| Steel structures have the advantages of high strength and light weight,and are widely used in industrial and civil buildings.However,with the development of the times,some existing steel structure buildings need to be reinforced,and the welding reinforcement method under load is the most commonly used.At present,there is a lack of in-depth research on the load welding reinforcement of the opposite steel tube column-H-beam joints in the steel frame structure.In this paper,a new reinforcement method is proposed for the steel tube column-H-beam joint,the outer rib ring plate joint.The mechanical properties were studied by combining experiments,ABAQUS finite element simulation and theoretical analysis.A comparative test of reinforced joints and unreinforced joints is designed to study the reinforcement effect of the outer rib ring plate reinforcement method.The static and quasi-static loading of each group of nodes was carried out,combined with the finite element model verification,it was found that the flexural bearing capacity of the reinforced nodes could reach twice that of the unreinforced nodes,and the seismic performance was good,and the reinforcement was effective.The joint reinforcement test under different column axial compression ratios was carried out to study the influence of column load on welded joints,and it was found that the joint bearing capacity decreased with the increase of the stress ratio.Under the static condition,the initial stress ratio of the front column should be controlled below0.7.In addition,two groups of joint reinforcement tests with different angle steel lengths were carried out,combined with finite element calculation,it was found that the yield bearing capacity would be reduced by about 10%-15% if the angle steel did not wrap the core area of the node.The strain and deformation of each member in the welding reinforcement test are analyzed,and it is found that when the rib plate is welded to the column wall,the rib plate does not transmit the axial pressure,and the maximum thermal strain is located at the column wall below the weld,which weakens the column stiffness and is unfavorable for the joint bending resistance.;When the rib plate and the angle steel are welded,the rib plate transmits force,and the maximum thermal strain is located in the rib plate.Comparing the finite element calculation results considering the welding heat effect and without considering the welding heat effect,a factor of 0.9 is obtained as the bearing capacity reduction factor considering the welding heat effect.The finite element parametric analysis of the vertical rib plate size and column wall thickness is carried out,and the structural design suggestions are put forward for the reinforcement method of the outer rib ring plate.It is obtained that in the joints of this paper,the thickness of the vertical rib should be greater than 6mm,the length should just wrap the expanded lower flange of the T-beam,the lap length with the angle steel should be 10-20 mm,and the column wall thickness should be 16 mm.The simplified mechanical model is used for theoretical analysis,and the stress mechanism and flexural bearing capacity calculation method of the square steel tube column-H-beam joint after reinforcement are studied.Combined with the finite element stress distribution,the load distribution ratio and stress distribution ratio between the vertical rib and the column wall are deduced.It can be seen from the calculation that in the design nodes of this paper,the load borne by the vertical rib is greater than that of the front column wall,and the maximum is about 50 times that of the front column wall;Finally,the formula for calculating the flexural yield bearing capacity of the reinforced joints is deduced. |
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