Mortenson Construction Meets Aggressive Schedule for University of Chicago Residence Hall
Since its founding 125 years ago, the University of Chicago has turned to some of the world's most well-known architects and builders. When the university sent out a Request for Qualifications in 2012 for the design-build process of the new $155 million Campus North Residential Hall and Dining Commons, dozens of designers and contractors from around the world expressed interest.
After a rigorous design competition with input from faculty, staff, students, and community stakeholders, the university awarded the work to the team led by the Chicago offices of Mortenson Construction and Studio Gang Architects. "We are delighted that, after looking around the globe, we found the best answer here in Chicago," Steve Wiesenthal, Associate Vice President and University Architect, said in the university's press release.
The winning design, now under construction, includes four interconnected buildings - a dining hall and three slender residence towers with 800 beds - as well as extensive green space designed not only for students, but also to invite the surrounding community onto campus. With a goal of LEED Gold certification and an aggressive schedule for the 395,000-square-foot urban site, the design-build team invested in a full-scale, onsite mock-up and numerous other steps to streamline construction and ensure quality.
Blending and Inviting
For the previous half-century, Pierce Tower Residence Hall and Dining Commons occupied the site. The university demolished the tower in 2013 and cleared the site before turning it over to Mortenson for the ceremonial groundbreaking in June 2014.
The design-build team tailored each of the new buildings to the context around it. Along the busy urban edge to the north on 55th Street, they built a 15-story tower with panoramic views of the city skyscape, Lake Michigan, and the entire campus. To the east, "We have a smaller, five-story tower on University Avenue, which is a more residential neighborhood," said Carl Kreiter, Mortenson's Senior Project Manager. The building faÃ§ade features 1,034 precast concrete panels with detailing designed as a modern interpretation of the university's gothic architecture.
The three residence halls connect through a second-floor community commons, with second-floor courtyards exclusively for students. Additional lawns and pathways at ground level - including a block of Greenwood Avenue that the university purchased from the City of Chicago and closed to vehicular traffic - offer green space for the campus and surrounding community.
A "portal plaza" on the northeast corner of 55th Street and University Avenue serves as a new gateway onto campus. "The university and the architects wanted it to be inviting to the community," Kreiter said. "They weren't trying to seal the building off at the corner; it remained open to the public so people can walk through a courtyard space onto campus."
In addition, the first floor of the 15-story tower offers retail space. "They're trying to not only invite people from the campus but also from the neighboring community to visit the businesses on that first story," Kreiter said.
Before construction began, "There were a lot of intricate exterior details we wanted to work through as a design-build team, so we elected to construct a full-scale, two-story mock-up of the reinforced concrete structure and the faÃ§ade - both the curtain wall and the precast panels," Kreiter said. "We wanted to validate the design and try to expose any details we might not see on paper or within our 3-D model."
After constructing the mock-up in fall 2014, the team tweaked a few aspects of the design. For instance, "We had some locations where our precast concrete tapered down to a very thin panel," Kreiter said. "To avoid any problems, we adjusted some of the precast edge details for constructability and durability."
In addition, when the waterproofer worked with the mock-up, "It allowed us to better develop our waterproofing transition details at the foundation," Kreiter added. "Our subcontractors' hands-on feedback helped us simplify details."
Even with construction well underway, the team still uses the mock-up. "We just had our spray foam insulator apply his product on the inside of the mock-up to make sure the detailing worked," Kreiter said. "We've continued to add little pieces to have better confidence before we get into the actual building."
Mortenson also applied interior finishes to exposed concrete columns and slabs to get the finishes right and deliberately chipped the precast concrete to confirm repair procedures.
LEED on an Aggressive Schedule
Practicing sequencing helped eliminate inefficiencies in the construction schedule. Mortenson used that strategy for the concrete deck with radiant heating, one of the elements contributing to the goal of LEED Gold certification. "We had a very aggressive schedule for our concrete deck cycles - from the day we started forming the columns to the point that we poured the concrete deck was only six days," Kreiter explained.
To stay on schedule, "We developed a method for prefabricating the radiant tubing on welded wire fabric, then used a crane to hoist mats of radiant tubing to the working deck. The pipefitters spread out the panels and spliced the tubes together, as opposed to going up with reels of radiant tubing and having to lay out the serpentine piping there."
The complete deck process involved first constructing a plywood deck and installing a mat of reinforced steel. Once workers placed the radiant tubing, they added another mat of rebar and slotted embeds for connecting precast panels and the curtain wall. After pressurizing all the radiant tubing to verify the system remained tight with no damage from construction, they poured a nine-inch concrete deck to encase all the elements. The radiant system reduces energy used for heating and cooling on all of the student housing floors.
To further optimize energy performance, the buildings incorporate natural ventilation, with operable windows imported from Germany. "The windows open in and they're very large, so we designed a metal screen that acts as a guardrail for fall protection," Kreiter said.
The screens extend from the faÃ§ade to cover the operable windows. In addition to safety, they provide shading to reduce thermal load and an architectural element with their decorative pattern.
The buildings also feature 38,200 square feet of green roof over a metal deck, concrete fill, and a rubberized asphalt waterproofing membrane. Half of the green roofing sits in a non-occupied area with growth media and a sedum mat; the other half resides in an occupied courtyard and consists of geofoam, intensive growth material, and a mixture of turf, perennial beds, and trees.
Other sustainable elements include the precast and curtainwall enclosure with low air leakage and high thermal resistance, a system for recapturing energy from hot water used in showers, sensors to automatically dim and shut off lights throughout the buildings, and meters to monitor and report energy usage. Infiltration basins capable of holding 274,000 gallons of rainwater reduce discharge into city sewers.
Elevations in a Tight Space
The congested urban work area required extensive coordination throughout construction. Two tower cranes stayed onsite; at one point, three mobile cranes joined them. "We had five pieces of equipment doing major hoisting," Kreiter said. "This required significant logistics planning to make sure all site activities were well-orchestrated at all times."
For safety on the busy campus, especially working at these elevations, "One strong area of focus has been controlling any falling objects," Kreiter said. "That required some different netting applications, tool lanyards, and other measures to ensure that everything stays within the confines of the building."
With the topping-off ceremony celebrated last August, the project remains on schedule for completion in June 2016.