Experimental And Theoretical Analysis Of Reinforced Concrete Members Under Corrosion Fatigue Condition

A study of characters of reinforced concrete members under corrosion fatigue conditions is an important aspect of engineering durability problems. In this thesis, an experimental program was carried out on fatigue properties of reinforced concrete members induced by pre-corrosion and corrosion. The fracture mechanism of corrosion fatigue for the reinforced concrete beams and the coupling action between corrosion and fatigue are analyzed. A check method of normal section of reinforced concrete members subjected to corrosion fatigue is proposed. Moreover, the development and prediction method of fatigue cumulative damage based on the test data are obtained. The thesis is an important part of the project of National Natural Science Foundation of China-Dynamical characters and reliability research of reinforced concrete structures under corrosion conditions (No. 50078009), the contents of which include nine chapters as follows.In the first chapter, the significance of this study and the relevant literatures are expounded. Meanwhile, the historical and present background of the research on corrosion fatigue of reinforced concrete is introduced systematically. Based on the existing problems, the objectives of this paper are put forward.In the second chapter, the experimental programs including the mechanics properties of materials, details of beam specimens, apparatus of static and fatigue test are introduced. Moreover, the test procedure, the test parameters and the test data acquisition method are determined.In the third chapter, experimental research is carried out on beam specimens subjected to static and cyclic loading under corrosion without pre-existed cracks, corrosion with pre-existed cracks cases respectively. The carrying capacity of beam specimens under static loading reduces a little with lower degree of corrosion, whereas, the fatigue life of beams reduces significantly under fatigue loading. It indicates that reinforced concrete members subjected to cyclic loading are more dangerous than that subjected to static loading when they are experienced the same corrosion.In the fourth chapter, experimental investigation of beam specimens is carried out subjected to cyclic loading under the conditions of air, fresh water and salt solutions respectively. The effects of conditions on fatigue life and fatigue damage evolution are analyzed. The results show that the fatigue life of beam specimens reduces significantly under corrosion conditions and fatigue loading. The fatigue damage criterion is that steel bar is ruptured rapidly, which is one of severe failuremodes of reinforced concrete members. Corrosion fatigue damage evolution is related to conditions and levels of cyclic stress.In the fifth chapter, the corrosion potential of steel bar embedded in beam specimens subjected to loading in fresh water and salt solutions is measured. Experimental results show that cycle loading accelerated the corrosion of steel bar. The conclusion that corrosion fatigue is caused by corrosion conditions and cyclic loading can be proved.In the sixth chapter, the tests of steel bar fracture extracted from the beam specimens subjected to corrosion fatigue aimed to scan electron microscopy and analyze chemical components of rupture surface are conducted. In corrosion media, cracks source region, fatigue development region and rupture region also exist on the steel bar rupture surface caused by flexural fatigue loading. The decrease of fatigue life is caused by the action of corrosion media and flexural tension stress. Meanwhile it is related to the complex stress of steel bar in cracking and the stress state of the cracking section. The actions accelerate the initial cracks emerging and spreading, which exists during the whole process from fatigue development to rupture.In the seventh chapter, the check method of normal cross-section of reinforced concrete flexural members subjected to corrosion fatigue is discussed. The determined method and principles for the failure mode, ultimate state and damage criterion etc. are...