Structural BIM

Kevin Lea, BIM business development manager at CSC, shares his personal view on the pivotal role the structural engineer plays in the BIM process.

The adoption of Building Information Modelling (BIM) within the construction industry now seems a formality. Recent surveys suggest the adoption rate for engineers continues to increase. Initiatives from governments worldwide to adopt BIM as part of their procurement procedures, probably means BIM is here to stay.

Despite this, there are parts of our industry that have neither embraced the concept of BIM nor consider their current work processes as BIM. Why?

The BIM story board

Over many years our industry has discussed the merits of sharing BIM data between members of the project team. We have all seen fantastic images and reports of projects benefiting from the collaborative use of BIM data, leading to enhanced design based on accurate information. Sophisticated software solutions such as Autodesk Revit, Tekla Structures, and Bentley MicroStation all provide tools to enable true collaborative working.

When BIM processes were initially introduced the benefits of sharing BIM models between the project team was very much the focus. Knowing that the structural column would not interfere with the architectural wall; or a hole through a web of a beam was in the right place for ducting to pass through, demonstrated how using BIM could offer significant advantages, reducing errors and therefore reducing costly onsite delays.

As time has progressed, opportunities to expand the use of the BIM data are now seen with 4D and 5D applications. This is evident with recent surveys showing a bigger take up of BIM technology with contractors than with any other discipline.

I have no doubt that structural engineers buy into the ‘external benefits’ the BIM process offers, however as a keen advocate of BIM, and a structural engineer myself, I cannot help think that the benefits for the structural engineer need to be closer to home for full adoption to be realised.

External BIM

Engineers worldwide are adopting BIM solutions. But how many are adopting BIM due to pressures placed on them from architects and contractors? I would suggest that many engineering firms are adopting BIM due to external pressures to ensure they are considered for future projects and in some cases because BIM is a prerequisite.

This has meant many engineering firms have purchased software, such as Autodesk Revit, to enable them to inform their peers that they ‘do BIM’. However, they often do not examine the benefits for their own internal processes, but use BIM only as a means to communicate externally.

In some cases, BIM is being adopted by engineers reluctantly, without seeing the commercial gain for the organisation. If engineering firms view BIM as a way to improve their internal design processes they will see an increase in productivity, a reduction in errors, better communication and will have external BIM for free.

In other words if the structural community embraced BIM for internal benefits, external BIM is a much more realistic and useful proposition.

Internal BIM

The true spirit of BIM is to utilise BIM data to maximum effect. With the increased adoption of external BIM we often see this in practice; however many engineers have not fully embraced the same approach to improve their own internal BIM processes.

As well as producing BIM documentation, such as 2D and 3D drawings, engineers are responsible for ensuring the structure is designed to the latest published code of practice (i.e. Eurocodes, British or AISC codes). The internal process of sharing a technician’s model with the structural engineer is often still seen as a manual process; even though they often already have the software tools that can communicate BIM data efficiently.

Communicating manually typically leads to the double handling of design data resulting in inefficiencies and the introduction of potential errors. As the very nature of the engineer’s role involves numerous iterations and refinement of the project data, these inefficiencies can quickly escalate due to the repetitious nature of design.

Improving the internal BIM process can only lead to a streamlined design process. For example the geometry in an Autodesk Revit or a Tekla model can quickly and efficiently be synchronised with design software, such as Fastrak and Orion, CSC’s steel and concrete building design software. If models can be synchronised together, project amendments can be made in one place, maximising the use of the BIM data even further which in turn removes repetition, increases productivity and reduces human error.

Understanding internal BIM (or sometimes described as lonely BIM), rather than focusing on the bigger picture of external BIM, will be the key for greater adoption of BIM within the structural community. This will naturally lead to greater acceptance and support for external BIM processes.

Pivotal role

At a higher level, BIM is often described in simple terms. For example, an architectural model can be passed through to the engineer, the engineer can use this BIM data to aid drawing creation, analysis and design and the same BIM data can be passed down to a fabricator for manufacture. Although there can be fringe benefits, (such as better communication through visualisation), in reality the process described will not work as no account for data refinement is being made.

By way of example, an architect would model a column in a building through 20 storeys as one element. The structural engineer would need to refine the column into spliced lengths or construction lifts to be able to design the structure correctly. This may mean editing, or replacing the column data.

The key aspect for refining the BIM data is for the engineer to ensure he or she has a connected model. Typically this is only a requirement for the structural engineer and the steel fabricator. If a connected model is not considered, the sharing of BIM data can stop in its tracks.

Engineers set out structures via node points or wire frames. This wireframe is then used to create a mathematical model to help the engineer predict how the building will behave structurally using analysis and design software. Architects typically do not consider this. For example an architect may set out a beam between the faces of columns. The model will look correct physically, but the engineer will not be able to use the data for analysis or design without refining it.

The majority of the BIM solutions in the market (including Autodesk Revit) already provide facilities to model via node or wireframes. However, as it is not the role of the architect to consider such topics, a connected model is not produced and it falls to the engineer to refine the data. In reality this is no different to traditional design methods as all project data is refining as you go through each design stage.

Without this refinement the data can become useless or require further refinement downstream to manufacture. For example a steel fabricator may use a detailing system such as Tekla Structures or SDS/2. These systems are based on connected node points. Fabrication models are also used for estimating, procurement, connection detailing, and construction sequencing. These benefits can really only be fully realised if the data is refined upstream by the engineer.

To maximise the benefits of BIM the structural engineer must take more of a lead in the creation of BIM data. This will ensure that both the construction sequence is considered earlier in the design process and that the BIM data can be used for design and planning purposes downstream. This also provides an opportunity for the engineer to pay a more pivotal role in the BIM process.

Code based solutions

Having worked with BIM solutions for many years, structural software developer CSC has been acutely aware of these issues for engineers and has specifically designed integration tools to help refine and manage the structural BIM process.

Orion, CSC’s concrete building design software, automatically creates a connected wireframe for the engineer based on the physical geometry of the structure. This in turn helps engineers create connected models when Orion is integrated with tools such as Autodesk Revit and Tekla.

There are also tools to help structural engineers audit the BIM data. They pick up errors and present warnings, such as unconnected, duplicate and poor design decisions on members.

Due to the iterative nature of design there are constant changes affecting BIM models. Models that can be automatically syncronised are impressive in demonstrations. But if there is no way to control these variations or to check on the changes that have taken place the modeller can quickly lose control and confidence in the process.

To overcome this, tools are provided to show the integration status graphically, by colour coding the structure to highlight added, deleted or modified members. This can take place at either end of the integration process. (i.e. within the BIM authoring tool or within the building design software). This feature has quickly become key functionality to ensure successful management of the BIM data for the structural engineer.

It is also important to recognise that there is specialist information an engineer creates that cannot be communicated, or indeed may not be appropriate to be published into the BIM world. For example, code-based information such as wind loading, live load reductions, codified member design results are not recognised in general BIM applications and should be documented directly from the building design software.

Maximising internal BIM

BIM is here to stay. It will eventually be a prerequisite for all projects, whether driven by the client, the project team, or a need to compete in the marketplace.

When considering BIM, it is advisable to firstly consider the benefits BIM will offer your own internal design process, to implement them in an efficient manner, and to allow time to get through the initial learning curve. Once these are established it will then be an easy transition to share BIM data externally with the rest of the project team (of course if you choose to).

Implementing BIM solely based on external pressures can become a costly exercise, as you will not be equipped with the skills or knowledge to manage what are sophisticated items of software.

Many engineering firms already have software packages that are ‘BIM compatible’. However many are unaware of their capabilities. It is well worth investigating this with your suppliers and establishing a good understanding of the benefits they can offer you.

The final topic that must be raised is the need for good quality training and support. Please do not expect technical staff to be productive without appropriate training. These solutions will involve new skills over and above those acquired through the use of AutoCAD. BIM is not complex but a topic that requires a good level of understanding.

These are exciting times for the industry. Seeing your designs come alive in a virtual world adds an excitement to the whole design process and as we move forwards there is no doubt it will be those who adopt BIM who will lead the way.

cscworld.com