words and images

I just finished writing an essay as part of a book we are developing at Grimshaw on EMPAC.  I am including that text here…

The development of the wood enclosure surrounding EMPAC’s Concert Hall was cutting edge in its processes and use of technology from concept to construction.  From the very beginning, references to the geometry of musical instruments guided the development of form and space at EMPAC.  This reached its culmination on the curving wood enclosure.

As part of the acoustic strategy, the Concert Hall at EMPAC is a double-shelled object.  Beyond the cast stone acoustic panels and waveform wood paneling lining the Concert Hall interior is a concrete shell encased by a secondary and offset wood shell.  Between these shells is housed circulation spaces supporting primary entries and exits, back-of-house areas, and the mechanical runs that are necessary for the proper operation of the performance space.

The Concert Hall wood enclosure, or “wood hull” as we called it, was developed as a unifying surface – giving continuity and polish to the outside of the Concert Hall and its amalgam of support program appendages.  The wood hull was created using lofted NURBS surfaces (Non-Uniform Rational Bezier-Splines), a three-dimensional geometric system that results in a continually smooth finish.  Long the domain of the car and industrial design industries, EMPAC’s NURBS surface was developed using high-end CAD (computer aided design) software.  This 3D model became the ultimate development and collaboration document for the hull, guiding the coordination of both mechanical and structural systems, and allowing for rapid yet accurate iterations of the design through all phases.  During the complex refinement process of reconciling the inner form of the concert hall with the smooth outer shell we generated over one hundred iterations of the surface model.

Continuous and smooth surface curvature suggests the fluid realm of art and nature, whereas hard edges and creases suggest the precise, man-made, and the known.  EMPAC, a venue where art and science exist in a constant dialogue, was expressed in both geometric types.  At the moment the continuous surface of the wood hull meets an entrance we have a clean-cut shape leading you into the Concert Hall interior.  This was accomplished by intersecting circular and elliptical cones with the original NURBS surface, resulting in a deliberate carving.

At each stage the surface was checked using curvature analysis.  Of interest were smooth blends between areas of greater curvature and their flatter neighbors, all the while keeping an eye out for surface inversions that would result in unflattering deformations and shadows.

The coordination effort with the hull was not limited to internal Concert Hall spaces.  Proximities and intersections with adjacent objects including the north curtain wall and the roof, and a recognition that the space around the hull was as important to its perception as the shape of the object itself, helped drive the final form development.  Where the hull penetrates through the glass façade to the outside, we transition materials from wood to metal panel.  Where the hull geometry intersects the roof we placed a continuous skylight allowing both direct and indirect washes of light to graze the wood surface.

The patterning of the wood surface was of great importance to how the form would be experienced in space.  At the outset, we believed using a tongue-and-groove array of boards would help accentuate the surface curvature while helping to bring down the details to a human scale.  Early studies began with a local shipbuilding company about how this fabrication technique might be realized.  These discussions led to a concern over the unpredictability of the patterning due to the complex nature of the surface.  In addition, the unrelenting nature of a single pattern across the surface led us to implement a variation by introducing a herringbone pattern that followed the cadence of columns along the north curtain wall.  This added much needed mid-scale texture and helped energize the surface.

Throughout the latter half of the project’s design phases, this 3D digital prototype was used as a coordination system between Grimshaw David Brody Bond and Buro Happold.  This transitioned into the subcontractor, AWI (Architectural Woodwork Industries), using the same 3D model to develop and coordinate fabrication and installation.  Led by Rick Herskovitz, AWI worked with us, the rest of the design team, and Turner Construction to digitally resolved any potential conflicts in the construction process well in advance of onsite construction.

Various mockups were developed to explore the appropriate wood species for the finish based on durability, workability, and the aesthetic desire for a wood of character and warmth.  Western Red Cedar, a wood commonly used as a sounding board for string instruments, was chosen as the finish material.  The cedar sourced for this project was sustainably harvested from the Queens Forest in British Columbia, Canada.  Based on the curvatures required on the hull, the cedar was air dried for 8 months to preserve its bending flexibility.

After selection of the wood species, a full-scale mockup was constructed as part of the fabrication development process.  The areas of tightest curvature, and the corner of an entry portal, were chosen as the best spot for the mockup as they represented the areas of greatest fabrication difficulty.  This mockup led to the development of the sub-frame system, wood board width and depth, applied finishes, and fastening methods.  Cedar is naturally flame resistant but a further mockup was fire-tested nevertheless to alleviate any lingering concerns about the combustibility of such a large amount of wood in a public space; the cedar passed this test resoundingly.

On the exterior of the concert hall concrete enclosure, the structural engineer developed a steel cage made of faceted wide flanges to help rough out the hull shape.  Then to achieve the extremely high positional accuracy that a panelized, double-curved surface requires, this steel superstructure was surveyed on site using a robotic laser transit and the data mapped back into the original 3D surface model for geometrical coordination.  The difference between the designed shape and the actual construction shape, in recognition of the rough faceting of the steel cage, was bridged using computer-controlled laser-cut steel blades welded to the steel cage.  The final edge of these steel blades matched the 3D surface model exactly as designed.  This created the fully calibrated framework onto which the final surface would emerge.

Using digital fabrication techniques driven by the 3D surface model, a series of 268 double-curved framed panels clad in sheet metal were CNC pre-fabricated offsite and numbered.  Each panel was unique and built to 0.005” tolerances.  These were then hoisted into place covering the surface of the entire hull.  Setout lines were inscribed onto the panels and the job began of bending and fastening each tongue-and-groove cedar board.  What began as an entirely digital process of form design, coordinating structural and mechanical systems, developing fabrication templates and simulating construction, ended with the hand placement of the natural wood finish.  Coming full circle back to the earliest material concepts, wood edge details took their cues from the shipbuilding industry.

The result is a labor of love from all those involved in its creation from design to construction. Through the common language of geometry and the exploration of a material’s innate qualities, the wood hull had become an emblem of EMPAC’s mission of yoking together art and science.

I am quoted in the most recent issue of The Economist: Technology Quarterly, in an article about BIM…
http://www.economist.com/search/displaystory.cfm?story_id=11482536&CFID=8986688&CFTOKEN=97523703

FROM BLUEPRINT TO DATABASE
Jun 5th 2008
From The Economist print edition
Computing: Aircraft and cars are designed using elaborate digital models. Now the same idea is being applied to buildings.

The advent of powerful computers has enabled architects to produce stunning images of new buildings and other structures. No proposal for a big project is complete without a photorealistic rendering of how the final design will look, or even a virtual walk-through. Perhaps surprisingly, however, those fancy graphics tend to be used only for conceptual purposes and play no role in the detailed design and construction of the finished structure. For the most part, this is still carried out with old-fashioned two-dimensional elevation and plan drawings, created by hand or using computer-aided design (CAD) software. “It’s still a 2-D profession,” says Shane Burger, an associate architect at Grimshaw, the firm that designed the Eden Project, a domed botanical garden in Cornwall, at the south-western tip of England.

And therein lies a problem, for even when it is generated by computer, a 2-D line drawing is just that: a bunch of lines. “There’s no structure that tells you that this line is a wall, stair or window,” says Chuck Eastman, a professor of architecture and computing at the Georgia Institute of Technology in Atlanta. “If you changed a window you would have to rebuild the wall around it to make it bigger or smaller.” Given that even a small building can require thousands of drawings, and producing drawings traditionally accounts for a big chunk of an architect’s fee, making changes can be a costly and time-consuming business. “If you adjust the shape of a building late in the game, you would have a lot of drawing to do,” says Mr Burger. Moreover, such drawings give no indication of the cost of construction. Instead, architects have to keep a schedule of materials that they continually update as the design progresses. Alter the design, and you also have to alter the entire schedule.

That is why Dr Eastman and others have long championed a more powerful approach, called building-information modelling (BIM). This involves representing a building as a full, three-dimensional computer model, with an associated database. It is as big a leap forward from conventional CAD as a computer is from a slide rule, says Dr Eastman. Instead of using just lines, which can only be interpreted by people, the model is based on objects, which are solid shapes or voids with their own properties. The model also includes information about the relationships between these objects, so that when one object is changed (a window is made bigger, say) any related objects are automatically updated (the wall surrounding it gets thicker). Both 3-D views and traditional 2-D drawings can then be generated from the model.

An immediate advantage of this approach is that the software can identify any mistakes within a design. Using 2-D drawings it can be hard to spot inconsistencies, such as measurements that do not add up, or geometric clashes. “A structural engineer could end up with a beam in one place while a mechanical engineer has an air vent in the same location,” says William Mitchell, a professor of architecture at the Massachusetts Institute of Technology (MIT). Experienced architects and engineers learn to catch such errors, but they often become apparent only after construction has begun, pushing up costs, says Dr Mitchell. As a result, inconsistencies can account for 2% of a typical construction budget, and clashes for up to 5%.

As well as spotting such “spatial conflicts” and saving money, BIM can also dramatically improve the communication and co-ordination between architects and engineers. Drawings have been the main documents of a construction project, says Dr Mitchell. With BIM, the 3-D model becomes the main reference, and any 2-D drawings produced from it merely perform a minor role. The model also makes it possible to calculate the quantities of materials needed, and hence construction cost.

As BIM software becomes more powerful, the model is no longer just a 3-D representation of a building, but is in a sense a digital prototype or simulation. The idea that an aircraft’s first flight might take place in the memory of a computer, which uses fluid-dynamics software to calculate the airflow over its wings, is becoming commonplace. Why not apply the same idea to a building? Finite-element analysis can determine its structural properties; with the right software, there is no reason why the building’s energy consumption, lighting, heat flow, acoustics and regulatory compliance cannot all be calculated too, suggests Dr Eastman. This has already been done, for example, to calculate how sunlight will affect internal temperatures at the new Qatar Petroleum Complex Project.

Dr Eastman has been talking about this sort of thing since the 1970s, when the first BIM systems were developed. “But architects aren’t really technology innovators,” he admits. So until recently, BIM has largely been ignored—except, that is, by a handful of pioneering architects whose radical designs have required it.

BIM was, for example, used to design the Eden Project’s geodesic domes, says Mr Burger. Another early adopter is Frank Gehry. His uniquely warped and fluid style of architecture—exemplified by the Guggenheim Museum in Bilbao, the Walt Disney Concert Hall in Los Angeles (pictured at the beginning of this article) and the Ray and Maria Stata Centre at MIT—results in structures so complex that it might not have been possible to build them at all without the help of BIM. But now other architects are catching up. America’s General Services Administration (GSA), the federal agency that oversees civilian buildings, ordered the use of BIM technology for all GSA-funded projects starting in 2007. Other countries have similar policies.

Here comes BIM
Two factors lie behind the recent shift. The first is the availability of off-the-shelf BIM software. Until recently, architectural firms pretty much had to develop their own BIM tools. Mr Gehry, for example, took a product-design tool called CATIA, developed by Dassault Systèmes, a French company, and tailored it to his own specifications when designing the Guggenheim Museum. It is now marketed as an architectural tool, called Digital Project, by Gehry Technologies, a company founded by Mr Gehry in 2002. Architects really started to take note that same year when Autodesk, a leading maker of CAD software, bought a smaller BIM company called Revit, says Dr Eastman. It had the same effect as when Microsoft invests in a new technology, he says: “It legitimised it.”

The second factor is a concern about the construction industry’s inability to predict its costs. Bids for new projects are usually tendered at the design stage, and the cost estimates often turn out to be far too optimistic once construction begins. “We should be planning in advance how we put our buildings together,” says Mr Burger. As a result, there is a lot of work being done to develop more accurate cost-estimation modules for use with BIM tools. “We can do cost estimation much better now than five years ago,” says Dr Eastman.

The spread of BIM itself could help, as suppliers of building materials and components start to make information about their products available in a format that can be applied to objects in BIM models. This will enable architects to build up a design using representations of real products, from steel girders to floor panels to light fittings, while keeping track of costs, structural properties and so forth. Manufacturers have been waiting for the leading BIM-software companies to agree on common formats. Now an agreement is indeed in sight and when it is in place, adoption will happen very quickly, says Mr Burger.

BIM will also enable architects to produce more efficient designs, thus reducing costs. “Historically, information was expensive and materials and energy were cheap,” says Dennis Shelden, chief technology officer at Gehry Technologies. Working out the exact properties required of every single element of a building was impractical, so a worst-case scenario would be used, resulting in some elements using more resources than necessary. “Now the cost of information is going down, and the cost of materials and energy is going up,” says Dr Shelden. “We’re at an inflection point where doing localised, honed engineering is much more economical.” The exact properties of every element can now be calculated precisely, and they can then be made individually using robotic cutting equipment.

The usefulness of BIM extends beyond design and construction. The model can also help to streamline the maintenance and management of the building, by showing where pipes run, for example, or listing the exact parts used in the heating and cooling systems. Having asked for BIM in new buildings, the GSA has even gone back and created models for several old ones, so as to simplify the retrofitting of security systems.

As well as having practical and economic benefits, BIM software will start to influence the designs that architects come up with. Enabling them to experiment more freely, without constant redrawing and recalculation, could help to liberate them from today’s engineering constraints. The ability to nudge and tweak a design, experiment with different approaches and immediately see the cost, structural and energy-consumption implications of those changes could lead to more imaginative architecture. Mr Gehry’s work may provide a glimpse of this future. Already, universities are turning out a new generation of architects and engineers trained in the new tools.

For Dr Eastman, who has seen many fellow BIM advocates retire or die before the technology was adopted, the transformation is hugely rewarding. And there appears to be no going back. “In ten years’ time there will be no drawings,” he says, “and ‘back to the drawing board’ will just become an historic phrase.”