Olympian challenge: towers instead of crawlers
By Alex Dahm12 May 2017
In the face of competition from large crawler cranes for a high profile refurbishment project in Canada, international tower crane specialist Morrow won through with its proposal to use a pair of tower cranes. Alex Dahm reports.
A spectacular concrete building in Montreal, Canada, built for the 1976 Olympic Games, is undergoing a CDN$100 million refurbishment to prepare it for new occupants.
The enormous Olympic Tower is one of Canada’s most recognisable buildings and needs refurbishment inside and out to bring it back to its former glory. At 165 metres, it is the world’s tallest inclined tower and that, coupled with the sheer size of the building and the underground structure below it, presented challenges for its refurbishment.
Oregon, USA-headquartered international tower crane specialist Morrow was working for main contractor Pomerleau. Montreal-based Pomerleau works in all Canadian provinces. Pomerleau was trying to find a way, using mobile cranes, to reach all points on the tower, including the roof, to carry out the refurb work.
Mark Forbes, Morrow Equipment sales manager in Canada, takes up the story, “These would have been very large mobile cranes and there is very limited access to the site and few suitable positions to set up such cranes. The biggest issue is the underground structure. When I first took a look at this, looking at the size of the mobiles, knowing the cost and limited availability of those cranes, I saw that it could be a worthwhile project for Morrow.”
Morrow’s local office in Montreal came up with a scheme for the high profile project that adressed concerns from the Olympic Park building’s owner, a government entity in Quebec, over safety and cost overruns.
The first phase of the project was demolition, removing the skin of the tower which was made from large precast concrete panels. “They weighed 16,000 pounds [7.3 tonnes] so, being a demolition project, we wanted close to 20,000 pounds [9 tonnes] of capacity to do that.” Morrow’s solution involved using a pair of large tower cranes instead of competing proposals using large wheeled mobile or crawler cranes.
To win the job, however, a solution was also essential for the second phase. It was to use man baskets suspended from cranes from where operators would refurbish the remaining surface of the tower’s structure. It would then have a whole new façade of glass, metal and LED lighting installed. “Current legislation in Quebec is such that it makes no sense: man basket use on tower cranes is not allowed. So that was the first problem. Behind the scenes I started work to get approval from CSST [the commission for standards, health and safety] in Quebec.
“In the meantime, we were still pursuing the project with Pomerleau on pricing. When Pomerleau went to see CSST to see what their opinion was on hanging man baskets, they were surprised to see that we had already initiated that effort and were well under way with it.
“Pomerleau picked up the points from there and came up with a detailed work plan with the assistance of Morrow and Morrow Engineering. At the end of the day that was acepted by CSST and was the basis of allowing them to move forward with tower cranes.”
Forbes continues, “The approval for this is ground-breaking and Pomerleau is still working with CSST internally to have province-wide acceptance of man baskets on tower cranes. At the moment it is site-specific. It is a first step towards new legislation for Quebec.”
Peter Juhren, Morrow vice president of operations, comments, “Using man baskets was the only available way to do this project, to access all points up and down and all sides of the tower. About 60 per cent of the work on the project involves using man baskets suspended from the cranes.”
Forbes says, “It was at least 30 % if not 50 % cheaper using tower cranes than using mobile cranes. Not only that, the timeline for installation and getting the project under way was much shorter with tower cranes.”
Morrow chose a 630 EC-H 20/40 Litronic saddle jib tower crane and a 700 tonne-metre 710 HC-L 32/64 Litronic luffer, both from Liebherr. The 630 was the principal crane. It lifts 40 tonnes and was configured with an 84 metre jib. The luffer can lift 64 tonnes and offers a maximum hoisting speed of 176 metres per minute.
Minimal modification was needed to use the cranes with man baskets. The 630 had a secondary brake added while the 710 already had one. In addition, Forbes explains, “We modified the hook blocks a little bit. The hanging man basket has rigging so that it doesn’t fall if the hook separated from the block or if the rigging fails, the same as for mobile cranes.”
The second biggest point, in particular with the 630, was its ability to have a hook height of 630 feet (200 metres) which is above the top of the tower, with one tie-in, Forbes explains. “First of all we determined that it was possible to do. The tie-in is 65 feet [20 metres] long. With Morrow Engineering we came up with an erection process where we could freestand the tower, make the tie-in connection to the building – which was a challenge – and then erect the crane on top of the tower after that with the tie-in connected.”
The tie-in is three extended custom struts to secure the 630 EC-H to the building. Lots of thought went into them, Forbes says. They have walkways on them as that is the only way to do the daily inspections. Inspecting the pin and keeper can only be done from the tower side. They have fall arrest lanyard attachment points and there are step-downs so that the erectors can get in to make the connections.
Forbes continues, “We erected the 630’s tower enough to get the climber on, put the tie-in collar and struts on, then the climber, then we erected the crane.” A 600 tonne capacity Demag CC 2800-1 lattice boom crawler crane with luffing jib from Grues JM Francoeur was used. The whole area had to be matted and there was 6,000 tons of fill to level the surface, compacted to 98 %, drainage added and then the mats on top. Extensive truss work was installed in the basement of the building to support the tower crane.
The 710 tower crane was erected using a 500 tonne capacity Liebherr LTM 1500 telescopic wheeled mobile crane with luffing jib, also from Grues JM Francoeur. The 710 sits on a portal base straddling a track for a funicular railway that runs up the spine of the tower to an observatory on top. Along with the rest of the building, the railway remains in operation. It was hard work to penetrate the stressed concrete to anchor the base to the building, Forbes says.
Both tower cranes are working at the same time. The 630 is working a double shift and it will be up well into 2018, coming down later in the first quarter. The 710 will come down at the end of 2017. Both cranes operate through 360 degrees and both have Hook Cam cameras with remote viewing stations in the safety director’s office.