Tight Site, Bright Future: UPMC’s Presbyterian Expansion

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A striking new presence has risen at the intersection of Fifth Avenue and De Soto Street in Pittsburgh, Pennsylvania’s Oakland neighborhood: its dramatic cantilevers and stylish glass facade a testament to innovative design. The addition to the University of Pittsburgh Medical Center (UPMC) Presbyterian is the largest healthcare project in the state and when complete, will create the city’s largest hospital, offering 1.2 million square feet and 636 private patient rooms. The structural design strategically incorporates a 22-story steel-framed bed tower, a 450-car post-tensioned concrete parking garage featuring a rooftop terrace, all necessary mechanical and hospital support areas, and an inviting public space dubbed the “Lifestyle Village.” The congested, steeply sloping urban site presented numerous engineering challenges, most notably the seamless integration of a street-level loading dock within the building's footprint and the implementation of a dramatic cantilever above the sidewalk-level urban courtyard.

Site constraints mandated an internal loading dock with sufficient column-free space for semi-trucks to maneuver before exiting. Access to the loading dock from the narrow and steeply sloping De Soto Street made reversing either into or out of the loading dock infeasible. The structural layout was further complicated by the central placement of the parking garage directly beneath the bed tower addition (Fig. 4). Each of these three distinct uses—the bed tower (configured for two patient rooms per bay), the parking garage (designed for three stalls per bay), and the loading dock (requiring a largely column-free area)—had its own optimal grid and column arrangement. The parking garage features a regular rectangular grid, while the reniform, or kidney-shaped, layouts of the bed tower and loading dock incorporate irregular, non-orthogonal grids. Consequently, it became apparent that a unified grid system accommodating all three uses was impractical.

The structural solution involved the extensive use of transfer girders, coupled with a strategic full-height column removal and a sloped frame column. The transfer members redirected upper-level columns to compatible positions within the loading dock and parking garage below. HGA examined options for an orderly layout of the transfers but was hindered by the irregular and non-uniform upper and lower grid layouts. The resulting system is a complex layout with seven primary transfer girders occurring at multiple levels incorporating wide-flange sections as heavy as W36x723 (rolled with high-strength ASTM A913 - 65 KSI steel) alongside substantial 72-inch-deep plate girders featuring 4-inch thick by 18-inch-wide flanges. Numerous secondary transfer girders were also utilized throughout the building. The column removal eliminated one difficult conflict creating a double-span bay that continued to the penthouse. Sloping a W14x500 frame column 12-feet over two stories allowed the column to be positioned optimally in both the bed tower and the loading dock.

The contrasting upper and lower grid systems also significantly complicated the layout of lateral braces. The reniform bed tower relies on a combination of single and multi-level X and chevron braced bays, with three transverse frames at each end and three additional longitudinal frames. On upper floors, the transverse frames needed to be situated within the central core to prevent interference with patient rooms; however, this alignment often conflicted with the spatial requirements of the levels below. The design team addressed this issue by strategically shifting brace locations to adjacent bays on lower floors (Figs. 4-5). Frame shears as high as 1,700 kips were transferred to the adjacent bay using directly welded connections.

Two levels below the bay transfers, structural analysis revealed that a significant portion of the lateral forces were being distributed out of the steel frames and redirected to concrete walls that were present at the lower floors. Accepting this inevitability, the design team provided a viable load path that would facilitate these diaphragm transfers through the slab-on-metal-deck. The movement of horizontal forces out of the steel frame into the diaphragm was achieved using collector beams designed for the large axial forces and shear studs. Diaphragm strength for the typical 6 1/2-inch composite slabs was exceeded for all critical loading conditions and would be supplemented using thicker, high-strength, reinforced slabs. At areas of highest diaphragm demand, the slab was increased to 9-inches of 5,000 PSI concrete and reinforced with #5 rebar at 6-inch centers in each direction.

Design wind loading for both strength and serviceability was based on wind tunnel testing, with a 3,000-year return period for strength and a 50-year return period for serviceability. The decision to pursue wind tunnel testing yielded a 20% reduction in wind forces as compared to ASCE 7 requirements. With a Seismic Design Category of A, wind would govern the design of the lateral system, with drift transverse to the slender kidney-shaped floors being the controlling factor. To limit the excessive movement that was noted in early studies, HGA interconnected the three columns that form each double bay frame within the mechanical penthouse. This hat truss concept utilized the third column as an outrigger to increase the overall frame length. With this system, frame column sizes ranged from W14x500 to W14x730, and the overall drift was reduced to around H/385.

To maximize patient room layouts on the upper floors, HGA extended the reniform floorplates as far south as permitted by property lines. The design team concluded that extending the lower floors the same distance would create an unwelcoming street presence. Recognizing UPMC's commitment to community engagement, the design allocated 30,000 square feet at the building’s southern end for a community-focused Lifestyle Village featuring wellness rooms, convenient food options, and outdoor urban spaces. The concept of cantilevering the upper floors above this space emerged as a key design strategy to maximize the function of both areas and would ultimately become part of the project’s identity.

HGA initially explored supporting the cantilever solely at the base using story-depth trusses, but this approach was not pursued as it sacrificed space that was allocated for a dramatic public dining area. Another option considered was locating the trusses in the penthouse at the top of the building, effectively suspending the cantilevered floors. While these trusses could easily be concealed within the two-story mechanical penthouse, this solution was also deemed infeasible due to the irregular grid layout at that end of the building and conflicts with the four large cooling towers.

After much consideration, HGA selected a system with independent cantilevers at each floor. Critical serviceability constraints that were considered included curtain wall deflection tolerances and susceptibility to vibration, resulting in heavier-than-average structural members to frame the 30-foot cantilever. As can be seen in Fig. 6, prominent cantilevered framing members as large as W40x503 were utilized. Although HGA designed most steel connections for the project, the larger, complex moment connections that frame through columns and girders were delegated to the steel fabricator, Sippel Steel Fab. This decision was made collaboratively with the input of Sippel, who was brought on board early, for both design efficiency and constructability. The steel fabricator was in a better position to optimize these connections based on their knowledge of material availability and their individual shop preferences. Allowing the steel fabricator to determine the type of connection also gave them more control over the tightly choreographed erection schedule of which the large cantilevers were a key component.

For the W40x503 beam-through-column moment connection mentioned, Sippel Steel Fab opted for bolted flange plate connections utilizing a total of (144)- 1 1/8-inch diameter A490 bolts. Bolts on the backspan side of the connection were designed as bearing bolts while those on the cantilever side were designed as slip-critical to eliminate bolt slop as a component of the overall cantilever deflection. HGA anticipated that post-erection slump of the larger cantilevers related to their substantial self-weight may still cause issues with deck installation and proactively addressed this potential by noting upward preset for larger girders on the construction documents. Rather than aiming for perfectly flat cantilevered beams, just enough preset was specified so the displaced shape of larger cantilevers was compatible with adjacent, smaller members. For the W40x503 example, the upward preset specified was 1/2-inch. HGA’s method was reviewed by the steel fabricator’s engineer and has proven effective in the field.

The increased beam depths at UPMC's Presbyterian Tower resulted in an explosion in the number of MEP beam penetrations being requested. It is common to coordinate a few holes through the web of a beam so that pipes or small ducts can pass through, alleviating conflicts in a few tight areas, but the number of requests at UPMC reached more than 1,000. A particularly challenging area above the loading dock, which was constrained by ceiling height, increased framing depth, and the above food service facility, required over 250 penetrations alone (Fig. 7). Recognizing the potential for issues with coordination, HGA helped to create an efficient and collaborative process which would bring together the design team, the Construction Manager's Virtual Design Coordination (VDC) experts, and the design-assist contractors from each discipline.

The process began with the MEP trade partners accurately modeling their components and working out as many conflicts as possible before submitting a list of requested penetrations to the VDC team, which were then compiled and forwarded to the design team for review. HGA required that requests be extremely specific, including the size of each opening, location along the beam, and location within the height of the beam, and provided rules of thumb to lessen the quantity of requests that would immediately be rejected. HGA's team then carefully analyzed each request and coordinated with the VDC team using direct communication and weekly coordination meetings. Often, slight adjustments were required in the depth or location of an opening, or sometimes multiple penetrations were grouped for simplicity. Once solutions were found for all penetrations, they were documented, and in some cases required separate framing plan sheets due to the sheer quantity.

This cycle of coordination repeated itself for each floor, a dynamic process occurring in parallel with the ongoing steel fabrication for lower levels and the shop drawing reviews for those to come. HGA leaned heavily on Sippel Steel Fab to identify the last responsible moment that revised Construction Documents were needed in order to be incorporated into the next scheduled shop drawing submittal. The process was tedious at times, requiring extreme perseverance from those directly involved, but was successful at preventing the need for last-minute coordination during the shop drawing review period.

A testament to ingenuity and collaboration, the UPMC Presbyterian Tower reached a significant milestone with its steel topping out on October 1, 2024. Pushing through the project’s inherent complexities and unique design challenges, this achievement underscores the efficiency and success born from creative problem-solving, persistent dedication, and effective collaboration among the project team. Set to become a prominent landmark upon its completion in Fall 2026, the bed tower addition will empower UPMC to further its mission of providing outstanding patient care and driving the future of healthcare through innovation, research, and education. ■

About the Authors

Ben Shock (bshock@hga.com) and Jeffrey Millmann (jmillmann@hga.com) are both Structural Engineers with HGA in Milwaukee, Wisconsin.