Topic
Modal testing
About: Modal testing is a research topic. Over the lifetime, 4047 publications have been published within this topic receiving 64772 citations.
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01 Jan 2000
TL;DR: In this article, the effects of raised access floors on the vibration serviceability of long-span concrete floors were investigated using electrodynamic shaker simulations, and the modal properties of three full-scale floor structures, before and after the installation of various configurations of a raised access floor.
Abstract: There is a current trend towards ever more slender concrete floor structures, which is
resulting in more frequent problems with their vibration serviceability. Predictive
methods for vibration serviceability must consider not only the structures themselves,
but also the non-structural elements which are attached to them, as these may have a
significant effect on the dynamic characteristics of the floor structural system. As there
has been very little past research in this area, this thesis describes an investigation into
the effects of raised access floors on the vibration serviceability of long-span concrete
floors.
The development of a new modal testing facility based on electrodynamic shaker
excitation, which was capable of producing high quality estimates of the modal
properties of full-scale floor structures, is described. This was subsequently utilised to
determine the modal properties of three full-scale floor structures, before and after the
installation of various configurations of raised access floors. The response of these
structures to controlled pedestrian excitation was also measured. Realistic finite element
models of all structures were developed and updated using the results from the
experimental work. These were subsequently utilised for investigation of the
experimentally measured effects of the raised access floors.
It was found that raised access floors had only minor effects on the modal properties of
the long-span concrete floors. Reductions in natural frequencies due to the increased
mass were, to some extent, offset by the slight increases in stiffness following the
installation of the access floors. Modal damping ratios increased for some modes of
vibration, but these changes were rather unpredictable and hence they were too
unreliable to be used in design.
The response of the structures under controlled pedestrian excitation reduced following
the installation of various configurations of raised access floors. The reduction appeared
to be greater for relatively deep access floors (500 - 600 mm) than for relatively shallow
access floors (150 - 200 mm). Therefore, it is recommended that the effects of access
floors may be included in vibration serviceability analyses by applying a reduction
factor to predicted responses calculated by assuming a bare floor. The proposed
reduction factors are 0.9 for access floors where the finished floor height is less than
500 mm and 0.8 for access floors where the finished floor height is 500 mm or greater.
23 citations
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TL;DR: In this article, the authors proposed a new reduction method for predicting the stability analysis of a brake system subjected to friction-induced vibration, which is based on a double modal synthesis.
23 citations
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TL;DR: In this paper, a frequency-modeshape based damage detection technique (FMBDD) was proposed to evaluate the crack location as well as crack depth easily and accurately.
23 citations
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TL;DR: In this article, the effects of multi-site damage on the vibration response of honeycomb sandwich beams, damaged by two different ways i.e., impact damage and core-only damage simulating damage due to bird or stone impact or due to mishandling during assembly and maintenance are studied.
23 citations
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TL;DR: In this paper, a semi-active control approach using a dry friction damper is presented to reduce transient vibrations of a space truss structure, where the control target is to maximize an equivalent damping ratio of the lowest bending mode, which is considered most dominant in its transient vibrations.
23 citations