Eight-stage guide for Structural Engineers to implementing BIM on a project

It’s been years since the UK government announced its BIM mandate, large parts of the industry are still getting to grips with what this really means to their business. Trimble guides readers through the key stages, documents, terminology and, above all, processes that are ‘Level 2 BIM’.

The BSI defines Building Information Modelling (BIM) Level 2 maturity as ‘a series of domain and collaborative federated models. The models, consisting of both 3D geometrical and non-graphical data, are prepared by different parties during the project life-cycle within the context of a common data environment’1.

To start on this journey, it requires a plan. In the UK, this is called a digital plan of work (DPoW); the Royal Institute of British Architects (RIBA) DPoW2, published in 2013, is probably best known within the industry, but other plans of work exist for specific organisations within the construction industry, such as Network Rail’s Governance for Railway Investment Projects (GRIP) stages. The RIBA DPoW divides a project into eight stages to cover the whole lifecycle of a built asset:

0.    Strategic definition
1.    Preparation and brief
2.    Concept design
3.    Developed design
4.    Technical design
5.    Construction
6.    Handover and closeout
7.    In use

 

It is this digital plan (Figure 1) that we will use to guide you through delivering BIM, as a structural engineer, on a project.

 

0. Strategic definition
Strategic definition is a new stage that wasn’t in the previous RIBA plan and has been created to ensure that the actual need for a new or amended asset is discussed with a customer. In some cases, it may be decided that no work is needed and a project stops here. This stage is all about identifying the business case for the project and it generally won’t involve a structural engineer, or even much of the collaborative behaviours required to deliver BIM.

1.  Preparation and brief
With an agreed business case in place, the project then moves to this stage, where the foundations for a good BIM project are created. As well as preparing for the physical delivery of the asset, it is at this point that the BIM strategy for a scheme must be determined in order to deliver the greatest benefits to the team.

As a structural engineer, it is at this point that you will probably be appointed to begin your services. As such, this is the time to check whether a project purporting to be a ‘BIM job’ is set up correctly to deliver in this
way. Some of the questions you should ask yourself include:

  • Is there a set of employer’s information requirements (EIRs) (See “Definition of key BIM terms” tab below)?
  • Has any sort of BIM execution plan (BEP) been published?
  • Have task information delivery plans (TIDP) been requested or are any available?
  • Is the BIM protocol included within the contractual documents?
  • Has an information manager (See “What is an Information Manager” tab below) been appointed on the contract?

While there are many other indications of the existence of BIM on a project, these documents, and the processes that project teams need to agree upon, are the key indications that a project is serious about delivering BIM.

2. Concept design
At this stage, the design is still probably quite fluid and so starting to create a detailed 3D model risks being an abortive and wasteful process. Instead, massing models from the architect are likely to be shared around the team in order to test conceptual assumptions. The choice of material for the structural solution may not be fixed either, so simple calculations may be all that are required. What will be more important is ensuring that the information is being prepared correctly and shared in accordance with your own TIDP and the overall project master information delivery plan (MIDP).

However, by the end of this stage of the project, the agreed structural solution should have been determined.

3. Developed design
By this point in the project, real BIM workflows should be taking place and models being created and shared in accordance with the guidance in BS 1192:20073. Domain- specific (i.e. individual discipline) models, such as ones created by a structural engineer, are developed and shared to the common data environment (CDE). These discipline- specific models are then assembled together to create a ‘federated’ model – a single, complete model of the building that allows the collaborative workflows, which BIM is advocating, to happen.

This is also where the suitability codes within BS 1192 become even more important to ensure that the rest of the team understand for what purpose a model or data file has been issued (See “What are suitability codes” tab below). Suitability codes are covered in BS 1192, Table 5 and should be used whenever documents are issued to other parties on the project.

It is at this stage that 3D modelling software can be used to create both geometrically accurate and code-compliant designs, which can be exported as models and shared around the rest of the design team.

4. Technical design
This is the stage where engineering information and the scheme design generally move across to the specialist structural frame fabricator. In a traditional 2D design process, this would normally be done by issuing a set of drawings and accompanying calculations, which would give the fabricator most, but not all, of the information.

However, in a correctly managed BIM workflow, the full design can be shared, via the model, and so the digital processes ensure that the information can be relied upon. This is because it has been coordinated with the rest of the design team and is therefore far more accurate. This thoroughness, the improved coordination and data transparency result in better designs at this point and help to reduce risk, thereby improving profit for all organisations on the project.

Typically, a design team’s model would be passed to the fabricator to work up and complete the design to a fabrication level of detail without the need to build the structural model from scratch; a less wasteful and much more accurate process for both parties.

5. Construction
For an engineer, the construction stage of a project should be the point in time where they can sit back, relax and watch the design take shape on site. However, in the past this has not been the case, with numerous queries and clarifications coming from the site team over the detailing of the project.

With a well-executed BIM project, this should not be the case. The time spent early in the design process creating, checking and coordinating models will ensure that few, if any, requests for information (RFIs) come from the site team. With well-managed BIM processes, coordination and a data-rich model ensure that the construction stage on site goes smoothly, without the need for the structural engineer to revisit their documentation. Therefore, by doing BIM, the risk of overspending on any remaining design fees during this stage is all but mitigated. Remember, good modelling = better fees!

6. Handover and closeout
When the asset has been completed, the handover of agreed construction information takes place, to allow the customer to manage their asset. This is effectively the digital version of issuing operation and maintenance manuals; the difference being that the customer and their team have agreed what was needed from the start, so there should be no surprises. The responsibilities for issuing data are clearly defined through the EIRs and the project BEP.

7. In use
Unless monitoring the structure of an asset is required, it is unlikely that a structural engineer will be required to deliver any services during this stage of a project. By their very nature, structural frames should be low or zero-maintenance items. Maintenance regimes such as painting of exposed steelwork will be covered in Stage 6 and refurbishment of the asset would trigger a whole new cycle of a digital plan.

As this stage-by-stage guide shows, a BIM process adds a much greater level of rigour to projects, but one that allows teams to collaborate far more effectively to the benefit of all concerned. Designs are more accurate, appropriate and less wasteful, with re-work and errors all but eliminated. This means that the overall risk of the project is reduced and the chances of increased profit are greatly increased. Even when the rest of the team may not be doing BIM, the internal benefits to an engineering practice of sharing data and coordinating their own processes will still reap benefits.

 

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