Editor's Note: This article was originally published on The Construction Manager Magazine's blog and was republished here with permission.
BIM is not just for build creation: it now extends to demolition. Mark Coleman, managing director of The Coleman Group and deputy chair of the CIOB’s Birmingham Hub, explains.
At The Coleman Group, we use 3D BIM for structural analysis and design, and 4D BIM to plan and programme.
A BIM model helps us understand the impact of removing structural elements, what kind of machinery the structure will support, how much articulation our demolition equipment will require, how our work will interface with other trades and detect clashes. It allows us to present visualisations of our work to clients, and it also makes the site much safer.
There is a tendency to see BIM as useful only for new build. We are now seeing more BIM questionnaires at prequalification stage and Revit models at tender stage, but generally, construction take up has been poor. With my CIOB role, I want to highlight how BIM can help on ‘cut and carve’ projects – we must take advantage of the safety and efficiency improvements possible through embracing technology.
Put into action
At Birmingham New Street Station, on the atrium demolition, the programme needed to be cut from 12 to six months. So we took the BIM model and worked with Mace to plan every single working day – highlighting sequence clashes, maximising utilisation of the plant, planning debris removal timings.
We used the BIM model to create exclusion zones around demolition works to improve safety of other site workers. We completed the programme in five months chiefly because BIM allowed high levels of collaboration while working in a lean environment.
On Three Snowhill, an office project, we had to make structural alterations to a five-level basement car park, and the programme meant our operations would interface with other trades carrying out permanent structural works. Main contractor BAM provided us with a Revit model, and we used it to plan the logistics, and flagged up clashes with the structural designer.
On some demolition projects, we will create our own BIM model. We have recently acquired a high-definition 3D Scanner to survey structures. It sits on a traditional survey tripod, can rotate around 360 degrees, and creates a 3D digital point cloud. From this, we can create the 3D model.
It helps communicate visually what we are doing to clients and the team on the ground. We have used the scanner on the demolition of Wolverhampton Bus Depot.
BIM and machinery use
The BIM model tells us what machinery loads the structure can carry and any constraints on operations. At New Street, we calculated we could use a 25-tonne excavator using significant temporary works, which would make the job far more efficient than a 2.5-tonne Brokk robot which would typically have
So we developed a bespoke excavator with JCB using 3D modelling, and imported this into the client’s BIM model. It is remote controlled, so the operator can be outside the cab when guiding the attachment, with a full 360-degree view. The excavator improved productivity immensely. It was also safer.
This is not exactly new in terms of the way projects have been carried out. On both Unilever House and Regent St demolition, the entire internal structure of the building was modelled to enable structural analysis and then programmed to show how it was to be demolished including the temporary works to keep the existing facades in place as these were to be retained. That was 2005!Chris Allen, 9 October 2017