Building in Design
Five years ago, Gerry Epp of Fast and Epp Partners was the consulting structural engineer working with Bing Thom Architects (BTA) on the Pacific Canada Pavilion extension to the Vancouver Aquarium Marine Science Centre (see CA November 2002). The project was geometrically and logistically complex, involving carefully detailed and finished parallel strand timber, combined with stainless and galvanized steel to create an exposed roof structure that included both king-post and pyramid trusses.
The project was further complicated by a challenging schedule, an extremely tight site, and the need for the facility to remain in operation throughout construction. Given these constraints, contractors were reluctant to submit firm prices for the structural package, and the tenders that eventually came in were considerably over budget. With the exposed clear span structure integral to the design, architects and engineers were faced with the unpalatable prospect of a substantial redesign that would undoubtedly compromise the project. A firm believer that well-crafted, exposed structures need not be expensive, and determined to see this project built as designed, Epp set up a construction company to erect the structure. With the encouragement of the architects and the approval of the client, the new company, StructureCraft Builders Inc., entered into a subtrade agreement with General Contractor Shimizu Canada. StructureCraft prefabricated the structure as a kit-of-parts and erected it successfully using a 35-tonne mobile crane. Since then, even as his consulting practice has continued to flourish, Epp and StructureCraft have found time to complete a handful of innovative projects in Canada and the U.S.
In this country, both architects and engineers are governed by similar codes of ethics–which cover such issues as disclosure and conflict of interest–but engineers enjoy more freedom when it comes to design-build situations. Provincial architectural associations vary considerably in their attitudes to design-build. The Architectural Institute of British Columbia (AIBC) is one of the more progressive associations, permitting architects to offer services as contractors on projects for which they are also the design architect. The by-laws of engineering associations typically do not mention design-build, so engineers are free to engage as contractors on any project, so long as they act within their code of ethics. Thus StructureCraft has been able to engage in a variety of contractual arrangements, not only on projects where Fast + Epp have been the consulting engineers, but also on projects where they have not.
While the projects have differed in scope and scale, they are connected by enlightened clients who have recognized the value of StructureCraft’s involvement. For some, the main priority has been speed–working with Busby + Associates Architects, StructureCraft completed the design and construction of a 400 m2 presentation centre for Concord Pacific in just six weeks–but for most the primary concern is quality. For Epp, client support is crucial to achieving the highest quality in each project and to maintaining the integrity of his consulting practice.
In this situation, Epp believes design-build offers a realm of expanded possibilities in which the boundaries between creation and production can be blurred, and designs developed and refined to a degree that would be impossible under traditional project delivery systems.
In a traditional scenario, a structural engineer might receive a design fee of three to five percent of the cost of the structure. While this may suffice where the design is straightforward, this fee can rarely be stretched far enough to adequately cover the detailing of highly articulated exposed structures or testing of non-standard connections. Inadequate fees produce conservative solutions, and this is nowhere more evident than in the case of timber structures, for which the detailing of connections is very time- consuming.
In this same scenario, the cost of shop drawings may be hidden in a stipulated price contract, but for an exposed structure it often runs to 10% of the cost, twice the engineer’s fee. It follows that, if the production of shop drawings can become an extension of design development, then the time and budget available to refine details, test solutions and identify economies can be greatly increased.
On Busby + Associates’ Gilmore Station (see CA March 2003), Fast + Epp Partners were the structural engineers and StructureCraft prefabricated and erected the platform canopies. Epp’s partner Paul Fast, who also has an equity interest in StructureCraft, declared this to the client, the Rapid Transit Project Office (RTPO), at the outset. RTPO agreed to the possibility of using StructureCraft on condition that the sub-contract be competitively tendered, and in the event of StructureCraft being successful, that inspections and assessments of progress payments be carried out independently by a third party.
While Gilmore Station was modest in scale, BTA’s Surrey City Centre project covers an entire city block. The scheme adds an office tower and a range of academic facilities to an existing shopping mall. Tying the complex together is a freeform galleria that measures 135 metres from end to end. From the outset it was envisioned that the galleria and circular atrium would be timber structures–visually warm and tactile public spaces that would enrich the experience of workers otherwise tied to the smooth synthetic environment of their computer workstations. Initially, Fast + Epp were subcontracted to project engineers Jones Kwong Kishi to work on the conceptual design of these structures.
When conceptual design was complete, and the client recognized the advantages of a design-build arrangement for these timber components, Fast + Epp withdrew from the project to allow StructureCraft to become involved. StructureCraft then worked speculatively with BTA on design development (much as a curtain wall manufacturer might do on a high rise project). Epp set out basic criteria for the design of the proposed timber structures that would facilitate efficient connection design, load transfer and ease of erection. As project engineers, Jones Kwong Kishi provided periodic reviews of the work to ensure general compliance with overall structural design parameters. At the end of this process, StructureCraft successfully negotiated the timber sub-contract for what is the company’s largest and most complex project to date.
The galleria roof consists of three-dimensional composite timber and steel cable trusses. Top chords and purlins are spruce glulam and the struts are turned and tapered solid spruce. Custom castings were designed for the exposed connections between the steel cables and the struts.
A fine-gridded space truss efficiently deals with the irregular geometry of the 85-foot high atrium by approximating the curved edges of the space. The seven foot deep tetrahedral space truss consists of nearly 4,000 Douglas Fir peeler cores, an inexpensive by-product of the plywood industry. Innovative confined lag screw connections, extensively tested for this project, allow these peeler core members to be used in tension as well as compression. StructureCraft prefabricated all the components in its Delta, B.C. workshop, including the 45-foot long, 24-inch diameter turned parallam mullions that support the glazed north wall of the atrium.
Epp is the first to admit that as a consulting engineer, he could not have designed these innovative structures without extraordinary fees, and even then might not have been able to incorporate some of the refinements that were made during the shop drawing process. Both Epp and the architects with whom he works value the creative synergy that seems to intensify with each refinement of the design. Matthew Woodruff of BTA has worked with StructureCraft on both the Pacific Canada Pavilion and Surrey City Centre projects. “For this kind of relationship to work,” says Woodruff, “there must be mutual respect and good will on both sides. On the Surrey project
we introduced many details that I’m sure were more expensive to build but which Gerry incorporated for the good of the project. That kind of commitment is hard to find, but then I believe that’s why he set up StructureCraft in the first place–to build better buildings than could be achieved by conventional means.”
Jim Taggart, a retired Vancouver architect, works as a freelance journalist and educator.