Reduction of equipment-generated damping in the low-frequency range Available to Purchase

Resonant column (RC) and torsional shear (TS) tests are widely used methods to measure the dynamic properties of soils—that is, shear modulus and material damping ratio. An error in material damping measurements related to the use of electromagnetic motors to excite the specimen has been identified (Kim, 1991; Hwang, 1997). The error arises from the interaction between the components of the electromagnetic motor—that is, the solenoids and magnets. An a.c. current passing through the solenoids generates a uniform magnetic field that interacts with the permanent magnets. An oscillating torque can be produced by switching the poles of...