Large-span corrugated steel utility tunnels are widely used owing to their large spatial spans and excellent mechanical properties. However, under seismic forces, they may experience significant deformation, making repair challenging and posing a serious threat to personal safety. To study the seismic performance of corrugated steel utility tunnels, an equivalent orthotropic plate was introduced, and a simplified three-dimensional refined finite element model was proposed and established. Considering the site conditions of the structure, the structural parameters, and different seismic input conditions, a detailed analysis was conducted using the endurance time analysis method. The results indicated that the simplified model agreed well with the experimental results. The seismic input conditions significantly affected the relative deformation of the structure. Under the action of P waves (compression waves) and P + SV waves (compression and shear waves), the deformation of the upper part of the structure was relatively uniform, whereas under the action of SV waves (shear waves), the deformation of the crown was more evident. The greater the burial depth of the structure, the stronger the soil-structure interaction, and the smaller the increase in relative deformation. In soft soil, the structure was more likely to be damaged and should be carefully observed. Additionally, increasing the corrugation profile of the steel plates during the design process was highly effective in enhancing the overall stiffness of the structure. Based on the above calculation results, the relative deformation rate was proposed as a quantitative index of the seismic performance of the structure, and corresponding values were recommended.

It is acknowledged that various sources of uncertainties play a vital role in the seismic vulnerability of slope systems, while many studies ignore these sources in seismic assessments. This is because seismic performance and fragility evaluation of large soil-structure systems is challenging and computationally intensive by conventional nonlinear dynamic analysis methods, especially when the modeling uncertainties are considered. To address this challenge, this paper proposes a new framework for addressing uncertainties in the seismic evaluation of earth slopes using the Endurance Time Analysis (ETA) method. The ETA method is a dynamic pushover procedure in which the slope is subjected to a limited number of artificial intensifying records, and seismic responses are obtained over a continuous range of seismic intensities. For the purpose of this study, probabilistic two-dimensional numerical simulations of earth slopes are created using the FLAC software by considering the soil parameters uncertainty. Latine Hypercube Sampling is employed to generate random simulations. The models are then subjected to the intensifying prefabricated excitations based on the ETA method, and the fragility curves of the slope are obtained in three damage states by considering and not considering uncertainties. The results indicate that as the endurance time, which is a kind of intensity measure, increases, the uncertainties of seismic responses also increase. This shows that the effects of uncertainties become more significant when the slope is subjected to strong ground motions. Additionally, the influence of modeling uncertainty is negligible in the slight damage state, but significant in the extensive damage state. The proposed framework provides an effective and rapid way for performing the fragility and associated risk analysis of earth slopes considering uncertainties.

The seismic response analysis of subway underground structures only considers the impact of a single mainshock, ignoring the aftershocks, which may cause more serious secondary damage within a short time after strong earthquakes. To investigate the seismic performance of underground structures under sequential earthquakes and improve the understanding of aftershocks, we analyzed the dynamic response of subway station structures under mainshock-aftershock sequences. A typical two-story and three-span subway station was selected as the prototype, and a finite element model of a soil-underground structure interaction was established. Based on the basic concept of endurance time and design response spectrum of relevant seismic standards in China, an endurance time acceleration function was generated, and nine mainshock-aftershock sequences were constructed. Thereafter, the seismic responses of subway stations under the action of mainshock-aftershock sequences, such as lateral deformation characteristics and damage failure law, were discussed and analyzed. The results show that the endurance time method can be used as a new and efficient method to study the seismic performance of underground structures subjected to mainshock-aftershock sequences. The effects of aftershocks on the damage and lateral displacement of underground structures were preliminarily revealed. The structural deformation response of each layer varies greatly due to the different damage states of the mainshock. The maximum story drift theta of the structure increases with the increase of loading seismic intensity. From the perspective of seismic damage and relative deformation, the structural dynamic response, considering the effect of sequential earthquakes, is greater than that of the mainshock alone, which reflects the disadvantage of aftershocks in seismic design. The results provide a reference for seismic analysis and damage assessment of structures under sequential earthquakes.