Accelerated Test Method And Damage Mechanism Of RC Beams Under The Coupled Loading And Acid Rain Environment

Acid rain,as a common environmental pollution problem in China,has posed a severe test on the durability and service life of reinforced concrete structures in service.Based on the Major National Natural Science Foundation for Research Instrument Development of China(Grant No.11627802),development of a structural fatigue testing system under complex environment,this essay was aimed at the accelerate test method of RC beams under acid rain environment and load coupling,to establish the accelerate test environment spectrum and carry out accelerate test research.With theoretical analysis,finite element numerical simulation and other methods,the bearing capacity deterioration and damage mechanism of RC beams corroded by acid rain and load coupling were studied,and the main research works and results were as follows.The accelerated test method of acid rain environment and load coupling was established.Combined with the meteorological data of the research area,the acid rain environment spectrum was obtained.After calculating the specific amount of each environmental factor in the accelerated test environment spectrum,and the conversion of the natural acid rain environment spectrum parameters,the time proportion of each environmental factor in the accelerated test environment spectrum was deduced to obtain the acid rain accelerated test environment spectrum.And with the acid rain accelerated corrosion test,through the corrosion degree comparison method,the equivalent conversion relationship that 5.17 d of the accelerated corrosion experiment was about the same as one year for service environment was acquired.Besides,combined with the orthogonal test design method,the corrosion test of concrete materials under acid rain environment was carried out.The results showed that within 30 d of the test,the sulfate ion concentration had the greatest effect on the compressive strength of concrete specimens,followed by corrosion time,and pH of the corrosion solution,but then time gradually became the dominant factor,and the extreme difference analysis showed that the decline rate of the compressive strength properties increased with the ion concentration.In addition,the corrosion time still affected the mass loss of the test block most severely,followed by the solution pH,and sulfate ion concentration.Combined with the test results,the corrosion depth calculation formula was derived and validated by COMSOL model for calculating the time-varying model of bearing capacity.And the comparative analysis of the load-bearing capacity test of RC beams after acid rain corrosion showed that during the same time,the ultimate structural load-bearing capacity of RC beams under coupled environment decreased by about 6.67% compared with RC beams corroded by only acid rain environment,the internal reinforcement corrosion depth and structural surface defect were also more serious,i.e.,the load coupling effect significantly accelerated the corrosion rate of the structure by acid rain environment,resulting in a more rapid decrease in structural mechanical performance.Combined with the accelerate test results,the bearing capacity time-varying model of RC beams corroded by coupled acid rain and load was derived,and with ABAQUS finite element software,the numerical simulation models of RC beams under different corrosion times were established to verify the reliability of the load bearing evolution equation,and the damage law of RC beams corroded by acid rain was analyzed.