轴压荷载下干湿循环—硫酸盐侵蚀耦合作用混凝土长期性能

发布时间：2018-01-19 06:33

本文关键词： 混凝土轴压荷载干湿循环硫酸盐侵蚀元胞自动机长期性能　出处：《北京交通大学》2013年博士论文　论文类型：学位论文

【摘要】：摘要：硫酸盐侵蚀混凝土的过程是一个涉及物理、化学、力学等多方面作用效应的复杂现象,其影响因素众多、危害很大,是混凝土耐久性研究的重要内容之一。实际工程中,当混凝土结构处于荷载与硫酸盐侵蚀环境因素耦合作用时,其作用机理更为复杂。在这种耦合作用下,如何判定结构的功能,即安全性、适用性与耐久性是否满足设计、施工、使用等方面的要求,需要对混凝土的长期性能等进行研究分析。然而,在现有的相关研究中,多因素耦合作用下混凝土性能试验方法还没有统一,造成研究成果缺乏规律性并存在普遍争议,尤其是环境因素作用下混凝土长期变形的试验方法还没有相应的标准遵循。这些因素都有可能会造成研究过程中出现偏差,并导致工程设计和施工的不安全,兹待解决。在混凝土结构的设计中,往往取混凝土28天的力学性能或者是一个定值作为其材料性能的判定指标。然而,混凝土材料性能是随时间不断变化的,导致结构性能也在随时间不断变化,当这一变化在结构处于危险状态时则更为突出,会危及结构的安全,因此,获取和使用混凝土当前状态的材料性能指标十分重要。目前,荷载与环境多因素耦合作用下混凝土性能研究还很不充分,处于起步阶段,尤其是对于荷载与干湿循环硫酸盐耦合作用下混凝土依时性力学性能的研究分析仍是空白。本文围绕轴压荷载、干湿循环、硫酸盐侵蚀三重因素共同作用下混凝土的力学、耐久、徐变性能开展了试验研究和理论研究。主要工作如下： (1)通过对国内外已有硫酸盐侵蚀混凝土试验方法比较与分析,根据工程实际环境下混凝土硫酸盐侵蚀的特点,设计了轴压荷载下干湿循环-硫酸盐侵蚀耦合作用混凝土长期性能演变规律的试验方案； (2)开展了压应力、干湿循环和硫酸盐侵蚀作用下混凝土长期性能的试验研究,主要考虑了浸泡方式、应力水平和硫酸盐溶液浓度等因素。试验结果表明,多因素的耦合作用,由于多因素之间选择的水平不同,耦合后对混凝土性能的复合作用会产生或延缓或加速的效应； (3)基于描述物理系统的元胞自动机模型,制定了混凝土内各元胞状态在时间和空间上的演化规则,并考虑由于混凝土的不均匀性引起的硫酸根离子在混凝土内传输的不确定性,建立了用于模拟多因素耦合作用下硫酸根离子侵蚀混凝土的元胞自动机模型； (4)基于材料损伤力学的有效应力理论与混凝土徐变B3模型,建立了硫酸盐侵蚀作用下混凝土轴心受压构件徐变模型。进一步考虑与干湿循环影响系数相结合,给出了干湿循环硫酸盐侵蚀下混凝土徐变预测模型。上述模型的预测结果与试验数据吻合较好； (5)在混凝土损伤本构理论的基础上,考虑硫酸盐侵蚀混凝土的特征,建立了硫酸盐侵蚀混凝土的损伤计算模型,并结合徐变对混凝土应力应变关系影响规律,建立了干湿循环硫酸盐侵蚀下混凝土依时性应力-应变关系模型。该模型能较好的与试验数据曲线对应,并能合理地模拟其破坏过程。
[Abstract]:Abstract: the process of sulfate attack of concrete is a complex phenomenon involving physical, chemical, mechanical and other aspects of the effect, its influence factors, great harm, is one of the important contents of the durability of concrete. In practical engineering, when the concrete structure in the coupling action of load and environmental factors of sulfate attack and its mechanism more complex. In this coupling, how to determine the structure of the function, namely the safety, applicability and durability whether meet the design, construction, use and other aspects of the request, the need for concrete long-term performance of research and analysis. However, in the existing research, test methods of concrete performance coupling factors are not unified, which results the lack of regularity and widespread controversy, especially the test method of long-term deformation of concrete under the action of environmental factors has not. The standards should be followed. These factors may cause a deviation in the research process and cause the unsafe design and construction of the project to be solved.
In the design of concrete structures, the mechanical properties of concrete is often take 28 days or a fixed value as the index to determine the properties of the materials. However, the material properties of concrete is constantly changing with time, the structural performance is also changing with time, when the change in the structure is in danger is more outstanding, will endanger the safety of the structure, therefore, get and use the index of the current state of material performance of concrete is very important. At present, the environmental load and multi factor coupling properties of concrete are not sufficient, in the initial stage, especially for research on cooperation and load coupling of concrete under sulfate wet and dry cycle dependent mechanics the performance analysis is still blank.
In this paper, the mechanics, durability and creep properties of concrete under the combined action of three factors including axial compression load, dry wet cycle and sulfate attack have been studied experimentally and theoretically.
(1) according to the domestic and foreign existing sulfate corrosion test method of concrete comparison and analysis, according to the characteristics of concrete sulfate attack engineering environment, the design of the axial load under dry wet cycle - sulfate long-term performance coupling evolution of concrete test scheme;
(2) the compressive stress, experimental study on the long term performance of concrete and wet dry cycles under sulfate attack, the main consideration of the immersion method, stress level and sulfate solution concentration. The experimental results show that the coupling effect of many factors, the choice between multiple factors at different levels, the coupling effect of composite action on the performance of concrete will be produced or delayed or accelerated;
(3) the cellular automaton model to describe the physical system based on the established rules of the evolution of cellular state in concrete in time and space, and consider the transmission of sulfate ions caused by inhomogeneity of the concrete in concrete uncertainty for analog cellular automaton model of concrete sulfate erosion coupling the role of multi factor is established;
(4) the effective stress theory and concrete creep model of B3 material based on damage mechanics, established the model of creep of axially compressed members of concrete under sulfate attack. Further considering the combination of wet and dry cycle effect coefficient, given the dry wet cycle under sulfate attack of concrete creep prediction model. The prediction results of the model agree well with the test data good;
(5) in the concrete damage constitutive theory, considering the characteristics of sulfate corrosion of concrete, a calculation model of sulfate corrosion damage of concrete is established, combined with the concrete creep stress strain relationship, a wet and dry cycle under sulfate attack of concrete stress-strain relationship model of the model should be in accordance with the. Well test data and curve, and can reasonably simulate its failure process.

【学位授予单位】：北京交通大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TU375

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