New construction projects are usually met with challenges, but the site and lifting needs are usually straight forward enough that several crane options fit the requirements.
Building reconstruction, however, usually includes its own unique challenges. There are often obstacles in the way that make selecting the right crane difficult, and bidding on the right crane can be the difference between getting the job and moving on to the next opportunity.
Major metropolitan reconstruction projects offer even more challenges for the lifting contractor. It’s virtually a certainty that the site will be surrounded by other structures, making it a tight fit for mobile cranes. Busy streets make it nearly impossible and sometimes cost-prohibitive to block off a road for a significant time period.
These are precisely the challenges contractor Smith Bros. & Wilson (SBW) faced when tasked with the demolition and reconstruction of the 8th and 9th floors at the downtown Vancouver Public Library.
The job included converting former provincial government offices into additional library space, meeting rooms and an urban green space, all while keeping the library open to thousands of visitors daily. The demolition and construction would require moving numerous materials, both large and small.
“All the demo material had to be removed,” said Tyler Brown, general superintendent for Smith Bros. & Wilson. “And the library only had service elevators to get material from the top floors to street level. During the tender phase, we saw the need to hoist many items, including large-span escalators to get people up to the green space. It was quite a challenging prospect.”
The library is a high-profile project in Vancouver, as the building’s distinct design makes the library a focal point of the downtown area. While the historical look allows it to stand out, it poses unique challenges that required extensive preplanning in order to properly bid.
“The library is designed after the Roman Colosseum and surrounded by an elliptical wall on the east side,” said Dean Arsene, crane rental and sales representative for Leavitt Machinery of Vancouver. “We started discussing the project with SBW in late 2016, and all options were reviewed.”
Like most contractors submitting bids, SBW considered mobile cranes to tackle the heavy lifting from street level. However, SBW saw several drawbacks that made planners rethink the mobile option.
“The structure’s shape required a minimum of a 500-tonne capacity class mobile crane to hoist large materials to and from the upper floors because it would be boom bound,” Brown said.
Given the possible set-up locations for a mobile crane at the site, smaller cranes did not offer the capacity to lift many of the objects at the required boom lengths and working range.
“This meant we would have had to shut down an entire street, and mobilization costs would have been high. By the time we counted everything that needed to be hoisted, it was cost-prohibitive to use a mobile crane.”
The next option for SBW was tower cranes, and they looked at flat top, hammerhead and luffing jib designs.
“The job required a 55-metre boom radius, and the flat top and hammerhead cranes didn’t offer the capacity we needed for the escalators without breaking them down,” Brown said, noting the crane would be placed about 15 metres from an adjacent structure.
“Those booms were too long, and they didn’t have the freedom to slew without hitting a structure, so these designs were not an option,” Arsene said.
For SBW, the only option to cost-efficiently support demolition and construction efforts on the VPL project was a luffing jib tower crane, and the Terex CTL 430-24 offered the reach and capacity for the job.
“Through our discussions with Leavitt, we calculated the luffing jib as the most economical hoisting logistics solution for us,” Brown said.
Steve Filipov, president of Terex Cranes, explained the company’s line of tower cranes are created to tackle challenging projects like the library.
“The library application is one of those unique cases where the mobile cranes we manufacture aren’t the most economical solution for our customers,” Filipov said.
Bidding the job using the CTL 430-24 crane helped SBW receive the contract. For the year-long renovation project, the contractor entered into a six-month rental agreement with Leavitt for the 24-tonne-class Terex crane. Its tower required seven HD23 22.6 segments to reach the needed jib base height of 45 metres.
To cover the entire site, the CTL 430-24 was equipped with a 55-metre jib. A 15-degree in-service radius was used throughout the project to lift materials to and from the rooftop.
“Using the luffing jib allowed us to position the tower closer to the library structure, but, even still, most of our lifts were made close to the tip radius of the 55-metre jib,” Brown said.
Arsene added when the crane was not in service, the jib was set to a 65-degree radius to allow it to slew without hitting any adjacent structure.
Meticulous planning led to the execution of the crane installation in June. The city allowed the adjacent Homer Street to be closed to facilitate installation.
“Using a 300-tonne capacity mobile crane, we installed the tower, counter jib and apex on day one,” Arsene said. “On day two, we installed the jib and counterweight. It was a very smooth set-up, and we were done in about one and a half days.”
Throughout the demolition phase, the crane was kept busy by removing large structural pieces and concrete from the rooftop. Choosing the tower crane for this project gave work crews more flexibility with material removal.
As work transitions to the reconstruction phase, the crane will be used to hoist large building materials and full concrete buckets from street level to the 8th and 9th floors. The largest and heaviest planned lifts will be the two, 5.4-tonne escalators, hoisted into position without disassembly to save time and money.
“The plan calls for the escalators to be placed toward the end of the 55-metre jib, and the crane’s load chart offers plenty of capacity to position the two pieces,” Arsene said.
If the project goes according to plan, SBW will stop using the tower crane at the end of the year.
“We’ll finish all the heavy lifting by December, and then we’ll have the smaller finishing stuff throughout the end of contract,” Brown explained.
Concrete base solution
To further reduce project costs, SBW’s plan for the CTL 430-24 crane included a freestanding tower that wasn’t tied into the library’s structure. Originally, SBW planned on using an undercarriage strut mounting for the tower section. However, the optional base’s availability was limited and not available in Western Canada.
SBW put its more than 100 years of concrete fabrication experience to work and consulted with the firm TNAI Engineering Ltd. of Vancouver, to construct a custom concrete base to serve as a tying point for the crane’s tower. TNAI came up with an ingenious way to anchor the crane in a manner that would not require it to be secured directly into the building’s foundation.
Anchoring to the foundation would require cutting through the street-level membrane and closing the three-level underground parking structure.
“You don’t know what type of utilities and electrical components you will run into when cutting into the membrane, and this could lead to significant expense and delays,” Arsene said.
TNAI’s engineering team came up with a floating 10 by 10 metre X-shaped concrete base.
“When reviewing the parking lot’s drawings, we found columns supporting the library’s parking structure that were built at a 10 by 10-metre spacing, so we tied directly into those columns,” Arsene said, adding the columns served as the anchor conduit to the foundation below the parking structure.
The concrete anchor measured 1.8-metres wide, and height along most of the cross section was 2 metres tall. The outside 1.2-metre end segments of the structure anchoring into the columns were 2.6-metres tall.
“This, in essence, gave us 61 cm of spacing between the concrete end segments and grade at the center of the X-shape to create the floating base required to properly disperse the load,” Arsene said.
By employing the solution, SBW saved time, lowered costs and allowed the parking structure to remain open during the project.
“It was a pleasure working with SBW on this project,” concludes Arsene. “They have the expertise to find the solutions to successfully complete a challenging project like (the library), and they don’t shy away from them.”