New Tower Trumps Others as the Tallest Reinforced Concrete Structure in North America
New Tower Trumps Others as the Tallest Reinforced Concrete Structure in North AmericaTrump Tower Chicago rises with 180,000 cu. yds. of concrete, 30 different concrete mixes and the technology of Putzmeister equipment
STURTEVANT, WI - (February 1, 2007) – The Sears Tower, Aon Center and John Hancock Center will soon welcome a new member to their “Tallest High-Rise Club,” on Chicago’s picturesque skyline. Trump International Hotel & Tower – Chicago, also known as, Trump Tower Chicago is creating a stir on the north bank of the Windy City’s Chicago River.
In true Trump fashion, Trump Tower Chicago will set itself apart from its peers. The Sears Tower, Aon Center and John Hancock Center are mainly built out of structural steel while Trump Tower Chicago is a reinforced concrete structure. Upon completion, the inhabitable portion of the new building will rise 1,136-ft. high and its spire will reach 1,370 ft.
“This is a monumental project for the city and an incredible event to be a part of,” says Andrew Weiss, Executive Vice President with 401 N. Wabash Venture LLC, the owner and developer for Trump Tower Chicago. The impressive project replaces the old Chicago Sun-Times building which stood at 401 N. Wabash Avenue for nearly 50 years.
According to Weiss, the tower will be the second tallest building in North America next to the Sears Tower at 1,454 ft., and will be the second tallest concrete building in the world next to the Burj Dubai in Dubai, United Arab Emirates, set to stand over 2,000 ft.
In early 2000, preliminary discussions took place between the Trump Organization and Skidmore, Owings & Merrill LLP (SOM), the designer, architect and structural engineers for the project. Based in Chicago, SOM is one of the world's leading architecture, urban design, engineering and interior architecture firms and has been in business since 1936. Initial concepts included a 2,000-ft. tall office building, but all that changed after a September 11, 2001 meeting at the SOM offices, according to Bob Sinn of SOM and Senior Structural Engineer on the project.
Since that meeting, the vision for what the structure would ultimately look like has gone through somewhat of a metamorphosis. “The tower was originally envisioned as partially an office complex built out of steel,” says Sinn. “Then conversations turned towards the tower being a residential-only building and finally an all concrete structure combining a hotel and condominium was approved.”
Reinforced concrete was selected over steel because of the economics of the design and the fact that the structure must maintain as little movement as possible because of its soaring height.
“We decided on the concrete design for a handful of reasons,” says Weiss. “Given Chicago’s extreme wind gusts, we wanted to minimize movement as much as possible, to make the future occupants of the building feel comfortable. The natural properties and heavier mass of concrete make that possible while providing a more efficient use of the space by utilizing concrete flat slabs for higher ceiling heights.”
Demolition of the Chicago Sun-Times Building began in October of 2004 and construction of the project began in March 2005. The 92-story Trump Tower Chicago will comprise 180,000 cu. yds. of concrete when it is complete in mid-2009.
McHugh Construction, a sub-contractor of 401 N. Wabash Venture LLC, is responsible for the placement of all of the concrete for the Trump Tower Chicago project. The company started with a Putzmeister Telebelt® truck-mounted concrete conveyor to place the mat foundation in September 2005. “5,000 cu. yds. of concrete for the 66-foot wide, 200-foot long and 10-foot deep mat foundation was placed,” notes Dale Hendrix, Senior Vice President for McHugh and general superintendent on the project. “The concrete pour lasted almost 24 hours non-stop.”
Using a combination of concrete buckets and Putzmeister truck-mounted boom pumps, McHugh will place 50,000 cu. yds. of concrete from elevation -57 to the top of the structure.
A respected name in Chicago construction, McHugh brings 100 years of concrete placing expertise to the Trump project. Hendrix himself has spent an impressive 47 years on the job with McHugh. Other high-rise building projects McHugh is currently working on in the Chicago area include the 520 N. Kingsbury 48-story apartment building, E. Chestnut St. condominiums, Kenzie St. Station and the 64-floor Elysian Hotel Project. “All of these high-rise projects are using various Putzmeister equipment including placing boom systems that are similar to the system being used on Trump Tower Chicago,” Hendrix comments.
“Trump Tower Chicago is a great challenge because it’s massive in every way possible,” notes Hendrix. “Everything you can think of in this structure is maximized; the soaring height, thickness of the columns and walls, the amount of concrete, amount of rebar and even the amount of people working together to build this structure. It’s almost like we’re building two buildings.”
McHugh will continue to place the additional 125,000 cu. yds. of concrete required to reach the very top of the structure through July of 2008. To place the massive amount of concrete, McHugh is relying on a placing system combining Putzmeister’s powerful BSA 14000 trailer-mounted concrete pump and a flexible Putzmeister 34/38Z-Meter Series II Detach boom.
The BSA 14000 is located in the basement of the structure where the ready mix concrete trucks drive up and deliver the concrete to the Putzmeister unit. “The durability and yardage that I can deliver through this pump is great,” notes Hendrix. “With the schedules and deadlines today, this machine is the only way to go. The 22,365-lb.
Putzmeister BSA 14000 has been pumping about 1,100 cu. yds. per day and can pump 100 cu. yds. per hour no problem with is powerful 630-horsepower engine. The BSA 14000 has pumped the large variety of concrete mixes very smoothly.”
According to Hendrix, McHugh has used their Putzmeister BSA 14000 on other high-rise building job sites similar to the Trump Tower Chicago with the same type of success.
“There are two towers at the top of the Trump structure where the 34/38Z placing boom can be positioned, one on each end of the building,” says Hendrix. “The two tower locations help us pour the concrete wherever it needs to be placed with ease. The pedestal is mounted to the structure’s own core-form by a clamped-down base.
“Flying the pin-connect boom and pedestal with the crane from one location the other is a relatively simple process,” says Hendrix. “It only takes 30 minutes and we’re back in business.”
The BSA 14000 and 34/38Z combination has placed about 65,000 cu. yds. of concrete to-date, and McHugh has reached the 27th floor. “The 34/38Z-Meter’s horizontal reach of 108’ 7” has been impressive and has helped us progress the project as efficiently as possible for our customer,” Hendrix adds.
“As the building gets taller and taller, the square footage for the upper floors gets smaller, which makes a pour go quicker as a smaller amount of concrete and formwork is required for each floor,” says Weiss.
“Up to floor 16, it took four concrete pours in a seven-day schedule and for floors 18 through 29, it’s taking three pours in a five-day schedule,” Hendrix explains. “Our goal for floors 30 to 48 is two pours in a four-day schedule and for floors 52 and above in one pour, within a three-day schedule. “We don’t place a floor all at once because of the great yardage of each floor. First we pour the horizontal floor, and then the vertical columns that support the next floor. There is a four floor Peri Skydeck form that is used to support each floor once a pour is complete.”
“There are at least 30 different concrete mixes being used on the Trump Tower Chicago,” reports Sinn. “Most of the concrete mixes needed to be very specific and were tested to be proven reliable ahead of time.”
The structure ranges in compressive strength of the concrete depending on use. The mechanical floors and the middle of the structure were specified at a high-strength self-consolidating concrete (SCC) 16,000 psi concrete mix due to the amount of steel reinforcement in the building. Some of the structural and all of the mat foundation used 10,000 psi concrete. The vertical elements of the building (columns and walls) ranged from 8,000 psi to 12,000 psi. According to Sinn, some of the horizontal and vertical elements used 16,000 psi mix as well. The lowest strength concrete mix was used for the floors, which ranged from 5,000 to 6,000 psi.
“The core walls, especially, are just massive at four-feet thick. That’s why we are pumping such a high volume of concrete,” Hendrix says.
According to Mike Pistilli, Technical Director for Prairie Material Company the ready mix concrete supplier, “All of the concrete mixes contain different percentages of a high-range water reducer, different amounts of Portland cement, fly ash, slag and silica fume. The outrigger walls are very impressive at up to seven-and-a-half-feet deep.” Prairie Material Company is based out of Bridgeview, Illinois and has been in business for the past 60 years.
“We’re using SCC in a variety of locations throughout the project,” continues Pistilli “this includes the foundation and the outrigger horizontal walls. Very few people use this type of concrete. We have more advanced technology than most ready mix companies and that has allowed us to do a lot of research over the past 20 years in concrete mixes for high-rise buildings with SCC. We know how it works and where it can be best applied.”
The SCC concrete mix has a maximum aggregate size of 3/8” and concrete
compressive strengths that range from 8,000 psi to 16,000 psi. The non-SCC concrete mixes on the project have aggregate sizes ranging from ½” to ¾” maximum size at varying strengths also at 8,000 to 16,000 psi.
“In addition to ensuring the right strength was specified for each mix, there was a learning curve for all of us in making sure a different characteristic was up to industry standards for each of the four zones of the structure,” says Sinn. He likened the process to a sort of on-going evolution, “The structure is made out of concrete and concrete provides significant inherent damping, a characteristic that takes motion away from a building, much more than steel does, so we had to ensure we found the right combination of materials for the concrete mixes.”
Sinn says this evolution of sorts includes the ongoing challenge of judging stiffness vs. motion for the concrete reinforced structure. According to Sinn, “This challenge is just as important as specifying the strength of the concrete mixes. Together with Prairie Material Company, we had to specify a stiffness characteristic, ‘modulus of elasticity,’ to determine the stiffness vs. motion for the structure’s concrete mixes. Our joint efforts are truly pioneering.”
Before ground even broke for the Trump Tower Chicago project, SOM commissioned a 1-500 scale model of the proposed structure and its neighboring buildings. This model was placed in a commercial wind tunnel laboratory. “The model moves on a 360’ pivot that tests winds out of the east and west,” Sinn notes. “We tested the modulus of elasticity very thoroughly because we had constructional obligations and industry standards we had to meet due to the building’s height.”
“With our technology and teamwork together with SOM, we were able to find the right ingredients for the right modulus of elasticity specification,” says Pistilli. He also adds, “We are continuing to develop mixes to measure stiffness of concrete as well as low-heat and low-shrinkage mixes. We want to continue to advance our mixes so we can continue to serve our customers’ needs.”
Sinn says they routinely receive concrete test reports on the Trump Tower Chicago site and have a full-time representative from SOM on the site every day to ensure each mix is “rising up” to its stiffness and strength specifications.
Trump Tower Chicago resembles the mixed use concept of the lavish Trump International Hotel & Tower – Tower 1 & 2 under construction in Las Vegas. In Chicago, separate residential, hotel and ballroom lobbies are located at street level along with a beautifully landscaped riverwalk and retail spaces. Above those spaces will be 10 floors of public as well as deeded parking. The building will also contain a world class health club and spa facility, two ballrooms, a restaurant with a terrace looking toward the landmark Wrigley building and Lake Michigan, hotel rooms and suites, and residential condominium units.
All things considered, Trump Tower Chicago is set to blow away visitors and residents of the Windy City when it opens in 2009. From its immense height and large volume of technologically advanced concrete mixes to the building’s plush amenities, the tower will be another milestone on the storied architectural landscape of Chicago.