It today’s digital world, it’s rare that a university will commit to keeping its entire research collection on campus – for the present, never mind for the next two decades. But the University of Chicago is not averse to taking the road less travelled – in more ways than one.
The University of Chicago’s new Mansueto Library is a testament to this scholarly endeavour, and an innovative example of a leading-edge architectural design that challenges the very core of structural engineering.
Lighting the way
Designed by world-renowned architect Helmut Jahn, the Mansueto Library takes the form of a soaring elliptical glass dome that rises above ground to offer a clear-span of 8,000 square feet, with comfortable seating for faculty, students, and visitors. The “dome” itself is an impressive engineering feat, never mind the structural engineering that has occurred beneath it.
“The dome is one of the more interesting construction features of the library,” explains Boyd Black, assistant vice president, Capital Projects Delivery for Facility Services, University of Chicago. “The dome was completely pre-fabricated in Germany. Entire sections of the dome were assembled in Germany before being disassembled and then shipped to the site piece by piece in the order it which they had to be erected.”
“This is a very unique space,” continues Black. “It is entirely column free.”
This elliptical dome acts as a beacon of light (especially at night) to the treasures that lie beneath it.
“The idea of taking this project underground was presented to the University by the architect Helmut Jahn,” explains Black. “He suggested that rather than have the library sit above ground, it would make more sense to take it underground, especially because there couldn’t be any windows because the main goal was to protect the books. We needed to be able to guard against sunlight and control the temperature and humidity.”
Because of this driving need to protect the millions of volumes of materials, the Mansueto Library extends 55 feet below ground. And it accommodates some of the most modern technology available in the form of an Automated Storage and Retrieval System (ASRS) that shelves the materials underground by size rather than library classification. The ASRS uses five mechanical cranes measuring 50 feet in height to store and retrieve volumes from some 24,000 bins and 1,200 shelf racks located in 12 columns of metal racks. This high-density ASRS requires one-seventh of the space of conventional library shelving and can retrieve materials in as little as five minutes.
“The system has a 3.5 million volume capacity,” adds Black. “We brought back the many volumes that had been stored off campus so we have already filled up a significant portion of that capacity. But we built the system for the future so there is still a lot of potential for growth.”
Building from the ground down
With two-thirds of the Mansueto Library designed to be underground, the University of Chicago needed the expertise of a company well established in offering geotechnical design and construction services. It turned to Hayward Baker, a company that has over six decades of experience in implementing effective and economical projects that include grouting, ground improvement, structural support, earth retention – and more.
“We were involved in the project many years before the actual construction,” explains Gregory Terri, Area Manager, Hayward Baker. “We were brought in early to review all underground technologies, logistics and constructability of each of them, and how to build the structure in the most cost-effective way possible.”
According to Terri, the firm’s valuable input enabled the University of Chicago to issue tenders for the project. Hayward Baker bid on it – and won.
“Once we won the bid, we were responsible for the design, excavation and installation of the permanent below-grade walls, including construction of the ground anchors,” adds Terri. “We oversaw everything that went on underground.”
There were a couple of interesting features about the site that added some complexity to the building of the underground library. One, the water table was quite high – around seven to 10 feet below grade. Two, there was sloping rock across the site, as well as some deep sand pockets. And third, the excavation and construction was located right beside the foundation of the neighbouring building: the Joseph Regenstein Library.
“The shape of the building was very unusual as well,” comments Terri. “The only permanent lateral support in it was the concrete slab located at street level and the concrete slab at 50 feet below grade. There were no interior slabs so we had to come up with a unique solution.”
The answer would lie in the use of an optimized anchored diaphragm wall.
The 30-inch thick diaphragm foundation system runs the entire 660-foot perimetre of the project. As the digging occurred, slurry was pumped in, filling the excavation and keeping the earth in place. Steel cages were lowered into the 30-inch, 60-foot deep excavated trench and, as the concrete was poured, the slurry was displaced and pumped out for later reuse.
In all, the foundation required a total of 26, 30-inch concrete panels measuring 24 feet wide by 70 feet deep. Once the panels were installed, end stops were put in place to prevent any water leakage in between the panels. Additionally, grouting was used along portions of the perimeter to minimize groundwater infiltration through the weathered rock below the wall. In total, there were over 330 permanent ground tiebacks used to hold and anchor the panels in place.
In addition to the use of end stops and grouting to prevent water or moisture leakage, the underground library storage area also has a separate corridor running around its entire perimetre and acting as a barrier to the treasures inside. This corridor does double duty as a maintenance area. It also allows for the temperature to be held at the desired 60 degrees F and the relative humidity at 30 per cent.
“This was a significant project for us both in terms of size and visibility,” states Terri. “It is certainly one of a only a handful that we have worked on that has garnered so much attention and accolades.”
These accolades include the 2011 Distinguished Building Award Citation of Merit from the Chicago Chapter of the American Institute of Architects.
A brilliant example
Although the Mansueto Library is attached to – and can only be accessed through – the Joseph Regenstein Library, it nevertheless stands apart in both its design and its usefulness.
“I think that the Mansueto Library has changed the University of Chicago in two distinct ways,” concludes the University’s Black. “First, there is a significant advantage to faculty, students and visitors in keeping all the library’s books on campus rather than building an off-site facility to house expanding collections. Second, this is an award-winning design and a wonderful piece of architecture that brings a new sense of excitement and added visibility to a very prominent part of the campus.”
Construction on the $81 million facility began in July 2008 and was completed in April 2011. The building came with a price tag of $81 million. But the result is a stunning piece of architecture and design that illuminates the future path forward for many young scholars yet to come.