Effect of weld reinforcement methods on bearing performance of large diameter tank bottom

Based on the finite element method, the influence of weld reinforcement methods (double symmetry reinforcement, inner surface reinforcement，outside surface reinforcement) on internal pressure bearing capacity of typical 10 m class diameter tank bottom was studied. The two-dimensional symmetric plane model was used for numerical calculation, and the effects of the real boundary conditions of the tube segment and the short shell and the weld on the bearing capacity were considered. The nonlinear numerical analysis model considering the plasticity of the material was constructed to accurately obtain the meridional stress on the inner and outer surfaces of tank bottom. Results showed that the weld area of the top and melon flap was a weak area of tank bottom. Under operating pressure, meridional stress difference between inner and outside surfaces of double symmetric reinforcement was smallest, and none of them presented plasticity. Meridional stress difference of single-side reinforcement was much larger than double symmetric reinforcement, and local plasticity occurred. Compared with inner surface reinforcement, the maximum and minimum meridional stress differences of outside surface reinforcement increased by 9.7% and 27.2%, and all of them led to uncoordinated deformation. Under design pressure, inner and outside surface meridional stress of tank bottom had local plasticity, and material plasticity had certain coordination effect on the inner and outside surface meridional stress difference, which can significantly alleviate the additional bending moment caused by the inner and outside surface stress difference. Double symmetric reinforcement was better than outside surface reinforcement, and inner surface reinforcement was better than outside surface reinforcement. The single-side reinforcement was easy to generate additional bending moment, which was not conducive to the uniform bearing and deformation coordination of tank bottom. The research results provide a guidance to the optimization design of the bottom structure of large diameter storage tank.