We perform vibration analyses to address atypical vibration-sensitive architectural features
Unusual and dramatic architectural features often tend to be very flexible and susceptible to vibration. A roof-suspended, glass-sided conference room was incorporated into the second floor of a corporate headquarters. The conference room was to be supported only from the roof structure above. Typically, roof structures are lighter-weight than floor systems because the gravity loads are significantly lower. In this case, walking-induced vibration in the conference room was evaluated to determine if the occupants would cause motions that others might find objectionable. Roof-mounted tuned-mass dampers were recommended to provide vibration mitigation.
Several occupants in a high-rise office building complained about the vibration on several floors of the building. In this case, an "open-office" concept is implemented in one corner of the floor. Cubicles with 5-ft high partitions are placed in the space with walkways between cubicle blocks for the occupants. There are no full-height partitions in this area of the building. The structural framing is identical in all four corners of the building, but the open-office fit-out is only present in one corner. The structural system is a 35-year-old poured-in-place reinforced concrete pan joist system and is in very good condition. A structural model of the floor system is created in SAP2000 and provides a fundamental resonance frequency of 5.6 Hz. A vibration survey was also conducted on the floors and confirmed the resonance frequency. The longer span joists in the corner of the building, combined with the absence of full-height non-structural partitions that add stiffness and damping are responsible for the higher perceived vibration in the area. Tuned-mass dampers were proposed to provide vibration mitigation.
Open-web steel joists spanning between steel beams and a thin, non-composite concrete slab provides a relatively cost-effective floor structure. However, this structural system is also extremely susceptible to walking-induced vibration that can be quite disturbing to others in an office space. This structural system is used quite frequently in shopping mall construction where most occupants are walking through the space and are much less sensitive to vibration. A structural dynamics analysis is performed and shows to low frequency modes of vibration that can be "excited" by people walking through the space as others try to work at their desk nearby. Walking-induced vibration analyses are performed to support the on-site vibration survey.
A trampoline park is planned for a second floor location in a shopping mall. Part of the occupied space below the trampoline park is occupied by a banquet facility with ceiling-mounted chandeliers and a projector system. A structural dynamics model of the floor system is developed in SAP2000 and used to predict the transient motion of the floor system to a typical "jump" as inferred from a YouTube video (https://www.youtube.com/watch?v=rLBiEXp1kaE). The analyses suggest the motion of the chandeliers and the projected images/video will be easily detected by people in the banquet space. Vibration mitigation options were presented to the Mall and Trampoline franchise owner.