Trump Update

Tower Making Its Climb Toward Chicago's Skyline

by Craig Barner

A rarity for a construction project is happening just west of Michigan Avenue in Chicago.

Pedestrians are watching, not scurrying past, the building activity at 401 N. Wabash Ave. on the North Bank of the Chicago River.

On a recent day, visitors from Europe were standing on the opposite bank and asking questions. "I wonder how tall it is going to be?" one asked.

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Office workers and other passersby slowed their pace to watch. Tourists on a boat trip were pointing.

The object of their interest was the $850 million Trump International Tower & Hotel, which is making its climb toward Chicago's skyline.

The importance of the parallelogram-shaped tower goes beyond its lofty price tag.

When the 1,360-ft.-tall tower is completed in April 2009, it will be the second tallest in Chicago and nationwide after the 1,450-ft.-tall Sears Tower. The Trump, which will be 92 stories, will be the tallest building constructed in North America since the 108-story Sears was completed in 1974.

Trump will be the 14th tallest in the world assuming each of the eight towers under way in Asia and the Middle East taller than it are built according to plan, according to Geri Kery, operations manager of the Council on Tall Buildings and Urban Habitat, an international association headquartered in Chicago.

In mid-August, Trump had reached the 14th floor where a health club will be located, said Tim Snyder, construction manager in Chicago for the New York-based The Trump Organization, the developer. The 1,000-car parking garage, which is on levels 3 to 12, is done, except for a helix-shaped ramp.
Tere Proctor, director of sales in Chicago for The Trump Organization, said 76 percent of the tower's 758 units-472 condominiums and 286 hotel-condominiums-are sold.

The condominium-hotel is on floors 16 through 27, with units ranging between 526 and 2,245 sq. ft. and prices between $850,000 and $3.3 million. The condominiums will be located on levels 29 through 89 and range from 580-sq.-ft. studios to 14,000-sq.-ft. penthouses. Prices range between $563,000 and $9 million.

Building amenities include the 60,000-sq.-ft. health club, restaurants, retail, ballroom and meeting rooms. A 1.2-acre park will surround the base, and the park's three tiers will face a walkway on the river.

Recently, Midwest Construction visited the site where details emerged about some of the above-ground construction issues and structural engineering.

Concrete Details

Concrete is an important project element early on in part because it forms the building's structural support.

Snyder said that about 150 of the 200 people on the job in mid-August were employees of Chicago-based James McHugh Construction Co., the concrete contractor.

Numerous details keep the crews busy.

For instance, the floor-slab thickness of the completed garage is 14 in., said Brett Szabo, senior project manager of concrete for McHugh. The depth will be 9 in. for a typical residential floor and 18 to 20 in. for a transfer level.

Supporting the garage are 30 6-ft.-diameter concrete columns, and 47 thinner concrete columns will support the residential portion.

Transfer levels are needed because setbacks at levels 16, 29 and 51 require column pressure to be transferred from some lines to adjacent lines, said Bob Sinn, associate partner with Chicago-based Skidmore, Owings & Merrill LLC, the architect and structural engineer. The transfer levels, which also hold mechanical equipment, are on 15, 28, 50 and 90.

Usually, mammoth outrigger beams that are typically 17-ft., 6-in. deep and 5-ft., 6-in. wide are on each transfer level. They provide lateral stability against the city's winds.

"The outriggers don't occur on the typical floors like parking and residential," Sinn said. "They're in the mechanical floors so they're out of the way."

The outrigger beams extend from the perimeter columns to the 197-ft.-long, 49-ft.-wide central core, also concrete. The core, which is composed of four I-shaped walls and one C-shaped wall, will hold the elevators and stairs.

More important, it provides additional lateral stability.

Since the building started coming out of the ground, approximately 60,000 cu. yds. of concrete have been poured.

"A typical 30- to 40-story condominium in Chicago runs about 20,000 to 25,000 cu. yds.," Szabo added. "So (the Trump) is about two typical condos, but we're only up to the (Trump's) 14th floor."

A seven-day pour cycle was the norm early in the project, but in mid-August, a large amount of time was expected for the 15th to be formed, because it is a transfer level.

"A couple months are needed to get them (transfer floors) built," Szabo added.

About 300 trucks full of concrete are received every week because the material is so important to the project.

Mixing a Mat

About 20 different concrete mixes are being used on the project. The care taken with the 10-ft.-thick mat slab shows how important concrete recipes are.

The building has four below-grade levels, and the 200-ft.-long, 60-ft.-wide slab, which is below Lower Level Four, was poured over a 22-hour period between Sept. 30 and Oct. 1, 2005. The slab serves as a juncture between the below-ground caissons and the above-grade core.

The mix was composed of self-consolidating concrete that features specialty additives and low-water content, Snyder said.

Key benefits include strength and less labor during the pour. Because of the chemistry, the material is poured without having to be vibrated. And, as the name implies, the concrete has a high slump rate.

"That concrete is so sticky and dry because it has so little water and so much cement and other additives that within 15 to 20 minutes of striking it off, it goes hard," Snyder said. The pour was done with only six laborers, but with a conventional concrete, three times the amount would have been needed.

More important, the concrete's temperature and strength were carefully monitored to ensure strength and solidity.

The concrete was poured on a day not greater than 80 degrees F to try to control the concrete's heat gain, and 36 temperature probes had been attached to rebar cages inserted in the mat for monitoring.

"We didn't want it to reach temperatures internally greater than 150 degrees F," Snyder added.

Readings were taken every minute for each of the 36 points and downloaded onto a computer so a curve could be plotted.

Within 24 hours, the temperatures spiked at 150 degrees because of hydration but receded over weeks. After 10 days, the concrete averaged around 120 to 125 degrees.

Similarly, six full-depth cores were made in the mat to measure the concrete's strength. The concrete was poured at 10,000 psi. It measured at 7,000 psi after seven days due to heat gain but averaged 13,000 psi after cooling.

"It was a 56-day design mix, but we were reaching design strength in less than 28 days," Snyder added.

SIDEBAR 1

A Stiff Trump

The stiffness of the concrete was specified on the Trump International Tower & Hotel in Chicago.

Bob Sinn, associate partner of Chicago-based Skidmore, Owings & Merrill LLC, the architect and structural engineer, said the "modulus of elasticity" was specified for the columns, walls and other concrete elements on the project.

"It's pretty unheard of," he added. "Most concrete suppliers know about strength tests of concrete. Modulus of elasticity is a different animal for them."

Ensuring the stiffness is important so that the eventual residents do not perceive sway in the building after it is completed. Other elements to ensure stability include a concrete core and the placement of mammoth outrigger beams on some floors.

Because the modulus of elasticity was specified, mechanical means to counteract a tall building's natural sway, like auxiliary dampening devices, were avoided.

"We're using the stiffness of concrete to control the motion instead," Sinn added.

The building is expected to reach the 20th to 22nd floor by the end of the year, said Tim Snyder, construction manager in Chicago for the New York-based The Trump Organization, the developer. Topping-out is expected in June 2008 and completion in April 2009.

SIDEBAR 2

A Way Safe Project

Several elements were incorporated in the Trump International Tower & Hotel in Chicago to ensure safety.

The owner, 401 N. Wabash Venture LLC, is paying for insurance with an owner's controlled insurance policy.

Two full-time safety managers staff the project, one with the owner and one with the construction manager on the project, the Chicago office of New York-based Bovis Lend Lease Inc.

Tim Snyder, construction manager in Chicago of the New York-based The Trump Organization, the developer, said their responsibilities include performing safety audits, monitoring construction and training laborers.

Fundamentals are stressed. For instance, controlled access zones permit only laborers trained in fall protection to work near the slab edges of floors.

"There is a monitor there-a nonworking individual who monitors the activity in the controlled access zone-to make sure somebody isn't backing up close to the edge," Snyder said.

A safety office is located onsite, and full-time paramedics are onsite every day.

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