FUNDAMENTAL STUDY ON EVALUATION METHOD OF HORIZONTAL TRAFFIC VIBRATION FROM THE VIEWPOINT OF HABITABILITY (PART 2): CONSIDERATION OF FORE-AND-AFT VIBRATION AND DUAL-AXIS VIBRATION

Traffic vibration causes problems from a viewpoint of habitability. In recent years, due to the densification of the city and the development of the transportation network, it is difficult to take enough distance between living space and road or railway which are vibration sources. Therefore, the problems due to traffic vibration are increasing. The aim of our study is to establish assessment measures for traffic vibration. The characteristics of traffic vibration are non-stationary vibration whose amplitude changes momentarily and multi-direction vibration. In this study, we conducted sensory evaluation tests using the vibration waveforms measured in the housing, and considered a performance value that is relative to a human sense of vibration. The investigated procedure is described as follows; 1) The traffic vibration waveforms measured at the upper floor of a wooden house near a road or railroad were selected. 2)Two sensory tests were conducted in the same way. The first sensory test is for fore-and-aft vibration, and the other sensory test is for dual-axis vibration. 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 were made by changing the amplitude each of waveforms selected 1) to several 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. The results are described as follows; 1)The performance values VLT(630ms, 57dB), VLT(630ms, 60dB) and VLT(630ms, 62dB) of lateral vibration presented in the previous paper are applicable to the evaluation of fore-and-aft vibration. These performance values consist of the maximum value of vibration level and duration time of vibration. It is written as follows; VLT=VLmax+20 · log10T1/4 Where, VLmax is the maximum value of vibration level (time constant is 630ms), T is total time when vibration level is exceeding 57dB or 60dB or 62dB. 2)Human’s sense of vibration is more severe in the fore-and-aft direction than lateral direction. VLT(630ms, 60dB) corresponding to the same evaluation is smaller by about 2.4 to 4.1 dB in the lateral vibration than in the fore-and-aft vibration. 3)The performance value C(1:√2)VLT(630m