Membrane Reinforcement in Shells

Some shortcomings in the present United States practice for designing membrane reinforcement in concrete shells have been pointed out. Using several existing methods, it is possible to calculate less than the necessary amount of reinforcement, which would lead to an unsafe structure. On the other hand, some of the requirements may be impractical, such as providing reinforcement in principal directions. When there is more than one governing load case, it would be impossible to meet such a requirement. Rational equations for calculating the reinforcement capacity on the basis of the principle of minimum resistance are presented. The state of strain and its magnitude have been examined. Higher tensile strain would lead to larger cracks in the concrete. Recommendations have been made to limit the strain magnitude for the cases in which limiting the crack width is important.