| The steel-concrete composite beam has the advantages of both steel structure and concrete structure,comprehensive benefits,and has been widely used in the field of bridge engineering.Research on shear bond of steel-concrete composite beam is a hot topic in the field of composite structure,and adhesive steel-concrete composite beams use structural adhesive as shear connectors.Stress concentration and large thickness of concrete slab are common problems in mechanical steel-composite beams,which can be released and reduced in adhesive steel-concrete composite beams.In order to study the structural behavior of adhesive steel-concrete composite beams,several experiments and calculations are carried out to explore from simple to complex in this thesis.Using epoxy and magnesium phosphate cement as the shear connectors,basic performance tests are carried out to design mix proportion of magnesium phosphate cement.The pulling bond properties and shear bond properties of adhesive shear connectors are studied through pulling bond test and push-out test.According to the push-out test results,the calculation formula of shear stress bearing capacity of epoxy is derived.The four-point bending test is carried out to study the bending resistance of adhesive and mechanical steelconcrete composite beams,taking shear connector type,concrete slab thickness,adhesive type and adhesive layer thickness as test parameters.Finally,ANSYS is used to build a threedimensional finite element model for nonlinear simulation,and the calculated results are compared with the experimental results.The main conclusions are as follows:(1)Epoxy shear connector has high shear strength,small slip and good stability,so it can be used as a new type of shear connector.According to the stress-slip relationship curve,the slip of adhesive shear connector increases with the increase of load,but the ultimate slip is very small.Therefore,this kind of shear connector belongs to rigid shear connector.(2)The prediction formula of epoxy resin carrying capacity is modified according to the push-out test results in this thesis.Referring to the suggested formula of stud bearing capacity in national codes,another prediction formula of epoxy resin carrying capacity based on bonding area,elastic modulus and tensile strength of adhesive is established,which is in good agreement with the experimental results of other scholars.(3)Adhesive steel-composite beams may have a bearing capacity equal to or higher than that of mechanical composite beams under the premise of ensuring good bonding state,and the effect of stiffness keeping is better under the same load condition.The reduction of concrete slab thickness in steel-concrete composite beams may significantly reduce the bearing capacity of mechanical steel-concrete composite beams.Cracks occur at the end of the concrete slab due to shear connector slip,and cracks along the beam length occur at the top of concrete slab in mechanical steel-composite composite beams,both of which affect the integrity of concrete slab.(4)When the thickness of the concrete slabs is equal,the height of the neutral axis of the section of the adhesive steel-concrete composite beams is significantly higher than that of the mechanical steel-concrete composite beams.Whether it is concrete slab or I-beam,the section stress of adhesive steel-concrete composite beam has a higher contribution efficiency to the overall section bearing capacity.(5)Under normal use conditions,the maximum slip of the adhesive steel-composite beam is about 60 microns and can be controlled within 100 microns.The slip of mechanical steelconcrete composite beam is more than 5 times of that of adhesive type.(6)The shear adhesive property of epoxy gets better with the increase of adhesive layer thickness in composite steel-concrete beams.Increasing the thickness of adhesive layer can improve the adhesive performance to a certain extent,so it is suggested that the thickness of adhesive should be more than 4mm,and 6mm is the best. |
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