Research On Ultimate Capacity Of Y-type SHS Joints With Cranked-chord

At the end of some Pratt or Warren truss, there often is a Y-joint with cranked-chord. Currently, CIDECT guidelines roughly classifies it as a K-overlap joint, and code for design of steel structures in our country has not yet mentioned the calculation method of this joint. Based on existing research including domestic and foreign scholars in recent years, a systematic research about static behavior of Y-joint with cranked-chord is carried out in this paper. The concrete content includes:Firstly, a previous joint model is rebuilded with SOLID95 in ANSYS software, and by comparing with the test results, it verifies the validity of operation and possibility of joint analysis in ANSYS. Then this paper establishes a FE model of Y joint with cranked-chord, considering the factors of boundary conditions, member length, rounded effect, size of weld, geometrical nonlinearity and material nonlinearity, ignores the influences of welding residual stress and initial imperfection.Secondly, in the case of brace under axial tension, nonlinear analysis has been carried out for static behavior of typical joint. And ratio of the width of chord to the width of brace β, 1/2 times of ratio for the width to the thickness of chord γ, ratio of the thickness of brace to the thickness of chord τ, angle of chord and cranked-chord θ1, angle of brace and chord θ2 conduct extensive study of geometric parameter. Next, results of parameter study are compared with calculation formula of T, Y, K-gap and K-overlap joints in CIDECT, which reveals deficiency for evaluating ultimate capacity of joint by using existing formula, at the same time, on the basis of calculation formula for K-gap joint, this paper revises and obtains accurate formula to calculate capacity. In addition, with the help of multi-parameter regression, a more accurate formula for evaluating ultimate capacity has also been conducted.Finally, in view of brace under axial pressure, by means of study about static behavior of typical joint and extensive geometric parameter analysis, this paper also investigates the influences of ratio of the width of chord to the width of brace β, 1/2 times of ratio for the width to the thickness of chord γ, ratio of the thickness of brace to the thickness of chord τ, angle of chord and cranked-chord θ1, angle of brace and chord θ2 on strength, stiffness, failure mode of joint. Then results of parameter study are compared with calculation formula of T, Y, K-gap and K-overlap joints in CIDECT, which reveals deficiency for evaluating ultimate capacity of joint by using existing formula, at the same time, on the basis of calculation formula for K-gap joint, this paper revises and obtains formula to calculate capacity under different failure modes of joints. In addition, with the help of multi-parameter regression, a more accurate formula for evaluating ultimate capacity has also been conducted.