A Study on Seismic Response Analysis in Consideration of Non-linear Restoring Force Characteristics of Escalator Truss Structure

In the Great East Japan Earthquake, fall accidents of four escalators occurred. In one of these accidents, the escalator that linked the third floor from second floor dropped. This occurred in the commercial facilities of the low-rise, steel-frame building. In general, escalators are usually installed in buildings with one side of them in fixed connection and the other side in free condition. In contrast, they might be installed both sides in the non-fixed style in order to mitigate undesirable excessive deflections induced in the truss-like structures of escalators. However, an escalator truss might break off from the building beams, due to excessive lateral deformations induced in the storey-layers. In a new public notice about the reinforcement of the falling off prevention structure of the escalator after these accidents, a new and improved structure was determined: 1, The structure must include enough overlap allowance, 2, The structure must take backup measures to ensure enough overlap allowance for the escalator truss to not come off from the beam of building, and so it is less likely to drop. During these accidents, it was also considered that a non-fixed part might collide with the beam of building by larger deflections than expected; this collision might cause excessive compressive force and residual displacement. It is necessary to clarify the seismic behavior of the escalator to prevent such an accident. From the above-mentioned background, the object of this research is to construct an analytical model to clarify the seismic response behavior using the non-linear restoring force characteristic of the escalator truss model. In this paper, the multi-linear model is built based on the load-displacement. In addition, the seismic response analysis of an escalator installed in the building is performed using the multi-linear model and the bi-linear model. As result, the bi-linear model is acceptable to evaluate the seismic response.