Christian Otto Mohr

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Christian Otto Mohr 1897, photo by Wilhelm Höffert.

Christian Otto Mohr, mostly quoted as Otto Mohr (born October 8, 1835 in Wesselburen ( Holstein ), † October 2, 1918 in Dresden ), was a German engineer and structural engineer .

life and work

Before his career as an engineer, Otto Mohr worked in 1850 as a clerk in the parish of Wesselburen. A year later he began at the age of 16 years his studies engineering at the Polytechnic Institute in Hannover . His teachers and the students belonged to Schubert , Moritz Rühlmann . In 1855 he became an engineering assistant and later an engineer and building officer at the Royal Hanover State Railways (HSEB) in Lüneburg . In 1860 he published a paper on the continuous bending beam as an assistant in the service of the HSEB . This enabled the reliable dimensioning of continuous beams and attracted attention from experts.

On November 18, 1852, together with Joachim August Danielsen and Max Stegemann, he founded the Landsmannschaft Slesvico-Holsatia, from which the still existing Corps Slesvico-Holsatia emerged .

Following his work at HSEB, he was involved in the construction of the Grand Ducal Oldenburg State Railways . During this time Mohr designed one of the first steel bridges in Germany with a clearly designed triangular framework and developed a simple calculation method that was perfected by August Ritter in 1863 and has since been known as the Ritter'sches cutting method (or Ritter cutting method ).

In 1867, Mohr's scientific achievements were so popular that he was appointed to the Polytechnic in Stuttgart (predecessor of the University of Stuttgart ), where he took over the professorship for technical mechanics , routing and earthwork. He was able to present the theoretical material of mechanics in an easily understandable form, so that his lectures were very well attended and were later even published in autograph form. In science he achieved a considerable simplification by developing a graphical method (also: Mohr's analogy) to determine the bending line as a rope curve , which until then was only possible mathematically through double integration .

Mohr remains best known to posterity through the simple method he developed to graphically derive the main stresses of the plane stress state with the help of Mohr's stress circle named after him from the shear and normal stresses, or to assign the plane stress values ​​between local, Cartesian coordinate systems transform. The method can also be used in an analogous manner for elongations; the same applies to Mohr's circle of inertia . Mohr introduced the tension circle in 1882.

Grave of Otto Mohr in the Johannisfriedhof in Dresden.

In 1873 Mohr was offered a position at the Dresden Polytechnic . The chair for road , hydraulic and railway engineering that was created in 1869 was vacant because the previous owner, Claus Koepcke, accepted an appointment as the top manager of all railway construction in the Saxon Ministry of Finance . When he took office, he was entrusted with taking over Wilhelm Fränkel's courses on graphostatics . Just three years later, from 1876 onwards, his area of ​​responsibility was expanded to include the subject of strength theory . Mohr was also a colleague of Ludwig Burmester , the inventor of the Burmester stencils named after him .

Between 1874 and 1875 Mohr published a framework theory that he had developed on the basis of the general working set and the external virtual work.

In 1894 there was a change from the engineering department to the general department, where he took over the chair for technical mechanics and strength theory as the successor to Gustav Zeuner . He stayed in this office for another six years until he stepped down from the chair in 1900 at the age of 65.

Mohr worked as an academic teacher for 33 years, 27 of them in Dresden alone. There he bought the Villa Leubnitzer Str. 7 (from 1890 Villa Haniel ) in 1877, which he lived in until 1884. He spent his retirement on his property in Wachwitz near Dresden, continuing to do research. Otto Mohr died on October 2, 1918, six days before his 83rd birthday. His resting place is in the Johannisfriedhof in Dresden-Tolkewitz .

Fonts

  • Treatises from the field of technical mechanics. 3rd ext. Ed. v. K. Beyer, H. Spangenberg. Ernst & Son, Berlin 1928
  • Contributions to the theory of wooden and iron structures. In: Journal of the Architects and Engineers Association of Hanover . 14 (1868), col. 20-52, 397-400. Schmorl & von Seefeld, Hanover 1868 ( digitized and full text in the German text archive ).
  • Contributions to the theory of earth pressure. Journal of the Hannover Architects and Engineers Association, Volume 17, 1871, p. 344, Volume 18, 1872, p. 67, 245.
  • Contribution to the theory of the framework. Schmorl & von Seefeld, Hanover 1874/75.
  • About the representation of the state of tension and the state of deformation of a body element and about the application of the same in strength theory. In: The civil engineer. Organ of the Saxon Engineers and Architects Association. (Leipzig) NF, Vol. 28, pp. 112-156, 1882.
  • Which circumstances cause the elastic limit and the breakage of a material? In: Journal of the Association of German Engineers . No. 24 , 1900, pp. 1524-1530 and 1572-1577 .

Awards

  • In 1856 the Corps Slesvico-Holsatia made him an honorary boy.
  • Because of his scientific merits, he was appointed a secret councilor.
  • In 1898 he was awarded the Commander's Cross II. Class of the Albrechts Order .

literature

Individual evidence

  1. ^ Mohr, Civilingenieur 1882, p. 113, after Timoshenko, History of strength of materials, McGraw Hill 1953, p. 285
  2. ↑ 100 years of Zeunerbau. ( Memento from May 31, 2011 in the Internet Archive ). PDF with pictures by Otto Mohr and Ludwig Burmester.
  3. ^ Corps Slesvico-Holsatia, Corpslist. Winter semester 1981/82, p. 78, No. 03.
  4. ↑ Official notices. . In: Zentralblatt der Bauverwaltung. Volume 18, No. 18 (April 30, 1898), p. 205.

Web links

personal data
SURNAME Mohr, Christian Otto
BRIEF DESCRIPTION German engineer and structural engineer
DATE OF BIRTH October 8, 1835
PLACE OF BIRTH Wesselburen , Norder-Dithmarschen
DATE OF DEATH October 2, 1918
Place of death Dresden