Photoelastic analysis of stress waves in building subjected to vertical impact under laboratory earthquake experiments

In an earthquake occurring directly under a city, the vertical impact induced from the source may cause a large amount of damage to a column and beam of the building. Model-based simulations are carried out with photoelastic material in order to examine the effect of a vertical impact on the building in the case of a near-field type earthquake. The dynamic photoelastic method combined with strain gages is utilized to conduct direct full field and real time observations of stress waves in a building due to vertical impact in laboratory earthquake experiments. The conditions under which vertical impact loading is applied to the model building in a controlled laboratory environment are derived from the data recorded for the 1995 Hanshin-Awaji earthquake in Japan. The experimental apparatus with which an impact of a longitudinal stress pulse is able to be applied to a model of a real building is shown. It is estimated from our earthquake simulations that large dynamic stress concentrations are produced in the beam–column joints of the building by the vertical impact arising from a seismic source located directly below a surface.