加劲环钢管均匀外压弹性屈曲解的对比分析

加劲环钢管广泛应用于水利水电等工程领域,其外压稳定性是关注的重点问题。针对受均匀外压作用的加劲环管的弹性屈曲解进行了分析,将加劲环管的屈曲外压求解归结为非线性整数规划问题。详细比较了加劲环管的屈曲外压计算的精确式和近似式,证明目前设计所采用的近似式给出的临界压力总是比精确式给出的小,是更为保守的。以屈曲外压计算的精确式和设计采用的近似式为基础,推导了加劲环临界间距的表达式,从而明确了屈曲外压计算公式的适用范围,因考虑了管道的厚径比的影响,与现有文献的结果相比更为合理。对不同加劲环间距和加劲环约束程度的钢管进行了弹性屈曲有限元分析,利用所得的临界外压值详细考察了屈曲外压解析解的适用性和精度,进一步证明解析解和设计规范的公式都是偏于安全的,实际加劲环钢管的临界外压相比理想加劲环钢管都有不同程度的提高。

Comparative analysis of the elastic buckling solutions for ring-stiffened steel pipes under uniform external pressure

Ring-stiffened pipes are widely applied in water conservancy, hydroelectric and other engineer-ing and their stability under external pressure is the key issue of concern. The estimation for the elastic buckling pressure of a ring-stiffened pipe subjected to uniform lateral external pressure was discussed, and solving the critical pressure was formulated as a nonlinear integer programming problem. The equations for analytically evaluating the buckling pressure,including exact one and simplified ones,were compared in de-tail, which proved that the simplified equation adopted in the current steel pipe design gives lower critical external pressure and is very conservative. Based on the exact equation and the design adopted equation for buckling pressure, the critical spacing between stiffening rings was deduced to clarify the applicable range of these equations. The critical spacing is much more reasonable in comparison with the existing counter-parts because of the incorporation of the ratio of thickness to radius. The finite element analysis was car-ried out for the elastic buckling of the steel pipes with different spacing and different constraints of stiffen-ing rings. By using the critical pressures obtained,the applicability and precision of the equations for buck-ling pressure were examinde comprehensively. The comparisons show that both the analytical solution and the design used solution for buckling pressure are conservative and overly safe, and that the critical pres-sure of actual ring-stiffened pipes increases to some extent in comparison with ideal ring-stiffened pipes.