3-D Finite Element Analysis Of Steel Bifurcation In Huaneng Baoxin Hydrostatic Project

Underground steel bifurcation are being widely used in middle and large-scale hydrostatic projects, whose scales are getting larger and larger. People play a great attention on its structure design as its complexity structure and undefined stress stated. After retrospect the law of the art and design concept of steel penstock and present nonlinear finite element method briefly, base on the 3-D FEM, embedded steel penstocks in Bao xing project during different cases are investigated:(l)Under the excavation case, the opening face advancing is simulated with stresses relaxed and transformed and the grouting pressure is also simulated with the equivalent joint load around 120' in the tunnel crown.(2)Under the operation case, considering the gap between steel lining and concrete lining as imperfect contact, contact layer is proposed to simulate the gap in the combined work analysis.(3)Under the repair case, stability theory of arciform structure is employed to qualitative comparison of critical external compressive resistance between unsymmetrical Y-shaped branch pipe and cylindrical penstock. Then, FEM buckling analysis is employed to quantitative comparison of critical external compressive resistance between them. The result from variation of axis length and shell thickness reveals that critical external compressive resistance of branch pipe is less then that of general penstockin some cases.