基于多维多点非平稳随机振动的山区高墩桥梁抗震计算理论及应用研究

The objective of this proposal is to present a stochastic seismic analysis approach and to conduct theoretical stochastic parametric analysis for developing the China design specifications on high-pier railway bridges under spatially varying ground motions (SVGMs). The stochastic seismic analysis approach of bridges under tridirectional nonstationary spatial ground motions has been proposed and implemented in the general finite element platform with high computational efficiency, using which the high-pier railway bridges in the mountainous areas are studied in details. The proposal firstly resolves the shortcoming of conventional pseudo-excitation method (PEM) that requires large time-of-computation and being very hard to be implemented on the general finite element platform, in the stochastic seismic analysis of large yet complex structures under SVGMs. The proposed achieves high computational efficiency and accuracy and can be readily implemented on the general finite element platform for stochastic seismic analysis of structures under multiple excitations. Secondly, the high-precise integration method in conjunction with absolute-response-oriented method is proposed to achieve thousands of times' computational efficiencies without loss of accuracy, which is very promising in stochastic analysis of some very complex engineering structures. Finally, the proposed theoretical scheme is applied to seismic analysis of high-pier railway bridges located in mountainous sites, where effects of ground motion spatial variability, local site effect, soil-pile interaction effect, ground motion dimensionality and nonstationarity are considered. In addition, comparative analysis of different bridge type and pier type, various pier height and difference of adjacent pier height, and other factors affecting seismic performance of high-pier railway bridges are included in the theoretical parametric studies. The proposed theoretical stochastic seismic analysis approach is anticipated to be adopted as a theoretical approach in the design code, while conclusions obtained from the theoretical parametric studies would be of prime significance on developing the China seismic design specification for high-pier railway bridges under SVGMs.

本研究目的是为多点地震激励下高墩铁路桥抗震规范草拟提供一套理论计算方法，同时通过大量参数分析为未来此规范的草拟奠定基础。首先，提出了虚拟激励法对复杂结构在多维多点地震动下随机响应分析的理论框架，解决了传统虚拟激励法计算繁琐及在通用有限元中模拟困难的问题，该方法更高效地实现复杂结构多维多点虚拟激励法与通用有限元软件的结合；其次，提出了将精细积分法与绝对位移直接求解法结合算法，上千倍地提高计算效率，进一步推动随机理论在实际工程中的应用；最后，将该理论用于山区高墩铁路桥抗震分析，研究地震动空间效应，场地效应、桩土耦合作用、及地震动多维性和非平稳性对山区高墩铁路桥梁的影响，同时对比分析不同桥式、墩型、墩高、墩高差等结构因素对高墩桥梁抗震性能的影响，为其桥抗震规范的实现提供重要的分析结论。本文提出的理论计算方法与大量的参数分析结论将对未来多点地震激励下高墩铁路桥的抗震规范的实现具有重要的意义。

本项目以山区大跨度高墩桥梁为实际工程背景，为高墩铁路桥梁抗震规范的草拟提供了一套快速的随机振动计算方法，且研究了多点地震激励下高墩桥梁的动力行为。将随机振动的虚拟激励法与有限元软件紧密结合，解决了传统虚拟激励法在有限元中实现困难的问题，首次完成了虚拟激励法的非平稳地震动在有限元软件的实现；基于ANSYS平台将精细积分法与虚拟激励法结合，大大提高了非平稳地震作用下桥梁动力响应的计算效率，将随机振动理论推广并应用到实际工程之中；详细研究了地震动空间效应，场地效应对大跨度高墩桥梁碰撞间隙的影响，建立了多点激励地震动空间模型，推导了场地条件与桥梁墩底处地震加速度的关系；也建立了高墩铁路桥梁的有限元模型，并推导了高墩桥梁梁体碰撞间隙宽度需求量与场地条件和震级的关系；同时，进一步将虚拟激励法与系统可靠度理论结合起来，提出了快速系统可靠度计算方法，并获得了中国博士后基金项目，本项目也正在向桥梁结构参数和地震动双随机性发展，能更全面的考虑随机性对桥梁结构响应的影响。本项目的研究成果为山区高墩桥梁抗震设计规范的制定提供理论和数据支撑。本项目已发表相关论文SCI 6篇，EI 6篇，获得软件著作权1项，资助硕士生5名，博士生5名。项目投入经费25万元，各项支出基本上与预算相符，剩余5.5824万元，将用于后续研究之中。