Eccentric Mass Shakers
Three large eccentric mass shakers have been developed to enable forced vibration testing of full-scale buildings.
- MK-14A: An omni-directional eccentric mass shaker capable of low frequency, high amplitude harmonic loading. It has an operating frequency range of 0.1 - 4.2 Hz and maximum load of 20 kips.
- MK-15: Two uni-directional eccentric mass shakers with a wide frequency range (0-25 Hz) and large force capability (100 kips each).
MK-15 eccentric mass shaker during UCSD Elliot Field phase 1 testing
For all three large eccentric mass shakers (MK-14A and MK-15's), a wireless control option was added to enable the operator (in the mobile command center) to remotely control the shakers. Furthermore, synchronization between the MK-15 shakers is possible with the use of the new Vector motor drives. Two or more shakers, spaced apart on a structure, can provide the tested structure with torsional as well as translational forcing. It can also enhance the response of one particular mode over another by force appropriation, which can be very helpful in distinguishing between closely spaced modes of vibration.
|Footprint||JPG PDF||JPG PDF|
|Force-Frequency Curve||JPG PDF|
Portable Eccentric Mass Shaker
4600A portable eccentric mass shaker
A portable eccentric mass shaker has been added to the shaker profile of the nees@UCLA facilities. The shaker consists of a bolted aluminum frame which supports two vertically oriented shafts or axles. Two sets of circular weights, whose total eccentricity is continuously adjustable over the range of 0-980 lb-in., are permanently installed, one set about each vertical axle. The 0-980 lb-in. weight set is referred to as the "small" weights. The small weights are intended for use over the frequency range of 0-20Hz. To generate more force at lower frequencies, a large set of weights can be attached to the small set resulting in shaker eccentricity which can be adjusted between 0-4600 lb-in. Shaker operation is limited to 10Hz with the large weights installed.
The linear inertial shaker capable of broadband excitation was developed jointly by Anco Engineers, dSPACE Inc. and Sysendes. The linear shaker is replete with digital controllers (PID, linear quadratic and adaptive) for more accurate control. The controllers were implemented on a dSPACE D1103 DSP board, and are capable of either force or displacement control. The nominal performance specifications for the linear shaker are a peak force amplitude of 15 kips, 30 inch stroke and 90 gpm servovalve capacity.