Seismic performance of tunnel-building-urban bridge systems in soft clays

Abstract

Seismic performance evaluation of on-ground structures can be significantly affected by their interaction with underground structures. This effect becomes more relevant in densely populated areas where transportation systems such as tunnel metro lines and stations are located nearby urban bridges, and buildings. This paper presents the findings of a numerical study carried out to conduct the seismic evaluation of a typical urban bridge-building-tunnel system, located in the high plasticity Mexico City clays. Through a series of three-dimensional finite difference numerical models developed with the software FLAC^3D, both detrimental and beneficial interactions effects among these structures are analyzed, establishing zones around each structure in which this interaction leads to ground motion variability, as well as the impact on both the building and bridge seismic performance. The parametric study was carried out considering both normal and subduction events for a return period of 250 years. Distances among each structure were varied to cover a wide range of scenarios and to narrow potential interaction effects. From the results gathered here, the effect of this interaction on the modification of building and bridge accelerations, and displacements, and, in turn, the seismic demand in on-ground structures due to underground structures, was established.