For more than 30 years, the design of platform and jackup conductors has been based on Stahl and Baur's famous hypothesis that internal string loads do not contribute to buckling (Stahl and Baur 1983). It is a vital result, allowing significant weight and cost savings. However, no derivation was ever given, and the result has remained a folk theorem: widely used, but never proved. The industry has, therefore, been at risk should the result prove to be a severe approximation, or to have unduly restrictive assumptions and/or limitations. This paper provides a rigorous proof of the hypothesis. It shows that it is an approximation, though an acceptable one, and gives a thorough exposition of its meaning, assumptions, and limitations. Finally, it derives the exact counterpart of Stahl and Baurs' result. The improved result gives minor weight and cost savings.
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