Seismic responses and failure mechanism of the superstructure-integrated underground structure considering the seismic aboveground-underground interaction

The superstructure-integrated underground structure (SIUS) is an innovative infrastructure in an urban city, in which the aboveground part and underground part are coupled together to be a large synthesis structure. During earthquakes, the SIUS is primarily influenced by the soil deformation and structural vibration, and the seismic aboveground-underground interaction (SAUI) would be considerable due to structural characteristics. This paper aims to investigate the seismic response and failure mechanism of the SIUS and reveal the influence mechanism of the SAUI with a quantitative method for the seismic aboveground-underground interaction coefficient (SAUIC). In this paper, a credible numerical model of the whole soil-SIUS system compiled with the viscous-spring artificial boundary is established. The modal analysis of the SIUS is carried out, and the distinctive structural characteristics are discussed. The seismic responses of the SIUS are thoroughly investigated, and the failure mechanism of vulnerable positions is further revealed. Based on the modal frequency response analysis and a novel correlation analysis, the SAUIC is quantitatively proposed to evaluate influence effects of the SAUI on seismic responses of the SIUS. The results show that the SAUI has great influence effects on seismic responses of the SIUS, even changes the seismic failure mode of the underground part to be flexural failure; the quantitative SAUIC demonstrates the SAUI increases with the increasing seismic intensity and increases from outside to inside of the SIUS, and the SAUI would be highly considerable on positions with irregularities in structural stiffness, especially on the aboveground-underground interface.