Experimental Study On Flexural Rigidity Of Reinforced Concrete Beams Under Combined Corrosion And Fatigue

As the most widely used bridge structure in the world,the durability of reinforced concrete beams is particularly important.In the actual service state,RC beam bridges will bear the coupling effect of steel corrosion and fatigue load due to the influence of external forces such as environmental climate and vehicle load.Therefore,the study of bending mechanical properties of RC beam bridges under the combined action of corrosion and fatigue is helpful to evaluate the safety service performance of bridges more accurately.At present,there is no standardized and unified understanding of the failure mechanism and structural performance degradation law under the coupling state of corrosion and fatigue.Aiming at the corrosion fatigue problem of reinforced concrete beams,the bending stiffness and related mechanical properties of reinforced concrete beams are experimentally studied.The specific work is as follows:1)According to the current research status of mechanical properties of corroded steel bars and corroded reinforced concrete beams,the existing theoretical research on fatigue properties of corroded reinforced concrete members is comprehensively analyzed,and the theoretical characteristics and calculation models of corroded fatigue problems of reinforced concrete members are summarized.2)By designing 12 beams to simulate the working state of fatigue,corrosion and their combined action,the flexural behavior of RC beams under the combined action of corrosion and fatigue was tested by electrochemical accelerated corrosion test beams,including material selection,test preparation,loading scheme selection and test mode selection.3)After steel corrosion,the internal bond performance of members decreases,the bond slip between steel bar and concrete increases,the displacement coordination relationship changes,and the non-uniform coefficient of steel bar strain increases.The effects of fatigue load and stress cycles on the mechanical properties of reinforced concrete beams are studied through experiments.4)By setting different loading and corrosion conditions,the effects of combined action and single action of corrosion or fatigue on the corrosion rate of steel bars,concrete strain,mid-span deflection,load-deflection variation law,beam failure characteristics and other aspects of RC beams are compared and analyzed.5)Combining with the existing theoretical research,the applicability of the assumption of flat section is discussed by considering the degradation law of bond performance under the combined action of corrosion and fatigue.The flexural strength of beam section is analyzed by the rigidity analytic method,and the non-uniformity coefficient and non-conformity coefficient of steel strain are introduced.The numerical method of the flexural stiffiless of RC beam section under the combined action of corrosion and fatigue is established.The validity and correctness of the predicted results of the model are validated by the rigid reading value derived from the measured deflection.