Abstract
There are few studies on the dynamic-response mechanism of near-fault and far-field ground motions for large underground structures, especially for the branch joint of a utility tunnel (UT) and its internal pipeline. Based on the theory of a 3D viscous-spring artificial boundary, this paper deduced the equivalent nodal force when a P wave and an SV wave were vertically incident at the same time and transformed the ground motion into an equivalent nodal force using a self-developed MATLAB program, which was applied to an ABAQUS finite element model. Based on near-fault and far-field ground motions obtained from the NGA-WEST2 database, the dynamic responses of a utility tunnel and its internal pipeline in different input mechanisms of near-fault and far-field ground motions were compared according to bidirectional input and tridirectional input, respectively. Generally, the damage to the utility tunnel caused by the near-fault ground motion was stronger than that caused by the far-field ground motion, and the vertical ground motion of near-fault ground motion aggravated the damage to the utility tunnel. In addition, the joint dislocation of the upper and lower three-way joints of the pipeline in the branch system under the seismic action led to local stress concentrations. In general, the branch system of the utility tunnel had good seismic performance to resist the designed earthquake action and protect the internal pipeline from damage during the rare earthquake.
Highlights
Traffic jams and the lack of public space caused by the old urban form have greatly restricted the development of cities
As an important infrastructure in the urban underground space, utility tunnels refer to the underground construction of a tunnel space that integrates electricity, communication, water-supply, and
It is necessary to study the seismic response of the utility tunnel to near-fault and far-field ground motions
Summary
Traffic jams and the lack of public space caused by the old urban form have greatly restricted the development of cities. It is necessary to study the seismic response of the utility tunnel to near-fault and far-field ground motions. The research form is relatively narrow, which is not enough to meet the development trend of the diversified structure of utility tunnels, the integrated construction of underground spaces, and the changing social needs [23,24,25]. To study the seismic response of complex underground structures such as the branch system, an input model of the ground motion is explained, which includes the viscous-spring artificial-boundary theory and the deduction of an equivalent nodal force when the P wave and SV wave are vertically incident.
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