考虑主余震型地震动随机场的高墩大跨刚构桥抗震整体可靠度研究

Recent seismic hazards due to large-size earthquakes reveal that the strong aftershock causes significant damages on structures. While the present provisions have not involved these effects. The modelling of mainshock-aftershock sequence-type ground motion field and the relevant theories and methods of structural seismic design are of pressing issues. In this project, the random function based spectral representation and proper orthogonal decomposition (POD) schemes with merely 2 or 3 elementary random variables are systematically developed. The dimension reduction model of multi-dimensional and multi-support random ground motion excitation is established to simulate stationary or non-stationary, Gaussian or non-Gaussian, and mainshock or mainshock-aftershock earthquake processes. The effectiveness of the dimension reduction model of random ground motion field is validated by Monte Carlo simulation and strong earthquake records, respectively. In essence, the dimension reduction model of stochastic ground motion field is consistent with the principal of probability density evolution theory. Thus, it is natural to integrate the dimension reduction model with the probability density evolution theory to implement the probability density evolution analysis of high-pier and long-span continuous rigid frame bridge under the mainshock-aftershock sequence-type earthquake excitation. According to the principal of equivalent extreme-value event, an updated structural reliability method, involving different ground motion inputs, multiple failure indexes and multiple failure modes, is developed to implement the global seismic reliability evaluation of high-pier and long-span continuous rigid frame bridge subjected to the mainshock-aftershock sequence-type earthquake. Besides, the applicability of the proposed approach is validated by model tests. The present project would lay a solid foundation for the seismic performance optimization design and control of the complex engineering structures.

近年来的大震震害表明，强余震对结构的破坏作用显著，而现有抗震设计规范尚未考虑主余震序列对结构的不利影响，亟需开展主余震地震动场建模和相关结构抗震设计理论与方法研究。本项目拟基于随机函数的谱表示和本征正交分解方法，建立用2~3个基本随机变量精确表达平稳或非平稳、高斯或非高斯、主震型或主余震型的多维多点地震动随机场降维模型，通过Monte Carlo模拟和强震记录验证降维模型的有效性。进而，结合概率密度演化理论，开展主余震序列作用下高墩大跨刚构桥非线性随机地震反应的概率密度演化分析。在此基础上，基于等价极值事件的思想，通过合理选择损伤指标和破坏准则，考虑不同地震动输入、多个破坏指标、多种失效模式，建立主余震序列作用下高墩大跨刚构桥的抗震整体可靠度精细化分析方法。进一步，通过模型试验验证上述理论和方法的正确性。本项研究将为复杂工程结构基于整体可靠度的抗震性态优化设计与控制奠定关键基础。

大震震害表明，强余震对结构的破坏作用显著，而现有抗震设计规范尚未考虑主余震序列对结构的不利影响，亟需开展主余震地震动场建模和相关结构抗震设计理论与方法研究。首先，在随机向量过程的谱分解（包括谱表示SRM和本征正交分解POD）以及时空随机场的波数谱表示（WSRM）理论基础上，采用随机函数的降维思想，系统地发展了基于谱分解和波数谱表示的降维模拟方法。建立了用2~3个基本随机变量精确表达平稳或非平稳地震、一维或多维地震、主震型或主余震型、离散型或连续型的地震动随机场降维模型，并将该模型拓展到了强风和海浪等随机动力灾害作用的建模中。其次，根据国家抗震规范和实测强震记录，进行了地震动随机场降维模型的参数识别研究，通过对大量实测强震记录的深度分析，建立了主余震的模型参数之间联系，并通过Monte Carlo模拟和实测强震记录验证了降维模型的精确性、高效性和工程实用性。最后，结合概率密度演化理论，开展了多点多维地震作用下高墩大跨刚构桥随机地震反应的概率密度演化分析。同时，基于等价极值事件的思想，提出了可用于评估高墩桥梁结构抗震整体可靠性的失效评价准则，建立了多点多维随机地震作用下高墩大跨刚构桥的抗震整体可靠度精细化分析方法。此外，本项目还对大坝结构在随机地震作用下的整体可靠性进行了综合评价研究，对基于性能的框架-核心筒结构多维抗震整体可靠度进行了研究，以及对考虑结构参数和地震作用双重随机性的框架结构抗震整体可靠度进行了研究。本项目的研究为复杂工程结构基于整体可靠度的抗震性态优化设计与控制奠定关键基础，核心成果可直接服务于第三代结构设计理论。