Correlation effects of seismic components near field in urban circular tunnels with unreinforced concrete liners

Exact seismic evaluation of underground structures such as tunnels requires dynamic analysis, due to the complex dynamic behavior of soil and the interaction of soil and structure. Dynamic analysis in order to simulate the actual seismic response of a structure is possible only with the appropriate acceleration time history (compatible with the local site soil conditions). Considering the vertical component of the earthquake on the site is one of the important factors for achieving the real responses of the structure (such as near fault earthquakes). In this paper, using ABAQUS finite element software, the soil and tunnel system was modeled using linear time histories analysis under four near field recordings of the earthquake, taking into account the various proportions of horizontal and vertical components in the twelve loading combinations, and the correlation effect Seismic components have been investigated by combining different loads on acceleration, stress and strain, axial force, bending moment and shear force maximum in tunnel lining. The studies showed that increasing the vertical to horizontal ratio has a very small effect on the maximum horizontal acceleration on the tunnel Liner. By examining the axial forces, bending moment and shear force, increasing the ratio of vertical components to horizontal has the greatest effect on the axial force response. Also, by comparing the maximum stress and strain under the twelve loading combinations for the selected records, the maximum strain in the tunnel liner is less than the allowable strain rate for the concrete and in the case of loading, the stress in the tunnel liner is greater than the permitted stress Concrete and in the opposite direction are confident.