Richmond Olympic Oval "Wood Wave" Roof
The Richmond Olympic Speedskating Oval is a world class facility built for the 2010 Winter Olympics. Its all-timber roof is the largest of its kind in the world. In conjunction with architects Cannon Design, we proposed the unique panellized roof system comprised purely of standard dimensional 2x4' lumber.
Our
WoodWave panel concept for this enormous 6 acre roof was borne out of a
desire to utilize 2x4's in a larger span structural application, while addressing
the need for unique aesthetics, excellent acoustics, and stringent fire
protection requirements. The design of
this panel was a year in research and development in our shop. In our shop we engineered, tested and fabricated all 550 panels and then erected them on site with our own crews.
Design
The bones of the structure are created by 15 composite Glulam and steel arches which span the 330ft (100m) across the building, resting on 30 enormous concrete buttresses. Each arch has a distinctly V-shaped hollow cross-section that conceals heating, ventilation, air conditioning, plumbing, acoustical, electrical and lighting systems. Spanning the 42ft (12.8m) between arches are our prefabricated WoodWave structural panels. These consist of ordinary 2x4 lumber arranged geometrically to optimize both structural and acoustic efficiency. The panel design is not only economical but provides a striking aesthetic for this high-profile facility.
Use
of solid sawn dimensional lumber such as 2x4s is one of the least energy
intensive and least polluting form of construction. Use of this lumber for large and long-span structures
is uncommon.
The Mountain Pine Beetle
This panel concept provided an opportunity to use lumber from forests killed by the mountain pine beetle, a species native to North America. Normally these insects are vital players in the life cycle of forests – they promote young growth by weeding out older, weakened trees.
But recently, unusually hot summers and mild winters have caused their populations to explode across Western Canada and the US, destroying millions of acres of pine forests. Instead of letting these trees simply fall to the forest floor where they would decay, releasing their stored CO2 into the atmosphere, the WoodWave product provided a unique way to showcase the structural adequacy of properly harvested beetle-killed pine. The project created a net CO2 store of over 2500 tonnes of Carbon, enough to offset more than 600 cars driving on the road for a year.
The use of mountain pine beetle lumber from British Columbia forests and mills means the Oval's roof sets an important precedent in the effort to mitigate the impact of this unfortunate effect of climate change.
The WoodWave Panel
The idea for the unique “Wood-wave" panels began with our desire to use ordinary short 10-20ft (3-6m) pieces of 2x4 to somehow span the 42ft (12.8) metres between the primary arches. A number of constraints including structural efficiency, acoustics, fire safety, aesthetics, and fabrication processes guided the design of the panel.
An arch creates structural efficiency, while forming the pillowed appearance of each roof bay. Our challenge was to create this arch from small pieces of timber, and allow hidden integration of services – sprinklers, ducts, and lighting – while achieving the required acoustic and fire performance.
Breaking down the typical solid rectangle of a timber arch into an aggregate of much smaller elements allowed each element to be placed where needed structurally, and left the remainder open for service integration. A 26in (660mm) deep zigzag timber truss with a unique triangular 'V' cross-section was thus formed, with three of these 'Vees' forming one WoodWave panel, joined with stressed-skin plywood across the top.
The naturally straight Vee-shaped sections were bent into an arch using a custom-built hydraulic press and tied with a steel rod to keep the curved shape.
Acoustics of the enormous hall were a key consideration, and the semi-open pattern of 2x4s allowed sound to be captured by the acoustic insulation layers on the inside of the panel. Dimensional lumber such as this would not typically be permitted by fire codes, so we concealed mineral wool in the panels, and with LMDG Building Code Consultants performed extensive fire modelling to prove the systems' acceptability.
The Oval, which houses a 400-metre speed-skating track and seats approximately 8,000 people, was home to 12 olympic medal events.
Engineering
We set out and agreed the global geometrical principles of the project with Cannon Design early in the design process. Using Autodesk Inventor, we created a parametric geometrical model of the overall building geometry. This parametric model allowed the complex internal geometry of each WoodWave panel to respond to the changes in span, height, and radius required by the different roof geometry conditions.
Every second 2x4 "strand" in the WoodWave cross section is continuous, connected intermittently with splice pieces to its neighboring strands. We built complex rules into our governing parametric model to ensure each of the panel configurations incorporated structurally appropriate positioning of the splice pieces and associated screwed connections. Over 50 bespoke panel types were created automatically using these rules, seamlessly driving the shop fabrication drawings and CNC data we used to fabricate the panels downstream.
Each instance of this parametric panel knew where it was in the global building model, and its geometrical and structural design responded accordingly. The parametric model also contained both "states" of each panel – pre-bending (straight) and post-bending (arched), allowing accurate dimensional checks to be performed at each of the manufacturing stages. Several rules embedded in the model drove the geometric layout of the openings and splice locations, ensuring adequate acoustic performance for each panel.
The digital parametric model allowed changes in global form to be easily accommodated and reflected down to the smallest level of detail, eliminating the need for manual re-work. This model evolved over the length of the project, becoming a true Building Information Model, and containing more than just geometrical information. It also included structural requirements (nailing patterns and layout of splice connectors), details of services integration, and part numbering to aid with the site erection process. The 500 WoodWave panels in the project were each one of 55 unique panel forms created using this process.
Fabrication
The unique structural design of this panel was without precedent, so we undertook an extensive testing regime. We created structural analyses, conducted connection testing, and built 14 full-size prototypes of the panel to ensure that we understood its structural behaviour completely.
We linked our 3D model geometry to the structural analysis and fabrication models, creating a digital prototyping process. This allowed us to investigate parametrically the impact of changing geometry on both structural behaviour and physical aesthetics.
During fabrication each triangular section was hydraulically pressed into a curve and tensioned with a steel rod, giving it a camber 660mm from the ends to the crown. Factory fabrication of the panels included the installation of sprinkler lines, a black fabric liner and mineral wool insulation to meet fire codes and acoustical requirements.
Installation
Installation of the WoodWave roof panels followed the erection of successive pairs of main twin arches and temporary arch bracing. While the first pair of arches was erected and braced, ground personnel ensured the roof panels were properly secured for lifting. A second team, in man lifts, waited to position each panel and bolt it into place at the six connection points. After a number of bays were completed, a third group completed the panel installation by adding and stitching the continuous layer of plywood that creates the diaphragm for the roof.