| Reinforced concrete(RC)frame columns are the main load-bearing and lateral force-resisting members of structures.In the offshore environment of chloride ion erosion,RC frame columns suffer from chloride ion erosion for a long time,which results in corrosion of internal steel bars and progressive expansion and cracking of concrete cover,resulting in the decrease of bond performance between steel bars and concrete under earthquake,thus seriously reducing the service life of RC frame structure as a whole.Therefore,based on the experimental results of accelerated corrosion of RC frame columns under simulated climate,the bond-slip constitutive relationship and reliability calculation of RC columns with rust expansion and cracking under cyclic loading under chloride ion erosion environment are studied in this paper.The main contents include:(1)First of all,based on the experimental results of accelerated corrosion of RC frame columns in simulated climate environment,the existing theoretical calculation models for predicting the area loss of corroded steel bars based on the crack width of corrosion expansion are verified and analyzed.The theoretical calculation model of corrosion crack width of corroded RC frame column and loss of section area of corroded steel bar is obtained by fitting the experimental data under the environment of chloride ion erosion.(2)Based on the existing bond-slip(?-s)constitutive model of corroded and cracked reinforced concrete under monotonic loading and the ?-s constitutive model of uncorroded reinforced concrete under reciprocating loading,?-s constitutive relation of reinforced concrete subjected to reciprocating load is established.The applicability of the constitutive relation of ?-s established in this paper is verified by ANSYS modeling analysis.The calculated hysteretic curve is compared with the experimental hysteretic curve,and the error reason is analyzed.Combining with the calculation model of the width of rust expansion crack and the loss of cross section of rust steel bar,the friction bond stress attenuation coefficient and bond degradation coefficient in the constitutive model of ?-s are further corrected,and the appropriate results are obtained.A constitutive model for RC columns with rust expansion and cracking under reciprocating loads can provide help for accurate numerical modeling and analysis.(3)Based on the design parameters of the cyclic loading test of corroded RC columns and the modified constitutive relationship of corroded RC ?-s under cyclic loading,15 groups of finite element models are established by ANSYS,which are the same as the test specimens.The interlayer displacement angles of 30 groups of corroded RC bottom frame columns obtained by experiment and numerical simulation of ANSYS are taken as performance indexes.At the same time,considering the failure process of corroded RC frame columns under reciprocating loads and the limitation requirements of the seismic codes for the inter-story displacement angle under different magnitudes of earthquakes,the quantitative values of performance indicators are further determined.The function is determined,and the fuzzy failure criterion is introduced to fuzzily the seismic response spectrum.The dynamic analysis of a RC frame structure with two spans and three stories is carried out by inputting the fuzzified seismic response spectrum,and the horizontal load term based on the horizontal displacement angle is solved.Finally,using Monte Carlo reliability calculation method and MATLAB programming,the reliability calculation of corroded RC frame structure under different earthquake magnitude is realized.Comparing with the code,the calculation results meet the requirements of the code.The results can provide a theoretical reference for seismic reliability evaluation of corroded RC frame columns in the life cycle. |
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