Vibrations induced in buildings by road traffic or railways generally exhibit larger amplitudes in the vertical direction than in the horizontal direction. However, in small-scale buildings such as detached houses in Japan, structural vibration modes of the building dominated in motions in the horizontal direction can be excited, which results in amplifications of horizontal vibrations at upper floors in the building. As a result, both vertical and horizontal vibrations can affect the habitability of those floors. The guideline for evaluating environmental vibrations in buildings published by the Architectural Institute of Japan prescribe evaluation methods for horizontal and vertical vibrations separately by direction. Therefore, there are challenges in applying these methods to evaluate combined vertical-horizontal vibrations. In this study, laboratory experiments were conducted to measure subjective responses to combined vertical–horizontal vibrations. University and college students participated in each experiment using an electrodynamic shaker capable of presenting biaxial, i.e., vertical and horizontal, vibrations to a person on the shaker platform. Input stimuli used in the experiments were generated based on traffic-induced vibrations measured in residential environments. The measured subjective responses were compared with several metrics defined in the current international and national standards.
Matsumoto et al. (2025) studied this question.