Ready to Meet Changing Needs

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Design for the modern scientific workplace is most successful when the architectural and structural configuration of a building is directly linked to its purpose. This philosophy dictates that a research facility should be much more than a controlled environment for academic study; it should actively support and promote the science within.

Seeking to become the nation’s leading research program for National Institutes of Health (NIH) funding, stakeholders in the Washington University School of Medicine (WUSM) in St. Louis, Missouri, envisioned a laboratory facility that could readily adapt to the rapidly evolving science happening within. They wanted a building with dynamic spaces for research collaboration across a broad range of diverse but related disciplines to accelerate the development of “bench-to-bedside” treatments and improve patient outcomes.

Now completed, the Jeffrey T. Fort Neuroscience Research Building (NRB) is one of the largest facilities of its kind in the United States. The 11-story, 609,000-square-foot NRB is home to more than 100 research teams working together in a building where architectural and structural design is intrinsically tied to the goals and needs of the institution.

One of the most important guiding principles of the design was to create a research environment with the flexibility to adapt as needs evolved. Rather than the typical approach of assigning space based on departments, WUSM planned the layout of the research spaces around specific themes to facilitate team-based science beyond that of traditional departmental boundaries. As a result, the structural systems were required to accommodate the ever-evolving needs of these research groups throughout the life of the building.

Given these requirements, reinforced concrete proved to be the optimal structural system for the project. In keeping with local construction practices, the design features a one-way pan joist floor system that spans between concrete beams. In addition to providing a vibration-resistant floor that efficiently balances damping and self-weight, a pan joist floor can accommodate future floor openings and penetrations more easily than a comparable two-way flat slab system.

As part of a broader strategy to maximize flexibility, all laboratory spaces were designed to meet a Vibration Criteria (VC) of 2000 µ-in/s, or VC-A, to satisfy typical requirements for sensitive equipment. A 10-foot cantilever along the building perimeter at each floor was reserved for office spaces and designed to satisfy an acceleration limit of 0.5%g for occupant comfort.

The use of RAM Structural System and RAM Concept guided the design toward a cost-effective solution with an optimized column grid of 21 feet by 31.5 feet. A 6000-psi concrete mix was used for the structural framing to optimize the size of the columns and improve the vibration and deflection performance of the slab and framing due to the higher stiffness properties. Typical lab space floor system consisted of a 6-inch slab over 14-inch-wide by 14-inch-deep concrete joists (22-inch total structural depth) utilizing 53-inch wide pans. 42-inch-wide girders spanning between the columns matched the 22-inch joist depth. The vibration performance of this design was initially evaluated using RAM Concept and then verified by vibration consultant, Colin Gordon Associates (CGA), using their own proprietary finite element modeling software. To balance efficiency and adaptability, floors dedicated to mechanical systems were only designed to meet strength and deflection requirements. Despite the higher applied load to the floor to accommodate the mechanical systems, the concrete joist web widths were reduced from 14 inches to 10 inches and the concrete girder web widths were reduced from 42 inches to 36 inches with the structural depth remaining consistent at 22 inches.

Unlike the 15.5-foot story heights for the typical lab spaces, the mechanical rooms located in the basement, second-floor, and eleventh-floor feature 22-foot to 24-foot story heights to accommodate double stacked air handling units. Additional concrete beams were required to support the localized heavy equipment on the second floor and eleventh floor, and supplemental reinforcement was provided in the slab above to support the substantial point loads imparted by suspended piping and ducts. Planned plumbing penetrations on all floors were accommodated by sizing and reinforcing the girders to include an allowance for 4-inch diameter sleeves.

The depth of the basement level, coupled with the effects of surcharge loads, required 22-inch-thick concrete walls around the perimeter of the building. The first structured floor above the basement was designed to support an extensive system of steel-framed catwalks, mechanical equipment, and suspended elevator pits. Because the basement has a larger footprint than the structure above, portions of the first-floor slab were designed to accommodate drive lanes that provide access to a new garage located immediately south of the research building. These portions of the structure feature closely spaced pan joists to support multiple topping slabs, soil, sidewalks, and vehicle traffic.

Despite the challenges posed by the construction of the basement level, a significant benefit was realized from the improved soil conditions, rock bearing, and skin friction capacity present at the depth of excavation. Even with the heavy loads applied to each column, drill pier sizes for the foundation system were on average 42 inches in diameter with 9-foot-deep rock sockets. In addition, the geotechnical investigation of the subgrade conditions established that a soil site classification of B would be appropriate for the NRB, which lowered the Seismic Design Category from typical C in St. Louis to B. This development provided the welcome benefit of reduced seismic loading, which was particularly beneficial given the mass of the building, and reduced requirements for nonstructural seismic bracing within the facility.

The building’s design needed to provide spaces for both laboratory research as well as collaboration/knowledge transfer. A grand atrium space and an auditorium on the first floor were central to realizing a building that actively fosters knowledge sharing. The program needs for each of these spaces could not be accommodated within the standard column grid, so story-high transfer beams were designed to support the eleven stories above that could be constructed within the second-floor mechanical space.

Above the atrium, a concrete beam cantilevers 11 feet from the shear walls that wrap around the elevator core. At the auditorium, a story-high beam spans 72 feet between columns to support a column above that transfers near the middle of the span. The design of the transfer beam above the auditorium was complicated by the need to accommodate a door through the member. Analysis of each transfer beam was performed using the strut and tie method with validation from RISA 3-D.

Near the facade, the grand atrium is open further from the first level to the underside of the fourth level, resulting in a ceiling height of nearly 76 feet. Rising unbraced through this space, large 44-inch diameter concrete columns at the perimeter of the building support wind girts to which the curtain wall is attached. Given these considerations, it was essential to cast each column in a single pour or incorporate moment splices at each cold joint. Leveraging their previous experience, McCarthy chose to construct each column monolithically using a specialized self-consolidating concrete (SCC) mix.

WUSM is affiliated with BJC HealthCare, which includes the nationally recognized Barnes-Jewish Hospital and St. Louis Children’s Hospital. These facilities are connected across the medical campus by an extensive system of skywalks. To connect the NRB visually and physically with the rest of the campus, this network needed to be extended through the construction of a new pedestrian bridge that, in addition to enhancing movement across the campus, serves as a bold design statement.

To replicate the aesthetic of the current pedestrian skywalk system, the new bridge incorporates cantilevered concrete columns that support long-span steel girders, the longest of which spans 120 feet. Because the columns supporting the bridge are categorized as a cantilever column lateral force resisting system and designed to meet Seismic Design Category C, the 2018 International Building Code and Chapter 12 provisions of ASCE 7-16 restricts the permitted column height to 33 feet, 11 feet below what the design required.

Posed with this challenge, the team turned to the 2009 AASHTO Pedestrian Bridge Code for guidance. Unlike IBC, this design code does not have a prescriptive height limit for the seismic design of cantilevered column systems, though its application to a building structure required engineering judgement. To overcome this hurdle, the design team sought a variance from the City of St. Louis, which proposed using the most stringent design forces and detailing requirements of both ASCE and AASHTO. Ultimately, the approach was accepted by the AHJ. RISA 3D was used for design of the steel sections, and use of SP Column was required for the slender column design.

Although the pedestrian bridge is structurally independent from the parking garage it connects to, structural upgrades of this existing building were required. Linking the end of the bridge to the rest of the pedestrian walkways required the construction of an enclosed pathway across the parking structure. The higher live load within this zone coupled with the need for a topping slab to create a level walking surface exceeded the design capacity of the existing parking deck.

Collaborative efforts from CannonDesign, McCarthy, and specialty engineer Norton and Schmidt determined that the most economical solution was to reinforce the existing garage using fiber-reinforced polymers (FRP). The applied loads along the planned walkway were given to Norton and Schmidt for analysis and design of the FRP system. The top of the existing slab was scored so that FRP rods could be inserted to provide negative flexure reinforcement. The bottom of the slab and sides of the existing post-tensioned beams were reinforced with a carbon fiber wrap to resist positive flexure and shear.

Every aspect of the Jeffrey T. Fort Neuroscience Research Building represents a meticulous response to the institution’s goals, exemplifying the harmonious marriage of form and function between architectural and structural design. While the design of this massive building frequently posed new challenges, each one offered an opportunity to implement a creative solution. With construction complete, the researchers who now call this building home can address more profound sets of challenges as they seek a deeper understanding of the human neurological system with the ultimate goal of improving patient outcomes. Today, this magnificent structure stands as a beacon of hope and a testament to the relentless pursuit of scientific progress and medical excellence. ■

Kurt Bloch, SE, and Julie Shaw, PE, are Structural Engineers with the St. Louis, MO, office of CannonDesign. This article was written in tribute to the late Ruofei Sun, the EOR of the project and longtime Structural Lead of the St. Louis office. (kbloch@cannondesign.com and jshaw@cannondesign)