Evans J.

Abstract Parking garages designed to be separate, stand-alone facilities, are often very limber, longer-span, slender-section structures. They exhibit vibration characteristics ill-suited for human-occupied office, residential, hospital or other occupancies. Structural expansion or extension of the garage structure proposed for human occupancy should incorporate appropriate floor vibration design parameters. Two garages were investigated, one for an expansion above the parking level and one for continuous slab between garage and occupied structural bays. Vibration spectrum analysis measurements were conducted on garage structural slab surfaces to obtain ambient and vehicle-pass disturbance conditions. There were no ambient activities (other sources) on the measured slabs, but some vibration transmissions from other garage levels contributed to ambient levels. Structural response to heeldrop impacts were measured to determine apparent structural resonant frequencies. Simultaneous measurements were conducted on driveways and adjacent parking bays to determine losses for (a) continuous span and (b) separate spans of different length and resonant frequency. Decoupled topping slabs, 25-38 mm (1-1.5”), on resilient underlayments, 6-20 mm (0.25-0.8”) were measured simultaneously with untreated driveway (no decoupled topping) to determine source to receiver losses. Ambient and disturbed conditions are compared with human perception criteria for “feelable” vibration (re: ISO 2631). Differences between source and receiver are compared for (a) double tee-beam versus post-tensioned flat-slab structures, (b) damped (superimposed mass load) versus undamped slabs and (c) normal slab versus decoupled slabs. Vibration result charts will be shown for narrowband apparent resonant frequency and 1/3 octave spectrum analyses for ambient and disturbed conditions. Garage plans and photos will be incorporated showing the structural column and slab layouts with measurement transducers and analyzer. Design implications for structural continuity between garage structural slabs and floor slabs for human occupancy are discussed with conceptual methods of reducing vibration amplitudes on receiver slabs for continuous and discontinuous slabs.