Research Of Ultimate Compressive Bearing Capacity Of Circular Tubular Y-Joints Reinforced With Doubler Plate

Due to their multiple advantages, unstiffened steel tubular joints are widely applied to the hollow section structure. But their bearing capacity is inadequate on some occasions. Improvements have been made on the structure, the way of connecting and the way of production. Thus this kind of joints is reinforced joints.Joints reinforced with doubler plate are one kind of reinforced joints relatively commonly used. But the study on its bearing behavior is on the elementary phase. The formula to calculate the bearing capacity hasn't been provided in the codes for design of steel structures. The paper studies the bearing behavior of circular tubular Y-joints reinforced with doubler plate under the axial compression of the brace. The finite-element analysis is carried out on the joints at anglesθ=30°45°or 60°.Through an orthogonal experimental analysis with as parametersβ(the diameter ratio of brace to chord),τp (the thickness ratio of doubler plate to chord),ξp (the raito between the length of doubler plate and the diameter of brace), andγ(the ratio between the diameter of chord and the thickness of chord), a conclusioin can be reached that under the brace axial compression, the effect posed by the four parameters on the strengthening coeffientφp of the ultimate compressive bearing capacity of circular tubular Y-joints reinforced with doubler plate isβ>τp >ξp >γ. Omitting the secondary effect posed byγ, the effects of the other three parameters on the compressive behavior of joints are studied with another set of species in the aspect of load-displacement curves, plastic deformation and failure mode, and dimension effect of doubler plate. The conclusion is that the doubler plate of proper size can strengthen the ultimate compressive bearing capacity and deformation-resistance capacity of unstiffened circular tubular Y-joints.Based on the regressive computation of the results of the finite element analysis, the paper offers the design formula to cacluate the strengthening coeffientφp of the ultimate compressive bearing capacity of circular tubular Y-joints reinforced with doubler plate. Then the paper offers the design formula to cacluate the ultimate compressive bearing capacity of circular tubular Y-joints reinforced with doubler plate. The study of this paper can serve as some reference for the setup of the formula in the codes for design of steel structures to accurately caculate the bearing capacity of reinforced joints and for the engineering practice.