冻融环境下预应力混凝土受弯构件的疲劳性能研究

发布时间：2019-05-20 05:15

【摘要】：预应力混凝土结构与普通混凝土结构相比具有明显的优越性能，因此被广泛地应用到土木、建筑、水利和交通工程等各个领域。与其它结构一样，预应力混凝土结构长期在侵蚀环境作用下也会出现耐久性失效，，近年来预应力混凝土结构在环境侵蚀作用下的耐久性问题已成为结构工程领域的研究热点之一。从气候条件来看，我国有相当大的地区处于严寒地带，有调查指出我国东北地区很多水工建筑物、桥梁的混凝土或预应力混凝土结构局部或大面积地遭受冻融破坏，造成重大经济损失。对长期处于严寒环境中的预应力混凝土结构，冻融作用是影响结构耐久性一个非常重要的因素，其抗冻性已引起工程界的重视，另一方面，预应力混凝土结构在服役期内承受着静载和频繁的反复荷载作用，如结构自重、车辆荷载、随机波浪力等，其抗力将随损伤的累积而衰减最终导致结构功能退化或失效。目前如何对已建及新建预应力混凝土结构在冻融环境下的疲劳性能进行分析和评估是工程界急需解决的问题，基于此，本文结合国家自然科学基金资助课题“双指标侵蚀环境作用下预应力结构耐久性试验与寿命预测研究”，通过对预应力混凝土构件在冻融与疲劳荷载交替作用下的试验研究，研究了预应力混凝土构件在冻融环境下的疲劳性能。本文完成的主要工作如下： 1.对16根预应力混凝土试件进行了试验研究，探讨了混凝土强度、预应力度、冻融与疲劳交替次数比及疲劳荷载上限的大小对试件外观形态、动弹性模量、跨中挠度、混凝土和钢筋应变变化的影响； 2.通过正交试验分析方法研究了冻融疲劳交替次数比、疲劳荷载上限和预应力度对动弹性模量衰减速率影响的大小；验证了对于试件动弹性模量的衰减，冻融与荷载疲劳之间存在着一定的交互作用； 3..基于疲劳损伤累积理论以动弹性模量为损伤指标建立了冻融疲劳作用下构件的损伤模型并验证了模型的适用性； 4.对冻融与荷载疲劳后的试件截面进行了理论应力分析，并将理论值与试验值进行了对比分析； 5.建立了基于试件动弹性模量衰减和考虑普通钢筋疲劳断裂的寿命预测模型。本课题对预应力混凝土试件在冻融与疲劳荷载交替作用下的耐久性进行了研究，研究成果对于我国北方寒冷地区已建及新建工程在冻融环境下的疲劳耐久性进行评估具有较高的理论意义和实用价值。
[Abstract]:Compared with ordinary concrete structure, prestressed concrete structure has obvious superior performance, so it is widely used in civil, building, water conservancy, traffic engineering and other fields. Like other structures, prestressed concrete structures will have durability failure under the action of erosive environment for a long time. In recent years, the durability of prestressed concrete structures under environmental erosion has become one of the research hotspots in the field of structural engineering. From the point of view of climatic conditions, quite a large area of our country is in the severe cold zone. Some investigations have pointed out that many hydraulic structures in Northeast China, concrete or prestressed concrete structures of bridges are subjected to freeze-thaw damage locally or in a large area. Cause great economic losses. For prestressed concrete structures in severe cold environment for a long time, freeze-thaw is a very important factor affecting the durability of structures, and its frost resistance has attracted the attention of the engineering community. On the other hand, Prestressed concrete structure is subjected to static load and frequent repeated load during the service period, such as structural self-weight, vehicle load, random wave force and so on. The resistance of prestressed concrete structure will decline with the accumulation of damage and eventually lead to the degradation or failure of structural function. At present, how to analyze and evaluate the fatigue performance of newly built prestressed concrete structures in freeze-thaw environment is an urgent problem to be solved in the engineering field. In this paper, based on the project supported by the National Natural Science Foundation of China, "Research on durability Test and Life Prediction of Prestressed structures under the Action of double Indexes erosion Environment", the experimental study of prestressed concrete members under the alternating action of freeze-thaw and fatigue loads is carried out. The fatigue behavior of prestressed concrete members in freeze-thaw environment is studied. The main work accomplished in this paper is as follows: 1. Sixteen prestressed concrete specimens are tested and studied, and the effects of concrete strength, prestress, alternating times ratio of freeze-thaw and fatigue and the upper limit of fatigue load on the appearance, dynamic elastic modulus and mid-span deflection of the specimens are discussed. The influence of strain change of concrete and steel bar; 2. The effects of freeze-thaw fatigue alternation ratio, fatigue load upper limit and prestress on the attenuation rate of dynamic elastic modulus were studied by orthogonal test. It is verified that there is a certain interaction between freeze-thaw and load fatigue for the attenuation of dynamic elastic modulus of specimens. Based on the fatigue damage accumulation theory, the damage model of components under freeze-thaw fatigue is established with dynamic elastic modulus as damage index, and the applicability of the model is verified. The theoretical stress analysis of the section of the specimen after freeze-thaw and load fatigue is carried out, and the theoretical value is compared with the experimental value. 5. A life prediction model based on dynamic elastic modulus attenuation and fatigue fracture of ordinary steel bar is established. In this paper, the durability of prestressed concrete specimens under the alternating action of freeze-thaw and fatigue loads is studied. The research results have high theoretical significance and practical value for evaluating the fatigue durability of new and built projects in cold areas of northern China under freeze-thaw environment.
【学位授予单位】：江苏科技大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU378

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