154 B. Pridham et al. The results from Fig. 19.3 were reviewed together with the dynamic deflection characteristics of the FEM to identify ‘quiet’ areas of the level two garage floor structure where a smooth surface and slower vehicle speeds are expected. Following the recommendations, the design evolved to include patient rooms and multiple surgical suites, and a more detailed study was proposed during the construction phase of the project. 19.4.4 Detailed Assessment: Construction Phase Detailed design of the surgical clinic commenced following completion of construction of the parking garage. Consequently, it was possible to conduct vibration testing on levels one and two as part of the design process. Testing was completed with a Chevrolet Silverado Pickup truck travelling at a maximum speed of 15 mph. Three test setups were completed: • Setup #1: truck traversing level two ramp up to level 3 (above future ORs); • Setup #2: truck traversing level 1 speed ramp up to level 2 turn (above patient area); and • Setup #3: truck traversing level 2 turn area, through small parking zone (above patient area). Setups #1 and #2 included recordings of vibrations caused by the truck traversing the expansion joint. Vibration acceleration data was collected for three axes of motion for each test (vertical, north–south, and east–west). Data was recorded concurrently on the level two slab, building columns and on ground on level one. The measurement locations are shown in Fig. 19.4. The locations are labelled according to setup, e.g., location 1.2 is measurement location two, for setup #1. Some key vertical axis measurement results from setups #1 and #2 are summarized in Fig. 19.5. A summary of key results from the tests is as follows: • Structural resonances due to vehicle movements occur at frequencies between 7 and 12 Hz. • Level two slab motions during vehicle movements were as much as 100 greater than recommended vibration criteria for ceiling-mounted surgical equipment and as much as 12 greater than recommended vibration criteria for ceilings in patient care areas. • Measured vibrations on the slab in ramp areas (1.6, 2.5 and 3.2) were 5 to 10 greater than levels measured at location 2.8. This is a result of higher possible speeds and the presence of the expansion joint (surface roughness). • Motions at the columns satisfied the recommend thresholds for patient care areas but marginally exceed recommended thresholds for ceiling-mounted surgical/procedure equipment at the planned OR locations (see Table 19.1). • Vibrations on ground on level one satisfied all recommended vibration criteria during the testing. Based on these observations the team was advised against mounting of medical equipment to the underside of slab or to the building columns. To avoid visual cues of parking garage motions and disturbance to occupants, the team was advised against support of lighting fixtures, screens and monitors from the underside of the slab. Finally, a high risk of structure-borne noise was identified in the areas near the speed ramp and the team was advised to avoid connection of building services or architectural elements in this area. 19.4.5 Vibration Control Solutions Following a review of the results from the testing the Design Team and Owner adopted the following strategies to control noise and vibration disturbances from the parkade: • speed bumps were not permitted in the parking structure (source control); • secondary steel grillage was added between columns in the level one ceiling space to support building services and architectural elements (path control); and, • framework ‘cages’ supported off an isolated floor slab were added to the ORs and Procedure Room on level one (receiver control). The vibration design of the overhead grillage and OR cages was developed during detailed design. Finite element models of the systems were constructed using the SAP2000 package for use in dynamic analyses. The measurements obtained from the site testing were applied as inputs to response simulations, and changes to framing proposed to arrive at systems satisfying the design criteria. Given the small footprint of the ORs, the response of the systems were estimated using a uniform base excitation applied to the supports. The response of the grillage system was estimated using a multiple-support excitation
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