The Leadenhall building Digital collaboration and · Conferences & seminars The Leadenhall building...
41
Conferences & seminars The Leadenhall building Digital collaboration and complex fabrication Damian Eley
Transcript of The Leadenhall building Digital collaboration and · Conferences & seminars The Leadenhall building...
Conferences & seminars
The Leadenhall building Digital collaboration and complex fabrication
Damian Eley
Presenter
Presentation Notes
Good morning. I am a bit daunted about talking at a BIM conference, as I am very much a designer rather than a BIM person. To be honest I don’t really understand what BIM means exactly. My interest is in producing really good designs, and in understanding how technology can improve our ability to do this better.
The Leadenhall building
Presenter
Presentation Notes
The Leadenhall Building is unusual in the amount of pre-fabrication that is involved. 80% of the building is fabricated off-site. It is also unusual because the primary stability structure, or megaframe, is placed outside the main façade and is left exposed to view. This complex structure therefore has to address both engineering and aesthetic issues, and required very careful development.
The Leadenhall building
Introduction Digital collaboration Complex fabrication Conclusions
Presenter
Presentation Notes
In this talk I will demonstrate how Arup met some of these challenges by working collaboratively with the rest of the team around shared digital models. I will start by introducing the building. I will then talk about some of the digital processes that were used on the project to help deliver it more efficiently I will focus in particular on the processes that we used to deliver some very complex steelwork fabrication, before summarising with some lessons learned and other closing thoughts.
Key facts
50 storeys 224m high 56,000 m2 of office floor space 42 office floors Some retail at lowest levels 4-storey basement
Presenter
Presentation Notes
Leadenhall is a 224m tall office tower with a four-storey basement. It provides 56,000m² of office space with some retail at ground level.
Programme and parties
Parties Client: British Land and Oxford Properties Architect: Rogers Stirk Harbour + Partners Engineer: Arup Contractor: Laing O’Rourke Steelwork contractor: Watson Outline programme Project start Nov 2001 Planning application Feb 2004 Start on site Jan 2007 Project put on hold Sep 2008 Appoint main contract August 2011 Topping out June 2013
Presenter
Presentation Notes
The Client is British Land, who went in a joint venture with Oxford Properties to fund the construction. The architect is Rogers Stirk Harbour. Arup provided multi-disciplinary engineering services. The project began in 2001 and achieved planning in 2004. Early enabling works were carried out in 2007 under a construction management form of contract, and then the project ground to a halt in 2008. It was resurrected in 2010 and in August 2011, Laing O’Rourke won the contract to complete the building with Watson as the steelwork contractor. The design team was novated and things have continued at breakneck speed ever since. The building topped out in June this year and is due to complete next summer.
Competition scheme
Presenter
Presentation Notes
The architectural ambition was always to feature the engineering as much as possible in the building. The tapered shape and the placing of both the structure and the lift cores around the outside were evident within the competition-winning scheme.
Typical floor
Office
North core lobby/toilets
East/west fire fighting cores
On-floor plant and risers
Passenger lifts
Goods lifts
Presenter
Presentation Notes
As with many Rogers buildings, the floor is as open and uncluttered as possible. The main services and lifts are in an external core to the north supported by two fire fighting cores on the east and west.
Typical floor
Presenter
Presentation Notes
The typical floor structure is composite steelwork with solid pre-cast concrete floor slabs. These floor slabs were one of several prefabricated elements that Laing O’Rourke proposed for the project.
Prefabrication
Presenter
Presentation Notes
Others included pre-cast walls into the east and west cores and modular assemblies for the vast majority of the services. In total, over 80% of the Laing O’Rourke’s contract by value was manufactured off-site.
Megaframe
Presenter
Presentation Notes
Around the perimeter of the office the megaframe bracing system provides stability, removing the need for a central concrete core. Geometrically, it divides the height of the building into eight equal portions or ‘megastoreys’, each seven normal storeys high.
Galleria
Presenter
Presentation Notes
At the base of the building the lowest megastorey is opened up into a 28-m-high public space known as the ‘galleria’. Escalators within this space take people up to the main lift lobbies at first and second floor level.
North core
Presenter
Presentation Notes
On the north side of the building is the lift core, and this has a very different structure to the rest of the building. Painted bright yellow, the primary framework is a system of beams, columns and bracing which runs like a spine down the middle of the core. Outboard of this are the lifts, contained within a hanging system of steel and glass.
North core
Presenter
Presentation Notes
The primary structure of the north core is a feat of volumetric prefabrication. Each floor level is split into three tables. These have concrete floors and services pre-installed in the factory. They arrive on site on the back of a lorry where they have temporary handrails added before being lifted into place and bolted to one another like huge pieces of lego. This process means that a complete north floor structure can be erected, with its services, in a single day.
Attic
Presenter
Presentation Notes
At the top of the building is the ‘attic’, a complex four storey plant room containing the generators, boilers and cooling towers.
The Leadenhall building
Introduction Digital collaboration Complex fabrication Conclusions
Presenter
Presentation Notes
I’m now going to talk about some of the collaborations that were involved in this project, and the extent to which these involved digital models.
Structural optimisation
Presenter
Presentation Notes
Initially at concept stage, i.e. up to planning, the design was very fluid. While the architects were using CAD extensively to test their ideas, Arup stuck with hand sketches in place of CAD drawings.
Structural optimisation
Presenter
Presentation Notes
We focussed our 3D efforts on analysis, developing automated design processes which linked our Oasys GSA models with Excel spreadsheets in order to test options for efficiency and optimise the stability system.
Tekla BIM model
Presenter
Presentation Notes
At the start of scheme design we began to assemble a Tekla model which was to be used for the entire project. We first used XSteel, the precursor to Tekla, to deliver a project back in 1997 for the Merrill Lynch headquarters in London. It has remained our preferred software for complex steelwork 3D modelling and drawing production ever since.
Services co-ordination
Presenter
Presentation Notes
We also developed local 3D models of the MEP services in CADDUCT and checked the co-ordination of areas such as the attic, the basement and the typical floor using Navis works, and later on also using Tekla BIMSight.
2D drawings
Presenter
Presentation Notes
We never stopped producing 2D drawings however. Both Rogers Stirk Harbour and we felt that 2D drawings were the best way of presenting our ideas. We periodically exchanged models with one another to check co-ordination. But we also invested time to ensure that we were producing good quality 2D drawings of everything, with as much information coming direct from the model as possible. By the time we reached tender we had over 300 structural drawings, of which the majority were generated from the model, which always remained accurate and up to date.
Construction planning
Presenter
Presentation Notes
We handed the Tekla model over to the contractors at tender. Laing O’Rourke used it to explore the construction methodology and co-ordinate the temporary works. They presented this through an impressive animation sequence, and have continued to use it extensively ever since to manage the construction process.
Detailed co-ordination
Presenter
Presentation Notes
I have mentioned already that Laing O’Rourke pushed for as much of the project to be prefabricated as possible. This meant that everything had to happen earlier than would otherwise have been necessary. Secondary items such as cladding brackets, lift guide brackets and temporary works attachments had to be co-ordinated up front with the structure and services, so that they could be incorporated into the components during manufacturing. This co-ordination effort involved everyone. The foundations were already in place when Laing O’Rourke were appointed, and the first steel column arrived six weeks later. There was no time to waste in getting the details right. Laing O’Rourke’s approach to this was to take ownership of a combined digital model which they used as the basis of a series of regular BIM workshops throughout the design process.
BIM workshops
Presenter
Presentation Notes
These workshops could be very large meetings, because they needed to involve all the relevant parties. Each party had to develop their own designs in 3D and issue models on a regular basis for co-ordination to Laing O’Rourke’s BIM co-ordinator, who identified what the issues were that needed to be discussed and sent out agendas with snapshot images attached. This made the meetings themselves very efficient. Most designs were ultimately issued as drawings, but the elimination of reliance on these for co-ordination was very effective in enabling problems to be resolved very quickly. And in the case of the builderswork details for the fixings between the cladding and structure, Yuanda issued this information to Watson in 3D without any associated setting-out drawings, and Watson simply added it to their fabrication model. This approach did require trust within the team, and I believe that this was significantly enhanced by Laing O’Rourke’s commitment to a no blame culture.
The Leadenhall building
Introduction Digital collaboration Complex fabrication Conclusions
Presenter
Presentation Notes
I am now going to talk about some of the processes we used when designing the megaframe nodes, the 4m high pieces joining the megaframe members together. Arup was fully responsible for the design of these components, which had to resolve a variety of complex member relationships.
Connection strategy
Presenter
Presentation Notes
The initial focus of design was to establish a connection strategy, and at this stage many decisions were made on the basis of simple sketches and hand calculations.
Connection strategy
Presenter
Presentation Notes
We agreed that the site connections should be bolted rather than welded, and we recognised that there was value in using large bolts, similar to those used on tower crane masts and oil rigs, for strength and to speed up the erection process.
Connection strategy
Presenter
Presentation Notes
As we started to understand the spatial requirements of these connections, they in turn informed the shapes of the members themselves.
Developing geometries
Presenter
Presentation Notes
The second stage was about developing the fabrication geometry for each node. There were 11 distinctive nodal geometries, and many sub-variations of each.
Developing geometries
Presenter
Presentation Notes
This process was guided by engineering principles such as the need to identify the load paths through the nodes. There were also important architectural principles. They needed to present themselves as a family of similar details, and clearly express the idea of the building as a kit of parts.
Developing geometries
Presenter
Presentation Notes
In order to do this we began to add nodes to the same Tekla model as we had already built for the members. We worked closely with the fabricators William Hare at this stage. They placed one of their technicians in our office. As we were not used to modelling complex connections in Tekla, this helped to ensure that the node models were set up in a way which was consistent with their fabrication processes. We held weekly design workshops with Hares and Rogers in our office. These provided an opportunity for engineer, architect and fabricator to review the Tekla model together. Because of the geometric complexity of some of these nodes and the demanding architectural aspirations, this was a very challenging task, and the gathering of different skills around a single model was critical to achieving it.
Developing geometries
Presenter
Presentation Notes
The architect also prepared his own parametric study models to investigate options in parallel, and exchanged these regularly with the engineering team.
Developing geometries
TEKLA RHINO GSA
Presenter
Presentation Notes
During this stage, which was Stage D, we exported geometry directly from the Tekla model, via Rhino, to our analysis software Oasys GSA, in order to study the structural behaviour of some of the nodes.
Final node design
Presenter
Presentation Notes
The third stage of the process was the final design of the nodes. This was largely just a task for Arup, although we still held regular model reviews with Rogers through this stage to ensure the architects were happy with each design.
Final node design
Tekla Drawing Model
Rhino Transition Model
Excel Load Input
GSA Global Analysis
D3 Plot Stress checks
Excel/VB Weld checks
ANSA Meshing
Nastran Analysis
Presenter
Presentation Notes
For the final design checks, the geometry from our Tekla model was converted into a Nastran finite element analysis model. This transition was carried out using Rhino and the meshing software ANSA. We also used spreadsheets extensively to identify critical loadcases and to carry out automated stress checks on welds.
Final node design
Presenter
Presentation Notes
Weld stresses were presented in a graphical form, enabling us to see exactly where the minimum weld size needed to be supplemented with additional passes. We completed the design of all the ground level and level 5 nodes prior to tender. This was very valuable to the client because he was able to get a confident and competitive price for the steelwork. The steelwork contractors Watsons were also able to use our models to get a real head start in planning their fabrication processes.
Final node design
Presenter
Presentation Notes
As with the rest of the structure, we also produced 2D drawings of the nodes. These provided the nodes and information about weld detailing principles. We had references for each of the plates and gave their thickness in different locations in tables, so as to avoid the need for us to model and draw every single variation of each node.
Final node design
Presenter
Presentation Notes
We also produced a set of fabrication sequence drawings illustrating how each node could be assembled. We did this because we wanted to be sure that the contractors fully understood the thinking behind our design. Initially this gave them confidence that this complex project was buildable. Subsequently it helped ensure that they made things correctly as we had intended.
Final node design
Presenter
Presentation Notes
The client’s up-front investment in design paid off because all of the nodes were fabricated very much as the architect and we had intended, with almost no change from what was issued at tender.
The Leadenhall building
Introduction Digital collaboration Complex fabrication Conclusions
Presenter
Presentation Notes
I will finish with some personal conclusions that I have drawn from this project.
Conclusions
Rely less on 2D for co-ordination Work collaboratively around a single model Establish an environment of trust Use the right specialist tools for the purpose Recognise the value of 2D drawings Work out how to produce these efficiently Some information should only be 2D drawings We need to identify the right balance
Presenter
Presentation Notes
Firstly, it is ever clearer that reducing one’s reliance on 2D drawings is highly effective during co-ordination. Progress can be made much more quickly once everyone is working in 3D, especially when they do so collaboratively in one room. This is particularly powerful for resolving complex geometric problems involving several parties. The audit trail is less clear, however, when working in this way. This approach therefore requires genuine trust between the parties. The client and main contractor have to set the tone for the project. It is important to choose the appropriate specialist modelling methods for the design task, and then find other software that can be used to link the results of this to the other activities for co-ordination. There will never be one package that does everything. It is also useful to involve manufacturers early, not just for reviewing designs for buildability but also to help establish the right modelling methods. On Leadenhall we chose to present everything in 2D. This required extra effort. In future projects I would want to reduce the number of drawings. At the moment I am unsure how far to go with this, however, as I am convinced that the clarity of our drawings was as big a factor in reducing errors further down the supply chain as the fact that we had a 3D model. People read information in 2D, whether this is on a screen or a sheet of paper, which means that the best way to explain almost anything is through a 2D representation. Watching a 3D film does not tell you more of the story, it just makes the experience more exciting. Reasonably clear drawings can now be fairly easily generated from the 3D model. I think we need to work to improve the quality of drawings produced in this way, and the process of generating drawings from the model. We should also recognise that some design information will always be more efficiently conveyed if it is simply drawn in 2D. We therefore should try to identify the right balance of 2D and 3D methods. I would like to see a clearer consensus across the industry about what information should be drawn in 2D, what information should only exist in 3D, and what information should be both included in the 3D model and presented in 2D. When we have done this, I am not sure what BIM level we will have reached, but I do think we will have worked how to use our digital models intelligently.
The Leadenhall building
Presenter
Presentation Notes
Thank you.
