Abstract
Traffic vibration causes problems from a viewpoint of habitability occasionally. The characteristic of traffic vibration is non-stationary vibration whose amplitude and frequency change with time. It has been clarified that non-stationary vibration can be evaluated by considering the duration time of the vibration in addition to the amplitude and frequency by previous study. Another characteristic of traffic vibration is multi-axis vibration in which vibration in multiple directions are combined. However, there are few studies on evaluation methods for multi-axis vibration. The aim of our study is to establish an evaluation method for horizontal and vertical dual-axis traffic vibration.
In this study, we conducted sensory evaluation test using the shaking table which can vibrate simultaneous horizontal and vertical dual-axis, and examined the relationship between human sensation for the vibration and acceleration measured on shaking table.
The investigated procedure is described as follows;
1) 18 traffic vibration waveforms measured at the upper floor of a wooden house near a road or railroad were selected.
2)The sensory evaluation test was conducted. At the sensory tests, the panels were made to experience sample vibration on the shaking table and answer how they felt it. The sample vibrations are 72 lateral and vertical dual-axis vibrations and 72 fore-and-aft and vertical dual-axis vibrations which are made by changing the amplitude each of waveforms selected 1) to 4 levels.
3)From the panels answer, we constructed psychological scales of feelings of amplitude, annoyance and discomfort against various vibrations using a method of successive categories.
4)We calculated several kinds of performance value candidates which were supposed to correspond to human sense and examined the correspondence with the psychological scales.
In this study, we revealed that the performance values C(1/√2:1:1)VLT(630ms, 60dB) applicable to the evaluation of horizontal and vertical dual-axis vibration. C(1/√2:1:1)VLT(630ms, 60dB) is a value that takes into account the maximum value of the level value obtained by converting the combining acceleration to a level value and the total time which the level value is 60dB or more. Where, the combining acceleration is the value obtained by combining the RMS acceleration values in each direction. When combining, multiply the RMS acceleration value in the lateral direction by 1/√2, taking into account the fact that the human sense of vibration in the lateral direction is insensitive. The method of calculating from the maximum value of the level value and the duration time is the same method as the performance value of vertical vibration, horizontal uniaxial vibration and horizontal dual-axis vibration presented in previous research. In this study, we clarified the combining ratio in tri-axis even although it targeted horizontal and vertical dual-axis vibration, it appears to be important knowledge for performance value of tri-axis vibration.
