Fundamental study on seismic response of escalator (Seismic response analysis using SDOF escalator model)

Abstract

The escalator is one of most important vertical transportation measures to connect each every one of storey-layers in buildings. During severe earthquakes, escalators are not only shaken by themselves, but withstand lateral relative deflexions induced in the structures or buildings installing them. Therefore, escalators are usually installed in the buildings with one side of them in fixed connection and the other side in free condition or utilized both sides in the non-fixed style in order to mitigate undesirable excessive deflexions induced in the truss-like structures of escalators. However, in the 2011 Pacific Ocean Tohoku-Oki Earthquake, fall accidents of four escalators occurred in the three locations. Escalator truss might come off from the beam of the building, because excessive lateral deformations were induced in the storey-layers with more than assumption where the accidents happened. During these accidents, it was also considered that a non-fixed part might collide with the beam of building by larger deflexions than expected occurred in the sliding parts; this collision might cause excessive compressive force and residual displacement in the escalator truss might be caused (Miyata et al.). Projects for the building standard development promotion program have been conducted by Japanese ministry of land, infrastructure and transport (MILIT) in order to improve and maintain the building standard by applying non-government organizations such as research institutes, private enterprises and universities. In these projects, investigations regarding elevators and escalators have been implemented since 2010. Especially in 2014, the loading tests were carried out to clarify the behaviour in such excessive condition using eight full size escalator-truss model at the Chiba NT campus testing cite of Tokyo Denki University. The results obtained in the tests have already been applied to the building standards law revision and the notice amendment (Tokyo Denki University and MILIT). From the above-mentioned background, the object of this research is to construct an analytical model to clarify the seismic response behaviour using the non-linear restoring force characteristics of the escalator truss model. In this first step of the study, an analytical model using a single degree of freedom model considering not only the non-linear behaviour of escalator truss but also the sliding friction occurring between the beams of buildings and escalators has been developed.