Ground motion duration effect on responses of hydraulic shallow-buried tunnel under SV-waves excitations
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EARTHQUAKE ENGINEERING AND ENGINEERING VIBRATION
Earthq Eng & Eng Vib (2020) 19: 887-902
October, 2020
DOI: https://doi.org/10.1007/s11803-020-0602-x
Ground motion duration effect on responses of hydraulic shallow-buried tunnel under SV-waves excitations Sun Benbo†, Zhang Sherong‡, Wang Chao§ and Cui Wei§ 1. State Key Laboratory of Hydraulic Engineering Simulation and Safety, Tianjin University, Tianjin 300072, China 2. School of Civil Engineering, Tianjin University, Tianjin 300350, China
Abstract: Although intensive research of the influence of ground motion duration on structural cumulative damage has
been carried out, the influence of dynamic responses in underground tunnels remains a heated debate. This study attempts to highlight the importance of the ground motion duration effect on hydraulic tunnels subjected to deep-focus earthquakes. In the study, a set of 18 recorded accelerograms with a wide-range of durations were employed. A spectrally equivalent method serves to distinguish the effect of duration from other ground motion features, and then the seismic input model was simulated using SV-wave excitation based on a viscous-spring boundary, which was verified by the time-domain waves analysis method. The nonlinear analysis results demonstrate that the risk of collapse of the hydraulic tunnel is higher under long-duration ground motion than that of short-duration ground motion of the same seismic intensity. In a low intensity earthquake, the ground motion duration has little effect on the damage energy consumption of a hydraulic tunnel lining, but in a high intensity earthquake, dissipation of the damage energy and damage index of concrete shows a nonlinear growth trend accompanied by the increase of ground motion duration, which has a great influence on the deformation and stress of hydraulic tunnels, and correlation analysis shows that the correlation coefficient is greater than 0.8. Therefore, the duration of ground motion should be taken into consideration except for its intensity and frequency content in the design of hydraulic tunnel, and evaluation of seismic risk.
Keywords: hydraulic shallow-buried tunnel; SV-waves; significant duration; energy dissipation; damage index 1 Introduction The evaluation of seismic risk in hydraulic tunnels remains a crucial problem for the construction process of hydraulic shallow-buried tunnels, particularly in estimating the seismic demand the tunnel could be subjected to from earthquake loading. Earthquakes have three common characteristics that directly influence a structure's response, frequency content, amplitude, and ground motion duration (Towhata, 2010). The main focus of current seismic designs, performance evaluations, and experimental testing of structural responses is on the frequency content and amplitude. While these have been recognized as crucial factors, the definition of the impacts of ground motion duration on structural responses are still not well established (Montejo et al., Correspondence to: Cui Wei, State Key Laboratory of Hydraulic En
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