Structural change

Most of us are well acquainted with the benefits of CAD/CAM/PLM technology when used in manufacturing.

We have also seen US architect Frank Gehry use CATIA V5 3D solid modelling to design complex prestige structures such as the Bilbao Guggenheim, and by others in the restoration of the Sagrada Famila in Barcelona. So why isn’t the 3D revolution embraced by more of the architectural fraternity?

There are many reasons. Some architects cite the general availability of ’adequate’ 2D tools, while others complain that before you can carry out effective ’what if’ design in solids you have to model a complete scheme. And while the architectural world has been on the brink of 3D solids for a while, an alternative 3D revolution has been taking place in the shape of BIM (Building Information Modelling) that is somewhat analogous to PLM in manufacturing.

Put simply, BIM provides a consistent database for the whole structure, including integrated/collaborative data for all disciplines involved: architecture, structural engineering, MEP (mechanical, electrical and plumbing) engineering and contracting. Everyone in the design and execution chain would access the system in much the same way as the various collaborators in an automotive/ aerospace project would access the PDM systems of the main players.

BIM is in its infancy, with Autodesk Revit and Gehry Technologies’ Digital Project (based on CATIA) leading the way. While the system is trying to gain a foothold with architects and engineers, Bentley Systems is beavering away with a parametric 3D approach called Generative Components (GC). This is part of MicroStation and has been developed in the UK by Bentley’s director of research, Dr Robert Aish.

GC offers a parametric and programmatic way for designers to develop complex geometry relatively easily and to ring the changes and interactively adjust and interact with complex frameworks for optimal architectural and structural forms.

Aish, who collaborated with Lars Hesselgren, Hugh Whitehead and J Parrish at the architectural practice YRM, pioneered the idea of parametric design in architecture over a decade ago. In the intervening years, each has brought parametric design to fruition; Aish (at Bentley), Hesselgren (at Kohn, Pederson, Fox Associates International), Whitehead (at Foster and Partners) and Parrish (at Arup Sport).

The emphasis here is not just on software tools that embody parametric concepts, but the way designers and engineers think about the design process.

To promote a wider understanding of parametric design in architecture, the group has founded ’SmartGeometry’ whose aim is to educate the next generation of designers by introducing them to design tools which need new approaches and higher degrees of geometric and programming skills. (www.smartgeometry.com).

A major benefit of parametric systems is that they automatically update entire drawing sets based on changes in the model as small as the placement of a screw, or as large as a modification to the geometry of a building’s footprint. GC’s uniqueness lies in its general geometric scripting core which allows designers to easily create their own tools based on relationships (much like a spreadsheet for 3D modelling).

Generative Components is a model-oriented design and programming environment which combines direct interactive manipulation design methods based on feature modelling and constraints, with visual and traditional programming techniques, and represents Bentley’s response to the requirement for a ’programmatic design’ environment — a fusion of geometric modelling and software development. What the company is searching for in the development of GC is the minimal abstraction of design, that when implemented in software and used by creative designers, provides for the most expressibility and extensibility.

’Generative Components is a practical yet rigorous approach to what I call blobby architecture, and it shows once again how Bentley’s evolutionary approach to software development works in the user’s favour,’ said Hesselgren.

His company, Kohn, Pederson, Fox Associates, is now using Generative Components on London’s 60-storey helter-skelter-shaped Bishopsgate Tower which promises to be Europe’s tallest building. Meanwhile, consultant engineer Buro Happold has used GC on a number of projects, including the Fashion a Design Events building in Milan designed by London architects Nicolas Grimshaw.

The Generative geometry group at Buro Happold constructed a fully parametric model of the roof. This was used by all the different disciplines involved — including the architect. ’GC gave us the capability to visually manage the flow of data,’ said Buro Happold’s Jalal El-Ali. ’All data was extracted independently to be used either for structural, environmental or quantitative analysis.’

GC allowed the engineering group the freedom to explore different design options with minimum effort. Its use elevated the discussion forum between different disciplines and allowed them to visually and interactively explore how different elements of the buildings are directly connected to others.

The building’s exhibition halls are constructed as column-free areas on both floors, which can be connected to one large hall or separated into four smaller units. This central volume of the building is constructed simply on a rational and economical grid and flanked by cores that provide toilets, lifts, staircases and mechanical riser spaces.

The outside surface also functions as a support structure to the circulation floors and is built as a structural skin. It is constructed from glue laminated timber ribs and timber planks, its geometry designed to be self stabilising so that lateral and vertical restraint points can be minimised.

This kind of geometry is virtually impossible to generate or quantify manually. Moreover, no other software would let you to explore the multitude of design possibilities in this way at the concept design stage. CATIA and others would allow some parametric and/or variational flexibility, but only after weeks of modelling the final scheme.

Recently Hesselgren indicated that the Bishopsgate project had a number of last-minute height changes which were easily accommodated by the Generative model with changes rippling down to the detailed drawing level.

At first glance it would appear that a reasonable amount of programming knowledge was required to use Generative Components. Building simple frameworks, using the standard MicroStation interface is fairly straightforward. Once the concepts have been mastered, some programming knowledge is required, but the benefits of automatic generation and resolution of complex geometry far outweigh the necessity for people to skill up to drive the system to solve complex problems.