Study On Degradation Law Of Service Performance Of Bolted Connections In Steel Concrete Composite Beams Under Corrosive Environment

As a very important component in steel-composite beams,stud connectors may be eroded by the environment in practical engineering,leading to the rust of stud connectors.The corrosion of stud connectors in steel-concrete composite structures under corrosive environment is a very slow process,which takes several years or even decades to corrode,which indicates that steel-concrete composite structures are likely to work under the corroded condition of stud connectors.It is of great significance for the analysis and evaluation of the mechanical behavior of steel-composite beams to study the degradation law of the service performance of stud connectors under the condition of corrosion.In this thesis,a simple test beam immersion experiment and finite element method are used to study the concrete cracking caused by the rust expansion of the stud and the extruded model of the stud in different corrosion areas and corrosion forms.The main conclusions are drawn as follows :（1）The experiment is conducted on the test beam,and it is inferred from the experimental phenomenon that chloride ions are easy to enter through the interface between the steel beam and the concrete plate,and the root of the stud may corrode.（2）For the unilateral symmetric constraint,the horizontal crack of the free edge appears earlier than the vertical crack,but the connection is later.For symmetric constraints,the crack on the free edge is more difficult to crack than the crack on the symmetric boundary.For the trilateral symmetric constraint,the corrosion depth and swelling force of the pin are greater than those of the bilateral symmetric constraint.The concrete does not crack under four-sided symmetric constraints.（3）With the increase of the distance between the longitudinal and transverse bridge,the crack of the outer edge needs greater corrosion depth.With the increase of the longitudinal bridge distance,the corrosion depth needed to connect the crack decreases.With the increase of the diameter of the stud,the concrete will crack earlier,and the crack will be through faster;With the increase of load perpendicular to the direction of crack propagation,a greater depth of corrosion is needed to crack and coalesce.（4）For the four different corrosion patterns,when the corrosion depth of the pin is the same,the shear bearing capacity of the pin will decrease with the increase of the corrosion height,and most of them will reach the lowest when the corrosion height is 10 mm.The greater the corrosion depth is,the greater the degree of reduction will be,but the stiffness is always decreasing.When the corrosion height of the pin is the same,the shear bearing capacity and shear stiffness decrease linearly with the increase of corrosion depth.When the corrosion height and depth of the stud are the same,the shear bearing capacity and stiffness of uniform ring corrosion decrease the most,even about 60% compared with the other three cases,and the least decrease degree is the semi-ring corrosion under compression.