Twenty-four unique, thin-shelled canopies (5.1 m x 6 m and just 20 mm thick / 18 ft x 20 ft and just 3/4 in thick) supported on single columns, protect commuters from the elements at Calgary's new Shawnessy LRT Station.
This new walk-on LRT station located south of Shawnessy Boulevard and west of the CP Rail tracks is designed as a side-loading platform. The platform is staggered to improve passenger safety across the LRT tracks. At-grade access will be provided from an adjacent Park 'n Ride facility and bus terminal (situated east of the CP Rail tracks). Easy station access will be provided for buses and Park 'n Ride commuters. The area around the station will have extensive landscaping.
The innovative project is owned by The City of Calgary, managed by the Transportation Project Office (TPO) and constructed by general contractor, Walter Construction.
Ductal is a cement-based composite which can be made with either metallic or organic fibres. It is stronger and more durable than concrete and doesn't require steel reinforcing as concrete does. With strengths similar to metals, Ductal is significantly stronger than normal concrete. Compressive strengths range between 130 to 200 MPa (compared to 15 to 50 MPa for normal concrete) and flexural strengths range between 20 to 50 MPa (compared to 3 to 7 MPa for normal concrete).
The precast concrete canopy components are manufactured using Ductal, an ultra-high performance material that provides a combination of strength, ductility, durability and aesthetics. The Ductal components, manufactured by Lafarge's Calgary Precast division, include the 24 white, curved canopies, struts, columns, beams and gutters. The volume of Ductal concrete used is 80 m3.
Ductal's superior properties and design flexibility facilitated the architect's ability to create the attractive, off-white curved canopies. At night, the shells provide a dual function, diffusely reflecting the artificial light to the platform below and animating the facade through the louvred windows. Furthermore, the canopies are extremely durable, easy to clean and require very little maintenance.
Canopy Component Manufacturing and Installation
The precast Ductal canopy components were individually cast and consist of half-shells, columns, tie beams, struts and troughs. The columns and half-shells were injection cast in closed steel forms; the troughs were cast through displacement molding while struts and tie beams were produced using conventional gravity two-stage castings.
The right and left half-shells, along with the tie beams, were pre-assembled in the plant, then transported to the site and set on temporary scaffolding.
The struts were then attached to the shells and previously installed columns with welded connections.
University of Calgary Testing
To validate the performance of the structural system and material, a full-sized canopy prototype was sent to the University of Calgary's "Calgary Centre for Innovative Technology" for intensive, full-scale load tests, utilizing a series of 90 strain gauges. The test data confirmed the Ductal canopy not only surpassed the test criteria, it easily carried full-factored live and dead loads, without cracking.
Researchers in the Calgary Centre for Innovative Technology (CCIT) awarded a strong passing grade to an innovative construction material that promises new design possibilities for buildings, bridges and other structures. "This is one of the biggest steps forward in structural engineering in 50 years," says U of C civil engineering researcher Tom Brown, "This is very, very innovative material."
Brown and colleague Nigel Shrive along with six graduate students and two undergraduate students performed wind uplifting and snow loading simulations, as well as computer-modeled calculations on the canopy. "It passed the tests with flying colours," Shrive says.
U of C master's student Blair Scholefield was part of the research team. He says the contract research project allowed him to put classroom theory into practice as well as earn cash to support his grad studies. "It was a great opportunity to learn how things work in industry and how people work together on these types of projects."Civil engineering professor Lynne Cowe Falls is also impressed by Ductal's test results. She adds that pigments can be mixed into the Ductal to "move concrete out of the boring greys" and allow for more vibrant new buildings and structures.
Enzo Vicenzino of CPV Group Architects & Engineers Ltd. (Calgary) says Ductal made his vision achievable "because of its unique properties and design flexibility".
Founded in Calgary, Alberta in 1952 by J.H. Cook, FRAIC, CPV Group Architects and Engineers celebrate five decades of designing and administering the construction of a wide variety of building types. The firm's reputation is founded on the skilful transformation of buildings from abstract ideas to built form, assuring appropriate building quality and secure investment value for their clients.
The CPV Group provides professional services in urban design, architecture, space planning, interior design, and structural engineering. Such services include work in the sub-disciplines of programming, project feasibility analysis, site planning, functional planning, process engineering and building science. The firm has been recognized for this effort through the popularity of its built work and by its recognition through national awards.
Project: South LRT Extension - Shawnessy Station
Location: Calgary, Alberta
Substantial Completion Date: November 21, 2003
Owner: The City of Calgary
Managed by: TPO (Transportation Project Office)
Architect/Engineer: CPV Group Architects & Engineers Ltd.
General Contractor: Walter Construction Ltd.
Precaster: Lafarge Canada Inc. (Calgary)
For more information about Ductal, see: www.imagineductal.com