Cylindrical Shell Finite Strip Element Method Used for Stability Analysis of Buried Penstock under External Pressure

The semi、analytical cylinder shell finite strip element method is adopted in stability analysis for buried penstocks with stiffener rings under external water pressure, in which the analytic function is used in the axial direction, and the discrete Hermite multivariate function in the circumferential direction. The displacement mode obtained with the combination of the analytic function and the discrete multivariate function not only decreases the freedom degree, but also increases the accuracy of calculation. In addition, it is quite convenient with the method to simulate the wave shape changes of the buckling with variable element width due to circumferential off、stability. Compared with the Amstutz method, this method can overcome the insufficient calculation of the former, which does not consider the restraining function of the stiffener rings and must simplify a penstock into a circular ring arc in penstock stability analysis. The Euler curve of thin shell structural off、stability due to external water pressure is obtained and the correctness and reliability of the method are proved.