基于性能的抗震设计是我国桥梁抗震规范的未来发展方向，它目前迫切需要一种简化分析方法来计算桥梁的塑性地震反应。推倒分析方法有希望满足这种需要，但目前其塑性范围的理论基础尚不严密，导致计算效果不稳定，因此有必要进一步研究。本项目以包括非规则梁桥在内的连续梁桥为例，拟采用理论推导、非线性时程分析、振动台试验等手段，开展以下研究工作：（1）进行连续梁桥的弹塑性地震反应特征的精细化研究，探索桥墩屈服后的振型耦合机理，揭示结构瞬间振型、惯性力模式、位移形状等的变化规律；（2）开展能力谱和非弹性需求谱的构建机制研究，确定获得能力谱的合理推倒分析方法，建立适应结构屈后刚度比变化等需要的非弹性需求谱；（3）在考虑偶然性因素的基础上，进行基于推倒分析的地震位移需求的简化预计方法研究。本项目研究成果将完善推倒分析的塑性理论，并提出通用于不同形式连续梁桥（主要为直线桥）的基于推倒分析的地震位移需求的简化预计方法。

Performance-based seismic design is the future development direction of Chinese seismic design code for bridges, which extremely needs one simplified analysis method to calculate the plastic seismic response of bridges. The simplified prediction of seismic displacement demand based on pushover analysis is capable of facilitating the process of displacement-based seismic design and achieving the idea of performance-based seismic design. However, more research work is required to improve the theoretical basis in plastic range and stabilize the calculation convergence. With continuous bridges, including the irregular continuous bridges, as the object of study, this research project will use theoretical analysis, inelastic time history analysis, shaking table test and other approaches to improve the theoretical basis of pushover analysis. Firstly, the study of elastic-plastic seismic response characteristics of continuous bridges will be carried out to explore the modal coupling mechanism, and to reveal the evolution rules of the structure instantaneous modes, the inertia force model, the displacement figure and other parameters. Secondly, the structural mechanism of the capacity spectrum and the inelastic demand spectrum will be studied to obtain the reasonable pushover analysis method which can build the capacity spectrum, and to get the reasonable inelastic demand spectrum which can adapt to the variations of post-yield stiffness ratio and other parameters. Finally, influences of the material nonlinearity, the earthquake uncertainty, and other accidental factors will be considered to study the simplified prediction method of the seismic displacement demand based on pushover analysis. The project outcome can improve the theoretical basis of pushover analysis in plastic range, and obtain the simplified prediction method of seismic displacement demand based on pushover analysis, which is applicable to various kinds of straight continuous bridges, and can reduce the their seismic design cost and improve their seismic design theory.