Reinhold Krohn

From 1869 to 1873 Reinhold Krohn studied civil engineering at Karlsruhe Polytechnic, where Hermann Sternberg (1825–85) was professor and introduced him to bridge-building, along with Friedrich Engesser, Hermann Zimmermann and August Föppl. After a number of years spent working for various consulting engineers and authorities in Hamburg, he became an assistant at Aachen RWTH in 1876 and was soon giving lectures on moving bridges, the theory of statically indeterminate trussed frameworks and graphical statics. He became a professor in 1881 and at the same time acted as a consulting engineer. It was in this capacity that he was introduced to the balanced cantilever method of building bridges at the former Southern Germany Bridge-Building Company in Gustavsburg. Since Krohn’s publication on Maxwell’s exchange theorem (1884), this theorem had become established as the theorem of the reciprocity of displacements (Maxwell’s reciprocal theorem) in the classical phase of structural theory. From 1884 to 1886 he worked as an engineer, becoming familiar with American methods of bridgebuilding and learning about the much-admired truss bridge with pin joints, initially with C. C. Schneider, then with G. S. Morison and finally as senior engineer at the Pencoyd Steelworks. Upon his return to Germany, he joined the Gutehoffnung Foundry. Krohn adapted the new US industrial methods of fabrication to suit German bridge-building techniques. For example, under his leadership the Sterkrade Bridge- Building Company became the largest bridges operation in Germany with the highest export quota. Krohn paved the way for the building of large arch bridges in Germany. Together with Mehrtens and Kintzlé, he replaced wrought iron by mild steel. He founded the Association of German Bridge & Iron Fabricators in 1904 (renamed the German Iron Construction Association in 1913 and the German Steelwork Association in 1928). In the same year, Krohn was appointed professor of theory of structures and bridge-building at the newly established Danzig (Gdańsk) TH, where he taught and carried out research until being granted emeritus status. One of his last students was Kurt Klöppel. Krohn received numerous honours, e. g. election to the Prussian Parliament’s Upper Chamber as the representative of Danzig TH, an honorary doctorate from Aachen RWTH.

Main contributions to structural analysis:

Resultate aus der Theorie des Brückenbaus und deren Anwendung [1882/1883]; Der Satz von der Gegenseitigkeit der Verschiebungen und Anwendung desselben zur Berechnung statisch unbestimmter Fachwerkträger [1884] 

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. 742/743