Fermilab, the premier particle physics laboratory in the U.S., will soon add a new building to its campus: the Integrated Engineering Research Center (IERC). IERC will unite scientists and engineers from across the 6,800-acre Fermilab campus into a new facility, designed with a primary focus of fostering a collaborative spirit. When completed, IERC will be the most high-profile building constructed on the campus since the iconic Wilson Hall opened in 1973.
The approximately 85,000 ft2, two-story structure is a combination of laboratories, offices, and collaborative spaces to support ongoing particle physics research, including the Deep Underground Neutrino Experiment (DUNE). Currently, scientists and engineers at Fermilab are spread throughout the sprawling campus, and IERC seeks to improve operational efficiency by co-locating research and engineering teams to a single building, with direct access to the principal administrative hub of Wilson Hall. Site work began in 2019. Building construction began in December 2020 and is expected to be completed in 2022.
Architecture firm Perkins & Will designed the IERC, while Arup provided structural engineering, as well as the mechanical, electrical, plumbing and fire protection engineering (MEP/FP), fire & life safety consulting, acoustical consulting, lighting design, information technology & communications (ITC) design, and audiovisual design. TERRA Engineering Ltd. provided civil engineering design services and Patrick Engineering Inc. provided the geotechnical services.
Existing Site Conditions and Utility Work
The location of the building provided numerous challenges to the configuration of existing campus distribution utility arrangements. It will be constructed on top of an existing parking lot hosting major utility distribution and a reflecting pond, which was previously utilized as part of the campus’ stormwater management strategy. The building extents were constrained by the linear accelerator beam line and required safety offsets to the east, the existing Wilson Hall and horseshoe drive to the west, and an access drive to the south.
The list of civil and utility items to address in the design and site construction was significant, and included:
- Modification of the site drainage strategy due to the elimination of a surface detention pond
- Relocation of a portion of the campus’s primary communications duct bank and a significant electrical distribution artery
- Relocation of major storm lines and addition of a lift station
- Relocation of domestic and industrial cooling water distribution pipe networks
Floor Framing Systems
The IERC includes one elevated occupied floor (Level 1), a large roof and a sloping clerestory along the west side of the building. The footprint of the building is roughly 415 feet long and 105 feet wide. Figure 1 shows an isometric of the structural BIM model and Figure 2 is a cross section through the structure.
Level 1 consists of structural steel framing supporting concrete on composite metal deck slabs. A 3” deck with 4.5” normal weight concrete topping was used for enhanced acoustical and vibration performance. The roof and clerestory utilize structural steel framing and an un-topped metal roof deck. Large portions of the roof will support a green roof assembly requiring increased design loads on these areas. The ground floor is composed of slab-on-grade construction.
Based on required lab modules, the typical column spacing in the long direction of the building is 33 feet. Column spacing in the other direction varies with a maximum of ~41 feet. Due to the overall floor-to-floor heights needed to align the IERC with Wilson Hall, as well as required clear height and ductwork for the labs, structural framing depth at Level 1 is limited. As a result, W24s are the largest beams and girders used. The load demands at the roof are less, and lighter W24 sections are suitable in all girder conditions.
As can be seen in Figure 2, there are a number of cantilevered conditions at the perimeter on both levels and the clerestory. On the east face, posts were added between Level 1 and the roof near the ends of the cantilevers to control differential deflections between the floors and limit the required façade joint sizes. These deflections are due to live load and potentially superimposed dead load as the installation of the green roof will likely occur after the façade is installed. On the west face, the Level 1 cantilevers support a portion of the narrow segment of propped roof cantilevers above it via posts.
Initially, it was thought that moment-resisting thermal breaks in the cantilever steel framing would be required at all overhang conditions. After working with Perkins & Will and Arup’s mechanical engineers on revised insulation details and ventilation approaches, it was determined that these thermal breaks would not be required at Level 1 and the roof. Thermal breaks are required at the clerestory cantilevers as it was not possible to get the necessary insulation and air movement in the narrow profile.
Lateral Loading and Systems
The structure was evaluated for both wind and seismic loading. As would be expected, seismic loads control in the direction perpendicular to the short face of the building. In the other direction, the broad face winds exceed the seismic loads by about 8 percent.
Structural steel ordinary concentric braced frames are used as the lateral load resisting system in both primary directions. A seismic response modification factor, R, of 3.0 was used in the design.
The available locations for the brace frames was limited so as not to interfere with project labs. As a result, they are concentrated near the north and south ends of the building. Figure 3 illustrates where these braced frames occur.
Soil borings and analysis indicated that either spread footings or drilled caissons were suitable for the site. Caisson options were provided for 20-foot and 40-foot depths, but would not extend to bedrock as this was 75 to 80 feet below grade. Shallow spread footings could be designed for 3,500psf bearing pressure. Both options were studied early in the design process, and it was determined that caissons were significantly more expensive. As a result, spread footings are used throughout the project.
In most cases, there is limited floor and roof area supported by the columns in the braced frames leading to significant uplifts at the interface with the foundations. Large combined footings are located under the braced frames to provide ballast to the uplift reactions.
Providing a building which would be flexible for current and future uses was an important design driver. From a structural perspective, this is addressed in the following ways:
- Level 1 Design Load: While the majority of Level 1 could have been designed for typical office loading, it has instead been designed for a live load of 100psf. This will allow for future program changes that may be more demanding from a strength and serviceability perspective.
- Cabling Trenches: The western side of Level 1 has included 2” deep trenches at 11 feet on center running along the top of the beams. These align with the typical office modules and allow the ITC cabling feeds to be connected to workstations anywhere along the length and reconfigured as needed without the need for dropdowns from the ceilings.
- Column Transfers: The locations of columns in the east-west directions, which work for both the ground floor labs and Level 1 spaces, are not the same in some areas. In the middle of the Level 1 floorplate, an MEP-dedicated zone occurs over a large length of the building. Columns are placed directly adjacent to this on each side so as not to impact the layout and flexibility of the surrounding office and collaboration spaces. The western column does not align with the ground floor columns and has to be transferred (refer to Figure 2).
- Braced Frame Locations: As noted above, the braced frames have been located to the north and south of the ground floor labs. While it was possible to find locations in the current lab layouts that would have accommodated braces between them, this was not done to allow future reconfiguration or expansion of the labs.
Very sensitive equipment will be used in the ground floor labs, requiring vibration criteria up to level VC-C, which is 32 times more stringent than typical office spaces. Two sources of potential vibrations were considered – the surrounding site and adjacent spaces within the building.
Initially, a survey of the existing site was contemplated to determine if any significant sources of vibration were present. After consultation with Arup’s acoustic and vibration consultants who noted that the site is not located near any typical source issues, such as railroads, it was decided the site survey was not necessary.
However, it is very possible that vibrations from the spaces next to or above the labs could find their way in and cause issues. Each of the labs also have overhead cranes for moving components, which are supported from the building columns or, in some cases, dedicated crane columns. In order to mitigate this possibility, the slabs within each of the labs are isolated from the surrounding slabs and all columns are kept outboard of these isolation joints. Based on past experience with labs requiring VC-C, a 12” thick slab is used in all labs and an 8” thick everywhere else.
At the northern end of the building, there will be a lab known as the Argon Cube. The lab will feature a large, five-foot-deep pit, which will support large vats of liquid argon. A 25-ton overhead crane will be used to move the vats and other components around this lab. The north face of the Argon Cube will be all glass and will be column-free for over 60’. To span this distance while supporting the crane, an approximately 70” deep, architecturally-featured castellated beam will be employed. While most cranes run on top of the supporting beam, in this instance, it will be supported on the inside face of the bottom flange. Figure 4 shows the isometric of this lab.
Wilson Hall Connection
An important part of the collaboration aspect of the IERC is a two-story connection to existing Wilson Hall. The ground floor connection is slab-on-grade construction and aligns vertically. Level 1 and the roof of the connector are steel-framed and require a slight slope down to align with the existing floor elevations. An expansion joint is provided at the interface with Wilson Hall to avoid any vertical or lateral load added to it. A pair of columns are added just before the interface to support the connector, and lateral loads are taken back to the IERC. A feature stair connects the two levels within the connector. Figure 5 illustrates an isometric view of the connector structure.
When completed in 2022, the Integrated Engineering and Research Center (IERC) will be a fantastic addition to the world-renowned Fermilab campus, allowing for much enhanced collaboration between engineers and scientists. Allowing for flexibility in how the building will be used now and in the future was a major driver in the structural design.