Selecting the severest seismic design ground motions for cut-and-cover underground structures

This paper proposes an innovative method for selecting the severest design ground motions based on overall damage characterization of underground structures. The selection procedure is elaborated using 4749 ground motions, exemplifying various forms of underground structures in class III sites. Initially, an overall damage index, predicated on dual-parameters of deformation and hysteretic energy dissipation, is proposed as an engineering demand parameter to quantitatively depict the failure state of underground structures. Subsequently, given the inadequacy of a single intensity measure in evaluating the damage of underground structures, composite intensity measures with higher correlation to the index are constructed using partial least squares regression method. The composite intensity measures served as the damage potential characterization parameter for ground motions concerning underground structures. Consequently, alternative databases of severest design ground motions are derived through these composite intensity measures. The ground motions in this alternative database are employed as inputs for nonlinear dynamic analysis of underground structures. The severest design ground motions are identified by ranking the overall damage index to underground structures. Finally, a comparison with traditional selecting method demonstrates that the proposed method yields more accurate results.