Experimental Seismic-Performance Evaluation of Isolation/Restraint Systems for Mechanical Equipment; Part I: Heavy Equipment Study
by S. Fathali and A. Filiatrault
This report describes an experimental research aimed at evaluating the seismic performance of an
isolation/restraint system, typical of the systems designed by the ASHRAE members, supporting heavy
mechanical equipment. The ASHRAE-type isolation/restraint system consisted of coil springs and rubber
snubbers constraining the displacement in the horizontal and vertical direction. The heavy HVAC-type
mechanical equipment used as test specimen was a centrifugal liquid chiller. System-identification and
seismic shake table tests were conducted on the test specimen mounted on four of the isolation/restraint
systems. The test plan included variation of design parameters of the restraint component of the systems
namely the gap size, rubber pad thickness and hardness, and the static capacity. The tri-axial acceleration
response at the center of mass and corners of the chiller, displacement response of the chiller, and the
dynamic forces induced into the isolation/restraint systems were recorded in each test. The experimental
results were analyzed to determine the response amplification due to the engagement of the restraint
components, to investigate the sensitivity of the seismic performance of the isolation/restraint systems to
the variations of their restraint component design parameters, and to compare the static design capacity of
the restraint components to their dynamic (actual) capacity. A companion report, MCEER-07-0022, focuses on light mechanical equipment.
