CN Tower

• 1. Origins And Conception

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  In 1968, the Canadian National Railway faced a growing crisis in Toronto. The city was expanding rapidly with new skyscrapers like First Canadian Place rising downtown. These glass buildings reflected broadcast signals and blocked line-of-sight microwave links that carried most data communications at the time. CN needed a solution to serve the Toronto area with television and radio platforms. They also wanted to demonstrate the strength of Canadian industry through this massive project.

  The original plan envisioned three independent cylindrical pillars linked by structural bridges. This tripod design would have been considerably shorter than what eventually rose from the ground. Engineers realized they could build higher to improve signal quality while attracting tourists. The idea for the main level evolved around this period, but the Space Deck was not part of early plans until later. Bud Andrews, president of the Metro Centre Developments Group, felt visitors would pay extra for a higher observation deck. Construction costs were not prohibitive enough to stop them from adding it.

  By 1972, the project became official. Key team members included NCK Engineering as structural engineer alongside John Andrews Architects and Webb, Zerafa, Menkes, Housden Architects. Foundation Building Construction handled groundwork while Canron managed steel fabrication. The tower would stand on former Railway Lands south of Front Street, an area becoming redundant after MacMillan Yard opened in 1965.

• 2. Construction Engineering Feats

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  Construction began on the 6th of February 1973, when workers removed 40,000 cubic meters of earth and shale to reach depths of 18 meters below center. A base incorporating 12,000 cubic meters of concrete with 1,500 tons of rebar and 1,000 tons of steel cable formed the foundation. This portion took only four months to complete before construction could begin upward.

  Workers built a hydraulically raised slipform at the base that lifted itself on jacks at about one meter per day as concrete set below. Concrete poured Monday through Friday until the 22nd of February 1974, when the structure surpassed the Inco Superstack in Sudbury as Canada's tallest building. All 33,000 cubic meters of concrete mixed on-site ensured batch consistency throughout the pour. Vertical accuracy stayed within two centimeters over the entire height by comparing slip form location to massive plumb bobs hanging from it.

  In August 1974, construction of the main level commenced using 45 hydraulic jacks attached to cables strung from temporary steel crowns anchored to the tower top. Twelve giant steel and wooden bracket forms slowly rose over about a week to their final position. These forms created brackets supporting the main level plus bases for its construction. The Top section used concrete poured into wooden frames attached to rebar at lower deck levels then reinforced with large steel compression bands around the outside.

  The antenna originally planned for crane lifting became impossible when Sikorsky S-64 Skycrane helicopters appeared after U.S. Army sales to civilian operators. Named Olga, this helicopter removed cranes first then flew antenna pieces up in 36 sections. Flights became minor tourist attractions themselves with schedules printed in local newspapers. This phase took only three and a half weeks instead of six months, topping off the 2nd of April 1975, after 26 months total construction time.

• 3. Height Records And Comparisons

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  On the 31st of March 1975, the CN Tower officially became the world's tallest free-standing structure while still under construction. It held that record for 32 years until the 12th of September 2007, when Burj Khalifa surpassed it during Dubai's development phase. The tower remained the world's tallest tower until 2009 when Canton Tower in Guangzhou exceeded its height. As of 2022, it stands as the tenth-tallest free-standing structure on land globally.

  Current rankings place the CN Tower as the third-tallest tower worldwide behind Tokyo Skytree at 634 meters and Canton Tower at 604 meters. Within North America, it remains the tallest free-standing structure on land in the Western Hemisphere. Two other structures exceed 553 meters nearby: Willis Tower in Chicago reaches 527 meters to pinnacle, while One World Trade Center in New York City measures 541 meters but is unlikely to grow further due to symbolic significance attached to 1,776 feet.

  Guinness World Records classified the CN Tower differently over decades. Initially listed under tallest buildings once, they later moved it to tallest towers category omitting building status. Emporis and Council on Tall Buildings and Urban Habitat both recognized it as world's tallest free-standing structure on land specifically stating it was not a true building because floors do not extend continuously from ground up. CTBUH defines buildings as structures designed for residential or business purposes with essential floor characteristics missing here.

• 4. Public Access And Attractions

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  When the CN Tower opened the 26th of June 1976, three public observation points existed immediately available to visitors. The Top stood at 447 meters above ground level then known as Space Deck. Indoor Observation Level reached 342 meters height while Outdoor Observation Terrace sat at 342 meters same elevation as Glass Floor. One floor above Indoor Observation Level housed Top of Toronto Restaurant completing revolution every 72 minutes.

  A glass floor installed in 1994 at Lower Observation Level covers 10 square meters area capable of withstanding pressure equivalent to 18 people standing simultaneously. Thermal glass units measure 5 centimeters thick consisting laminated panes separated by airspace creating transparent viewing platform allowing direct sightlines down to street level below. In 2008, one elevator received upgrade adding glass floor panel establishing world record highest vertical rise feature equipped with this capability.

  On the 1st of August 2011, EdgeWalk opened offering thrill-seekers hands-free walking experience around roof edge of main pod located directly above 360 Restaurant. Visitors walk on metal floor tethered overhead rail system extending approximately 1.5 meters beyond building perimeter. Attraction closes during winter months plus electrical storm periods and high wind conditions ensuring safety protocols remain intact throughout operation seasons.

• 5. Cultural Impact And Stunts

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  Stuntman Dar Robinson jumped off the CN Tower twice within two years starting in 1979 for movie Highpoint scenes receiving $10,000 compensation per jump. First attempt used parachute deployed three seconds before ground impact while second employed wire decelerator attached backside. These stunts garnered worldwide media attention transforming the tower into an icon of daring feats alongside its engineering achievements.

  High-rise firefighter Dan Goodwin climbed outside structure using hands and feet alone the 26th of June 1986 marking tenth anniversary celebration. He performed ascent twice same day then descended via multiple rappels demonstrating physical capabilities required scaling such heights without equipment assistance. From 1985 to 1992 basement level hosted world's first flight simulator ride Tour of Universe based Space Shuttle flights replaced later by Space Race attraction dismantled eventually yielding space for additional rides installed 1998-1999.

  Canadian comedian Rick Mercer appeared as first episode ninth season CBC Television show Rick Mercer Report accompanied pop singer Jann Arden walking EdgeWalk the 10th of April 2013 broadcast date. The tower became central figure during 2015 Pan Am Games opening ceremony featuring track athlete Bruny Surin passing flame sprinter Donovan Bailey parachuting Rogers Centre stadium concluding ceremonies fireworks display off tower top.

• 6. Safety Systems And Incidents

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  Freezing rain storm the 2nd of March 2007 created ice layers several centimeters thick forming sides tower plus surrounding downtown buildings. Sun thawed ice followed winds reaching speeds up to 40 kilometers per hour blowing chunks away from structure threatening nearby cars windows smashed large falling pieces. Police closed streets surrounding tower morning rush hour March 5 expanding area include Gardiner Expressway 1 kilometer distance where taxicab window shattered King Street West location 2 kilometers away before reopening March 6 after winds abated completely.

  the 16th of April 2018 incident saw falling ice puncture roof nearby Rogers Centre stadium causing Toronto Blue Jays postpone game following day doubleheader third held venue. Tower reopened April 20 same year ensuring public safety measures remained effective despite weather conditions creating hazardous situations occasionally. Fire broke out Ostankino Tower Moscow August 2000 killing three people extensive damage blamed poor maintenance outdated equipment sparking fears similar disaster might occur CN Tower lacking safeguards present there.

  Canadian officials stated highly unlikely tragedy could happen here citing fireproof building materials frequent stringent inspections extensive sprinkler system 24-hour emergency monitoring operation two reservoirs holding 68,160 liters water automatically replenished top floor hose base sending water any location ban natural gas appliances anywhere including restaurant elevator usable during fires running outside building powered three emergency generators base structure.