The assessment of fragility of underground civil defense structures is of paramount importance in ensuring their functionality and enhancing safety in seismic-prone regions. This study aims to explore the evolution law of seismic fragility for a shallowly buried large-section underground civil defense structure in soft soils, employing advanced data-based approaches. To achieve this, a two-dimensional (2D) nonlinear finite element model of the soil-civil defense structure interaction system was established, integrating data-based parameters and insights. Subsequently, the cloud and incremental dynamical analysis (IDA) methods were employed to develop a probabilistic seismic demand model for the shallowly buried large-section civil defense structure, effectively utilizing data-based approaches to account for the nonlinear characteristics of the soil and the uncertainties of input seismic motions. Based on this model, seismic fragility curves were generated using different seismic intensity measures (s), and the evaluation of s was carried out by the efficiency and practicality analyses of s. These curves were then systematically compared with other existing empirical and analytical fragility curves. The developed fragility curves were subsequently applied to assess seismic risk and resilience for a typical underground civil defense structure in soft soils, offering valuable data-driven insights into the structure's performance under various scenarios. The results indicated that the seismic fragility of the civil defense structure increases with the softening of the soil. Moreover, this study highlighted the substantial influence of structural typologies and local soil conditions on the fragility of civil defense structures, particularly the seismic fragility of underground structures characterized by shallowly buried and large-section, and demonstrating the utility of data-based approaches in comprehending complex interactions. The efficiency and practicality analyses highlighted that ground surface s outperform bedrock s and acceleration-type s over velocity-type s. The proposed seismic fragility curves indicated that the exceedance probability for each damage state gradually approaches 100% with the increase of seismic intensity. Finally, a case study was presented on the use of seismic fragility curves to assessment of seismic risk and seismic resilience of civil defense structure. The outcomes of this research, enriched by data-based approaches, can serve as invaluable references for seismic performance assessment, risk analysis, and resilience evaluation of typical civil defense structures in similar soft soil sites.

中文翻译：

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软土中浅埋大断面地下人防结构地震脆性与回弹评估：框架与应用

地下民防结构的脆弱性评估对于确保其功能和提高地震多发地区的安全性至关重要。本研究旨在采用先进的基于数据的方法，探讨软土中浅埋大断面地下人防结构的地震易损性演化规律。为了实现这一目标，建立了土壤-民防结构相互作用系统的二维（2D）非线性有限元模型，整合了基于数据的参数和见解。随后，采用云和增量动力分析（IDA）方法开发了浅埋大断面民防结构的概率地震需求模型，有效利用基于数据的方法来考虑土壤的非线性特性和不确定性输入地震运动。基于该模型，利用不同地震烈度测度生成地震易损性曲线，并通过对s的效率和实用性分析对s进行评价。然后将这些曲线与其他现有的经验和分析脆弱性曲线进行系统比较。随后，开发的易损性曲线被用于评估软土中典型地下民防结构的地震风险和弹性，为各种情况下结构的性能提供有价值的数据驱动见解。结果表明，人防结构的地震易损性随着土体的软化而增大。此外，本研究强调了结构类型和当地土壤条件对民防结构脆弱性的重大影响，特别是浅埋大断面地下结构的地震脆弱性，并展示了基于数据的方法在理解地震脆弱性方面的实用性。复杂的相互作用。效率和实用性分析强调，地表优于基岩，加速型优于速度型。所提出的地震易损性曲线表明，随着地震烈度的增加，每种损伤状态的超越概率逐渐接近100%。最后，给出了利用地震易损性曲线评估人防结构地震风险和抗震能力的案例研究。这项研究成果通过基于数据的方法得到丰富，可以为类似软土场地中典型民防结构的抗震性能评估、风险分析和复原力评估提供宝贵的参考。