Buckling Constitutive Of Corroded Steel Bars In Compression Concrete Pieces

Reinforced concrete structures are widely used in housing construction,highways,bridges and bay ports due to the advantages of easy access,durability and integrity.Nowadays,reinforced concrete structures are facing many problems and challenges.In the offshore environment,freezing environment and saline-alkali environment,reinforced concrete structures are suffering from different degrees of corrosion,which often significantly reduces the durability and bearing capacity of the structures.In areas with active crustal plates,the safety of building structures is threatened by earthquake,and the steel bars in concrete are prone to buckling after being subjected to earthquakes,thus reducing the bearing capacity of the structures or even completely losing the bearing capacity.Under the action of earthquake,the performance of structures is affected by corrosion degrades faster,and the coupling effect of steel bars corrosion and steel bars buckling will have a worse impact on the safety of building structures.Therefore,it is very necessary to carry out research on the buckling of corroded steel bars in compression concrete specimens,the proposed reinforcement buckling constitutive model considering the effect of corrosion provides a reference for the prediction of the damage degree and performance degradation of steel bars in reinforced concrete structures.The main research contents are as follows:(1)Based on the research background and significance,the research status of steel bars corrosion and steel bars buckling at home and abroad was investigated and analyzed.The influence factors of steel bars corrosion,the influence of chloride ion corrosion on the performance of steel bars and concrete,the influence of reinforcement corrosion on the seismic performance of RC specimens,the influence factors of steel bars buckling and several classical steel bars buckling constitutive models are summarized.Finally,the main research contents of this paper are introduced from the material level,component test level and finite element analysis level.(2)This paper introduces the whole process of specimen design and manufacture under four conditions of corrosion rate and four conditions of slenderness ratio,carries out material property test to determine the performance of concrete and steel bars,conducts electrified accelerated corrosion test and axial load test on the specimens,observes the corrosion damage and stress damage patterns of the specimens under different conditions at different periods,and finally analyzes the influence of different steel bars corrosion rate and slenderness ratio on the force-displacement curve trend,initial stiffness,peak load and ductility of the specimen was studied.The results show the corrosion of steel bars has a significant adverse effect on the bearing capacity of the specimens,but has a small impact on the initial stiffness of the specimens;the increase of slenderness ratio has no significant effect on the initial stiffness of the specimens,but has a significant adverse effect on the bearing capacity and ultimate displacement.(3)Based on the design of test conditions,Open Sees is used to establish the solid models of non-corroded and corroded specimens、analyze the modeling process、observe the model simulation phenomenon and compare the simulation results with the test results to verify the correctness of the solid element modeling method.Adding five working conditions of corrosion ratio,establishing the model according to the same modeling method,extracting the stress-strain curve and data of steel bars,and discussing the trend of stress-strain curve of steel bars with different corrosion ratios and slenderness ratios,and the influence rule of yield strength,initial stiffness and ultimate strain of steel bars.The analysis shows that with the increase of steel bars corrosion ratios and slenderness ratios,the yield strength and ultimate strain of steel bars decrease,but the initial stiffness of steel bars changes little.(4)The Reinforcing Steel model and the Dhakal-Maekawa model are briefly introduced.Based on the steel bars stress-strain curve and data,and the Reinforcing Steel model,the construction method of the Dhakal-Maekawa model considering the steel bars buckling is applied,the relevant parameters are modified,and the effect of corrosion on the steel bars mechanical properties is considered.A steel bars buckling constitutive model with universal applicability that can consider the effect of corrosion is proposed.(5)The newly proposed steel bars constitutive model is redeveloped by using Visual Studio,and new materials are programmed by means of parameter modification and introduction of new parameters.The fiber model is established and the newly proposed steel bars constitutive model is applied in the model.The force-displacement curve of the fiber model column and the solid model column are compared and analyzed,and the quantitative comparison is made from the initial stiffness,the peak load and the post-peak load difference,which verifies the rationality and applicability of the new constitutive model of steel bars.