The 'CN Tower', located in
Toronto,
Ontario,
Canada, is a communications and tourist
tower standing 553.33
metres (1,815
ft 5
in) tall. Since its completion in 1976, it has been the
world's tallest free-standing structure on land. The Tower is the signature icon of the
city, attracting more than two million international visitors annually.
[1]
''CN'' originally referred to
''Canadian National'', the railway company that built the tower. Following the railway's decision to divest non-core freight railway assets, prior to the company's
privatization in
1995, the CN Tower was transferred to the
Canada Lands Company (CLC), a federal
Crown corporation responsible for
real estate development. Since local residents wished to retain the name ''CN Tower'', the abbreviation is now said to expand to 'Canada's National Tower'
[2] rather than the original 'Canadian National Tower'; however, neither of these are commonly used.
Structure
View through the Glass Floor.
The CN Tower consists of several substructures. The main portion of the Tower consists of a hollow concrete hexagonal pillar containing the
elevators,
stairwells and power and plumbing connections. On top of this is the metal broadcast antenna, carrying TV and radio signals. There are two visitor areas: the main deck level (formerly known as ''SkyPod'') located at , and the higher 'Sky Pod' (formerly known as 'Space Deck') at , just below the metal
antenna. Between the two areas the structure is "bare" and the hexagonal shape can be seen, but below the main deck, three large supporting legs give the tower the appearance of a large
tripod.
The main level consists of seven floors, some open to the public. Below the public areas are the structure's microwave receivers in a large white donut-shaped
radome, at . At is the
Glass Floor and Outdoor Observation Deck. The glass floor has an area of and can withstand a pressure of 4,100,000
pascals (595
psi). The glass floor consists of thermal glass units that are thick, consisting of a pane of laminated glass, a 25 millimetre airspace and a pane of 13 millimetre laminated glass. Some people experience
acrophobia by standing on the glass floor and looking down at the ground below. At is the Horizons Cafe and the Look Out level, and at is the 360 Restaurant, a
revolving tower restaurant which completes a full rotation once every 72 minutes.
Inside the 360 Restaurant.
The Sky Pod is the highest public
observation deck in the world. On a clear day, it is possible to see 100 to 120
kilometres (62–75
mi) away, to the city of
Rochester across
Lake Ontario in the
United States, or the mist rising from
Niagara Falls.
A metal
staircase with 1,776 steps reaches the main deck level, reaching 2,579 steps by the Sky Pod, and is the tallest metal staircase on Earth. These stairs are intended for emergency use and are not open to the public, except for three times per year for charity stair-climb events: around
Earth Day in the spring by
World Wildlife Fund Canada and in the fall by the
United Way's Toronto chapter. The average climber takes approximately 30 minutes to climb to the base of the radome, but the fastest climb on record is 7 minutes and 52 seconds in 1989 by Brendan Keenoy, an Ontario Provincial Police Officer. The fastest record for a woman belongs to Chrissy Redden, who climbed the stairs in 2000 in 11 minutes and 52 seconds. In 2002, Canadian
Olympian and
Paralympic champion
Jeff Adams climbed the stairs of the CN Tower in a specially designed
wheelchair.
History
The concept of the CN Tower originated from a
1968 Canadian National Railway desire to build a large TV and radio communication platform to serve the Toronto area, as well as demonstrating the strength of Canadian industry, and CN in particular. These plans evolved over the next few years, until the project became "official" in
1972. The Tower would have been part of 'Metro Centre' (see
CityPlace), a large development south of Front Street on the Railway Lands, a large railway switching yard that was being made redundant by newer yards outside the city. Key project team members were NCK Engineering as structural engineer;
John Andrews Architects; Webb, Zerafa, Menkes, Housden Architects; Foundation Building Construction and Canron (Eastern Structural Division).
At the time, Toronto was a "boom town" and the late
1960s and early
1970s had seen the construction of numerous large
skyscrapers in the downtown core. This made broadcasting into the downtown area very difficult due to reflections off the buildings. The only solution would be to raise the antennas above the buildings, demanding a tower over tall. Additionally, at that time most data communications took place over point-to-point
microwave links, whose dish antennae used to cover the roofs of large buildings. As each new skyscraper was added to the downtown, former line-of-sight links were no longer possible. CN intended to rent "hub" space for microwave links, visible from almost any building in the Toronto area. The CN Tower can be seen from at least as far away as Gamble Street in
Richmond Hill, Ontario, approximately to the north, and from several points on the south shore of
Lake Ontario, to the south.
The original plan for the tower envisioned a tripod consisting of three independent cylindrical "pillars" linked at various heights by structural bridges. This design would be considerably shorter than the Tower as it is today, the metal antenna located roughly where the concrete section between the main level and the Sky Pod lies today. As the design effort continued, it evolved into the current design with a single continuous hexagonal core to the Sky Pod, with three support legs blended into the hexagon below the main level, forming a large Y-shape structure at the ground level.
The idea for the main level in its current form evolved around this time, but the Sky Pod was not part of the plans until some time later. One engineer in particular felt that visitors would feel the higher observation deck would be worth paying extra for, and the costs in terms of construction were not prohibitive. It was also some time around this point that it was realized that the Tower could become the world's tallest structure, and plans were changed to incorporate subtle changes throughout the tower to this end.
Construction
Construction on the CN Tower started on
February 6,
1973 with massive excavations at the tower base for the foundation. By the time the foundation was complete, 56,000
tonnes (61,729
short tons) of
dirt and
shale were removed to a depth of in the centre, and a base incorporating 7,000
cubic metres (9,156
cu yd) of
concrete with 450 tonnes (496 short tons) of
rebar and 36 tonnes (40 short tons) of
steel cable had been built to a thickness of . This portion of the construction was fairly rapid, with only four months needed between the start and the foundation being ready for construction on top.
To build the main support pillar, a hydraulically-raised
slipform was built at the base. This was a fairly impressive engineering feat on its own, consisting of a large metal platform that raised itself on jacks at about per day as the concrete below set. Concrete was poured continuously by a team of 1,537 people until
February 22,
1974, during which it had already become the tallest structure in Canada, surpassing the recently built
Inco Superstack which was built using similar methods. In total, the tower contains 40,500 cubic metres (52,972 cu yd) of concrete, all of which was mixed on-site in order to ensure batch consistency. Through the pour, the vertical accuracy of the tower was maintained by comparing the slip form's location to massive
plumb-bobs hanging from it, observed by small telescopes from the ground. Over the height of the tower, it varies from true vertical accuracy by only .
A bolt of lightning strikes the CN Tower. The CN Tower is struck by lightning at least 40 to 50 times annually compared to other places in
Toronto which are struck, on average, 2 times per
square kilometre (5 times per sq mi) every year.
[3]
In August of the same year, construction of the main level commenced. Using 45 hydraulic jacks attached to cables strung from a temporary steel crown anchored to the top of the tower, twelve giant steel and wooden bracket forms were slowly raised, ultimately taking about a week to crawl up to their final position. These forms were not only used to create the brackets which support the main level, but also as a base for the construction of the main level itself. The Sky Pod was built of concrete poured into a wooden frame attached to rebar at the lower level Deck, and then reinforced with a large steel compression band around the outside.
The antenna was originally to be raised by crane as well, but during construction the
Sikorsky S-64 Skycrane helicopter became available when the
United States Army sold off their examples to civilian operators. The helicopter, named "Olga", was first used to remove the crane, and then flew the antenna up in 36 sections. The flights of the antenna pieces were a minor tourist attraction of their own, as the schedule was printed in the local newspapers. Use of the helicopter saved months of construction time, with this phase taking only three-and-a-half weeks instead of the planned six months. The tower was topped off on
April 2,
1975 after 26 months of construction, officially capturing the height record from
Moscow's
Ostankino Tower, and bringing the total mass to 118,000 tonnes (130,073 tons).
Two years into the construction, plans for Metro Centre were scrapped, leaving the Tower isolated on the Railway Lands in what was then a largely abandoned light-industrial space. This caused serious problems for tourists to access the tower. Ned Baldwin, project architect with John Andrews, wrote at the time that "All of the logic which dictated the design of the lower accommodation has been upset," and that "Under such ludicrous circumstances Canadian National would hardly have chosen this location to build."
The CN Tower as seen from its base
Opening
The CN Tower opened to the public on
June 26,
1976, although the official opening date was
October 1. The construction costs of approximately
CDN$75 million ($330 million in 2005) were repaid in fifteen years.
Canadian National Railway sold the Tower prior to taking the company public in
1995, when they decided to divest themselves of all operations not directly related to their core freight shipping businesses.
As the area around the Tower was developed, particularly with the introduction of the
Metro Toronto Convention Centre and
Rogers Centre (known as the SkyDome before
2005), the former railway "wasteland" disappeared and the Tower became the centre of a newly developing entertainment area. Access was greatly improved with the construction of the 'SkyWalk' in
1989, which connected the Tower and SkyDome to the nearby railway and subway station,
Union Station. By the mid-
1990s it was the centre of a thriving tourist district. The entire area continues to be an area of intense building, notably a recent boom in
condominium construction.
From
1997 to January
2004,
TrizecHahn Corporation managed the building and instituted several expansion projects including a $26 million entertainment expansion and revitalization that included the addition of two new elevators (to a total of six) and the relocation of the staircase from the north side leg to inside the core of the building, a conversion that also added nine stairs to the climb.
Reassurance following Ostankino Tower fire
In August of 2000, a devastating fire broke out at the
Ostankino Tower in Moscow, only shorter than the CN Tower, killing three people and causing extensive damage. The fire was blamed on poor maintenance and outdated equipment. The failure of the fire-suppression systems and the lack of proper equipment for firefighters allowed the fire to destroy most of the interior and spark fears the tower might even collapse.
Canadian officials subsequently stated that it is "highly unlikely" that a similar disaster could occur at the CN Tower as it has safeguards that are superior to those of the Ostankino Tower. Specifically, officials cited:
★ the fireproof building materials used in the tower's construction,
★ frequent and stringent safety inspections,
★ an extensive sprinkler system,
★ a 24-hour emergency monitoring operation,
★ two 15,000-
imperial gallon (68,191
L or 18,014
gal) water reservoirs at the top which are automatically replenished,
★ a fire hose at the base of the structure capable of sending 600 imperial gallons (2,728 L or 721 gal) a minute to any location in the tower,
★ a ban on gas appliances anywhere in the tower,
★ an elevator that can be used during a fire as it runs up the outside of the building and can be powered by three emergency generators at the base of the structure.
[4]
Falling ice danger
A
freezing rain storm on
March 2,
2007 had resulted in a layer of ice several
centimetres thick forming on the side of the tower and other downtown buildings. The sun thawed the ice, and winds of up to 90
km/h (55
mph) caused some of it to dislodge and be blown away from the structure. There were fears that cars and windows of nearby buildings would be smashed by large chunks of ice. In response to this, police closed some local streets surrounding the CN Tower. At the height of morning rush hour on
March 5, police expanded the area of closed streets to include the nearby
Gardiner Expressway away from the tower, as increased winds were causing the ice to be blown farther away, even as far north as
King Street, away, where a
taxicab window was shattered.
On
March 6, the Gardiner Expressway was reopened after winds died down.
[5] It was the first time such an event had posed a threat to public safety.
LED lights
The CN Tower illuminated, as seen from downtown Toronto.
The CN Tower was once lit at night with
incandescent lights, but they were removed in
1997 because they were expensive and inefficient to repair. However, on
May 30,
2007, it was announced that the CN Tower was to be outfitted with 1,330 super-bright
LED lights inside the elevator shafts, shooting up over the "bubble" and upward to the top of the tower's mast to light the tower from dusk until 2:00 a.m. The lights were completely installed by early June, with the official opening ceremony taking place on
June 28 before the
Canada Day holiday weekend.
Programmed from a
desktop computer with a
wireless network interface card, the LEDs use ten percent less energy than the method the tower used to light the tower after the incandescent lights were removed and sixty percent less energy than when incandescent lights lit the tower prior to
1997. The estimated cost to use the LEDs is $1,000 per month.
During the spring and autumn
bird migration seasons, officials have stated that the lights will be turned off to comply with the voluntary Fatal Light Awareness Program, which "encourages buildings to dim unnecessary exterior lighting to mitigate bird mortality during spring and summer migration."
[6]
Size comparisons
In 1995, the CN Tower was declared one of the modern
Seven Wonders of the World by the
American Society of Civil Engineers, and also belongs to the
World Federation of Great Towers.
There are currently six proposals for towers whose final heights are to exceed the CN Tower's
[7], three of which are currently under construction. At the forefront, the
Burj Dubai would, according to present claims by its developers, become a taller freestanding land structure than CN Tower sometime in 2008; work on that tower has, as of
August 12,
2007, reached the 145st floor and . The Burj Dubai is expected to be finished by the end of 2009 and its planned final height has been kept secret. The state-owned development company Emaar Properties, one of the main builders in rapidly developing Dubai, said only that the tower would stop somewhere above . In North America, the
Chicago Spire's height is currently planned to exceed CN Tower's height, currently planned at .
[ Dubai tower is now 'world's tallest']
Controversy over the "World's Tallest" title
Guinness World Records has called the CN Tower "The world's tallest self-supporting tower" and "the world's tallest free-standing tower".
[8] [9] Although Guinness did list this description of the CN Tower under the heading "tallest building" at least once
, it has also listed it under "tallest tower", omitting it from its list of "tallest buildings."
In 1996,
Guinness World Records officially changed the CN Tower's classification to "World's Tallest Building and Freestanding Structure". Today, the Guinness World Records state the CN Tower as the "Tallest Freestanding Tower," because the
Petronius Platform oil platform in the
Gulf of Mexico is taller at , yet most of the rig is underwater, earning it the title of tallest free-standing structure in the world.
Emporis and the
Council on Tall Buildings and Urban Habitat both list the CN Tower as the
world's tallest free-standing structure on land, and specifically state that the CN Tower is not a true building, thereby awarding the title of
world's tallest building to
Taipei 101, which is shorter than the CN Tower.
[10][ Council on Tall Buildings and Urban Habitat high rise database criteria ]. The tower's official web site, however, unequivocally claims it is the "world's tallest building".
[CN Tower official web site]
Although the CN Tower contains a restaurant, a gift shop and multiple observation levels, it does not have floors continuously from the ground, and therefore
it is not considered a building by the Council on Tall Buildings and Urban Habitat (CTBUH), Emporis, or any other architectural authorities. The CTBUH defines a
building as "a structure that is designed for residential, business, or manufacturing purposes. An essential characteristic of a building is that it has floors."
[ The CN Tower and other similar structures, such as the Ostankino Tower in Moscow, Russia, the Stratosphere Tower in Las Vegas, Nevada, and the Eiffel Tower in Paris, France are categorized as "towers", which are free-standing structures which may have observation decks and a few other habitable levels, but do not have floors from the ground up. The CN Tower is the tallest tower by this definition]
Even if the CN Tower were considered a building, it might not be recognized as the world’s tallest. Taller than the CN Tower are numerous radio masts and towers (which are essentially very tall frameworks that support TV and radio signals) which are held in place by guy-wires, the tallest being the KVLY-TV mast in North Dakota at tall, leading to a distinction between these and "free-standing" structures. Additionally, the Petronius Platform stands above its base on the bottom of the Gulf of Mexico, However, only the top of this oil and natural gas platform are above water, and the structure is thus partially supported by its buoyancy. Like the CN Tower, none of these taller structures are commonly considered buildings.
Use
The CN Tower has been and continues to be used as a communications tower for a number of different media, and by numerous companies:
Television broadcasters
★ Canadian Broadcasting Corporation (CBC)
★ CTV Toronto (CFTO-TV)
★ Citytv Toronto (CITY-TV)
★ Global Ontario (CIII-TV)
★ SUN TV (CKXT-TV)
Radio
There is no AM broadcasting on CN Tower.[11] The FM antennas are situated above ground.
| Callsign[12] | Frequency | ERP | Branding | Notes |
|---|
| Master FM | Consortium of Toronto broadcasters for Digital Audio Broadcasting#Canada |
| CJRT | 91.1 MHz | 40 kW | JAZZ.FM91 | |
| CJAQ | 92.5 MHz | 40 kW | 92.5 Jack FM | |
| CBL | 94.1 MHz | 38 kW | CBC Radio 2 | |
| CFMZ | 96.3 MHz | 38 kW | Classical 96 | |
| CJEZ | 97.3 MHz | 4 kW | EZ Rock 97.3 | |
| CHFI | 98.1 MHz | 44 kW | 98.1 CHFI | |
| CFMX | 99.9 MHz | 40 kW | 99.9 Mix FM | |
| CHIN | 100.7 MHz | 4 kW | CHIN Radio | Primarily in Italian and Portuguese |
| CFNY | 102.1 MHz | 35 kW actual (100 kW ERP) | 102.1 the Edge |
| CHUM | 104.5 MHz | 40 kW | 104.5 CHUM FM | |
| CILQ | 107.1 MHz | 40 kW | Classic Rock Q 107 | |
Cellular and paging providers
★ Bell Mobility
★ Rogers Wireless
★ Motorola
Communications
★ Bell Canada
★ Toronto Transit Commission
★ Amateur radio repeaters "2-Tango" ( VHF) and "4-Tango" (440/70 cm UHF) – owned and operated by the Toronto FM Communications Society, under callsign VE3TWR.[13]
Facts and figures
★ The CN Tower is 13 m (43 ft) taller than Moscow's Ostankino Tower, is almost twice as tall as the Eiffel Tower, and is the tallest member of the World Federation of Great Towers.
★ Only one person died as a result of the construction of the CN Tower.
★ The CN Tower has a wind tolerance level of 420 km/h (117 m/s, 260 mph).
★ The elevators ascend and descend at over 22 km/h (6 m/s, 15 mph), taking 58 seconds to reach the Look Out level (indoor observation deck) and 61 seconds to reach the 360 restaurant levels.
★ In winds of 200 km/h (120 mph) the tower sways 1.05 m (3½ ft) from centre at the Antenna, 0.45 m (1½ ft) from centre at the Sky Pod, and 0.25 m (9 in) from centre at the main level.
★ The CN Tower is designed to withstand an earthquake of 8.5 on the Richter Scale.
★ In 1979, Norman Alexander and Joe Squire hauled a 200 kg (440 lb) piano up the stairs in 7.5 hours.
★ On July 23, 1999, Ashrita Furman became the fastest person to go up the CN Tower using a pogo stick.
★ In 2001, a group of environmentalists illegally scaled the outside of the Tower, in order to place a banner protesting the policies of United States President George W. Bush.
★ The tower is the only landmark from Canada that appears in the city-building/simulation computer games ''SimCity 3000'' and ''SimCity 4''.
★ The tower is occasionally mistaken by some for the Seattle Space Needle, due to their similar appearances, however the CN Tower is exactly three times taller than the Space Needle. While filming in Toronto, American talk show host Conan O'Brien staged a mock fight on his show between two men costumed as the respective towers.
★ The CN Tower can be accidentally seen numerous times during scenes in the ''Police Academy'' series.
★ The vertical warning marker lights of the CN Tower can be accidentally seen in the movie ''Bulletproof Monk'' during scenes shot at night.
★ The tower was featured in the 1995 film ''Canadian Bacon''.
★ The CN tower has been featured numerous times on the Canadian Television series Kenny vs Spenny.
★ A segment of "Weird Al" Yankovic's live concerts contained a short video mockumentary about why it is inadvisable to throw bananas from the top of the CN Tower.
★ The song "''The CN Tower Belongs to the Dead''" by Owen Pallett makes obvious reference to the Tower.
★ The song "''I Don't Want to Go to Toronto''" by Radio Free Vestibule complains that "there's a tower in Toronto that controls people's minds," an obvious reference to the CN Tower.
★ The CN Tower was featured on the front cover of the 1996 ''Guinness Book of World Records''[14].
★ The CN Tower is featured in the music video of ''Another Postcard'', a song on the 2003 ''Everything to Everyone'' album by the Barenaked Ladies.
★ The CN tower (along with the rest of the Toronto skyline) can be seen easily on a clear day from the shore of Lake Ontario and the brim of the Niagara Escarpment in the Niagara Peninsula.
★ Tour of the Universe was a space ride located in the base from 1986 to 1987
★ The movie ''Highpoint'' (1982) includes the highest stunt fall in motion pictures. Dar Robinson falls from the tower, a height of 1,170 ft, before opening his parachute 90 m (300 ft) above the ground. His pay was $150,000 for the stunt.
★ The original walkway from Front Street to the tower was removed and now used by Weber's Restaurant on Highway 11 near Orillia, Ontario.
★ Displayed inside the Tower, the Latitude and Longitude is stated as 43 degrees 28 minutes 36 seconds north, 79 degrees 23 minutes 15 seconds west. This would place it about ten miles into Lake Ontario. A more accurate positioning would be 43 38 34 north 79 23 13 west.
★ At one stage of the tower's construction, the radio broadcasting system that tops the tower was laid out at the base of the structure, awaiting placement on top. During this period, several construction workers helping build the tower wrote their names on it. These names remained on the broadcasting section when it was placed atop the tower, although they have most likely faded from exposure to the sun by now.
Media placement
★ ''
★ ''Strange Brew''
★ ''The Sentinel''
★ ''
★ ''Exit Wounds''
★ ''Canadian Bacon''
★ ''Highpoint'' (1982)
★ The Super Dave Osborne show
★ Kenny vs Spenny, where both contestants raced up the staircase. Kenny did not climb, and later climbed the staircase as a humiliation.
See also
★ List of tallest buildings and structures in the world
★ List of towers
★ List of masts
★ List of skyscrapers
★ List of tallest structures in Canada
★ World's tallest structures
★ CityPlace (Toronto)
References
External links
★ Official CN Tower Website
★ CN Tower Lights
★ CN Tower Webcam
★
★ Community photos from Flickr
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