Experimental Study On Load-carrying Behavior Of H Section Steel Beam-columns Strengthened By Steel Plates

Steel structure has been widely used in industrial and civil buildings,However,due to the inevitable mismanagement,unsatisfactory steel quality,changes in the use function,and insufficient durability of the steel structure during the design,construction,and use,it is necessary to reinforce the existing steel structure.The bonded steel reinforcement method is more and more applied to the steel structure reinforcement project because of its effective reinforcement effect,no use of open flame,no influence on the shape of the structure,small required working surface,simple and light construction.Most of the experimental researches on steel structures strengthened by bonded steel method are focused on axial steel columns and flexural members.The experimental research on steel-reinforced steel structures under compression and bending has not yet been carried out.The calculation formula for the stable bearing capacity of the steel-reinforced reinforced steel columns in the existing specifications in China is determined according to the design method of the increased section method,and the strength reduction factor is introduced.The necessary test basis is lacking.Based on the shortcomings of the existing research,it is urgent to study the mechanical behavior of the bent steel column after the bonded steel is strengthened.In order to study the influence of the thickness of the steel plate and the eccentricity on load-carrying behavior of the steel beam-columns after strengthening by the steel plates,the static test of four strengthened steel beam-columns and one comparative unreinforced steel beam-columns was conducted,The hot-rolled middle flange H section was adopted,and the grade of steel was carbon steel type Q235 B.The reinforcement method is the outer steel plate of the steel flange and the full length of the column is reinforced.Cylindrical hinges were used at both ends of the column to achieve eccentric compression in the plane of the steel column.The displacement variation,the strain distribution of the web,the strain change between the steel flange and the steel plate,as well as the buckling mode and the ultimate bearing capacity were discussed.In addition,the test results were compared with the theoretical calculation results.The experimental results show that the reinforcement method of sticking steel plates on the flange can effectively improve the out-plane stability bearing capacity of the steel beam-column.The plasticity of the the websection of the steel beam-column after reinforcement is more obvious.the eccentricity is the main factor affecting the stability bearing capacity of the steel beam-column after reinforcement.Besides,the smaller eccentricity is beneficial to the joint work between the steel plate and the section steel through the bond layer.The theoretical value of the out-of-plane overall stability bearing capacity of the reinforced post-pressed steel column obtained according to the relevant formula in the specification is lower than the experimental value.Finally,the ABAQUS software was used to simulate the nonlinear buckling of the bent steel column,and the cohesive unit was established to simulate the force of the rubber layer.The results show that the failure mode,ultimate bearing capacity,load-displacement curve and load-strain curve of the specimen obtained by numerical simulation agree well with the experimental results.The numerical simulation shows that the interface process of the adhesive layer has experienced three stages: elastic deformation stage,rubber layer softening stage and rubber layer peeling stage.The interface stress at the end rubber layer is the largest,and the end rubber layer stress is along with the end part.The distance increases rapidly.The numerical simulation also shows that the thickness of the externally-adhesive steel plate and the eccentricity will affect the interfacial stress performance of the adhesive layer of the steel-reinforced steel bar.The smaller steel plate thickness and eccentricity facilitate the joint work between the reinforcement and the reinforcement through the glue layer.