Push the boundaries with parametric design

BIM (Building Information Modelling), and its counterpart BrIM (Bridge Information Modelling), are frequently heralded as having an integral part to play in the future of construction and engineering. However, while its intelligent modelling and data sharing capabilities are well documented, there is also the potential to push this further, through the incorporation of parametric design. 

Here, Stuart Campbell, Business Development Manager – Engineering at Trimble, explores how parametric design could aid engineers in efficiently dealing with last-minute changes, as well as automating repetitive tasks and achieving the structurally complex.

What is parametric design?

Parametric design is guided by a set of interconnected parameters and rules, defined and inputted by the engineer. These parameters then generate or control the design output into a parametric BIM or BrIM tool. Combining BIM with parametric design provides engineers with an opportunity to truly transform the way they model, assess and analyse their structures, benefitting not only their business and its processes but also the service to clients. 

Despite these very real advantages, and while more engineers are starting to explore and develop the value that such a way of working could offer, parametric design is still a relatively new development within the engineering industry. For example, at a recent IStructE event hosted by Trimble, a live poll revealed that 46% of attendees knew only ‘a little bit’ about parametric modelling design and 16% admitted to knowing ‘nothing’, with all participants reportedly eager to learn more about the parametric enabled workflows.

Automation

Perhaps the first advantage offered by parametric design is automation, particularly with regards to last-minute design changes. A common occurrence on all construction projects, whether originating from the client, architect or elsewhere, they can be hugely time-consuming to resolve. Even if the change was initially to just one structural component, such as changing the position of a column on a bridge deck, it could affect numerous other related components; resulting in a potentially long, intricate and repetitive rectification process.  

In comparison, by using a parametric design input and output tool, such as Grasshopper and Rhinoceros 6, the structure and its components would already have been modelled in a connected way. With all parameters, inputs and outputs being interconnected and the data relationships maintained, changing a single parameter would automatically adjust all associated components in line with the new inputted data.  

In many ways, this idea of parametric design and interconnections may not be entirely unfamiliar, with engineers potentially already having some level of parametric capabilities within their BIM workflows. For example, with Tekla Structures and Tekla Structural Designer, all drawings, schedules and plans are linked with the original model, meaning that a change within the model would automatically be reflected in the associated documents.

Facilitator of the complex 

As well as saving valuable time and helping to more efficiently manage last-minute design changes and repetitive modelling tasks, parametric design also signals a shift to more creative engineering, facilitating the complex and the architecturally challenging. It is perhaps for this reason that parametric design stands to bring particular value to the civil engineering discipline. 

Civil engineering projects can be especially complex; often involving curved structural elements, a wide array of loads and deflections to consider, existing infrastructure (such as road or rail) to be seamlessly coordinated with the new structure, a balance to strike between the structural performance and initial architectural vision and the creation of the most efficient design - all presenting civil engineers with many challenges. 

Used correctly, parametric modelling - and perhaps more specifically, data-driven design - can be a means of allowing computer software to drive geometry creation for the structurally complex; structures that would have been incredibly challenging – if not impossible – to model and analyse manually. 

For example, when designing the Paris Metro line 11 extension, due to the track variability and tight tolerances involved, it was clear that a manual insertion of all elements would be a lengthy and time-consuming process. Therefore, a bespoke Grasshopper file was developed – using the live-link with Tekla Structures – in order to automatically place the elements, so that they were correctly aligned with respect to the rail track. 

Parametric design also offers an opportunity to transform the structural analysis process through automation. By using input and output programming parametric tools, setting the required parameters and live-linking with a suitable structural analysis BIM software package, the algorithmic script could run various design iterations at high speed, helping engineers to more quickly identity the most efficient and optimum design solution. 

As with any technology, BIM and BrIM are in constant development. While BIM may be fast becoming the norm for civil engineers, there are further tools and workflows emerging, such as those relating to parametric design, ready to open up even more design doors and push the capabilities enabled by BIM to the next level.  

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