Numerical Analysis and Tuned Damping of a Floor System

In order to design and specify vibration abatement solutions (via tuned damping) for a multi-bay floor system, a reasonably accurate knowledge of the dynamic attributes of that floor system is required. These can be evaluated numerically (using finite element analysis) and verified experimentally by vibration measurement. Finite element modal analysis allows for the prediction of the natural frequencies, their corresponding mode shapes and modal masses. Vibration measurement enables the finite element model to be fine-tuned and the inherent level of damping in the structure measured. The correlated model can then be used to design tuned mass dampers for the floor system.

floor vibration 1 DEICON recently completed the modeling and analysis of a 16-bay dance floor, with some irregularities in its geometry. As in most floor systems, the vibratory motion of a mode was not just confined to a single bay. For example, the first mode shown in Figure has the shape of a spatial sinusoidal wave vibrating the two adjacent bays an out of phase manner, i.e. as one bay is moving up the other is moving down. The outcomes of the analyses are being used in designing 10 tuned mass dampers (TMDs) for the floor system.

 
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Vibration Control of an Office Floor System Using Tuned Mass Dampers

installed tuned mass damperFollowing the occupants’ (office workers’) complaints about the floor vibration at a certain area in an office building, vibration measurements were conducted by an acoustics consulting firm, the results of which indicated that the floor system was lightly damped and that the vibration associated with occupant activities (mainly walking) was exacerbated by resonant amplification of the first mode of the floor system. Based on the consultants opinion, improvements in the perception of floor vibration could be achieved by installing tuned mass dampers.

DEICON designed and fabricated tuned mass dampers (TMDs) to abate the vibration of the composite steel beam and girder framed floor system. The TMDs were tuned to the first natural frequency of the structure (floor system). The tuned mass dampers added substantial damping to the floor system, lowering its vibration level to an imperceptible level. More

 
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Publication on Tuned Damping of a Balcony System

Cantilevered structures, such as balconies, when subject to human activity such as walking and jumping, can be susceptible to levels of vibration that may be deemed annoying by some users. If the structure is an irregular shape, the affected areas can often be fairly localized, with the rest of the space performing appropriately. Traditional approaches to controlling vibration include stiffening the structure and adding mass. However, in many cases, architectural, structural or cost constraints mean that these are not acceptable solutions, particularly where wholesale design changes would be required to achieve the desired effect in the localized area being considered. Adding damping to the structure, using tuned mass dampers, is a very effective way of controlling vibration. By increasing the amount of energy that is dissipated when the structure oscillates, excessive build-up is avoided. <\p>

ASCE Journal Vol28 article on balcony vibration control

The paper titled “Tuned Damping of Balcony Vibration” on abating the vibration of a balcony system in a performing arts center has recently been published in “Journal of Performance of Constructed Facilities”, a publication of The American Society of Civil Engineers. The subject of the paper is about a collaborative project between ARUP of New York and DEICON on mitigating the vibration in a stack of three balconies using tuned mass dampers. The citation for the paper is:
Kashani, R., Pearce, A., and Markham, B., 2014 “Tuned Damping of Balcony Vibration,” ASCE Journal of Performance of Constructed Facilities, Volume 28, Issue 3 (2014). More

 
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Webinar titled ‘Using Tuned Mass Dampers to Control Floor Vibration’

Walking, amongst other Human activities, is the most common cause of floor vibration that can lead to nuisance in building occupants. Walking-induced floor vibration can cause discomfort in people working or living in the building. Adding architectural features, mass and/or stiffness are commonly viewed as possible solutions to floor vibration problem. Such solutions are costly to install and architecturally unattractive in a new building and difficult to implement in, and cause inconvenience and disruption to the occupants of, existing buildings. An attractive alternative to the above-mentioned solutions for mitigating floor vibration is adding tuned damping to the floor by installing tuned mass dampers (TMDs). Negligible weight penalty, low cost, and ease of installation make tuned mass dampers (TMDs) the most practical, cost-effective, and least disruptive floor vibration control solution for both new and existing floor systems.

DEICON presented a webinar, thru the SE University, titled ‘Using Tuned Mass Dampers to Control Floor Vibrations’ in which the use of tuned damping in reducing the vibration of floor systems was discussed. In the webinar, following a short introduction to floor vibration and commonly used vibration mitigation practices, the concept of tuned damping was discussed. The session continued with the introduction of tuned mass dampers including their make-up, optimal design, and installation. After reviewing case studies, the design of tuned mass dampers for a floor system were demonstrated. The session concluded with a brief discussion of other applications of tuned mass dampers.

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Air Suspended ‘Adjustable Tuned Mass Damper’ Patent

DEICON recently received the ‘Notice of Allowance’ and ‘Notice of Allowability’ from the U.S. Patent and Trademark Office allowing the claims listed in DEICON’s air suspended ‘adjustable tuned mass damper’ patent application. In these tuned mass dampers, only air springs are used as the suspension elements. Active control enables the air springs to provide both damping adjustability and stiffness adjustability and thus be used as both the resilient element (spring) and energy dissipating element (viscous damper). Fine-tuning and re-tuning of air suspended adjustable tuned mass dampers can readily be accomplished thru the software, using their active and semi-active stiffness control features, without physically modifying the hardware. Moreover, self-tuning capabilities can be incorporated into the controller of air suspended tuned mass dampers so that they continuously and automatically fine-tuned themselves to the target frequency.

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