内加强月牙肋钢岔管具有水头损失小、受力比较均匀、外部无明显突出构造物、洞室开挖断面较小等优点，因此广泛应用于地下埋藏式压力管道。但布置在地面上的明式月牙肋钢岔管尚不多见，特别是当钢岔管承受的水头和直径较大时。以某水电工程钢岔管为例，以满足结构受力和水力条件为前提，优化岔管体形，然后按照钢衬钢筋混凝土岔管结构进行了有限元计算，得到了一些有益的结论。

A composite stucture for penstock bifurcations, comprising a steel lining and outer reinforced concrete shell, is proposed as a method to increase structural integrity and reliability as a result of the interaction of the two materials. This method represents an economical solution for developing countries. Model studies for the concept are described.

考虑了回填混凝土、围岩的弹塑性、初始地应力及开挖支护引起的二次应力的影响和在内水压力作用下钢衬的弯曲、剪切效应，并将罚函数的思想应用于地下埋藏式压力钢管的非线性有限元强度分析，编制了相应的非线性有限元程序，结合工程实例，通过方案比较得出了对工程设计有参考价值的结论.

Structural research into the performance of a composite steel-reinforced concrete penstock designed for use at the Three Gorges power station in China is described. The stress state, load capacity and mechanism of deformation of the penstock under internal water pressure were obtained from theoretical analyses based on a non-linear finite element simulation of the original design. Using the results from the numerical research, a large-scale prototype model has been developed and tested to verify the modified penstock. The conclusions obtained have potential value with respect to other similar projects both in China and elsewhere.