| China has a vast territory,complex and diverse natural environment,and the areas affected by freeze-thaw erosion are widely distributed.The research on the safety and long-term performance of transportation infrastructure in severe cold areas is helpful to solve the core common technical problems in the field of transportation infrastructure construction and safety operation in severe cold areas,and is of great significance to further improve the scientific level of bridge infrastructure construction and management in severe cold areas.The mechanical properties of stud shear connectors in steel-concrete composite structures under freeze-thaw cycles wrere investigated in this thesis.Firstly,the freeze-thaw cycle tests of shear connectors and their raw materials were carried out.According to different freeze-thaw times(0 / 50 / 100 / 150 times)and different stud diameters(13 / 19 /22mm),12 types of specimens were combined,3 in each type,and 36 stud shear connectors were poured,which were used to simulate the push out test of stud shear connectors under different freeze-thaw environments.Then,combined with the finite element software,the finite element model of push out test of freeze-thaw cycle is established,and the test results are calculated and compared to verify the test results.After ensuring the reliability of the finite element model,the influence of freeze-thaw cycle on the composite structure with different stud diameter,length diameter ratio and concrete strength was analyzed.Finally,the test results are compared with the existing shear bearing capacity calculation formula,and combined with the finite element calculation results,the shear bearing capacity calculation formula suitable for freeze-thaw environment is fitted.After the above work is completed,the following main research results are obtained:(1)Combined with the calculation theory of ordinary concrete freeze-thaw cycle in the existing literature,the calculation parameters of material properties of C60 ordinary concrete in freeze-thaw environment are supplemented.(2)The results show that the freeze-thaw cycle has obvious adverse effects on the composite structure,such as the decline of the ultimate bearing capacity of the stud shear key,the aggravation of the damage of the steel-concrete interface,the increase of the damaged cracks,and the change of the failure mode from stud failure to concrete failure.With the increase of freeze-thaw cycles,especially after more than 100 cycles,the phenomenon becomes more obvious.(3)The deterioration effect of freeze-thaw cycles on shear connectors with different stud diameters and length diameter ratios is similar,but for shear connectors with different strength concrete,the lower the concrete strength is,the more obvious the deterioration effect is.(4)The calculation formula of shear connector in freeze-thaw cycle environment is derived.The formula considers the influence of freeze-thaw times and relative dynamic elastic modulus.Comparing the results of the formula with the results of the test and finite element analysis,it is found that the fitting degree is good and the formula has a certain degree of reliability. |
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