Theoretical And Experimental Research On Large Welded Hollow Spherical Joint

The welded hollow spherical joint of reticulated structure has got a wide application according to its simple construct, convenient connection and regular shape.As the span of reticulated structure has been increasing for years, the size of the welded hollow spherical joint become larger. However, data about mechanics and bearing-capacity of large welded hollow spherical joint is short of up to now.So it makes good sense to study the static performances of such joints and propose a method to conduct practical projects.In this paper, the project of the stadium is considered which is built in Huazhong University of Science and Technology. Comprehensive researches for the large welded hollow spherical joint used in the stadium steel roof are conducted by using the finite element method and full scale test. The research results provide warranty for design. To begin with, joints of the reticulated structure are briefed, especially structural characteristics and mechanics features of welded hollow spherical joint are described in detail. Systemic summarizations and analysis are given about the static performances of the joints, including both experiments and theories area. Then, theory of nonlinear finite plate and shell element method are made clear. By using the nonlinear F.E.M, the author analyzes this welded hollow spherical joint with the finite element program named ANSYS. The calculation is based on ideal elasto-plastic mechanical and the Von-Mises collapse criterion, both geometric nonlinearities and material nonlinearities considered. The Newton-Raphson increment iterative method is adopted with accelerating convergence technique as line search, DOF predictor, and automatic time stepping. Through the calculations show that under 1.5 times of the designed loads, the stress at the bottom of the fourth wimble pipe reached the yield point. At the same time the distribution of the stress, on the surface of the spherical joint is revealed. When the load grows to 2.2 times of the designed loads, the spherical joint is destroyed. At last, full-scale experimental research on large welded hollow spherical joint is carried out. The results show that under 1.4 times of the designed loads, the stress at the bottom of the fourth wimble pipe reached the yield point at first, which is close to the results of calculations. Through the comparison of the test results and finite element results, the finite element calculation method used in this paper is proved accurate and viable. The analysis method and test results for the large welded hollow spherical joints will be more valuable for similar projects.