基于损伤量化的预应力混凝土梁安全性评价研究

发布时间：2018-04-25 14:07

本文选题：钻孔释放 + 钢筋锈蚀　；参考：《东北大学》2015年博士论文

【摘要】：在役预应力混凝土桥梁结构损伤是造成桥梁承载力不足的主要原因,这些损伤主要包括钢筋锈蚀、预应力水平降低、混凝土强度下降、截面缺损和裂缝等。其中混凝上截面缺损和裂缝可直接简单测量,混凝土的强度下降也可由回弹法或钻孔取芯法测量。在役混凝土梁在不破坏的情况下,钢筋的锈蚀无法直接测量,在无预埋传感器的情况下,预应力水平的降低也无法直接测量。本文以钢筋锈蚀和预应力水平下降这两类损伤的量化研究为出发点,基于混凝土的损伤理论,通过试验和有限元模拟,对各种损伤侵蚀下的在役预应力钢筋混凝上梁开展安全性评价研究,主要内容如下：首先,基于钻孔释放的原理,通过有限元手段、实验室内预应力梁的钻孔试验与在役混凝土桥梁的现场试验,通过测量混凝土内的应力水平反推预应力筋的预应力水平,通过与设计初值的比较,引入预应力筋名义锈蚀率的概念把预应力筋预应力的下降等效到名义锈蚀率上来。具体如下：(1)基于混凝土的弹塑性损伤理论与ABAQUS生死单元模块模拟了混凝土钻孔应力/应变释放的初步规律；(2)通过室内与现场试验进一步探讨了应力/应变释放规律、最大释放率及影响因素,并据此给出了被测点混凝上的应力水平和释放工艺过程,为工程应用打下良好基础；(3)基于混凝上的应力水平推导了预应力筋的应力水平,进而计算了预应力筋的名义锈蚀率,为安全性评价提供合理数据。其次,依据不同部位钢筋的锈蚀特点可分为均匀锈蚀和非均匀锈蚀两种情况,对于均匀锈胀,考虑锈蚀产物在界面间隙和裂缝中的填充效应,对Bazant理论模型进行修正,同时引入损伤的概念对混凝土保护层内环向应力进行修正,建立了混凝上保护层开裂时的锈胀力与钢筋临界锈蚀率的损伤模型。对于非均匀锈胀,考虑锈蚀产物在界面间隙和裂缝中的填充效应,以ABAQUS为平台,基于USDFLD子程序,建立钢筋混凝土锈胀开裂的有限元模型,讨论了钢筋直径、保护层厚度、锈胀系数等因素对临界锈蚀率的影响。在这两种模型的基础上,结合Vidal模型,建立裂纹宽度与锈蚀率的关系。最后,基于有限元模型讨论了不同载荷下钢筋锈蚀、混凝土强度下降、混凝土截面缺损以及竖向裂缝四种典型损伤对于梁挠度的影响,并将主要损伤进行两两结合分析,探讨其相关性。应用理论分析法讨论了各类损伤对梁的抗弯承载力及抗剪承载力的影响,并据此给出了各类损伤的权重。在此基础上建立基于规范及损伤相关性的扣分评价方法,并与基于规范的扣分评价方法比较,探讨两种方法的优点与不足。并以后丁香桥为例,把检测方法与安全评价方法应用在现役桥梁上,取得了良好的效果。
[Abstract]:The structural damage of in-service prestressed concrete bridges is the main cause of the lack of bearing capacity of the bridge. These damage mainly include the corrosion of steel bar, the reduction of prestress level, the decrease of concrete strength, the section defect and crack, and so on. The defect and crack of the upper section of concrete can be measured directly and simply, and the strength of concrete can also be measured by rebound method or drill core method. The corrosion of steel bars can not be measured directly without the failure of in-service concrete beams, and the reduction of prestressing force level can not be measured directly in the absence of preset sensors. In this paper, based on the damage theory of concrete, based on the quantitative study of the corrosion of steel bar and the reduction of the prestress level, the experiments and finite element simulation are carried out. The main contents of this paper are as follows: firstly, based on the principle of borehole release, finite element method is used to evaluate the safety of concrete reinforced concrete beams in service under various damage and erosion. The experiment of drill hole of prestressed beam in laboratory and the field test of in-service concrete bridge, through measuring the stress level in concrete and pushing back the prestress level of prestressed tendons, and comparing with the initial design value, By introducing the concept of nominal corrosion rate of prestressed tendons, the reduction of prestressing force of prestressed tendons is equivalent to the nominal corrosion rate. (1) based on the elastic-plastic damage theory of concrete and the ABAQUS birth and death element module, the preliminary law of stress / strain release from concrete boreholes is simulated. The maximum release rate and the influencing factors are given, and the stress level and the process of release on the coagulant at the measured point are given. The stress level of the prestressed tendons is deduced based on the stress level on the basis of the stress level on the basis of which a good foundation is laid for engineering application. Furthermore, the nominal corrosion rate of prestressed tendons is calculated, which provides reasonable data for safety evaluation. Secondly, according to the corrosion characteristics of steel bars in different parts, it can be divided into two cases: uniform corrosion and non-uniform corrosion. Considering the filling effect of corrosion products in interfacial gap and crack, the Bazant theoretical model is modified. At the same time, the concept of damage is introduced to modify the inner circumferential stress of concrete cover, and the damage model of corrosion expansion force and critical corrosion rate of steel bar is established. Considering the filling effect of corrosion products in interfacial gap and crack, the finite element model of corrosion expansion cracking of reinforced concrete is established based on USDFLD subroutine based on ABAQUS, and the diameter of steel bar and thickness of protective layer are discussed. The influence of factors such as the coefficient of rust expansion on the critical corrosion rate. On the basis of these two models, the relationship between crack width and corrosion rate is established by combining with Vidal model. Finally, based on the finite element model, the effects of four kinds of typical damage, such as corrosion of steel bar, decrease of concrete strength, defect of concrete section and vertical crack, on beam deflection are discussed, and the main damage is analyzed by pairwise analysis. To explore its relevance. The influence of various kinds of damage on the flexural and shear bearing capacity of beams is discussed by means of theoretical analysis, and the weight of various kinds of damage is given. On the basis of this, the evaluation method based on criterion and damage correlation is established, and the advantages and disadvantages of the two methods are discussed compared with the method based on criterion. In the future, the clove bridge is used as an example, the detection method and the safety evaluation method are applied to the existing bridges, and good results are obtained.
【学位授予单位】：东北大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TU378.2

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