The Fatigue Properties Of Pre-stressed Concrete Structures In An Erosive Environment With Fatigue Subjoining Freezing-thawing Circle

Modern pre-stressed concrete structures are popularly applied to civil engineering, hydraulic engineering and communication engineering, due to their good behaviors. Like other structures, pre-stressed concrete structures may occur durability failure under long-term action of aggressive environments. Engineering some pre-stressed concrete structures, such as the railway bridges and highway bridges, crane beam, marine platforms, in addition to under static load, we must also always bear repetition, such as the role of cyclic loading. With these repeated load to bear, as well as the structure of high-strength concrete, high strength reinforced by the wider use of high stress in the structure of many pieces of state, makes pre-stressed concrete structure of fatigue as a problem that can not be overlooked. However, as domestic and foreign pre-stressed concrete structure application history is still short. System of pre-stressed concrete structure antifreeze study is little, so the pre-stressed concrete structure fatigue properties under conditions of the freeze-thaw cycle is rarer. The study on pre-stressed concrete structure in freezing environment on the fatigue properties, for many freeze-thaw conditions at the Railway Bridge and highway bridge crane beam, marine platforms in the design, theory is of great significance and value.Based on the National Natural Science Foundation project, the design of ordinary concrete beams and two different pre-stressed level of pre-stressed concrete, in the limited time component freeze-thaw cycle fatigue test. Through experiments to study and analyze the number of freeze-thaw cycles and pre-stressed of pre-stressed concrete beams fatigue properties, Focusing on the pre-stressed concrete beams under the freeze-thaw environment fatigue properties, mainly on the following:1,Selection of pre-stressed concrete used in the framework of unilateral configuration tendons of the beam as the object of study. the design of ordinary concrete beams and two different pre-stressed level of pre-stressed concrete, A total of 15 beams, in the limited time component freeze-thaw cycle fatigue test;2,Comparative study of different stress level pre-stressed concrete components antifreeze properties;3,Right engineering major bearing the pre-stressed concrete components antifreeze properties, pre-stressed concrete members in freeze-thaw cycle through different frequency after the fatigue load-damage mechanism;4,Interviewed on the frost-resistant properties of a series of research-based, Through the component dynamic elastic modulus changes in the analysis, pre-stressed concrete itself to freeze-thaw performance.The results showed that pre-stressed level and the number of freeze-thaw pre-stressed concrete beams fatigue properties are quite apparent. Along with the increase in the number of freeze-thaw, pre-stressed concrete beams fatigue properties is significantly declining trend. High levels of pre-stressed beams in the same relative frequency of freeze-thaw dynamic elastic modulus, which showed that The existence of pre-stressed concrete delayed the freeze-thaw damage, therefore, The presence of pre-stressed concrete structure of the anti-fatigue properties is a significant improvement.Fatigue pre-stressed concrete structure in the process of dynamic elastic modulus relative attenuation was the change in the phase two, the second phase of the pilot about the life of about 90%, the relative phase of dynamic elastic modulus of fatigue cycles with linear relationship between changes. Based on experimental measurement, the use of a relatively dynamic elastic modulus of the damage variable attenuation to the definition put forward by a small number of a fatigue test to determine the relative dynamic elastic modulus of the decay rate, which predict the fatigue life of the beam new methodBased on above analysis of experimental results, it can be found that the damage mechanism of PC structures in freezing-thawing circle in test is simulated as the initial damage formed inside concrete under the fatigue loading for fatigue circle. This means that the freezing-thawing circle can be regarded as another kind of fatigue circle. In this paper, two damage models of PC structures are conducted. Based on criterion of revised Miner fatigue damage, twice fatigue damage model is established according to damping phenomenon of relative dynamic elastic modulus in freezing-thawing circles.In this paper, the results of research on the injury mechanism provide a scientific basis and method to pre-stressed concrete structure' design and the durability of pre-stressed concrete structure design studies is improving, so it have important theoretical value and practical significance.