October 8, 2015
by Elsa Lam
View from northwest
Acton Ostry Architects have released renderings of Brock Commons Phase 1, a 404-bed student residence at the University of British Columbia. When completed, the $51.5-million residence building will stand 53 metres tall, making it among the tallest mass timber buildings in the world.
The use of a hybrid mass wood and concrete structure was investigated to demonstrate the applicability of wood in BC’s development and construction industries. Rigorous analysis concluded that the cost of a mass timber structure was similar to that for a typical concrete or steel structure. “Advances in wood technology and manufacturing make tall wood buildings not only possible but also safe and cost effective, while providing a way to lessen the carbon footprint of the built environment,” explain the architects in a press release.
Ground level view
The structure is comprised of a one storey concrete podium and two concrete cores that support 17 storeys of mass timber and concrete structure. Vertical loads are carried by the timber structure while the two concrete cores provide lateral stability. The floor structure is comprised of 5-ply CLT panels that are point-supported on glulam columns on a 2.85m x 4.0m grid. This results in the CLT panels acting as a two-way slab diaphragm.
The structural concept is similar to that of a concrete flat plate slab. To avoid a vertical load transfer through the CLT panels, a steel connector allows for a direct load transfer between the columns and also provides a bearing surface for the CLT panels.
The CLT panels and glulam beams are encapsulated with gypsum board to achieve the required fire resistance rating. The roof is made up of prefabricated sections of steel beams and metal deck with the roofing membrane pre-applied to achieve quick watertightness during construction.
Ground level view
To comply with university planning requirements, the design reflects the character of international style Modernist buildings on the campus. The base is wrapped with curtain wall glazing, coloured glass spandrel panels and transparent coloured glass. An extensive CLT canopy runs the length of the building. The façade is a prefabricated panel system comprised of white and charcoal panels punctuated by floor-to-ceiling clear-glazed openings with accents of coloured blue glass. Glazing wraps the corners to dematerialize the edges of the building. Further accentuating the vertical expression, a series of vertical splines rise up to a metal cornice that crowns the building.
View from northeast
The project will connect to the university district energy system and has been designed to target LEED Gold. The mass timber structure reduces the volume of concrete that would be typically used by 2,650 cubic meters, which is equivalent to reducing up to 500 tons of CO2 emissions.
The fire safety design underwent a peer-review process involving a panel of leading fire safety experts, scientists, authorities and firefighters. Although construction of the first floor and cores could technically be constructed utilizing mass wood, concrete was used instead, in the interest of facilitating the approvals process and for familiarity from a life safety and fire fighting perspective.
Common lounge area
The building is comprised of a series of repetitive, highly compartmentalized small rooms, so that in the event that a fire originates in one suite it is extremely likely the fire would be contained in the compartment in which it originated. To enhance compartmentalization, the typical one-hour fire separation required by the building code has been increased to two hours.
Studies have shown that automatic sprinkler systems are effective in controlling over 90% of fire incidents. For this project, an automatic sprinkler system with a back-up water supply offers additional protection for events that might originate during an earthquake. Exit stairwells incorporate mechanical pressurization to keep the exit stairs protected from smoke, thereby offering enhanced fire safety for those evacuating the building and to protect firefighter respondents.
Due to the characteristics and properties of charring, mass timber construction provides an inherent level of fire-resistance. Large timber members are difficult to ignite and if they do ignite they burn slowly. The CLT and glulam components used for the project have an inherent degree of fire-resistance that has been enhanced through encapsulation of the mass wood with three to four layers of fire rated Type X gypsum board, dependent on location.
Construction of the 18-storey tall wood student residence will begin later this fall, and the building is set to open in September 2017.