STRUCTURAL BIM: DISCUSSION, CASE STUDIES · breed’ solutions, one of which will be the structural BIM. Structural BIM is the most important area for structural engineers and their

Title: Structural BIM: Discussion, Case Studies and Latest Developments

Author: Clive Robinson, Tekla

Subjects: Building Case StudyIT/Computer Science/SoftwareStructural Engineering

Keywords: BIMStructure

Publication Date: 2007

Original Publication: 2007 CTBUH / Wiley Tal Journal

Paper Type: 1. Book chapter/Part chapter2. Journal paper3. Conference proceeding4. Unpublished conference paper5. Magazine article6. Unpublished

© Council on Tall Buildings and Urban Habitat / Clive Robinson

ctbuh.org/papers

http://ctbuh.org/papers

STRUCTURAL BIM: DISCUSSION, CASE STUDIES AND LATEST DEVELOPMENTS

CLIVE ROBINSON*Tekla (UK) Ltd, Leeds, UK

SUMMARY

This paper discusses the current state of building information modelling (BIM) from the structural point of view, incorporating the migration from 2D to 3D solutions. Open interfaces are also considered and how they provide access to BIM information away from the specialist modelling solutions to more conventional software tools, allowing closer design team collaboration. Two case studies are also highlighted to identify the benefi ts obtained from the structural BIM solution. Copyright © 2007 John Wiley & Sons, Ltd.

1. OVERVIEW

Building information modelling (BIM) technology has advanced in recent years to become a hot topic in the building and construction IT sector. BIM allows the design team information to be visually explored and integrated through the three-dimensional (3D) computer model. Even though it is a recent concept, the foundations for this technology have been in development since the mid 1990s with structural steelwork modelling and detailing systems. This has been further driven by advanced inter-operability utilizing the industry standard formats, such as IFC (Industry Foundation Classes),1 and other technologies such as the Microsoft .NET platform and the resulting application program interface (API) technology to allow computer applications to communicate directly with each other.

2. THE MIGRATION FROM 2D TO 3D

Various industry sectors have moved from two-dimensional (2D) information to 3D models after getting over the ‘Why change?’ syndrome. Some sectors of the construction industry are unfortunately still asking the same question. Ultimately they really should be asking the question ‘Can I afford to stay with 2D designs?’ After all, 2D drawings are just a collection of lines and text which relies on the skill and training of the producer and reader to interpret the presented information. With 3D infor-mation the previous mental visualization is presented to the viewer as it is visually processed by the algorithms in the software. For various reasons, either due to time constraints or lack of experienced personnel, 2D drawing production has become an issue over recent years, especially in the construc-tion sector.

Copyright © 2007 John Wiley & Sons, Ltd.

* Correspondence to: Clive Robinson, Tekla (UK) Ltd, Tekla House, Cliffe Park Way, Morley, Leeds LS27 0RY, UK. E-mail: [email protected] IFCs refer to the International Alliance of Interoperability’s website, http://www.iai-international.org/.

THE STRUCTURAL DESIGN OF TALL AND SPECIAL BUILDINGSStruct. Design Tall Spec. Build. 16, 519–533 (2007)Published online 23 October 2007 in Wiley Interscience (www.interscience.wiley.com). DOI: 10.1002/tal.417

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Copyright © 2007 John Wiley & Sons, Ltd. Struct. Design Tall Spec. Build. 16, 519–533 (2007) DOI: 10.1002/tal

It should also be remembered that 3D information can be presented on drawings in a coordinated form, ensuring all information is correct on the corresponding plans, elevation and sectional drawings and everything is to scale. The coordination and checking part of a 2D design is often overlooked and this is the source of many requests for further information and design team confl icts. This in itself sometimes does not seem to be a major issue. However, it should always be remembered that schemes go to tender, manufacturer and construction, months or even years after the drawings have been pro-duced. In revisiting 2D information it can sometimes take hours to resolve the confl icts and many drawings could be involved. Also, because of the time-scale involved the originators of the informa-tion may no longer be available to the design team.

Provided the 3D model is passed through the supply chain, or produced by the contractors using modern systems, the 3D elements can automatically have their production drawings created and manufacturing information can be provided to allow the members to be fabricated by numerical con-trolled (NC) machines, thus eliminating another interface where error can occur.

3. HOW DESIGN TEAMS COLLABORATE

At the start of every project there is an information void. Currently, design teams produce a mass of information through the project supply chain to populate this void. Contract details are rarely pure and do suffer from information entanglement, especially when different design sectors and trades are involved. Also, the information produced by the architect, engineer and all the various contractors cannot always be represented in a drawing format. So in this case the information cannot be readily passed on as the contract workfl ow is normally only interested in scheme, tender, construction and as built information. Also, this does not allow for design changes as the scheme develops nor does it allow for any changes made by the client.

Figure 1. Project workfl ow

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Currently, most of the scheme information is passed on 2D drawings. In recent years, due to the BIM platform, 3D model information has been passed between the architect, engineer and some of the structural contractors. Now that 4D (the fourth dimension being time) information can be encap-sulated within BIM, general contractors have shown more interest in the model as it can now be utilized for programming and production. This will become a future way of working, with perhaps specialist contractors just producing BIM information, and they will become part of the design team. Where the modelling specialists will be positioned is a matter for conjecture as they could be directly employed by the client for contract control, or by any of the other design team members. Again costs could be controlled through the model, which will then be a major interest for the client, quantity surveyor or project cost controller.

Visual project management is currently possible using BIM when utilizing 4D functionality as a programming and time reversal tool. The BIM platform is also perfect for exploring different schemes and solutions.

4. WHAT IS BIM?

BIM is a collaborative tool used by any member of the architectural, engineering and construction (AEC) industry based upon a number of software solutions. BIM incorporates all the building com-ponents (or objects), including their geometry, spatial relationships, properties and quantities, includ-ing all the services and equipment information for the full life cycle management of the building and even its demolition. One of the main advantages of this way of working is that different members of the AEC design teams can utilize physical or reference models from other team members, without having any specialized industry knowledge. For example, the integration of services and structure schemes could fi rst be coordinated by simply checking the objects from the two schemes to ensure clash avoidance.

It is commonly acknowledged that the only solution for managing building information effi ciently is with product modelling. This type of modelling was originally developed as a solution for the mechanical and plant design sectors. Since the early 1990s, structural steelwork detailing has made a remarkable shift from 2D drawing to 3D product modelling and a fi nite number of software solutions have played a pivotal role in facilitating this change.

The available solutions of modelling technology can be divided into two different categories: ‘bottom-up’ and ‘top-down’ systems. Originally driven by the mechanical and plant design, paramet-ric ‘bottom-up’ modelling technology was designed to create parametric models of known individual pieces. Building models created utilizing ‘bottom-up’ technology are based upon independent models of individual objects tightly integrated together. Complications can arise when thousands of building objects are used with intricately linked relationships. Unfortunately, this is the actual condition when considering even a very small development, as in its simplest form a straightforward steel beam is formed from many elements (section, plates, cuts, holes, notches, bolts and welds). The same applies to concrete elements.

Information management becomes more practical with the use of parametric ‘top-down’ modelling technology. This technology was specifi cally created for the thousands of objects required in a building model where the basic objects are fi rst modelled without detail, which also perfectly supports the normal conceptual design process. The logical relationships between building objects are created when applying the members’ physical connections and enhanced information. For example, if a beam is required from point A to point B, the material and size may not be known at the modelling stage as this is normally refi ned during the design process together with the actual length and hole positions, etc.

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5. STRUCTURAL BIM

The use of a single ‘total’ BIM on large projects, containing all the architectural, structural and serv-ices object information, is still some time away and may never be totally available, owing to the mass of information and subsequent data compression that will be required. When this type of solution occurs various linked databases will exist, as all interfaces will be modelled on their sector’s ‘best of breed’ solutions, one of which will be the structural BIM. Structural BIM is the most important area for structural engineers and their immediate supply chain and is currently available. This multi-mate-rial (steel, concrete, timber, masonry, etc.) subset can include the physical and analysis and design (A&D) information, and can be used for all drawing and report production.

Structural BIM is the part of the BIM process, where the majority of multi-material structural information is created and refi ned to form the actual structure. Architects’ models are not included in the scope of structural BIM, as these are not based on the same concept as this model. Architects work with space, mass, texture and shapes; they do not work with building objects in the same way as defi ned in the structural BIM. However, the connection between architects’ models and structural BIM is a very obvious way to help in the future development of intelligent integration and these should always be available in the form of reference models, in the same way that the XREF function is used in a 2D drawing. These reference models could also be 2D information for collaboration with non-BIM applications.

The model starts to evolve during the engineering stage, where conceptual decisions of the structural forms are made. It is sometimes thought that the design portion of A&D is just the pure physical sizing of the structural elements. In practice it is more than that, as it should also include the engineering and the value engineering of the project, including all materials, their relationships and their reference to the architectural objects.

The load-bearing structures are designed and integrated into the model and A&D plays a signifi cant role at this stage, though not in the classical sense of using separate independent tools. Structural BIM A&D is not a primary phase in the process but just another output that could be generated and main-tained through the physical model. When changes occur, they are made directly in the structural BIM model, with all A&D results and all other output updated accordingly, as parametric objects can adapt and react to change.

Open interfaces are fundamental for a structural BIM solution, not only from an interoperability point of view but also from that of customization and localization. It is also easy to use open interfaces, which provide the opportunity to supplement the functionality of the structural BIM system with plug-in software modules.

Structural BIM is not an island of interoperability, so it needs to interface and synchronize with other applications and information. In the past the Steel Detailing Neutral File (SDNF)2 and CIMsteel Integrated Standard Release 23 (cis/2), together with other industry or proprietary neutral fi le transfer formats, have been adopted to transfer 3D element information, sometimes adopting agreed Globally Unique Identifi cation (GUID) numbers to track element history between the analytical and physical models and to monitor change.

The problem is that these formats have mainly been defi ned around the structural steelwork market requirements, as this was the lead sector. A multi-material solution will always be required as even the structural steelwork contractors need to model their industries’ interfaces. These formats have

2The Steel Detailing Neutral File was developed by the Intergraph Corporation. Refer to their Format Reference Guide for further information.3For further information on the cis/2 standard refer to their website: http://www.cis2.org/.

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provided a fi rm foundation for data interoperability; however, technically the future for data transfer has to be with the IFC developments, as this is the only way to support the round trip of true multi-material objects.

With the use of IFC and Microsoft .NET technologies, BIM will become more transparent and complete within the next few years, as these two developments will greatly advance the interoperabil-ity of the BIM platform. The structural BIM is also not restricted just to members, as loads and load combinations can normally be handled within the modelling application.

6. BACKGROUND

It used to be common practice to draw and sketch structural schemes, interfaces and connections, in order to explore various alternatives, as this was considered to be the only way to visualize and get a true ‘feel’ for various confi gurations. Adopting this way of working, countless aesthetic solutions and optimum structural designs were refi ned. Nowadays this is considered to be an expensive and time-consuming operation. Thus it should be remembered that, using 3D modelling systems, this method-ology can be easily and quickly adopted.

To produce this information as a 2D solution electronically, from fi rst principles, is intrinsically no quicker than the old manual methods. Due to current project time and design cost restraints, the designer currently does not have the resources to develop and refi ne their scheme in this manner. Using modern BIM solutions the schemes can be quickly developed, explored and improved. Also, many current geometric architectural solutions are so complex that the structural elements can only be accurately positioned and refi ned in a 3D environment, as a structural prototype is created within the computer model before any physical materials are involved, resulting in time savings, cost and error reduction.

7. BRIEF HISTORY

At the beginning of the 1980s, computer-aided design (CAD) revolutionized drawing practice by providing digital tools for creating 2D drawings. Since then, the construction industry has been search-ing for a solution that provides more than just automation of manual working practices. The develop-ment of drawing-based collaboration had begun.

Design teams started to communicate information by sharing and reusing drawing components in an electronic format. Layer conventions technology was developed and adopted, in which the archi-tectural layouts were used as reference layers on other design team member drawings. This drawing-level collaboration provided a low-level means of detecting change in individual drawings. The downstream design team members then modifi ed their own drawings accordingly. This collaboration and visual coordination was purely a manual process and project information was still distributed by numerous other partial drawings and sketches.

The Internet revolution opened up possibilities for effective information management. The next steps towards BIM were taken with trials to automate drawing-based information management. Project data banks were established to solve delays in information sharing and the initial results were encour-aging. Some hurdles were overcome; however, the basic problem of fragmented information manage-ment remained unsolved. Drawings are only refl ections of actual and assumed information no matter how well they are managed. Information was still scattered among many drawings with countless duplicated and confl icting information items. Change management was cumbersome and error prone.

Even though the information modelling concept has been reinvented many times, in different com-puter environments, the original concept is usually attributed to a paper written in 1970, by Dr E. F.

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Codd, an IBM researcher. In the paper (entitled ‘A relational model of data for large shared data banks’) he discussed the need for a tree-based hierarchy where objects are described in a relational view permitting a clearer evaluation of formatted information. The paper also defi ned the need to include time-varying relationships.

8. WHAT IS A STRUCTURAL PHYSICAL MODEL?

This can be simply defi ned as a collection of full-sized 3D model objects that contain suffi cient infor-mation for the completion of the building, with means of visualizing and interrogating the physical characteristics of the structure being modelled. As far as BIM is concerned, the physical model objects should also include all of the relevant information, or links, which are refi ned during the design and ultimately the manufacturing process.

9. SO WHAT IS AN OBJECT?

In object-orientated programming, which is the software design concept that models the characteristic abstracts of physical real-life items, an object is a collection of related variables and methods that defi ne the elements’ state and behaviour. For example: a car’s state would be its colour, number of doors and equipment. Its behaviour would be acceleration rate, stopping distance, handling, etc.

In software terms the state consists of the object’s defi ned variables and the behaviour the methods associated to the objects. The objects must also be subject to user-defi ned encapsulation, message passing, inheritance and polymorphism, which is the ability to process objects differently depending on their contained data.

10. INDUSTRY FOUNDATION CLASSES

IFC is the International Organization for Standardization (ISO) standards which have been developed by the International Alliance for Interoperability (IAI) and supports model-based construction objects and activities. Classes are defi ned to describe a range of object variables that have common charac-teristics and the standards form an open communication platform operating across the design and construction sectors.

The principal advantage of the IFC is that the format supports multi-material objects at all stages of the building and construction processes, resulting in the transfer of rich building information. The latest version of the IFC format is 2X3 and all the major software vendors are just receiving their formal accreditations.

11. THE ADVANTAGES OF STRUCTURAL BIM TECHNOLOGY

In order to prototype various schemes, the solution must be on the best context platform for the work to be completed, as easy input, modifi cation and control is required in a 3D environment. To adopt a general drawing platform out of context would not be appropriate, even if it were a well-known solution.

Using the multi-material structural BIM concept allows engineering practices to visually share structural information with other companies and platforms, providing true collaboration. Scheme development and refi nement can be quickly completed as all information is always concurrent and in one place, allowing the free-fl owing development of structural schemes and ideas. Any information can be encapsulated within the object database, which can be refi ned to suit any project requirement, including information from the client and architect.

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BIM can be used ‘upstream’ and ‘downstream’ in the project, so the model can be passed on to the main contractor, steelwork or concrete contractor and then back to the engineer or client for approval. All the construction drawing information can be stored in one place, allowing full life cycle support, providing a true 3D visual communication tool. Ownership and intellectual property rights also need to be addressed, as a secure object environment should be adopted.

Total control and the elimination of errors are possible, as all drawing and information requirements, in the form of reports, are automatically produced from the model. Also most users would agree that it is quicker and easier to interrogate a model than to wade through hundreds or thousands of drawings either presented in an electronic format or on paper.

Links to A&D systems and their analytical models can be made using cis/2 and other formats; or integrated solutions can be adopted and explored, together with propriety connection design systems or links to external systems. Parametric imports from other schemes or parts of previous projects are also possible to add value to current projects or company data.

There is a huge difference between a physical model and an analytical model, owing to the vast difference in information content, quality and extendibility. Using various object extensions, the 3D physical model can be extended to a 4D model by including the time requirements within the object. In fact, with a fl at hierarchy object system a 4D, 5D and even an nD system can be defi ned where the user defi nes all of their required additional dimensional requirements.

12. COM

Common object model (COM) is a transfer technology between applications, in which the agreed simplifi ed object variables are defi ned and transferred. A structural object could be a beam or a column where its physical location is determined and then its variables (material, size, loading, reactions, connections, fi ttings, etc.) are continually enhanced during the modelling operation. COM links are normally adopted between 3D applications and A&D engines where the full object information is not required.

Some standards are already defi ned. However, applications using this technology tend to be based on bespoke developments. This is the traditional way of linking A&D systems to the physical model. The largest problem with COM solutions for general linking of applications is that the format has to map itself as the COM’s view of the world is extremely limited. In order for modern software to develop it needs to be written less as gigantic standalone applications containing coarse information, and more as fi ner-grained intelligent components.

Modern tools are needed to allow the fl exibility of passing the total user-defi ned object information to other ‘best of breed’ applications and not to have some form of limited lookup table, or to transfer the object variables with some form of information wrapper.

13. APPLICATION PROGRAM INTERFACE

APIs act as vehicles to intrinsically bond and transfer the object information between applications. Using this type of interface, applications can already link various standalone A&D applications to utilize the vendor’s latest developments. However, using .NET technology as the transport device and an open interface, systems like Tekla Structures allow internal, client and even third-party development to take place to access and enhance all the 3D geometry and object information. The same model information can be used to drive external applications, without the need to report the results back to the 3D model.

This same technology applies to linking 3D geometry and information with everyday design offi ce tools such as Microsoft Excel, Word, Access, Project etc., or any VBA-compliant application.

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14. WHY .NET?

As a basic defi nition, .NET is a fl exible programming platform for connecting information, people, systems and devices together using a modern programming environment and tools. This is the next generation of COM and is based upon the Microsoft Visual Studio.NET development platform, which allows the APIs to be built upon.

15. OPEN INTERFACES USING .NET TECHNOLOGY

Before the .NET platform, all software solutions ran as separate entities with minimal or no integra-tion. When applications were integrated, limited information was shared, which meant that objects could not strictly interact. With COM developments, components can integrate. The main disadvantage is that each component must be individually plumbed together, as objects cannot directly interact and the applications also have to manage all of their respective internal housekeeping. Thus collaborative work is easily broken and will always be version dependent. .NET is built on top of the operating system, so multiple operating system platforms and devices are supported, allowing true fl exibility.

Adopting .NET technology simplifi es the development as objects can pass information between applications, so no linking is required. This is achieved as the .NET Framework provides a common foundation upon which all of the programming languages and system components are built. For example in Tekla Structures, a connection component can be simply linked to an engineer’s algorithm defi ned within an Excel spreadsheet and can react to the object revisions and change, even though the connection is written in C# and Excel is mainly enhanced using Visual Basic. The same applies to over 30 programming languages within the Microsoft .NET Visual Studio. When components are built in this way, there is no difference between the component, its internal structure and the programming interface, as there are no interface wrappers.

16. .NET EXAMPLES

An example of this is the Tekla solid interface, which has allowed Ficep, an Italian structural steelwork equipment manufacturer, to develop a scribing interface through the Steel Projects WinSteel applica-tion. This interface marks the fi tting positions and reference information (mark, angle of inclination, amount of weld, etc.), on to the actual structural steelwork member using a special milling head on their latest CNC-controlled saw and drill machines. This saves all the laborious workshop ‘marking out’ time, which in principle is no different from the way that the outline of a stamp is placed on envelopes to indicated their intended position.

Welders can then simply weld the fi ttings in the correct location with all the reference information and weld requirement on the member rather than referring to the fabrication drawings, eliminating another interface for error. All the 3D geometry is transferred to their software systems allowing all holes, copes, member bevels and weld preparation information to be transferred, as all of this informa-tion can be far too complex and is not totally supported by the current industry DSTV4 (Deutscher STahlbau-Verband) manufacturing format. In the near future this kind of technology will control welding robots and reinforcement placement robots for the precast concrete sector.

Another example is a frame builder, similar to that found in modern A&D packages, which has been written to construct the main structural frame within the model. The user can then apply the

4DSTV: standard descriptions of steel structural pieces for the numerical control. Recommendations of the DSTV Commission (various editions).

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Figure 2. Excel link example

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beams and columns to the structural grid or independent frame just by supplying some input information. This platform can also be used as a development tool in its own right, or for product localization.

This is just a start, as linking to design systems, RFI (request for further information) systems, costing systems, fi re engineering systems, management and manufacturing information systems, etc. means that all that is required is the development vision and that the remote applications are built upon the .NET platform. In fact really the only .NET boundary is the limitation of your imagination.

17. CONNECTION DESIGN USING EXCEL

From a user survey we found that many companies carry out connection design using algorithms imbedded within various Excel sheets, which have been developed over the years for their own inter-

Figure 3. Frame builder application

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nal use. These are generally simple orthogonal connections, but allowing these to be linked to the 3D geometry and model information would allow many standard conditions to be developed. We found that there is a growing demand, particularly in the UK and USA, for the support of different design code and conditions, especially with the Eurocodes on the ‘event horizon’ for adoption. This will then allow the engineer/modeller to do some in-house development rather than having to adopt an infl ex-ible and possibly conservative hard-coded solution that may be is inappropriate to the actual condition that is being considered.

From the Excel example, various worksheets exist where the cells are populated with the model information and geometry. This information is then manipulated with the user’s or company’s algo-rithms and the information linked to the output worksheet, which can be saved as a formal calculation sheet. The results and standard requirements are then passed back to the 3D model and the parametric component responds to any change, automatically updating the connection to include the revised confi guration. The Excel sheets can be viewed in a ‘step-through’ confi guration for debugging pur-poses, or completely in the background, so the user is unaware that they are not using a system com-ponent. True connection design is available rather than just a connection design check, as the design logic can be built into the spreadsheet with clash detection controlled within the modelling application. It is also a simple matter to write these spreadsheets considering a ‘component method’ solution, with separate designs for US and UK design standards, Eurocodes and any other national or international codes or industry requirements. It is also possible for third-party suppliers of connection design soft-ware to build an interface between their application and the connection component of the 3D physical model.

18. DRAWINGS AND REPORTS

With BIM the requirements for drawings will become less. However, good CAD tools will always be required on top of the 3D modelling system.

As all material, structural, technical and status information is always up to date and available in the same model, it allows the designer to be free to solve the structural design problems with confi dence while still allowing open-viewing access to any member of the design team. Project management is therefore always under control.

As another .NET development project, a scripting (macro) interface was developed to record the user’s actual selections and save these setting for other projects or reuse to save time as the project develops. This is extremely useful for performing tasks that are constantly repeated, such as drawing and report production.

The following case studies are utilized using the Tekla structural BIM solution.

19. CASE STUDY: SHANGHAI WORLD FINANCIAL CENTRE, SHANGHAI, CHINA

This development will, for a short time, become one of the tallest building in the world when it is completed in 2008. It is situated in the Lujiazui Finance and Trade Zone of Shanghai, which is the largest international fi nance and trade centre in Asia. Limited to a planning height of 492 m above ground level, the 101 fl oors and three basement levels of the Shanghai World Financial Centre consist of offi ce accommodation, a 15-fl oor fi ve-star luxury hotel, a six-fl oor observatory tower, together with conference facilities, shopping and 1100 m2 of car parking, with a total fl oor space of 381 600 m2, with 31 elevators and 33 escalators.

Designed by the US architects Kohn Pedersen Fox, this development was originally planned to be built in 1997 when the foundation stone was laid. The project was then temporarily stopped due to fund shortages caused by the Asian fi nancial crisis. The project has undergone many changes, includ-

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Figure 4. Shanghai World Financial Centre

ing changing the aperture at the top of the tower from a ‘circular moon gate’ shape to a trapezium, as controversially the original shape was seen to be too much like the form of the Japanese fl ag. The tower height has also been limited to 492 m from the 510 m of the original scheme.

The development team on this US $1·1 billion project was China State Construction Engineering Corporation (general contractor), Leslie Robertson Associates RLLP (structural engineer), with Shang-hai Grandtower, Jinggong, scksteel, and Yokomori steel structure being the structural steelwork con-tractors. The steelwork contractors were responsible for the fabrication of the 60 000 tonnes of structural steelwork. The BIM model was created by Shanghai Tongqing Technology Co. Ltd and Shanghai Rightfl y Building Technology Co. Ltd and was built and used for the steelwork contractors design coordination, drawing creation and the production of fabrication information and NC data. This may be an older way of looking at BIM integration. However, it should be remembered that this scheme has been designed over a protracted period of time and a number of steelwork contractors were employed on this project. This may then be seen as a typical way of working on projects produced over the last 10 years just utilizing modern technology.

20. CASE STUDY: 51 LIME STREET, UK

This development is currently being constructed on the site of the original Lloyd’s building and will become the fourth tallest offi ce complex in London’s fi nancial district. It is situated between the new

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Lloyd’s and 30 St Mary Axe (Swiss Re) buildings. The original Lloyd’s building was offi cially opened by Her Majesty the Queen Mother in 1957, so it is interesting to note that even iconic buildings sometimes only last for their 50-year arbitrary design life.

The complex is really two buildings linked together with a two-storey basement construction. The smaller building is a curved 10-storey building, while the main development is a shaped three-terraced building that steps down from 29 to 16 storeys. The client is the British Land Company and the development has been pre-let to the Willis Group as their new corporate headquarters and will be known as the Willis Building.

The setting out of the building is quite complex, both to incorporate the maximum available plan area of the landlocked site and the curved elevations of the architect’s aesthetic solution. The main structural design team was formed from Foster & Partners (architect); whitbybird (structural engineer); William Hare Ltd (steelwork contractor) and Mace Ltd (construction manager). The fl oor area is 66 000 m2 and contains approximately 5500 tonnes of structural steelwork. The perimeter fl oor connec-tions are complicated, with a ‘saw-tooth edge construction’ which forms a joint permanent formwork for the fl ooring and support for the glazing system. Due to the service requirements and coordination the main fl oors are constructed from ‘Fabsec’ cellular beam, with wind stability provided by the main concrete core. Fire engineering was a main consideration and the two-storey high external ‘Lancashire’ columns are formed from welded plates (100–120 mm thick), cover plates and an external tubular element, and all fi lled with concrete to act as sacrifi cial elements in the fi re engineering solution.

The structural BIM was created by whitbybird for engineering, fabrication and planning purposes and passed onto the steelwork contractor, William Hare Ltd. Once created, the model was also used

Figure 5. Willis Building

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by the architect and the construction management team for dimensional coordination and acted as a communication vehicle between other design team members and contractors, including the concrete and glazing specialists.

On this project the benefi ts brought about by a BIM solution is integration between the main con-crete core of the building and the structural steelwork. The complex geometric relationship between the curved ‘saw-tooth edge construction’ and the glazing integration was also resolved by BIM, effec-tively linking the structural steelwork, fl ooring and glazing design together.

21. CONCLUSION

In the future, applications based upon the .NET platform and adopting API technology will no longer have to be based upon a huge application, but could consist of discreet pieces of development, each coming from other environments and even components hosted on the Internet utilizing web services. In fact, this will lead to even faster software development with these modern tools.

The user will be able to connect with his or her own preferred ‘best of breed’ software solutions. The structural BIM solution needs to a totally fl exible open solution, allowing modern computer architecture to support the engineering design platform requirements. This will allow not just produc-tivity gains but also the complete client’s business confi dence for their internal processes and for their

Figure 6. Willis Building 3D Structural Model

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hub clients. Advanced clients or independent developers will be able to create and link their own applications. In fact this type of cooperation has already started.

For the foreseeable future drawings will be required; however, the object information contained within BIM will rapidly increase in importance over the next few years. The whole building and construction industry is crying out for a solution to move beyond drawings and to consolidate the true project information that is residing in different organizations, much of which is in fact ignored, as after even a short period of time the status of the information becomes unknown.

Documents

STRUCTURAL BIM: DISCUSSION, CASE STUDIES · breed’ solutions, one of which will be the structural BIM. Structural BIM is the most important area for structural engineers and their