Q. How do you fit an 'elliptical' dome into an existing semi-circular structure?
A. An 'elliptical' dome derived from slicing horizontally through a toroid provides the solution.
Structural Restoration and Revitalization
Robson Domes, Ice Rink & Plaza, Vancouver, BC
When Arthur Erikson wants to fit an elliptical dome into an existing semi-circular structure, you simply have to figure it out.
The two domes create a visually exciting centrepiece for the restored Robson Plaza. They were also one of the most challenging to structurally engineer. RJC contributed groundbreaking ideas to tailor the shape and layout of the dome members to satisfy both the inherent structural requirements and stringent architectural demands.
To support the new domes, the existing cantilevered concrete beams required substantial upgrading. There was also the problem of fitting the elliptical domes into the existing semi-circular concrete support structures.
The toroidal surface of the dome gave birth to the diagonal grid-shell structure’s elliptical geometry concept. This created constant curvatures and a regular geometry such that the structural members and the triangular glass panels were similar in size. But more importantly, the facets and intersecting nodes were identical, vastly simplifying fabrication.
The intricate geometry for the domes required precise detailing in order to have all the connections work. The domes were created using a 3-D REVIT model and then transferred to the SAP program for analysis. Beyond normal load considerations (dead, snow, wind and earthquake), temperature differences and differential temperature in members were also considered in the design to estimate their maximum deflection and stresses.
The 3-D model enabled precise detailing of all members simplifying both manufacture and assembly. On-site, despite the 144,000 lbs. of stainless steel that make up the two domes, each dome was successfully erected within eight hours. Once the final fitting, welding and polishing were finished, the glaziers dropped the glass panels onto the stainless steel domes and the elliptical domes were completed. Stainless steel reduces the frequency and extent of maintenance and provides the slim, elegant lines envisioned by the Architect and client.
The elliptic domes are a crowning example of visionary architecture and innovative structural engineering working in unison. The judging architect for the CISC 2009 BC Region Steel Design Award said that from a distance, the domes are "The Jewels of the Ring."
In addition to the dome and the traditional aspects of structural design such as the ice rink slab, RJC was involved in the dome glazing design and the plaza envelope planning, including a new waterproof membrane for the entire plaza area to protect the UBC campus below.
This revitalization project created a unique, inspiring celebration space for the 2010 Vancouver Winter Olympics. The domes will be a contemporary landmark for Robson Square and the City of Vancouver for many years to come.