Originally only 30 percent of the Manchester Central Public Library was available to the public. A new public gathering space created below the main reading room has helped redefine the library for the 21st century. Morley Von Sternberg
With a grand reopening last month, the United Kingdom’s city of Manchester has launched its three-quarter-century old, reimagined Central Public Library.
April 15, 2014—The circular Central Public Library in the United Kingdom’s city of Manchester defies easy description. The building, designed by E. Vincent Harris and completed in 1934, is a highly symmetrical neoclassical building arranged around a radial, steel-framed structural grid and dominated by a large, square portico entrance. But according to the London-based firm Ryder Architecture, which designed recent renovations to the structure, the building is far more structurally complex than that. An outer four-story tiered ring supports a hidden central domed roof with a glazed skylight, enclosing the building’s interior void. Within that central core, an internal, circular structure was built, abutting the outer ring but remaining structurally independent of both the outer ring and the roof. This inner structure was constructed to hold four levels of the library’s stacks that were at one time accessible only to staff members, as well as an expansive public reading room known as the Great Hall.
A complicated series of stairways, corridors, and elevators within the 12,500 m2 library meant that the public was able to visit only 30 percent of the building’s space; the remaining 70 percent was accessible only to staff. But with the reopening of the remodeled structure last month, the library has been reinvented as a welcoming public space with those ratios reversed. A glass-encased bank of elevators and stairways in the eastern quadrant of the outer ring now enables visitors to visit each floor of the building, while the central core structure has been almost entirely removed and rebuilt. The four lower, central levels of book storage have been replaced with just two levels: one for visitors and one for a climate-controlled archive. The building’s historic exterior remained structurally untouched and intact through the entire process.
“It is a much-loved building in Manchester,” says Jim McNally, CEng, a technical director in the Manchester office of the global engineering, construction, and technical services firm URS Corporation, which performed the structural engineering on the project. “It has had a very positive impact on the community,” he says, and the city council decided that the renovation of the library needed to expand the library’s offerings to the community.
Originally completed in 1934, the Manchester Central Public
Library is a highly symmetrical circular neoclassical building
measuring roughly 60 m in diameter. Manchester Libraries,
Information and Archives, Manchester City Council
Since the building is listed as Grade II* with English Heritage, preservation of its facade and elements of historic significance were extremely important. (About 5.5 percent of listed buildings are identified as Grade II*, according to English Heritage. Such structures are “particularly important buildings of more than special interest,” according to the organization.)
To create the glass-encased vertical circulation system within an oversized opening, workers carefully worked from the top tier of the outer ring, down to the basement floor, and then back up again. The existing transfer structures were carefully removed and replaced with vertical columns that extended from the basement to the roof line without disturbing the facade or causing cracking in the original structure.
Because the tiers of the building’s outer ring step in at its second and fourth levels, a complicated transfer system was used to direct the building’s loads. The loads transfer from columns to beams in a stair-step pattern as they move down the structure, McNally explains.
“The circular nature [of the building], combined with the steps as you go up the levels—those two aspects made it complicated.” McNally says. “If it was just a single drum, [the vertical circulation core] would have been simpler to do.”
The design team made use of three-dimensional building information modeling, specifically the Revit software produced by Autodesk, of San Rafael, California. A point-cloud survey of the entire library was undertaken at the outset and converted to a Revit model. By doing so, the design team was able to fully understand the building and resolve any design clashes before arriving on-site, McNally says. (They also discovered that despite the fact that the structure is 80 years old, the 60 m diameter building was only 40 mm off a true circle.)
In preparation for the vertical circulation system, temporary structural steel reinforcement was placed on the undersides of each concrete floor slab, alongside beams that were to be removed. The construction team—led by Dartford, Kent-based Laing O’Rourke—carefully removed sections of beams at each floor once the reinforcement had been installed.
Ground excavations and the placement of a reinforced-concrete foundation ultimately provided support for the two large glass elevators, a glass service riser, and a curved staircase. Two rows of three tubular columns, measuring 406 mm in diameter, were built up in sections from the basement floor to the roof to carry the loads previously carried by the complicated transfer column and beam system.
In the library’s renovation, four levels of book stacks in the
building’s central core became two larger, more modern levels.
A glass-enclosed vertical circulation core was added to the interior
of the building’s outer ring. Courtesy of Ryder Architecture
To avoid the need for openings through the historical cast lead-covered roof, these tubular columns arrived at the site in sections and were welded together on-site. They were filled with concrete and reinforced to achieve both fire resistance and the finish desired for visible additions to a historic building, McNally says.
Once the steel columns were in place, “we jacked the columns against the existing structure to take the load, before the transfer beams were cut,” McNally says. “We jacked it up so that we knew all [of] the load was into the column, and the existing structure wouldn’t suddenly settle and crack.”
Once the load had been transferred to the new columns and a network of structural steel added to the floors, the new curved, floating glass-railed flights of stairs were built at ground level and lifted into position.
Another major structural effort involved removing the original four levels of book stacks, located underneath the Great Hall reading room in the building’s interior core. Above the stacks, reference books lined the edge of the Great Hall reading room in bookcases built to follow the wall’s curvature, behind a series of 24 circular scagliola columns. Readers placed requests for books located in the stacks at a central, circular desk—much as is still the case at the main reading room of the Library of Congress in Washington D.C. Rather than a mechanical system, as is used in Washington, however, in Manchester a book request resulted in a staff member descending a circular staircase located within the desk area, down to the stacks to retrieve the desired book.
The book shelving system for these levels was built so that the hollow metal tubes used as the bookshelf uprights supported both the weight of the books and the loads from the 75 mm thick cast-in-place concrete floors themselves. These uprights were placed on a grid measuring approximately 1.4 m by 0.9 m and extended between the levels, which were separated by a mere 2.3 m in height. In addition to creating tight floor-to-ceiling heights, the hollow tubes also provided the potential for a fire to spread quickly between floors. For these lower, internal floors, the estimated time to collapse once a fire was fully established was only eight minutes; the time needed to be four hours to meet existing codes, according to McNally.
Workers carefully scooped out the four levels of stacks, while preserving the internal curved bookcases and columns that lined the Great Hall reading room. To do so, a grillage of steelwork replicating the support given by the uprights was placed beneath a retained annulus of the 75 mm thick concrete slab on which the bookcases and columns sat in the reading room, according to McNally.
Two new reinforced-concrete levels were then built beneath the Great Hall reading room. In the basement, a climate-controlled archive containing approximately 1 million items—the earliest of which dates back to 1297—was created. At ground level, a new public gathering space, reading room, and cafe were installed. A series of columns on the new ground-floor public space mimics the scagliola columns in the main reading room, while four columns ring the center of the room.
At the location of the original circular stairway, a steel-and-glass circular insert has been placed in the center of the newly restored floor of the Great Hall reading room. The glazed insert has a dual purpose: it channels light from the library’s original glass skylight—located above the reading room in the original roof—into the new ground-floor gathering space and also provides a way for any potential fires to be controlled. If a fire occurs, four of the glass insets will pivot via a hydraulic motor to provide a way for smoke to ventilate through the reading room to the domed roof’s skylight.
Above the glass-and-steel insert, an original four-faced ornamental clock has been placed atop four scagliola columns. Originally located atop the spiral stairway in the reading room, the clock now holds a place of honor—and its original height—atop the central glazed oculus.
The Central Public Library in Manchester is the United Kingdom’s third most-visited library, according to material provided by Ryder. A cornerstone of the library’s transformation is its expansion as a “third space.” It is “a beautifully designed space for people to meet,” according to the firm.
The £48-million (U.S.$79.5-million) renovations to the library also included technological advances to bring the library into the 21st century. These include film-viewing pods; the library now houses the British Film Institute’s archives as well as the North West Film Archive.
With the expanded public areas and offerings, the number of visitors to the library is targeted to double to 2 million annually, according to Ryder.