【作者】 孙强；

【导师】 朱彤；

【作者基本信息】 大连理工大学 ， 水工结构工程， 2011， 硕士

【摘要】 近年来,工程结构的损伤检测成为建筑工程领域研究的热门课题。对于简单结构的损伤诊断与分析已经有比较成熟的方法,但对于大型复杂结构来说,损伤位置、程度等则难以诊断和分析。本文以辽宁省辽阳市中华大桥的承载能力和加固问题为背景,首先,建立了大型的钢筋混凝土结构梁桥的损伤模型,分两个步骤进行了准确分析。第一步采用直接损伤诊断方法,即运用全面的桥梁检测技术,对主梁和主要的连系构件进行了损伤检测,进行初步损伤诊断和分析；第二步是利用第一步所得到的直接损伤信息,使用基于优化设计和灵敏度技术的模型修正法,进而调整初始损伤桥梁模型的几何与物理参数等,以使模型计算值与实际测量结果相吻合(在合理的误差范围内)。从而,建立更加准确而且全面的大型结构的损伤模型。本文研究的主要内容包括：(1)对损伤中华大桥进行现场试验检测。辽阳市中华大桥为预应力钢筋混凝土T型梁式结构桥,对于评估既有桥梁的使用性能和承载能力、研究结构构件的受力行为等任务,都要以桥梁试验检测为前提。首先,通过无损检测技术检测T型主梁混凝土的强度、缺陷等数据,为桥梁的试验模型和有限元数值模型的材料性能提供数据依据；第二、通过检测仪器量测T型主梁间、主梁与桥墩支座间、表面铺装等的连接状况,并与损伤前的设计数据进行比较,为梁系间连接损伤程度进行评价,得出桥梁主要损伤类型；最后,通过静载试验、动载试验,得出最能反应桥梁承载力的各梁跨中关键位置(L/4、L/2和3L/4)点处挠度值、应力和应变值,为ANSYS建立损伤数值模型提供对比依据。(2)建立桥梁的初始损伤数值模型。经过桥梁全面检测,初步确定了能够直接影响承载力的损伤类型,采用考虑混凝土开裂的三维弹塑性实体有限元法,建立桥梁的初始模型,进一步分析了混凝土的开裂,对中华大桥的破坏肋梁和预应力锚固端进行了细部模拟,并且,材料的本构关系的选取,并不是采用ANSYS预定义的本构关系曲线,而是采用单元表自定义的本构关系。(3)基于优化理论的模型修正。本文采用优化理论的一阶优化方法对初始桥梁模型进行了模型修正。首先,对初始模型进行灵敏度分析,选取对结构最为敏感的设计参数,比如,杀死肋梁破坏单元的体积、模型网格划分尺寸、混凝土的弹性模量、结构几何尺寸等,有利于减小计算量,提高计算效率。选择具有突出优点的优化理论模型修正法,可以借助ANSYS中的优化计算模块进行计算,从而解决了多单元大型复杂结构在计算上存在的困难。(4)采用修正后的有限元模型进行极限承载力的仿真计算,对预应力混凝土T梁桥的开裂、屈服和破坏全过程进行模拟分析,包括开裂前、开裂后和极限状态时的应力、挠度和裂缝情况。在求得桥梁承载力的同时,对桥梁的剩余承载力进行了分析,对中华大桥做出了安全评价。(5)损伤桥梁的加固研究。本文在承载力评定基础上,对中华大桥严重损伤肋梁进行了钢筋焊接、填筑混凝土补强,外加钢板加固肋梁。然后,又建立了加固后的有限元模型,按照规范加载,求得反应承载力的主梁挠度,应力与应变值,并与加固前的承载力数值进行了比较,分析验证了加固方法的有效性。更多还原

【Abstract】 Recently, the structural damage detection is becoming a hot research subject in the present engineering field. There have been mature methods for damage diagnosis and determination simple structures, however not like this for the large complex structures. In this paper, based on ultimate bearing capacity and reinforcement problem of Zhong-hua bridge, creating damaged finite element model of large steel reinforced concrete structural bridge to accurately analyze the damaged bridge via two steps. First step:with comprehensive bridge detection technology so called direct damage diagnosis method finding out probable damage locations and degree, and then analyzing specific structures further more to prepare for the second step; two step:using model updating based on optimization design and sensitivity analysis technology to optimize the geometric and physical parameters in order to create comprehensive and accurate large finite element bridge model. The main contents include:(1) Field detection for damaged Zhong-hua bridge. Zhong-hua bridge is pre-stressed reinforced concrete structural bridge. Estimating created bridge service property and bearing capacity, researching on mechanics behaviors of structures etc. are on the premise of bridge detection. Firstly, with non-destructive testing technology detecting concrete strength and defect of T main beams to prepare for the comparison of detected model and finite element model; Secondly, with detecting instrument detecting structural components such as main beams, bridge piers, bearers etc., evaluating damaged degree of structural components based on comparison of detected results, even getting main damaged style; Last, via static test and dynamic test getting the deflection of (1/4,1/2,3/4) span and stress, strain to prepare for creating damaged model accurately.(2) Creating primary damaged model of bridge. Defining damaged styles which are directly related with bridge bearing capacity, and using 3-d elastic-plastic entity finite element method considering on concrete crack to create primary damage model of bridge. Further more, researching on the concrete crack nature and simulating damaged ribbon strips and pre-stressed anchor end precisely, and then, choosing material constitutive relation which are not predefined from ANSYS but from strength test value of concrete core-sample.(3) Model updating based on optimization theory. In this paper, updating the primary finite element modal of bridge with first order optimization method based on optimization theory and sensitivity analysis. Firstly, according to sensitivity analysis, choosing the most sensitive structural design parameters such as volume of killed ribbon strips element, finite element meshing size, concrete modulus of elasticity, structures size etc., which is beneficial to improve computational efficiency. Outstanding optimization theory model updating can use optimization module of ANSYS to deal with complicated calculation of multi-element complex structure.(4) Solving the updated finite element model of bridge and researching on crack, yield and destroy of T main beam including stress, strain and deflection on the pre-cracking, post-cracking and ultimate condition. After getting the ultimate bearing capacity of bridge, further more analyzing remaining bearing capacity of bridge and evaluating the safety of bridge.(5) Researching on damaged bridge reinforcement. Based on bearing capacity evaluation of Zhong-hua bridge, reinforcing the seriously damaged ribbon strips. There are three main measures, including pouring concrete, steel welding, steel plate welding reinforcement method. And then, creating reinforced finite element model, and calculating reflection of main beam and relevant stress, strain, comparing with non-reinforced damaged model to prove that reinforcement method is very efficient.更多还原