Chicago's Largest Vertical Expansion
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Chicago's Largest Vertical Expansion

Friday, January 23, 2015 - 09:00

Located in the heart of Chicago’s loop, famed Block 37 is in the midst of a major vertical expansion.   

The unique project involves adding 34 new floors, the most in the city’s history, on top of a fully-operating 4-story retail mall across the street from Macy’s department store on State Street.  With 690 apartments, Block 37 is also Chicago’s largest rental project currently in construction. 

Constructing a high-rise building on top of an occupied building in a dense commercial district is the project’s fundamental challenge.  Besides the myriad of logistical issues that must be managed daily, the most visible aspect of this expansion is the dual structural support design of steel trusses with a concrete mat slab.  Each system supports roughly one-third of the buildings weight and transfers the load “around” the retail mall to the caisson foundations below. 

Four jumbo steel trusses, each about 3 stories in height, were manufactured  overseas and shipped in pieces overseas by boat to Chicago.  These 120 ton trusses were then assembled on Randolph Street and lifted into place.  The crowning touch is a 30’ wide by 9’ tall steel girder weighing 30 tons.  This plate girder supports a 282’ tall, 18” thick concrete sheer wall that stabilizes the tower once completed.  The mat slab is a 5’-6” thick slab of steel-reinforced concrete that was poured in-place using two concrete placing booms simultaneously. 

Now that the critical structural supports and non-typical floors have been erected, the remainder of the 435’ tower will have a new concrete floor added every 4 days.  Occupancy is scheduled for July, 2016.

Key to the planning of such a complex, fast-paced project is the use of state-of-the-art computer technology, known as Building Information Modeling (BIM).  This detailed 3D computer model is then used by the entire team of contractors and designers to figure out precise dimensions and locations of each element of the project.  The team also uses the latest iPad tablets in lieu of paper drawings to coordinate, manage, and communicate project details.  

Power Construction is managing the design and construction, in collaboration with the architectural firm of Solomon Cordwell Buenz, and structural engineer, Thornton Tomasetti.