Jimena Rosas

In densely populated urban zones, seismic performance evaluation of strategic infrastructure during seismic events has become more challenging because the distance between surface and underground structures has been shortened to optimize the urban environment functionality. This is even more important in transit transfer stations, which usually comprise tunnels, bridges, and buildings, in which wave propagation interference is exacerbated. This paper explores the seismic interactions between on-ground and underground structures in soft-soil environments, focusing on a typical urban modal transfer station in Mexico City. The study is conducted through comprehensive parametric analyses using 3D numerical simulations in FLAC3D (v.6.0), considering both intraplate and interplate earthquakes, to assess the effect of differences in their frequency content, duration, and intensity. Multiple scenarios are considered in the numerical study, and the relative distances among the structures are varied to investigate both detrimental and beneficial interaction effects, and to identify the zone of influence where this interaction leads to ground motion variability. The study’s findings established the key variables in the interaction between underground and on-ground structures, providing valuable insights into the seismic design and retrofitting of urban infrastructure in densely populated areas.

Seismic performance evaluation of on-ground structures can be significantly affected by their in-teraction with underground structures. This effect becomes more relevant in densely populated areas where transportation systems such as tunnel metro lines and stations are commonly 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 modal transfer stations, comprised of bridge-building-tunnel systems, located in the high-plasticity Mexico City clays. Through a series of three-dimensional finite difference numerical models developed with the software FLAC3D, both detrimental and beneficial interaction effects among these structures are analyzed, establish-ing 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. Dis-tances among each structure were varied to cover a wide range of scenarios and to narrow poten-tial interaction effects. From the results gathered in here, the modification of seismic demand of the building and bridge is examined, and in turn, the cases where detrimental or beneficial interaction are established, identifying de interaction mechanisms within the simulated system.