Bidirectional seismic response of assembled monolithic subway station-aboveground structure system under artificial bedrock ground motions

Abstract

Assembled monolithic subway station partly synthesizes the advantages of cast-in-place and precast subway stations. However, the related seismic response analysis considering the influences of vertical ground motion and aboveground structure is still scant. In this study, we firstly performed the statistical analysis on bidirectional bedrock ground motion parameters (response spectrum, duration and envelope function) using KiK-net data, and obtained some suggested values of the above parameters. Then, four sets of artificial bedrock ground motions with statistical meanings were generated and a three-dimensional finite element analysis of the seismic response of an existing two-story three-span subway station was conducted. The main results are summarized below. (1) The significant damage to assembled monolithic station under far-field strong motion firstly occurred at side middle slab; middle slab, upper column and related grouting sleeve joints were more damage-prone. (2) When horizontal peak ground acceleration stayed constant, overall the damage of far-field motion was stronger than that of near-fault motion. (3) Vertical ground motion obviously accelerated the damage progresses of various structural members at various positions, then aboveground structure further enhanced the damages and vertical displacement responses of parts of top slab. (4) For the axial force time-history of upper column during far-field strong motion, aboveground structure uplifted the baseline, and vertical ground motion increased the amplitude and advanced the obvious drop of the baseline, among which the latter effect of vertical ground motion on assembled monolithic station was stronger than that on cast-in-place station. (5) Vertical ground motion enhanced inter-story displacement during far-field strong motion, among which the influence on the upper story of assembled monolithic station could be obviously amplified by aboveground structure, and the amplification effect lagged behind the influence of vertical ground motion. Based on the results of this study, some suggestions for the seismic design of subway station are also provided.