STUDY OF WHOLE BODY VIBRATION ON STANDING SUBJECT

Abstract

In present days of busy life people are using cars, buses and trains for commuting to other places or offices. They are daily exposed to vibrations not only in sitting but also in standing position in busses and trains. However, only a few studies of the transmission of floor vibration to the knees and to the heads of standing subjects have been carried out. Most of the relevant investigations concern the transmission of vertical vibration. There are many more variables that could influence the transmission of vibration in each axis, which needs to be investigated. In this study the transmissibility of the floor to head and floor to knee under the sinusoidal vibration magnitude of lm/s2 r.m.s in vertical as well as in lateral direction between the frequency ranges from 3-15 Hz, is found. In the present work, a handrail is constructed to provide support for standing subjects as found in U.P.S.R.T.0 buses. Transmissibility is calculated in two postures (holding the handle and handrail), it was found that transmissibility of floor to head is more in vertical direction while holding the handle than holding the handrail while the transmissibility of floor to knee is found to be almost same in both postures. The current study proposed a 4 degree of freedom analytic biomechanical model of the human body in a standing posture in vertical direction to investigate the biodynamic responses of different masses and stiffness. Model parameters were calculated using curve fitting technique, provided within Wolfram Mathematica 7.0. Based on the calculated model parameters, mode shapes and natural frequencies are calculated. The principal resonance of the vertical apparent mass, driving point mechanical impedance and floor to head transmissibility is found at 5 Hz. It is also found that changing the stiffness parameter directly affects the biodynamic responses and also affects the resonance frequency whereas changing the damping parameter has inverse affects on the biodynamic responses.