A discrete-parameter model of the human body under a variety of impact situations is developed, emphasizing the spine as the main load-carrying element. The model simultaneously accounts for axial, shear and bending deformations of the discs, the viscoelastic behavior of the discs, the variable size and mass of the vertebrae and discs, the natural curved shape of the spine, and the eccentric inertial loading caused by the head and trunk. A trapezoidal seat acceleration pulse is applied in the sagittal plane.
Numerical results generated for the pilot ejection problem, using a 10g peak acceleration pulse with finite rise time, show that bending deformations of the spinal column appreciably affect the overall body response. The effects of pulse rise time and horizontal components of acceleration are evaluated. Results are in the form of time-histories for the axial force, shear force, and moment at the disc-vertebra interfaces.