Guiding a Gilded Age Gem Into the 21st Century

To view the figures and tables associated with this article, please refer to the flipbook above.

Nestled into half a city block on Manhattan’s Upper East Side, just steps from the tranquil green expanses of Central Park, The Frick Collection is a world-class art museum and research center specializing in fine and decorative arts from the Renaissance to the late 19th century. The collection was initially enjoyed by Henry Clay Frick and family in their 1914 Gilded Age Mansion, which became a public museum 90 years ago in 1935. The property has expanded over the course of more than a century to consist of five separate buildings and three historic gardens (two outside and one inside). With an ever-growing collection attracting an increasing number of first-time and returning visitors with each passing year, The Frick Collection commenced a renovation project in 2016 to expand publicly accessible gallery spaces within, improve circulation and amenities, modernize back-of-house facilities, and improve energy efficiency. Simpson Gumpertz & Heger (SGH) was the Engineer of Record for this challenging project that included the repair and strengthening of numerous archaic structural systems throughout the historic buildings.

While renovations occurred in all of the institution’s buildings (Fig. 1), it was the three buildings with additions (Fig. 2) that required new lateral-load-resisting (lateral) systems and strengthening of existing lateral systems: the Frick Art Research Library (FARL), a 1935 extension, originally called the Music Room, and the reception hall. The additions provided more space for a new conservation studio, educational programming, and additional galleries, and they provided an interconnection of all buildings for the very first time. This trio of structures is now clad with a panelized facade system (a thin-stone system supported by metal backup framing) that harmoniously complements the original limestone cladding of the adjacent buildings. Although the impact of this new system is primarily aesthetic, it significantly affected the renovation’s structural design and presented some unique challenges for the SGH engineering team.

To provide more space for the museum, the project team designed a narrow, nine-story addition to the FARL (horizontal enlargement), a three-story “overbuild” (vertical enlargement) at the 1935 extension, and a one-story overbuild at the reception hall.

The FARL’s nine-story transitional masonry structure (the exterior steel frame is embedded in masonry) has two below-grade levels, and, as discussed in Part I of this series, the floor structure varies from the proprietary “stack-slab” system in the library stacks to draped-mesh cinder concrete slabs and slagblok (waffle) slabs. Large openings in the floor diaphragms were needed for a new egress stair and elevator at the south end of the building, adjacent to the steel framing for the new addition.

The 1935 extension was a two-story transitional masonry structure with two below-grade levels and floors that featured draped-mesh cinder concrete slabs spanning between steel framing. The recently-completed project included demolishing the upper floors and roof while keeping the perimeter steel columns, first-floor structure, and below-grade construction to allow for a new three-story overbuild above the first floor, reaching a full height of four stories. To provide a connection with the nearby reception hall, the building was also expanded south beyond the original footprint.

In 1975, The Frick Collection demolished existing townhouses east of the mansion and constructed the reception hall and 70th Street Garden on top of remnant brick masonry foundation walls. The reception hall included two original below-grade levels and featured a steel-framed roof. The structure abutted, but was separate from, the mansion’s masonry walls. The recently-completed renovation included the demolition of the roof framing, interior floors, and a portion of the north masonry wall. For the new construction, SGH designed an opening in the west masonry wall for access to new elevators located within the mansion, a one-story overbuild featuring glass curtain walls, a concrete core for a monumental stair, and the replacement of the east masonry foundation wall with a new corbeled concrete shear wall.

Given all the modifications over several decades, SGH had to decide whether to structurally connect the buildings or keep them separated. Unfortunately, there was no catch-all solution, as each building presented different existing conditions and constraints dictated by the architectural vision for the project. The team’s design followed the 2014 New York City Building Code (NYCBC), which included provisions for structural separations. They also relied on “Technical Policy and Procedure Notice 4/99” (TPPN 4/99) issued by the New York City Department of Buildings, which provides guidelines on the interpretation of seismic design requirements when renovating existing buildings. In this provision, a seismic retrofit of an existing building is not required if there is a seismic joint isolating it from the new construction. A seismic retrofit can also be avoided if the increase in seismic forces is less than 20 percent, even if the existing building is not isolated.

The first step was to understand whether the existing buildings were connected and, if so, how. Above grade, the FARL was separated from the adjacent 1935 extension (without a distinguishable joint), and both the 1935 extension and reception hall were connected to the adjacent portions of the mansion. Below grade, all of the buildings were not generally connected.

SGH decided to connect the FARL and its addition because the increase in seismic forces was below the 20 percent threshold, but the FARL was kept separated from the 1935 extension, above grade. The 1935 extension and reception hall were connected to one another, but the team disconnected them from the mansion as much as possible. However, in some locations, the columns of the 1935 extension were integrated with the bearing walls of the mansion and could not be separated (Fig. 3). Remaining below the 20 percent threshold avoided a costly seismic retrofit of the mansion. Per TPPN 4/99, the new superstructure at the FARL addition, three-story overbuild, and reception hall were designed for both the seismic and wind requirements of the NYCBC.

Next, SGH had to determine the required joint sizes between the above-grade separated portions of these buildings. This required a delicate balance between meeting the code-required minimum structural separations, while reducing the size of the joints in architectural finishes and limiting the movement of deflection-sensitive facades under lateral loads. The final design required substantial effort and coordination between SGH and the facade consultant. The spandrel beams needed to be iteratively designed to limit the facade joints considering the combination of lateral drift of the buildings under wind and seismic loading, along with the gravity deflections. After the facade consultant established the deflection criteria of the spandrel framing, SGH designed them, determined lateral drifts under wind and seismic loading, calculated resulting joint sizes and spandrel deflections, and repeated the process (typically by upsizing or downsizing the lateral and spandrel structural systems) until the results were satisfactory. In general terms, the controlling scenarios were the minimum inter-building joint size under ultimate limit-state seismic loading and the square root of the sum of the squares of the lateral drifts of adjacent buildings under service-level wind loads (MRI=50 years).

Because of the elevational difference of the foundations, the first floor was the lowest level to connect the three buildings via the 70th Street Garden slab, and SGH designed the new first-floor framing and slab diaphragms to withstand significant lateral force transfers. On upper floors, there were also pinch points in the diaphragms. For the FARL, it was near the new elevator and stair openings on every floor. At these locations, the engineering team added slab reinforcing or in-plane bracing at the concrete-on-metal-deck slab to withstand the forces. A similar pinch point existed between the elevator core of the three-story overbuild and the monumental stair of the reception hall on the first and second floors that generated high diaphragm forces. At the three-story overbuild and reception hall, SGH designed solid cast-in-place concrete slabs with heavy chord reinforcement that acted compositely with the steel floor framing.

To provide access to the FARL addition, the western portion of the exterior masonry wall on the south elevation of the existing FARL was removed and replaced by a new reinforced concrete shear wall, in between and encasing two columns, and the eastern portion was removed to allow for circulation to and from the addition (Figs. 4 and 5). The new shear wall extends from the subcellar to the eighth floor and replaces the lateral capacity of the previous transitional masonry wall. The new shear wall is the stiffest lateral element of the FARL and its expansion. On top of the resulting significant lateral forces, the design of the shear wall was complicated by the detailing to connect existing diaphragms of the FARL and the new diaphragms of the addition. The existing columns and spandrels encased by the concrete shear wall are detailed with welded studs at the webs of the columns and couplers at the top and bottom flanges of the beams to transfer gravity and lateral forces to the shear wall, rather than into the columns and their existing foundations. The diaphragm was laterally connected to the shear wall while the associated gravity loads were re-supported (Fig. 6).

Because the shear wall extended between and encased the existing columns, openings for the door and window were needed, and the proximity of these openings to the existing columns required close coordination with the boundary-element reinforcement.

The foundation for the shear wall needed to be independent from the existing column footings because strengthening the existing footings would be both difficult and costly. South of the shear wall, the rock excavation continued down to Subcellar 2, approximately 10 feet below the bottom of the existing column footings, and thus the shear wall foundation, which would also bear on rock, needed to be located away from the edge of excavation. Consequently, the new footing is eccentric with respect to the shear wall. It extends the full length of the shear wall but stops at the edge of the existing column footings and cantilevers over them (Fig. 7). To resist uplift, rock anchors were required below the boundary element zones of the shear wall. Due to the proximity of the rock face as well as the shear wall eccentricity, the rock anchors were inclined. (Fig. 8).

To accommodate new art galleries, offices, and a conservation studio, the museum added three stories to the 1935 Extension. As such, the three-story overbuild required a new lateral system that extended all the way down to the foundation. To maximize the use of the new space and minimize the size of the new structure, SGH designed an asymmetric lateral system comprising a reinforced concrete core at the south end of the building, a stepped reinforced concrete shear wall at the east end (adjacent to the FARL), and a horizontally offset steel frame at the north end. The steel frame features moment frames in the upper floors for large windows and braced frames on the lower floors at the solid masonry walls that separated the 1935 extension from the East Gallery.

The eccentric layout of the lateral system resulted in a large, concentrated transfer of lateral forces around the elevator’s concrete core. The programming of the new space also required stair and mechanical openings to be located adjacent to the core, exacerbating the lack of space to transfer forces. The design team utilized the shear studs of the composite steel framing around the openings to collect lateral forces, and a steel drag strut on the south edge of the opening connected to the concrete core through a series of angles and post-installed anchors (Fig. 9).

The team designed the below-grade portion of the east concrete shear wall as a liner wall inside the footprint of the existing foundation wall to avoid strengthening of the wall and its footing. Above the first floor, it “steps over” the top of the existing mass masonry foundation wall toward the FARL to maximize interior space. Between the first and second floors, the shear wall doubles in thickness to allow the formation of an inclined diagonal strut to transfer gravity and lateral forces to the lower portion of the wall at the step. The moment from the gravity eccentricity caused by the step was resolved by transferring the resulting force couple to the concrete diaphragms of the new second floor and the existing cellar floor (Fig. 10). At the cellar level, SGH specified the removal of the cement topping and cinder fill of the existing draped-mesh cinder-concrete slab and its replacement with a new structural concrete topping slab that was detailed to transfer the compression component of the force couple from the east shear wall to the concrete core and the braced frame. Transferring the tension component of the force couple to the new second-floor diaphragm was more straightforward, and it was detailed as a simple slab connection to the concrete wall and braced frame.

Several factors and constraints dictated the design of the new below-grade concrete shear wall along the east side of the reception hall. First and foremost, the new concrete wall needed to re-support the landmarked masonry wall on the east facade, which is eccentric to the new concrete wall below. In addition, the new concrete wall required a large opening for an entrance to the new auditorium below the 70th Street Garden, and many smaller openings for mechanical ductwork. The new concrete wall also needed to laterally connect the first-floor diaphragm of the reception hall and the 70th Street Garden slab diaphragm.

The top of the concrete wall was designed with a heavily reinforced corbel to re-support the eccentric landmarked masonry wall and reinstalled limestone-clad concrete stairs. The new concrete wall continues slightly above the corbel to support the framing of the new first-floor slab and to laterally tie the diaphragm to the wall. The “closed ties” that are required across the height of the corbel were particularly difficult to install, as the contractor only had access from the exterior side to install the ties. Access from above and from the interior side, something generally available in ground-up construction projects, was restricted by the construction sequence and the existing wall to be re-supported. As a workaround, SGH designed a series of hooked reinforcement and cross ties that could be installed from one side (Fig. 11).

Finally, SGH designed a horizontal steel truss to transfer lateral forces between the shear wall and the 70th Street Garden diaphragm. The truss, located just below the corbel base, is connected to the shear wall by cast-in-place steel plates embedded into the concrete wall and to the garden diaphragm by steel-plated connections welded to the long-span composite steel beams that support the garden slab.

Navigating the challenges of designing lateral systems for additions and overbuilds in historic buildings requires an in-depth knowledge of several archaic structural systems, an understanding of lateral load paths, some creative detailing, and extensive familiarity with relevant building codes and available literature. When all this takes place at an iconic, world-renowned museum like The Frick Collection, the journey becomes even more arduous.
After several years of seamlessly concealing structural systems behind lavish finishes, addressing unforeseen field conditions, and modifying the structural design to expedite construction, The Frick Collection finally reopened to the public in April 2025 to overwhelming acclaim and throngs of curious visitors (Fig. 12). Despite its array of complex challenges, the project proved to be a formative, unprecedented, and deeply rewarding experience—and one for which the authors remain profoundly grateful.■

About the Authors

Filippo Masetti, PE, is an Associate Principal in the New York office of Simpson Gumpertz & Heger, Inc. with extensive experience in assessing, analyzing, repairing, and strengthening existing structures. (Fmasetti@sgh.com)

David Ribbans, PE, was previously a Consulting Engineer in the New York office of Simpson Gumpertz & Heger, Inc. for the duration of this project and focused on the repair, restoration, and strengthening of existing structures. He now works for K2M Design. (david.ribbans@gmail.com)

Lauren Feinstein, PE, is a Senior Consulting engineer in the New York office of Simpson Gumpertz & Heger, Inc., focused on the restoration and rehabilitation of historic structures and the renovation of existing buildings. (Lpfeinstein@sgh.com)

Kevin Poulin, PE, is a Principal in the New York office of Simpson Gumpertz & Heger, Inc. He has a deep understanding of structural systems and historic materials, and his expertise has played a key role in revitalizing many landmarked structures. (Kcpoulin@sgh.com)