Sensitivity analysis of the spinal load model used in the draft standard ISO 2631-5

In the 90’s, Seidel et al. have applied a biomechanical approach to develop a new method to assess health effects caused by WBV on seated drivers. Their works were based on the assumption that the intervertebral pressure may cause damage to the lumbar spine and thus lead to low back pain. As the measurement of the intervertebral pressure is too invasive, a finite element model developed by Wölfel GmbH was used as an alternative to calculate transfer functions describing the relationship between vehicle accelerations and intervertebral pressures. These transfer functions were finally coupled to a risk model and encapsulated in a risk assessment software. This assessment method is specified by the draft standard ISO-2631-5.
The INRS has investigated the risk assessment software responses to various input conditions (acceleration input signals, anthropometrical driver parameters and seated postures). Particularly attention was paid on responses to Gaussian random accelerations. An alternative but equivalent method of calculation of the vibration dose used in the risk assessment software is presented. This alternative method, whose theoretical backgrounds were firstly published by Cartwright in 1956, is limited to Gaussian signals. However it has the significant advantage of being able to calculate the vibration dose value without requiring an automatic peak detection algorithm.