A Study on Seismic Response Analysis of Long Spanned Systems Subjected to Multiple Excitations Having Large Displacement

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Tuis study deals with the experimental response analysis of large scaled three dimensional structures such as plant piping systems and frame type structures.In this basic work, particular intension is focused on the dynamic behavior of these systems due to multiple seismic excitations simultaneously given load from different directions. A mock-up three dimensional piping model having about 18.0m length with flanges was taken as a typical structure and vibration test was performed by using large scaled shaking table and also actuator which can provide axial displacement loading to the piping. From this testing, characteristics related to displacement response of the piping elbow and bending moment of the flange part were evaluated.Followings are main results obtained from this experimemtal investigation.1. When large amplitude loading was additionally given to the axialdirection during table excitation, seismic stress and response force on the fixed portions such as restraints clearly increased. Also, 1st and 2nd model frequencies and corresponding dainpings became larger compared with the case having no axial loading.2. Displacement response of the straight portion of the piping remarkably increased after the axial loading. This value was much larger than the response at the resonant excitation by the shaking table.3. Large bending moment appeared at the flange portion when axial displacement loading was provided. This bending moment value kept quite stable at the axial shaking resonance, however, dominant fluctuation of the value was observed at the resonance excitation from the perpendicular direction.