent the 2D reinforcement drawings, 3D model and IFC export for S8 to BRC. BRC produced the bridge model in Tekla Structures, including modelling the reinforcement for the abutments, foundations and piles.
With the rebar modelled in 3D, BRC was able to give detailed comments to Jacobs and as a result, various changes were made. Commenting on the working process, Jacobs BIM Manager and UK Highway Structures Lead Anthony Oxford said:
We saw a number of benefits. Number one was ‘visualisation’. Being able to see the complex reinforcement as a 3D model meant spotting clashes easily and importantly, the visualisation truly allowed us to collaborate and solve queries swiftly.
Revisions were easier as new bar bending schedules were created easily. The digital file type also allowed for quicker and more efficient rebar ordering.
From 3D model to rebar output: improved workflow processes
BRC’s Maurice Hill explains some of the benefits of the software:
Tekla Structures is all about collaboration and as such can import and export to suit all software and machine vendors.
We are able to create a 3D construction model of the proposed structure, which at the very least minimises revisions between engineer and fabricator, at best eliminates them entirely. It also allows material quantity take off and production information to be transferred automatically, minimising manual work and errors. Drawings can be extracted from the model, and changes updated. Also, the single file can be used for more than one application without duplicating the source of the data.
Driving collaboration on the M1
Exploring true BIM collaboration has been vital as Sue Hyde, Skanska’s BIM Co-ordinator explains:
Communication generally is an issue surrounding BIM, it is a massive learning curve for everyone and this project allowed us to take another step forward in improving our processes.
On the S8 structure there were two abutments, the first was constructed traditionally. For the second, we brought the design team and steel fixers together to share the Tekla Structures models and review before the rebar fixing; alterations were made accordingly. Final model images were provided for the fixers to work from.
This process helped, especially as the team is working in a constrained area with close proximity of structures. The concrete pour out was completed successfully in February 2016 and the structure was finished and opened to traffic in August 2016.
In truth, collaboration like this has been happening for years but by doing it in a more structured way it is recorded centrally and happens faster.
Refining the process on the next structure
The final Tekla Structures model created by BRC was for the gantry foundation designated C14. This was a purely digital exercise. The concrete model was created and rebar added using Tekla Structures, employing Jacobs’ deliverables; the digital bending schedule was then generated directly from the model. The model was exported as an IFC file and checked by Jacobs. Once approved the digital bending schedule was used for the fabrication of rebar.
The de-brief: BIM lessons learnt and skills to build on
The amount of rework and waste most definitely reduced. BRC’s Maurice Hill explains:
This project focused on trialling the BIM technology throughout the design and construction, assessing the impact it has on the technical aspects of the process. All agreed it wasn’t perfect but was a valuable exercise.
Here, the team shares some of its real-life lessons learnt.
Design and visualisation is invaluable
With traditional 2D methods, items are detailed individually, and if mistakes are made, or clashes undetected it costs time on site, creating delays and frustration all round. Using a 3D modelling package such as Tekla Structures means less room for error.
Early involvement and a ‘no blame’ culture make for true collaboration
The earlier the involvement with the design team and sub contractors the better. This was a definite shared view. Operating in a safe ‘no blame’ environment ensured clashes and problems were solved swiftly and effectively. Adopting this culture from a project’s outset really does achieve results.
Complete responsibility for the certified model also needs to be agreed and signed off so that it truly is a model that teams can work from. There is no room for ambiguous information or blurred lines of responsibility.
Introduce tech planning early on
Skanska BIM Co-ordinator Sue Hyde explained:
It is important that we develop a BIM Execution Plan which outlines the process of sharing information, highlighting the key technology and software requirements.
Jacobs’ Anthony Oxford said:
We are now encouraging site engineers to use tablets for inspecting and site walkrounds for checking newly constructed elements against the model, instantly raising queries or potential issues.
In the case of the M1 J19 project, Skanska called off what was needed on site, when required, however as BRC’s Maurice Hill explains:
The software allows us to create lotting schedules.
This capability avoids rebar being delivered to site too early, often if this happens it gets moved around the site, which involves additional time, pressure on manpower and the associated carbon as a result of the machinery used. In addition, if rebar gets left on a site too long and bars from other lots get used, which creates problems further down the line.
BIM Education and training
In reality there’s limited real-life BIM experience and depth of capability. Industry-wide BIM education and training is essential. As Skanska’s Sue Hyde explains:
When it comes to BIM education, and training we needed to make sure that our clients, project team and sub-contractor are BIM aware and rolled out several BIM awareness sessions throughout the project.
Legacy models and asset management
What became clear from this process and the use of Tekla Structures is the potential of having the rebar detail to hand for future maintenance when it comes to asset management and FM.
Skanska’s Sue Hyde explained:
A high Level of detail and information within the 3D model is especially beneficial for asset management.
Going forward, where applicable on request by Highways England, legacy models will be passed back and fed into the Highways England system for future asset management purposes.
The fantastic wealth of knowledge in digital models will help efforts to keep major infrastructure, like this M1 project in optimum condition in the most efficient way.