Evaluation of Ramp-Induced Vibration Exposure Level for a Pregnant Woman Commuting Along Urban Roads in Ghana

Abstract

Vibration exposure on humans is a global concern for mechanical and structural engineers as well as occupational health safety regulators. A number of theories and vibration estimation equations have been propounded by researchers as well as international bodies and each technique is associated with some form of limitations in practice. This work is centered on evaluating the exposure level of the vibrations felt on the pregnant occupant’s tummy during wheel-to-ramp banging encounter for a vehicle maneuvering over speed ramps. An instrumented underwear jacket was used to pick signals from volunteered non-belted pregnant occupants during some routine trips along bumpy roads. The jacket makes use of accelerometers and gyroscopic and rotation sensors concealed in its pockets to sense and record the ramp-induced vibration signals. The data obtained from these subjects were evaluated using power spectral density (PSD) and estimated vibration dose value (eVDV). Routine trips for subjects along bumpy roads experienced high energy levels – based on PSD values – than those trips on roads sections that had no speed ramps. The eVDV levels realized were about three-fold that of the recommended levels per the ISO 2631-1and BS 6841 standards adopted. A typical eVDV values of between 58 to 70 ms^-1.75 was found for the average pregnant occupant during short travel times which is above the recommended maximum ISO 2631-1 permissible dose value of 17 ms^-1.75. It is suggested that a detachable pregnant occupant car seat ought to be developed to attenuate the excessive amplitudes of vibration felt by pregnant occupant.