The Stuttgart experiments
In 1904, tests were carried out on the resistance of concrete structures against torsion and the adhesive power of reinforcement bars in concrete under the guidance of Emil Mörsch at the material test institute in Stuttgart. The resistance against torsion was determined with hollow and plain cylinders, whereas what Mörsch had already previously assumed could be proved, namely that the resistance of concrete against torsion is different from the shear strength.
After evaluation of tests with various beams Mörsch found out that adhesion of bent reinforcement bars is double that of straightly laid reinforcement bars with stirrup reinforcement.