A Simplified Method for Estimating Differential Displacement in Consideration of Structural Nonlinearity and Coupling Between Adjacent Viaducts During Earthquake

Railway viaducts responds in different vibration period during earthquake, which causes relative displacement between adjacent viaducts. Seismic running safety of railway vehicles are significantly affected by the differential displacement at the ends between longitudinally adjacent viaducts. This study introduced a simple estimation method for the differential displacement based on the vibration characteristics of a single structure, in consideration of structural nonlinearity and coupling between adjacent viaducts during earthquake. First of all, Statistical investigation of the vibration characteristics of existing structures revealed that Equivalent natural period ratio ranges within 1.0 to 2.0 when the adjacent structure are different structural types. Secondly, time-history analyses are performed based on SDOF-system in order to quantify differential displacements during earthquakes considering the nonlinearity. Relative displacement increase with differential equivalent period between the adjacent structures. And then, the influence of the coupling between adjacent viaducts on the relative displacement depends on their vibration period ratio. The relative displacement decreased when the vibration period ratio of adjacent viaduct is close to 1.0, whereas it is increased when difference of vibration period ratio of adjacent viaduct is large. Finally, the proposed method can estimate the differential displacement in the structures with high accuracy of ±30%, independently of the hysteric character of the structure.