Tuned for Efficiency

The new Upstate Neuroscience Research Building (left) is linked with the older building by a two-story, 300-foot-long, light-filled atrium at the interface of the two buildings. Iridescent metal panels on the exterior of the new building contrast with the original building’s brick façade. Photo: Robert Mescavage

The State University of New York (SUNY) Upstate Medical University, Neuroscience Research Building, is a new building addition to the Institute for Human Performance (IHP) located in Syracuse, N.Y. This expansion allows the university to have more space for interdisciplinary research, encouraging scientists from various disciplines to advance studies into the causes and progression of diseases of the brain, spine, and visual system. Designed for LEED Silver certification, the 156,000-square-foot expansion was completed at a construction cost of $53 million and was opened and fully occupied in the spring of 2014.

Arup worked with architect Goody Clancy on the challenge of connecting the new addition, the Upstate Neuroscience Research Building, with the older building, the IHP, so the entire complex could function as one. The multidisciplinary design team achieved this goal by creating a two-story, 300-foot-long, light-filled atrium at the interface of the two buildings. The atrium acts as the facility’s spine, stretching the entire length of the new facility and linking the original building to the new addition. The spine also houses laboratories, conference rooms, and lounges. These flexibly designed spaces are clustered together to promote research collaboration and interaction.

Chameleon-like iridescent metal panels on the exterior of the new building contrast with the original building’s brick façade to give the addition a unique identity while livening up the surrounding neighborhood with its dynamic coloration.

As a research laboratory, the structural building frame needed to be as stiff as possible to accommodate the sensitive research equipment that would be adversely affected by rogue floor vibrations and accelerations. This design challenge was further complicated by the requirement for grade-level parking within the building’s tight footprint. The bespoke geometric layout of the parking garage was in direct conflict with the very prescriptive column grid required for efficient laboratory planning above.

Therefore, a system of column transfers was necessary. A structural steel solution was identified as the most appropriate structural system to satisfy both requirements; steel-braced frames and floor framing could be made sufficiently stiff to satisfy the laboratory acceleration limits and would result in a relatively lightweight system to accommodate the need to transfer the five floor levels above the parking level.

The atrium, which acts as the facility’s spine and links the original building to the new addition, also houses laboratories, conference rooms, and lounges. Photo: Goody Clancy

The column transfer was achieved by introducing an interstitial level between the second and third floors framed in story-deep structural steel trusses. The trusses are located on 21-foot centers and transfer the load of three floors above and the suspended level two below to accommodate the necessary column grid for parking below. The resulting 10-foot, 3-1/2-inch-tall interstitial floor level also creates an ideal space to house the building’s significant HVAC equipment, helping to facilitate the high degree of structural, mechanical, electrical, and plumbing coordination necessary for all such laboratory facilities.

The new building is completely separate from the existing building so that the new construction does not impose any additional lateral loads onto the existing structural stability system. A continuous movement joint located between the new addition and the existing structure was sized to accommodate relative movements between these two buildings under seismic and wind loads. The movement joint necessarily continues through the finishes of the adjacent walls, floors, ceiling, and cladding systems to enable unencumbered relative movement to occur.

The building is laterally restrained to the underside of the interstitial level by reinforced concrete shear walls. Supplemental reinforcing steel provided within the second floor slab enables the floor to act as a deep diaphragm in the east-west direction to transfer lateral forces from the braced frames above into the shear walls at the first level.

Arrow indicates the walking path for the fourth floor footfall vibration field measurements. Photo: Arup

The laboratory floors above the interstitial level are stabilized by steel-braced frames made concentric wherever possible to achieve good economy of material and high lateral stiffness. Braced frames are typically located adjacent to the building’s core shafts and atop continuous shear walls below to accommodate circulation and building services coordination.

Where necessary, diagonal member configurations have likewise been coordinated with the architect and the building services engineers to ensure that a workable, yet structurally efficient, design solution was achieved.

Sited on sloping topography, the new building is nestled into a deep excavation along its northeast corner. The project’s foundation engineering consultant, Ravi Engineering, designed a 16-foot-tall, cantilevering-reinforced concrete retaining wall founded on caissons that holds the large lateral earth pressures at bay along this corner. Subsequent structural attachment of the adjoining floor slabs and steel framing was made to the wall only after the concrete had achieved its full 28-day strength, and after all backfilling operations were complete. This ensured that all lateral earth pressures were absorbed by the perimeter retaining wall and not transferred through floor diaphragms and into the building lateral system. Once the connection was made, the retaining wall then also provided significant lateral stability to the building along this corner.

The vibration performance requirements of the building were the foremost driver of the structural engineering design of the laboratory floor levels. However, the team was equally keen to limit the building mass as much as possible to ensure the most efficient floor system and to limit the load demands imposed on the large transfer trusses. Once an acceleration limit of 2,000 µin/s was established for the design of all laboratory floor levels, the structural engineering team initiated an optimization process that sought to achieve this strict criteria at a minimum weight and minimum cost solution.

Structural framing model developed with RAM Steel. Image: Arup

Working in conjunction with in-house acoustics experts, Arup recommended that the steel floor framing be designed to satisfactorily accommodate two different dynamic scenarios: 1) fast walking along corridors adjacent to the laboratories, and 2) moderate walking within the laboratories themselves. The first criteria equates to a driving frequency of 100 steps per second or 1.67 Hz. The second criteria equates to a driving frequency of 75 steps per second and is equal to 1.25 Hz. These two conditions were reviewed and agreed among the architects, owner, and project acoustic consultants, Acentech, as an appropriate set of driving criteria for the design of the floors.

With both the dynamic input and acceptance criteria in-hand, Arup then developed a systematic matrix of structural framing options that were evaluated for strength, deflection, and acceleration performance. Arup Oasys GSA Footfall analysis software was used to analyze the acceleration response of each floor system considered, while RAM Steel was used to evaluate each system’s strength and deflection performance. The entire process was iterated multiple times for each floor until a minimum weight solution within the floor depth requirements was converged upon. In the end, a very efficient typical floor framing system of W24 primary and secondary structural steel beams supporting a composite slab of 4-1/2-inch, normal-weight concrete on 3-inch metal deck was achieved, with a resulting steel tonnage of less than 10 pounds per square foot.

Result of the footfall vibration analysis: peak acceleration (GSA). Image: Arup

Once the steel work and concrete floor slabs were erected on site, Arup structural and acoustic engineers conducted a series of field tests on the physical building to verify the analytical results obtained from the Arup Oasys GSA Footfall analyses. The tests were done off-hours and at night to avoid vibrational interference with construction activity and other transient activities. Acceleration monitoring equipment was placed within the region of the laboratories on each floor to record the response of the floors to fast heavy walking (1.67 Hz) along the corridor areas and moderate, but still heavy, walking (1.25 Hz) within the laboratories themselves. A tuned metronome was used during each test to establish the proper walking pace of the tester to ensure accuracy with the analytical inputs used in the design.

The results of these field measurements were in very close agreement with analytical results and so provide demonstrable evidence that floor systems have been properly tuned to within precise targets. Moreover, the field measurements were purposely conducted prior to the installation of any interior partitions, the presence of which affords considerable additional damping to the floor system and improves the overall dynamic performance.

The building has been designed to be both open and communal to bring together groups of investigators with vast expertise and resources necessary to solve complex medical problems. A similar team approach was applied to design of the new facility with tremendous success. The high level of coordination and attention to technical detail required in the design of any laboratory facility is exceptional. The ability to do so and still achieve the significant design efficiencies realized on this project is a testament to the spirit of intense collaboration, drive, and energy adopted by all members of the design team.

Successful execution of this project was realized by integrating an architectural vision for the building that is aligned with structural integrity and efficiency, resulting in an overall complex that works as a unified whole.

Patrick S McCafferty, P.E., LEED AP, is associate principal, and Jimmy Su, P.E., LEED AP, is associate, both with Arup Boston.

Posted in Uncategorized | August 26th, 2014 by

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