Canadian Consulting Engineer

Lest We Forget The Canadian War Museum

The newest national cultural venue in Ottawa has a somber but critically important purpose -- to teach us and future generations what it means to engage in war....

August 1, 2005   Canadian Consulting Engineer

The newest national cultural venue in Ottawa has a somber but critically important purpose — to teach us and future generations what it means to engage in war.

Opened in May, the Canadian War Museum sits on the LeBreton Flats along the southern banks of the Ottawa River west of Parliament Hill. The building is broad and angular, crouching low on the landscape. On the east it rises to face the Peace Tower with a pointed fin 24 metres high. Most of the building’s low sloping roofs are covered with vegetation. As a natural overlay, this vast 20,500-m2 green roof helps to carry through the architect’s theme of “regeneration”: the land suffers because of war, but nature heals itself over time.

There are four main exhibition galleries covering periods from indigenous and early Canadian battles and warfare, through the two World Wars, to the Cold War and current peacekeeping. Another gallery is a large open space for exhibiting military vehicles, artillery and air bombers, and the John McCrae Gallery is for special collections. The complex also incorporates a Military History Research Centre and conservation laboratories.

The curators’ aim is to give visitors, who are estimated to number 400,000 a year, an appreciation of the historical facts of military history, but at the same time let them experience the intensely personal and emotional aspects of war. The entry foyer is a broad, low space. One reporter described it as creating a feeling of “compression” and disorientation as it draws visitors inside. As visitors pass into different zones they wind through interconnecting spaces, through corridors and halls of complex angles and slopes. From time to time they come across huge audio-visual and graphic displays, such as of the horrors of Passchendaele. The intention is for them “to feel as if they are literally walking into a living archive.”

In the walls are punched out openings arranged in the Morse Code signals for “Lest We Forget” and the museum’s initials “CWM.” Perhaps the most memorable gesture is the cube of concrete suspended in the main lobby. It holds the tomb of Canada’s Unknown Soldier. Every year at 11 a.m. on November 11 the sun striking through the window will hit the headstone. The date marks Armistice Day in World War I. In that war alone a total of eight million soldiers died.

The LeBreton Flats site has seen its own struggles. A community of housing and factories in the area was erased in the 1960s by the National Capital Commission, causing lingering resentment among urban activists. There is also contamination on the land; so far about 700,000 tonnes of soil has been removed. Dessau-Soprin were in charge of the environmental clean up. After a long hiatus, the National Capital Commission area is redeveloping the entire area and eventually, besides the museum, there will be a festival plaza and housing.

The museum was designed by Moriyama & Teshima Architects in joint venture with Griffiths Rankin Cook Architects. It cost $169 million, including the exhibits. Project managers were Genivar. See page 31 for the full list of consultants.

In the following pages the structural, mechanical and electrical consultants describe their role in realizing this “living archive.” Engineering highlights include the complex structure of Regeneration Hall and the use of river water for cooling.–BP

Structural Engineering

By: Mike Allen, P.Eng. , Adjeleian Allen Rubeli

The new Canadian War Museum is a very large building about 250 metres long and 120 metres wide. It is relatively short in height, up to three stories above grade and two levels below grade.

The structure is a combination of reinforced concrete, post-tensioned cast-in-place concrete, and structural steel. Due to its size, the building is separated by two expansion joints across the width to create three separate building structures. The structural grid for the most part is 9 x 9 metres.

Following are highlights of the structural design.

Regeneration Hall

The architectural objectives for this portion of the war museum were for a dramatic, cathedral-like space. The hall had to be clear of crossing structure with a clear view of the Peace Tower on Capital Hill through an elongated narrow triangular window at the east end. The walls of the hall were to be comprised of random sloped planes with a support structure in keeping with the geometry of the walls.

The challenge for the structural engineers was to create a very high, narrow and long tower without transverse structural elements to link the sloping walls. The proximity of adjacent lower roofs in the museum provided some opportunity for support, but for the most part the structure had to rely on only the walls and roof of the hall.

The structural solution, conceptually, was to create a series of three hinged arches that define the longitudinal sloped walls and roof. Each arch is comprised of a vertical truss on the sloping north face of the tower, with the chords of the truss joined to create a pin support at the base and spreading out to a maximum width at the roof level. The truss then continues across to the south wall at the roof, where it is supported by a sloped steel column contained within the south wall. The practicality of the details resulted in essentially a two-hinged arch with normal steel connections at the “hinge” points in place of true moment free hinges.

There are 11 arch/frames in Regeneration Hall, each with a different geometry. The roof slopes up from west to east, and slopes down from the south to north wall. All the walls are sloped planes and each wall has a number of changes in the slope resulting in diagonal hinge lines where the different wall planes meet. In addition, for each arch/truss, the plane of the truss structure is sloped towards the east and, in plan, is angled off-grid.

For this complicated, three-dimensional geometry, the structural engineering team integrated three software package of AutoCad, SFRAME and SSTEEL into one design tool.

Main lobby, vegetative roof structure and exhibition areas

The main lobby is a column-free space 18 to 22 metres wide and about 75 metres long. At the north and south ends of this space the roof not only supports a grass roof, but also pedestrian walkways, walls and gardens. Its structure is comprised of a series of post-tension, cast-in-place concrete beams, 2,200 mm deep and from 600 to 1,500 mm wide, with spans varying from 18 to 27 metres. The details had to provide for post-tensioning in two directions and had to carefully locate sliding bearings. The balance of the roof that supports the soil for natural grass is comprised of 300-mm slab and 280-mm deep drop panels with columns on the 9 x 9 m grid.

The main exhibition floor on level 2 has to support equipment of various sizes and weights, including tanks of about 60 tonnes. The design live load is 22 kPa. The floor structure is comprised of a 315-mm concrete slab, 260-mm deep drop panels and 400-mm deep capitals on circular columns.

Exposed sloped concrete walls

Exposed concrete walls are used throughout the museum to define spaces, lobbies and corridors architecturally and to provide lateral resistance to seismic and wind forces. The majority of the walls are sloped with an angle to the vertical varying from 7 to 31.

The number of exposed walls presented a special challenge to the structural design team because they restrain shrinkage in the concrete floor slabs. As a result there is a potential for cracking to develop in the slab and walls. The sloped walls also presented a challenge to the formwork contractor who had to devise diagonal braces to support the walls after the formwork was stripped. Without the braces the walls would not be stable until the slab above had been constructed to restrain the top of the wall.

Site cast concrete cladding

Although the building had to be clad with concrete panels incorporating a r
ain screen and insulation, the architects did not want a pre-cast concrete appearance. The solution was to develop a custom poured-in-place cladding system.

Galvanized steel angels were bolted to steel W Tees cast into the supporting structure. Insulation and “mira drain” for the air space were then attached to the structure prior to forming the outer surface of the cladding and placing the concrete. The support angles provide a combination of vertical support, horizontal support, and sliding support to ensure the panels are not restrained from moving due to shrinkage and thermal effects. An added complexity during construction was that these wall panels are sloped inwards and in some cases outwards.

Mechanical Systems

By: Donald E. Cruikshank, P.Eng.

The Mitchell Partnership Consulting Engineers

The “regeneration” theme of the architects of the new Canadian War Museum pays respect to nature’s capacity to recover from the wounds of war. This theme is reinforced by many sustainable design features that are incorporated into the building and its mechanical systems.

The building architecture emerges seamlessly from Ottawa’s LeBreton plain by a gently sloping grass covered roof. The roof, one of the largest in North America, is a sustainable ecosystem that plays two important roles. First, it mitigates the storm water runoff impact of the 450,000 square foot building. Second, it provides an effective insulating barrier to reduce the building’s peak daily heat gains and losses, thereby reducing the size of the mechanical heating and cooling plant.

Thanks to a relocation of the National Capital Commission Parkway road system, the building borders on the Ottawa River and is able to use its water as an integral part of the mechanical air conditioning systems. A heat pumping system has been designed that takes advantage of the annual seasonal fluctuations of the river water temperature to provide cooling and heating to the building. As well, a portion of the water extracted from the river is diverted for non-potable uses such as for toilet flushing, vehicle washing and irrigating planters. River water is also pumped to the irrigation system of the adjacent Vimy Park parade grounds.

The building is provided with a 960 TR central cooling plant consisting of two high efficiency 0.6 kW per ton, electric centrifugal chillers and one rotary screw chiller. These all use a non-CFC refrigerant. The chillers are of equal capacity so that the most efficient chiller can be used, depending on the priority for cooling or heat recovery.

Water from the river is blended with heated water from the chiller condensers to optimize their performance. Blending also reduces the discharge temperature of the condenser water outflow, which is directed into storm water management ponds that have been built for the entire LeBreton site.

The use of river water for cooling is projected to save over $50,000 per year in operating costs. It is also preferable to conventional cooling towers that are less energy efficient, noisy, and so large as to be difficult to integrate into the pastoral river setting.

River water cooling and other energy savings

Water is taken from the river through low velocity intake structures that have been specially designed to resist the entry of marine life and large debris. The water is pumped to the cooling plant where a centrifugal separator removes finer sand and debris. No chemicals are added, but the water is treated with ultraviolet sterilization to remove odour and bacteria.

The chillers are used year round to cool air sent to the exhibit and exhibit support spaces. Two large outdoor air units have been provided for this purpose and intakes are on different building exposures to mitigate the impact of severe winter weather such as the ice storm that Ottawa experienced several years ago. There is also a large onsite twin diesel generator that enables portions of the mechanical plant to function during power failures.

Conditioned outdoor air is delivered to the exhibits’ individual air handling units where it is blended with returned air and further filtered with 95% final filters. It is humidified, de-humidified, heated or cooled to suit the environmental requirements of each exhibit space.

Public exhibit areas where the occupant level fluctuates have carbon dioxide monitors. These alert the electronic building control system to increase outdoor air levels as necessary. Electronic variable speed drives optimize the air delivery and save fan energy.

Another energy-saving approach is the use of heat derived from the building chillers. The heat is recovered in a low temperature heated water circuit and used in the air handlers as part of the dehumidification and space temperature control system. In areas that are not exhibits, a heat recovery exchanger on the central outdoor air handlers is used to extract “free cooling” and “free heating.”

The building also has a central heating plant with two 200-hp firetube boilers that provide higher temperature water for ventilation air heating and space heating. This system interfaces to the low temperature heat recovery heating system as a backup.

Special areas

The area with the most stringent environmental requirements is the Research/Reference area. It contains archival objects including books, periodicals, film, video and other multimedia. It also has storage areas, copying facilities and restoration laboratories. Close temperature and humidity controlled air conditioning has to maintain constant 68F/40% relative humidity on a 365-day, 24-hour basis.

Also closely controlled are the permanent and changing exhibits, the art gallery and collection services, the many dress, insignia and arms storage vaults, as well as associated restoration laboratories and receiving areas. Their conditions must be held relatively constant but can be allowed gradual seasonal variations within limits. They need to have a maintained temperature and humidity within narrow bands of 68F to 72F and 40% to 55% humidity.

To ensure air cleanliness, special measures are needed to treat any exposed pipe and duct insulation to prevent flaking and other deterioration from contaminating exhibits. Floor drains in the collection areas have been equipped with devices to prevent backwater and the entry of bugs.

The Barney Danson Theatre has the most stringent acoustic requirement at PNC 20. It also has highly varying occupancy levels. Consequently it is provided with a dedicated air conditioning system.

Building controls and fire protection

The building control system promptly alerts the operators about abnormal run conditions or equipment failures. It is an electronic direct digital control system with distributed controllers, which has been integrated into the communication network. Electronic temperature and humidity sensors transmit signals to computer controllers that can carefully adjust water valves and air dampers to maintain the required conditions. Abnormal conditions trigger alarms that are sent to operators in the building or in outside locations.

The building automation system also controls the operation of fans in the event of a fire to provide smoke venting to aid firefighters. It also works in conjunction with the building sprinkler system to limit damage to artifacts in the collections.

Sustainable design has been extended to the plumbing systems. At the outset, an evaluation was done for a complete onsite waste treatment and blackwater recycling system. When the river water option became viable, it was decided to simplify ongoing operations by using this renewable resource. The domestic water supply system has been separated into a potable and non-potable system. Low water consumption fixtures, flushing devices and faucets are also installed.

The Mitchell Partnership began an extensive commissioning process during the early design stages of the project. We prepared an 800-page commissi
oning manual which was used as the basis for an operator instruction manual and for testing the actual performance of the mechanical systems. The manual was provided to the museum building operators four months before the project was completed and 10 months before the May 8, 2005 opening.

Electrical Systems

By: Wally Eley, P.Eng. and Duane Waite

Crossey Engineering

Ottawa’s Canadian War Museum goes beyond the conventional idea of a war museum as a place where weapons are displayed and battles celebrated. As the electrical consultants, we worked closely with the architects to have visitors experience the mixed feelings that are inseparable from war. By carefully deploying the lighting, communications and other infrastructure we helped to ensure that the museum truly respects the fallen, while conveying the architects’ key theme of regeneration.

Lighting

Three areas in the building stand out from the perspective of innovative and carefully coordinated lighting design.

* The LeBreton Gallery. This large artifacts gallery, which measures roughly 3,250 square metres, houses the museum’s largest weaponry including tanks, canons as well as a jet fighter. Many of the larger pieces were moved into the gallery before the infrastructure was completed, which made it a challenge to create consistent and flexible lighting.

While the gallery could have been treated like a “parts garage,” we were able to use a combination of lighting to create a space more reminiscent of a showroom.

First, backlights are used to cast an even wash of light against the walls. Second, recessed lighting is placed at the base of the supporting columns to cast lights upward. Third, the exceptionally high and variable ceiling required globe fixtures in order to provide sufficient illumination as well as establish a welcoming but “industrial” environment. Each globe fixture contains eight compact fluorescent lamps with multiple ballasts. They provide general ambient lighting with maximum control.

* Passage lighting. As visitors make their way from the large artifacts gallery to the museum’s permanent exhibitions, they are meant to feel as if they are in the thick of battle. This sensation is created by using fixtures based on the rectangular dome lights found in army tanks. These fixtures and “tank lights” mounted throughout the passage’s concrete walls concurrently shine a white ambient light — which in the field signals all is normal — and a red light — which signals an attack. Here in the museum’s passage the white light serves to create ambient illumination while the red light is used to create a sense of drama.

* Permanent exhibit lighting. One of the museum’s more powerful exhibits takes the form of a winding labyrinth displaying war stories and artifacts throughout Canadian history. To protect the exhibit’s artifacts against potential lighting damage, ceramic metal halide lamps (75 Watts and 150 Watts) with UV blocking filters were used rather than using traditional halogen-based lamps. The ceramic metal halide lamps help the museum to conserve energy since they constitute more than half the lighting in the exhibit areas that total 4,645 square metres. They achieve the necessary wattage density yet minimize the cumulative heat generated by so many lights in the winding, confined spaces.

All the museum’s lighting systems are integrated into a lighting control server that allows them to be coordinated with the audio-visual displays. The communications system connecting these and other systems is based upon a fibre optic backbone, which to ensure speed includes continuous non-spliced optic lines, up to 300 metres in length.

All the museum’s core systems, i.e. communications, power, fire protection and security, were designed to meet several critical standards, including the region’s seismic standards and the National Building Code of Canada.

Fire protection and power distribution

While the vast majority of the building is constructed of fire-retardant concrete, the importance and rarity of the artifacts demanded a state-of-the-art fire protection system. Among the technologies used is a Vesda early warning smoke and central air sampling system that is a hybrid of ionization and photo electric detection. It closely monitors particles in the air so as to identify potential zones of fire risk within the building. The detection system is completely integrated into the extinguishing system to allow for pre-alarms to be sounded before any water is released.

The complete fire protection system is designed to be barrier-free as well as to accommodate the visually impaired.

An independent public address voice system was installed for use during emergencies as well as for making regular announcements.

Client: Canadian War Museum

Structural consultant: Adjeleian Allen Rubeli (Mike Allen, P.Eng., Jon Turner, P.Eng., Garry Vopni)

Mechanical consultant: The Mitchell Partnership (Donald E. Cruikshank, P.Eng., Jorge Osorio, P.Eng.,

Gunther Lammers, Lee Keeley, CET)

Electrical consultant: Crossey Engineering (Wally Eley, P.Eng., Duane Waite)

Project management: Genivar

Architect: Moriyama & Teshima, Griffiths Rankin Cook

Construction management: PCL

Equipment suppliers: Edwards (fire alarm), Lutron (lighting controls), Schneider (electrical distribution), Vipond (sprinklers)


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