Hardy Cross

From Wikipedia, the free encyclopedia

Hardy Cross, 1885-1959, born in Nansemond County, Virginia, was a U.S. engineer and the developer of the moment distribution method for structural calculation of large reinforced concrete buildings. The method was in general use from c.1935 until c.1960 when it was superseded by other methods. It made possible the efficient and safe design of many reinforced concrete buildings during an entire generation.

He obtained a BS in civil engineering from the Massachusetts Institute of Technology in 1908, and then joined the bridge department of the Missouri Pacific Railroad in St. Louis, where he remained for a year, after which he returned to Norfolk Academy in 1909. After a year of graduate study at Harvard he was awarded the MCE degree in 1911. Hardy Cross developed the moment distribution method while working at Harvard university. He next became an assistant professor of civil engineering at Brown University, where he taught for seven years. After a brief return to general engineering practice, he accepted a position as professor of structural engineering at the University of Illinois at Urbana-Champaign, in 1921. At the University of Illinois Hardy Cross developed his moment distribution method and influenced many young civil engineers. His students at Illinois had a hard time arguing with him due to the fact that he was hard of hearing.

Accurate structural analysis of large reinforced concrete building frames in the 1950s was a formidable task. It is a tribute to the engineering profession, and to Hardy Cross, that there were so few failures. When engineers had to compute the stresses and deflections in a statically indeterminate frame, they inevitably turned to what was generally known as the "moment distribution" or "Hardy Cross" method. In the moment distribution method, the fixed-end moments in the framing members are gradually distributed to adjacent members in a number of steps such that the system eventually reaches its natural equilibrium configuration. however the method was still an approximation but it could be solved to be very close to the actual solution.

Today the "moment distribution" method is no longer commonly used due to the fact that computers have changed the way that engineers evaluate structures and moment distribution programs are seldom created nowadays. Today's structural analysis software is based on the flexibility method, matrix stiffness method or finite element methods (FEM).

Another Hardy Cross method is also famous for modeling flows in complex water supply networks. Until recent decades, it was the most common method for solving such problems.^[1]

He received numerous honors. Among these were an honorary Master of Arts degree from Yale University, the Lamme Medal of the American Society for Engineering Education (1944), the Wason Medal of the American Concrete Institute (1935), and the Gold Medal of the Institution of Structural Engineers of Great Britain (1959).