Abstract
There are high demands on existing railway reinforced-concrete (RC) viaducts to improve not only seismic performance and durability but also utilization of space under the viaducts. Authors have proposed a method of column relocation in which new concrete-filled steel tubular (CFT) columns are installed and existing RC columns are removed. However, the structural system of the viaduct is changed by the column relocation and has columns with largely different stiffness and load-bearing capacity.
The purpose of this study is to observe the seismic behavior of the column-relocated viaducts, focusing on the effect of having frames with different stiffness, load-bearing capacity and deformation capacity. Authors carried out a series of dynamic response analyses and static push-over analyses with 3-dimentional frame models. As a result, it was found that the viaduct with different frames shows a small reaction displacement in 3-dimensional dynamic analysis comparing with the result of non-linear spectrum method using static push-over analysis results. This is because of the cancellation of the displacement components in each frame that have different vibration properties. For this reason, it is possible to calculate the response displacement of the column-relocated viaducts in safe side. On the other hand, the section forces, i.e. bending moment and shear force, increases in dynamic state. Based on these results, authors proposed a simple calculation method using 2-dimentional static push-over analyses for the design of column relocation.
