C+S March 2021 Vol. 7 Issue 3 (web)

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. Lab Vibrations Very sensitive equipment will be used in the ground floor labs, re- quiring vibration criteria up to level VC-C, which is 32 times more stringent than typical office spaces. Two sources of potential vibra- tions 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 sup- ported 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.

Figure 3: Location of Steel Braced Frames (noted in red)

on revised insulation details and ventilation approaches, it was deter- mined 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. Foundations 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 de- sign 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 col- umns 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. Flexibility Considerations 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 de- signed 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

Figure 4: Isometric of the Argon Cube Lab



march 2021

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