McLeod Athletic Park Spectator Grandstand | Township of Langley | Langley, BC
PBK Architects Inc.
The successful roof design/build proponent became part of the design team and the effort resulted in a unique composite wood/steel/polycarbonate roof structure delivered to the site on budget. The roof is suspended from nine trusses, which consist of 30 mm thick, stressed skin plywood panels that span 3 m between two 600 mm deep pine glulam beams. These were assembled in the fabrication shop then shipped and erected on site. The sleek profile of the wood beams is achieved through additional strength provided by a galvanized exoskeletal tubular steel frame positioned over the roof plane. The “mantis” truss chosen to support the cantilevered roof canopy is new and unique. High-strength steel tubes form three interconnected “V’s” constructed with unique bolted end connections for combining into one assembly. Secondary 6 m long roof purlins between modular roof panels were in-filled on site then clad with translucent polycarbonate roof panels.
A critical aspect of the roof design permitted no climbable structures at the underside of the cantilevered canopy. Unlike a typical open web steel joist and deck system, the inverted structural system is designed to avoid the potential of access and climbing as well as the potential for bird roosting over the spectators.
In order to address rapidly escalating local construction costs, the design team proposed soliciting a select number of roof design/build proposals during the early stage of design development and construction costing review. The strategy allowed for establishing a fixed cost for the roof early in the overall timeline of the project.
Due to unrestricted access to the McLeod Athletic Park, the grandstand functions as a gathering place for people at all times of the day. In order to avoid extensive maintenance costs for repairs caused by vandalism, the facility was designed with durability and CPTED (Crime Prevention Through Environmental Design) as significant considerations.
Wood materials used:
The design process of the facility resulted in the development of a unique structural roof component. The “Mantis” truss derives its name from the winged praying mantis. The design team coined the term for the composite structure based on the similarity of the segmental six-strutted steel frame to that of the graceful appearance and strength of the predaceous insect. Metaphorically, the grandstand connotes the image of the six-legged creature with translucent wings perched atop a tree branch.
Spanning between the mantis trusses are polycarbonate-glazed panels with a high light-transmittance coefficient. The combination of painted white plywood soffit panels and the translucent glazing promote the notion of a suspended open-air weather screen rather than a heavy overhead roof shelter. A secondary structural matrix of glulam purlins accentuates the liner composite of the structure.
The roof form and its assembly also resemble the profile and structure of an aerofoil. The vocabulary of aviation can be considered contextually appropriate in that the athletic park is directly adjacent to the Langley Airport.
The tensile roof form floats over a solid base of concrete bleachers. The galvanized guardrail system and the frameless glazing of the press booth then add an aspect of refinement to the solid concrete foundation. The hierarchy of ground plane/foundation/superstructure is likened to the relationship of meadow/rock outcropping/tree branch. As part of the design concept, this metaphor to nature is intended to further relate the appropriateness of the building form to its beautiful natural environment.
Design team:
Architect:
PBK Architects Inc.
200-1985 West Broadway
Vancouver, BC V6J 4Y3
604.736.5329
Design/Builder:
StructureCraft Builders Inc.
8279 River Way, Delta, BC V4G 1G9
Structural Engineer:
Fast & Epp Engineering
201 – 1672 West 1st Avenue
Vancouver BC V6J 1G1
