中文摘要：

为确保港珠澳大桥预制埋床式墩台的设计达到受力性能优良及布筋合理的要求,同时明确桥墩失效过程混凝土开裂及裂缝扩展情况及桥墩极限承载能力,采用强化有限元方法（AFEM）对桥墩失效过程进行了模拟分析。从网格分离技术、实体单元退化理论、桥墩中普通钢筋和预应力钢筋模型以及非线性问题处理方法等4个方面对钢筋混凝土结构开裂及破坏分析中的关键问题进行了讨论,建立了通用的钢筋混凝土结构性能分析技术框架;以受力最不利桥墩为对象,对2种配筋模式竖向荷载作用下的墩身非线性受力行为进行了全过程分析,比较了2种不同配筋对桥墩结构性能的影响,明确了混凝土开裂及裂缝扩展特点。结果表明：配筋方案1的混凝土一旦开裂,裂缝就急剧扩展,裂缝从上墩身快速向中墩身发展,出现竖向和横向变形跳跃;对于配筋方案2,当墩顶出现开裂以后,墩身刚度也明显下降,荷载-位移曲线有一个明显转折点,但未出现跳跃式变化,裂缝宽度也较第1种小,极限承载力提高了约10%,桥墩结构性能较方案1有明显改善;计算结果为桥墩结构设计提供了参考依据,同时也表明,基于增强有限元的混凝土结构失效过程分析方法,可考虑结构的空间效应、分析空间破坏形态,具有形式统一、概念简洁等优点,工程适用性强。

英文摘要：

To ensure that the design of prefabricated bridge satisfies the requirements of good mechanical behavior and reasonable layout of reinforcements in Hong Kong-Zhuhai-Macao Bridge and figure out the cracking process of concrete and its propagation and the ultimate capacity of these piers,the augmented finite element method（AFEM）was employed to simulate and analyze the failure process of concrete.Some key issues on steel concrete cracking and failure analysis were discussed from 4aspects including the strategy of dividing the mesh into mathematical and physical part,the degenerated solid element theory,modeling of regular and prestressed bars inpiers and solving methods for nonlinear equations.Besides,the technical framework of performance analysis for common concrete structures was established.Taking the piers bearing most unfavorable stress as research object,the nonlinear behaviors of the piers with two different kinds of reinforced bars under vertical load in whole process were analyzed and the effects of 2reinforced bars on structural performance of piers were compared and the concrete cracking and its propagation characteristics were determined.The results show that for the scheme 1,after cracking in concrete,cracks expand rapidly from the top part of a pier to the middle of the pier and there is a leaping in vertical and lateral deformation curves.For the scheme 2,when cracks initiate at the top part of a pier,the stiffness of the pier decreases significantly and there is an obvious turning point in the load-displacement curve.But there is no leaping change.Meanwhile,the crack width is smaller than that in scheme 1and its ultimate load capacity increases by 10%.As a consequence,scheme 2is better than scheme 1in terms of pier structure performance.These results provide a reference for the pier structural design which also shows that the method based on AFEM can analyze the spatial effect and the failure mode of the concrete structure.This method has the advantages of uniform form,concise concept and so on