Christian Otto Mohr (8 October 1835 – 2 October 1918) was a German civil engineer. He is renowned for his contributions to the field of

structural engineering Structural engineering is a sub-discipline of civil engineering in which structural engineers are trained to design the 'bones and muscles' that create the form and shape of man-made structures. Structural engineers also must understand and cal ...

, such as

Mohr's circle Mohr's circle is a two-dimensional graphical representation of the transformation law for the Cauchy stress tensor. Mohr's circle is often used in calculations relating to mechanical engineering for materials' strength, geotechnical engineer ...

, and for his study of

stress Stress may refer to: Science and medicine * Stress (biology), an organism's response to a stressor such as an environmental condition * Stress (linguistics), relative emphasis or prominence given to a syllable in a word, or to a word in a phrase ...

Biography

He was born on 8 October 1835 to a landowning family in

Wesselburen Wesselburen () is a small town in the district of Dithmarschen in the German Federal State of Schleswig-Holstein. It is situated near the North Sea coast, approximately west of Heide. Wesselburen is part of the ''Amt'' ("collective municipality ...

in the

Holstein Holstein (; nds, label=Northern Low Saxon, Holsteen; da, Holsten; Latin and historical en, Holsatia, italic=yes) is the region between the rivers Elbe and Eider. It is the southern half of Schleswig-Holstein, the northernmost state of German ...

region. At the age of 16 attended the

Polytechnic School Polytechnic School, often referred to simply as Poly, is a college preparatory private day school located in Pasadena, California with approximately 850 students enrolled in grades Kindergarten through 12. The school is a former member of the ...

Hannover Hanover (; german: Hannover ; nds, Hannober) is the capital and largest city of the German state of Lower Saxony. Its 535,932 (2021) inhabitants make it the 13th-largest city in Germany as well as the fourth-largest city in Northern Germany ...

. Starting in 1855, his early working life was spent in

railroad Rail transport (also known as train transport) is a means of transport that transfers passengers and goods on wheeled vehicles running on rails, which are incorporated in tracks. In contrast to road transport, where the vehicles run on a pre ...

engineering for the

Hanover Hanover (; german: Hannover ; nds, Hannober) is the capital and largest city of the German state of Lower Saxony. Its 535,932 (2021) inhabitants make it the 13th-largest city in Germany as well as the fourth-largest city in Northern Germany ...

and Oldenburg state railways, designing some famous

bridge A bridge is a structure built to span a physical obstacle (such as a body of water, valley, road, or rail) without blocking the way underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually somethi ...

s and making some of the earliest uses of steel

truss A truss is an assembly of ''members'' such as beams, connected by ''nodes'', that creates a rigid structure. In engineering, a truss is a structure that "consists of two-force members only, where the members are organized so that the assembl ...

es. Even during his early railway years, Mohr had developed an interest in the theories of mechanics and the

strength of materials The field of strength of materials, also called mechanics of materials, typically refers to various methods of calculating the stresses and strains in structural members, such as beams, columns, and shafts. The methods employed to predict the re ...

. In 1867, he became

professor Professor (commonly abbreviated as Prof.) is an academic rank at universities and other post-secondary education and research institutions in most countries. Literally, ''professor'' derives from Latin as a "person who professes". Professors ...

of mechanics at Stuttgart

Polytechnic Polytechnic is most commonly used to refer to schools, colleges, or universities that qualify as an institute of technology or vocational university also sometimes called universities of applied sciences. Polytechnic may also refer to: Educatio ...

, and in 1873 at

Dresden Dresden (, ; Upper Saxon: ''Dräsdn''; wen, label= Upper Sorbian, Drježdźany) is the capital city of the German state of Saxony and its second most populous city, after Leipzig. It is the 12th most populous city of Germany, the fourth ...

Polytechnic. Mohr had a direct and unpretentious lecturing style that was popular with his students. In addition to a lone textbook, Mohr published many research papers on the theory of structures and strength of materials. In 1874, Mohr formalised the idea of a

statically indeterminate In statics and structural mechanics, a structure is statically indeterminate when the static equilibrium equations force and moment equilibrium conditions are insufficient for determining the internal forces and reactions on that structure. Math ...

structure. Mohr was an enthusiast for graphical tools and developed the method, for visually representing

in three dimensions, previously proposed by Carl Culmann. In 1882, he famously developed the graphical method for analysing stress known as

and used it to propose an early theory of strength based on

shear stress Shear stress, often denoted by (Greek: tau), is the component of stress coplanar with a material cross section. It arises from the shear force, the component of force vector parallel to the material cross section. ''Normal stress'', on the ...

. He also developed the Williot-Mohr diagram for truss displacements and the Maxwell-Mohr method for analysing

structures, it can also be used to determine the displacement of truss nodes and forces acting on each member. The Maxwell-Mohr method is also referred to as the virtual force method for redundant trusses. He retired in 1900, yet continued his scientific work in Dresden until his death on 2 October 1918.

Bibliography

* Timoshenko, S. P. (1953), ''History of Strength of Materials''
George A. Lesieutre academic lineage
at www.personal.psu.edu {{DEFAULTSORT:Mohr, Christian Otto 1835 births 1918 deaths People from Wesselburen German civil engineers Engineers from Schleswig-Holstein

Biography

See also

Bibliography