KA Block Update- June 2016

Foundation work for Tower Crane 2 on the KA Block site

Construction at the KA Block continued in downtown Minneapolis.

On May 27, preparations were underway to erect the first of two tower cranes serving the Kraus-Anderson headquarters and the broader mixed-use development. Kraus-Anderson Development Company led development of the site.

Project Manager Chad Rempe shared details about tower-crane foundations, crane placement, excavation and construction sequencing.

How Was the Tower-Crane Foundation Built?

Rempe: The tower-crane foundation was poured in two stages.

First, the team placed a mud slab approximately 1 foot thick to create a stable surface for the tower-crane base section, which weighed about 21,000 pounds. After the mud slab cured, the crew formed and reinforced the foundation, set the tower-crane base section and poured the foundation.

The work took place over two days. The tower-crane foundation, including the mud slab, used 200 cubic yards of concrete, or approximately 405 tons.

How Was the Tower-Crane Location Selected?

Rempe: Tower-crane placement was determined by the need to maximize site coverage and minimize structural openings that would require infill after cranes were removed.

Other considerations for the KA Block hoisting plan included:

  • Federal Aviation Administration approvals
  • Tower-crane air-rights easement approvals from affected neighboring property owners
  • Tower-crane size, capacity, hook height and jib length
  • Project phasing
  • Layout of neighboring structures and cranes

When Was the First Tower Crane Installed?

Rempe: The first of two tower cranes was scheduled for erection beginning June 1 and expected to be operational by Friday, June 3, weather permitting.

Initially, the crane was installed with a 150-foot hook height to support parking-garage construction. Later that summer, it was scheduled to be raised to a final hook height of 243 feet to serve the 17-story residential tower.

At the same time, the second tower crane was scheduled for erection with a hook height of 161 feet to support construction of the eight-story hotel.

How Long Would the Tower Cranes Remain on the Site?

Rempe: The headquarters building would use mobile cranes to erect structural steel and set architectural precast wall panels. This allowed the two tower cranes to focus on the hotel and apartment buildings.

The tower cranes were expected to remain in use through 2016 and into 2017. The hotel tower crane was scheduled for removal in June 2017, followed by the residential-tower crane in October 2017.

 

What Was the Deepest Point of Excavation?

Rempe: The hotel elevator-pit foundation was the deepest excavation, reaching 34 feet below grade.

At the time of the update, mass excavation of the north half of the site was substantially complete. North-half foundation excavation was scheduled to begin the week of June 6, with hotel elevator-pit foundations planned within the following 30 days.

How Was Excavation Equipment Removed?

Rempe: Large excavation equipment would exit using a temporary access ramp. Excavators would remove the ramp as they backed out of the excavation.

Because not all of the ramp could be removed while maintaining safe operating slopes, smaller excavation equipment would remain below grade to remove the balance of the temporary access road. It would then be lifted out by crane or driven out once the permanent entry and exit ramp was complete.

Learn more about the KA Block mixed-use development, the start of headquarters and residential-tower construction, a tower-crane operator’s perspective and the hotel component of the KA Block.

CATEGORY: Construction