Friedrich Engesser

Friedrich Engesser studied at Karlsruhe Polytechnic from 1865 to 1869. Afterwards, he first worked on several structures for Black Forest Railways and then functioned as a central inspector for Baden State Railways in Karlsruhe. In 1885 he succeeded Prof. Hermann Sternberg at Karlsruhe TH, where he remained for 30 years as lecturer and researcher in structural engineering and theory of structures. For example, in 1889 he worked out the difference between deformation energy Π and deformation complementary energy Π* and in doing so opened up the theory of structures for the quantitative dominance of non-linear material behaviour. In the same year Engesser published an article explaining the mechanical cause behind the deviation of buckling trials from the Euler curve. However, it was not until 1895 – after he had concluded trials to verify the buckling theory of Considère (1889) – that he specified his modified Euler equation for the non-elastic buckling zone within the scope of a discussion with Jasiński published in a Swiss building journal, and frankly admitted he had made a mistake in 1889 [Nowak, 1981, pp. 147–148]. His contributions to the theory of secondary stresses and theory of frameworks also had a lasting effect on structural theory in the consolidation period. Together with Müller-Breslau and Mohr, Engesser forms the triple star in the firmament of classical structural theory. He contributed to the underlying theories of structural steelwork more than any other. His outstanding achievements were rewarded in many ways, including a doctorate from Braunschweig TH.

Main contributions to structural analysis:

Über statisch unbestimmte Trägersysteme bei beliebigem Formänderungsgesetz und über den Satz von der kleinsten Ergänzungsarbeit [1889]; Über die Knickfestigkeit gerader Stäbe [1889]; Die Zusatzkräfte und Nebenspannungen eiserner Fachwerkbrücken [1892/1893]; Über die Berechnung auf Knickfestigkeit beanspruchter Stäbe aus Schweiß- und Gußeisen [1893]; Über Knickfragen [1895]; Über die Knickfestigkeit von Stäben mit veränderlichem Trägheitsmoment [1909]; Die Berechnung der Rahmenträger mit besonderer Rücksicht auf ihre Anwendung [1913] 

Source: Kurrer, Karl-Eugen The History of the Theory of Structures, Wilhelm Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH, Berlin (Deutschland), ISBN 3-433-01838-3, 2008; p. 728