John Baker, Baron Baker
Encyclopedia
John Fleetwood Baker, Baron Baker OBE
(19 March 1901 – 9 September 1985) was a British
scientist and structural engineer.
and Clare College, Cambridge
and married Fiona Mary MacAlister Walker in 1928.
on structural problems of airships. At 28, in 1929, he contracted tuberculosis. Upon recovering, he became a Technical Officer with the Structural Steel Research Committee, which was investigating why measured stresses in structural steel bore little resemblance to theoretical ones. During his time in this post, he developed the plastic theory of design, a revolutionary method of design of steel structures which gives a lower bound on the collapse load, and is hence always safe. Until then, all design of steel structures was based on elastic theory of design, which gives an upper bound
on the collapse load.
In 1933 Baker became Professor of Engineering at Bristol University, after which he was scientific adviser to the Design and Development Section of the Ministry of Home Security
from 1939 to 1943. In this time he created the Morrison indoor shelter, using his plastic theory of structural analysis.
From 1943 to 1968, he was Professor
of Mechanical Sciences
and Head of Department at Cambridge University Engineering Department
. During this time the department more than tripled in size, from 24 lecturers to 111. He used the structure of the Forth rail bridge as the basis of explanations of structural design theory to his students.
During his time at Cambridge, plasticity theory was used to design the new Baker Building of the department, making it the first building in the world designed by this method.
In 1963 he became an honorary graduate as Doctor of Science at the University of Edinburgh
. He was made a life peer
as Baron Baker, of Windrush in the County of Gloucestershire on 1 February 1977.
Plasticity theory is based on plastic behaviour, and calculates a lower bound on the load that a structure can carry (the load at which it collapses will not be lower than that calculated). This allows a structure to be designed so it will always be able to carry the chosen magnitude of load, even if the exact way it does so is not understood.
Elasticity theory depends on guessing the way in which a structure works, and the loads it will be subjected to, and designing it to carry those loads in the assumed manner. This ensures it is safe if the structure is well understood, but it may not be safe if the structure carries the loads in a different manner. Therefore it gives an upper bound on the collapse load (the load at which it collapses will not be higher than that calculated). Elastic design is sensitive to deformation of the structure, and only works for small deflections.
During the 1950s Baker and W.Prager of Brown University
published a two volume account of the history of steel structures, with plastic theory integral to it. By the 1960s it was being taught in the undergraduate engineering course at Cambridge University, and Baker presented an undergraduate lecture on the principles of design of the Morrison shelter as an interesting introduction to his theory of plastic design of structures; in 1968 this lecture was attended by Prince Charles, and it can be summarised as follows:
It was impractical to produce a design of indoor bomb shelter for mass production that could withstand a direct hit, and so it was a matter of selecting a suitable design target that would save lives in many cases of blast damage to bombed houses. Examination of bombed buildings indicated that in many instances, one end wall of a house was sucked or blown out by an nearby blast, and the floor of the first storey pivoted about its other end (supported by a largely intact wall) and killing the inhabitants.The Morrison shelter was therefore designed to absorb the energy of the upper floor of a typical two storey house undergoing a partial collapse of this form. The shelter was designed to absorb this energy by plastic deformation, since this can absorb two or three orders of magnitude more energy than elastic deformation. Its design enabled the family to sleep under the shelter at night or during raids, and to use it as a dining table in the daytime, making it a practical item in the house.
Although plastic theory is theoretically superior to elastic theory, it is still not in common usage today. Elastic theory, in a codified form, is used for the design of most steel structures, mainly due to the relative ease of use of elastic theory and the computerisation of the calculations. Plastic theory is used in some structures and specialist applications, specifically in bridge design.
Order of the British Empire
The Most Excellent Order of the British Empire is an order of chivalry established on 4 June 1917 by George V of the United Kingdom. The Order comprises five classes in civil and military divisions...
(19 March 1901 – 9 September 1985) was a British
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
scientist and structural engineer.
Early life
Baker was born in Liscard, Cheshire, a son of J.W. Baker and Emily Fleetwood. He was educated at Rossall SchoolRossall School
Rossall School is a British, co-educational, independent school, between Cleveleys and Fleetwood, Lancashire. Rossall was founded in 1844 by St. Vincent Beechey as a sister school to Marlborough College which had been founded the previous year...
and Clare College, Cambridge
Clare College, Cambridge
Clare College is a constituent college of the University of Cambridge in Cambridge, England.The college was founded in 1326, making it the second-oldest surviving college of the University after Peterhouse. Clare is famous for its chapel choir and for its gardens on "the Backs"...
and married Fiona Mary MacAlister Walker in 1928.
Career
After graduation, Baker worked with the Air MinistryAir Ministry
The Air Ministry was a department of the British Government with the responsibility of managing the affairs of the Royal Air Force, that existed from 1918 to 1964...
on structural problems of airships. At 28, in 1929, he contracted tuberculosis. Upon recovering, he became a Technical Officer with the Structural Steel Research Committee, which was investigating why measured stresses in structural steel bore little resemblance to theoretical ones. During his time in this post, he developed the plastic theory of design, a revolutionary method of design of steel structures which gives a lower bound on the collapse load, and is hence always safe. Until then, all design of steel structures was based on elastic theory of design, which gives an upper bound
Upper bound
In mathematics, especially in order theory, an upper bound of a subset S of some partially ordered set is an element of P which is greater than or equal to every element of S. The term lower bound is defined dually as an element of P which is lesser than or equal to every element of S...
on the collapse load.
In 1933 Baker became Professor of Engineering at Bristol University, after which he was scientific adviser to the Design and Development Section of the Ministry of Home Security
Ministry of Home Security
The Ministry of Home Security was a British government department established in 1939 to direct national civil defence during the Second World War.-Background:...
from 1939 to 1943. In this time he created the Morrison indoor shelter, using his plastic theory of structural analysis.
From 1943 to 1968, he was Professor
Professor
A professor is a scholarly teacher; the precise meaning of the term varies by country. Literally, professor derives from Latin as a "person who professes" being usually an expert in arts or sciences; a teacher of high rank...
of Mechanical Sciences
Mechanical engineering
Mechanical engineering is a discipline of engineering that applies the principles of physics and materials science for analysis, design, manufacturing, and maintenance of mechanical systems. It is the branch of engineering that involves the production and usage of heat and mechanical power for the...
and Head of Department at Cambridge University Engineering Department
Cambridge University Engineering Department
The Cambridge University Engineering Department at the University of Cambridge is one of the largest departments in the university. The main site is situated at Trumpington Street, to the south of Cambridge city centre. The department is the primary centre for engineering teaching and research...
. During this time the department more than tripled in size, from 24 lecturers to 111. He used the structure of the Forth rail bridge as the basis of explanations of structural design theory to his students.
During his time at Cambridge, plasticity theory was used to design the new Baker Building of the department, making it the first building in the world designed by this method.
In 1963 he became an honorary graduate as Doctor of Science at the University of Edinburgh
University of Edinburgh
The University of Edinburgh, founded in 1583, is a public research university located in Edinburgh, the capital of Scotland, and a UNESCO World Heritage Site. The university is deeply embedded in the fabric of the city, with many of the buildings in the historic Old Town belonging to the university...
. He was made a life peer
Life peer
In the United Kingdom, life peers are appointed members of the Peerage whose titles cannot be inherited. Nowadays life peerages, always of baronial rank, are created under the Life Peerages Act 1958 and entitle the holders to seats in the House of Lords, presuming they meet qualifications such as...
as Baron Baker, of Windrush in the County of Gloucestershire on 1 February 1977.
Plasticity Theory of Design
Steel can either behave elastically or plastically. Elastic deformation is reversible, and with the removal of load the material will return to its original shape, position and stress distribution. Plastic deformation is not reversible, and with the removal of load the material will assume a different shape, position and stress distribution to the one it held originally.Plasticity theory is based on plastic behaviour, and calculates a lower bound on the load that a structure can carry (the load at which it collapses will not be lower than that calculated). This allows a structure to be designed so it will always be able to carry the chosen magnitude of load, even if the exact way it does so is not understood.
Elasticity theory depends on guessing the way in which a structure works, and the loads it will be subjected to, and designing it to carry those loads in the assumed manner. This ensures it is safe if the structure is well understood, but it may not be safe if the structure carries the loads in a different manner. Therefore it gives an upper bound on the collapse load (the load at which it collapses will not be higher than that calculated). Elastic design is sensitive to deformation of the structure, and only works for small deflections.
During the 1950s Baker and W.Prager of Brown University
Brown University
Brown University is a private, Ivy League university located in Providence, Rhode Island, United States. Founded in 1764 prior to American independence from the British Empire as the College in the English Colony of Rhode Island and Providence Plantations early in the reign of King George III ,...
published a two volume account of the history of steel structures, with plastic theory integral to it. By the 1960s it was being taught in the undergraduate engineering course at Cambridge University, and Baker presented an undergraduate lecture on the principles of design of the Morrison shelter as an interesting introduction to his theory of plastic design of structures; in 1968 this lecture was attended by Prince Charles, and it can be summarised as follows:
It was impractical to produce a design of indoor bomb shelter for mass production that could withstand a direct hit, and so it was a matter of selecting a suitable design target that would save lives in many cases of blast damage to bombed houses. Examination of bombed buildings indicated that in many instances, one end wall of a house was sucked or blown out by an nearby blast, and the floor of the first storey pivoted about its other end (supported by a largely intact wall) and killing the inhabitants.The Morrison shelter was therefore designed to absorb the energy of the upper floor of a typical two storey house undergoing a partial collapse of this form. The shelter was designed to absorb this energy by plastic deformation, since this can absorb two or three orders of magnitude more energy than elastic deformation. Its design enabled the family to sleep under the shelter at night or during raids, and to use it as a dining table in the daytime, making it a practical item in the house.
Although plastic theory is theoretically superior to elastic theory, it is still not in common usage today. Elastic theory, in a codified form, is used for the design of most steel structures, mainly due to the relative ease of use of elastic theory and the computerisation of the calculations. Plastic theory is used in some structures and specialist applications, specifically in bridge design.
Works
- A distribution method of stress analysis (Reports and memoranda) (1935)
- The Analysis of Engineering Structures Alfred John Sutton PippardAlfred PippardAlfred John Sutton Pippard MBE FRS was a British civil engineer and academic. Pippard was the son of a carpenter and joiner and spent much of his early life helping his father on construction sites...
, John Fleetwood Baker. 1st Edition 1937, many subsequent editions - The Plastic Design of Frames Jacques Heyman, John Baker, C.U.P. 1969
- Enterprise versus Bureaucracy : The Development of Structural Air-Raid Precautions during the 2nd World War (1978)