| China has a vast territory,and bridges in some areas serve in complex and extreme environments,in which steel-concrete composite bridges under the influence of freeze-thaw cycle and corrosion environment will generally encounter durability problems and lead to performance deterioration.Therefore,the study of the competitive failure mechanism of stud connectors of steel-concrete composite beams under the influence of freeze-thaw &corrosion has important engineering significance for the performance deterioration evaluation of stud connectors.In this thesis,the competitive failure mechanism of stud connectors of steel-concrete composite beams under the influence of freeze-thaw & corrosion was studied.Firstly,in order to study the performance changes of concrete under freeze-thaw cycle,12 cube specimens and 12 prism specimens are designed and made,and the freeze-thaw cycles were carried out for different times(0/50/75/100 times).Secondly,in order to analyze the degradation characteristics of mechanical properties of stud connectors under the influence of freeze-thaw & corrosion,based on the combination of different freeze-thaw cycles(0/50/75/100 times)and different corrosion results(10mm height area of stud root:uncorroded,corroded depth 1.5mm,corroded depth 2.5mm),12 groups of stud connectors were designed and made,with 3 in each group,and 36 specimens push-out were tested.Then,in order to obtain the deterioration law of shear performance of stud connectors with different diameters under the influence of freeze-thaw & corrosion,12 finite element models corresponding to push-out test were established by ABAQUS to verify their reliability,and the parameters of different stud diameters(19/22/24mm)were analyzed.Finally,in order to explore the competitive failure mechanism of stud connectors under the influence of freeze-thaw & corrosion,the formula for calculating the shear capacity of stud connectors under the influence of freeze-thaw & corrosion was deduced on the basis of experiments and finite element method.Some suggestions are put forward according to the freeze-thaw &corrosion environment of the steel-concrete composite bridge.(1)With the increase of the number of freeze-thaw cycles,the surface damage of the concrete block is more serious,and the compressive strength of cubes,the dynamic elastic modulus of prisms and the quality of prisms all decrease to varying degrees.(2)With the aggravation of freeze-thaw & corrosion effect,the two failure modes of stud shearing or concrete failure will change.When the number of freeze-thaw cycles is the same,the shear capacity decreases with the increase of corrosion depth;When the corrosion depth is the same,the shear capacity of the specimens dominated by concrete cracking decreases in a quadratic parabola with the increase of the number of freeze-thaw cycles,while the shear capacity of the specimens dominated by stud shear is positively correlated with the square of the section diameter after corrosion.;In general,with the increase of freeze-thaw cycles and corrosion depth,the shear stiffness decreases.(3)The influence of freeze-thaw cycle on the shear bearing capacity of stud connectors with concrete failure is dominant.Although the stud diameter and corrosion depth are different,the deterioration effect is similar;The competitive failure mechanism of stud connectors under the influence of freeze-thaw & corrosion is summarized: the freeze-thaw environment mainly affects the mechanical properties of concrete,and the corrosion environment mainly affects the shear capacity of stud roots.When the stud connector is in the environment in which the two coexist at the same time,one of the environmental conditions will play a leading role in the shear bearing capacity of the stud connector.That is,it determines the lower limit of its shear bearing capacity,and the failure mode will correspond to it.With the continuous change of the two environments,the dominant type of environment will also change. |
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