John Fleetwood Baker | |
|---|---|
| Born | (1901-03-19)19 March 1901 |
| Died | 9 September 1985(1985-09-09) (aged 84) Cambridge,Cambridgeshire, United Kingdom |
| Nationality | British |
| Education | Rossall SchoolClare College, Cambridge |
| Spouse | Fiona Mary MacAlister Walker |
| Children | Joanna and Dinah |
| Parent(s) | J. W. Baker, Emily Fleetwood |
| Engineering career | |
| Discipline | Structural engineer |
| Institutions | Institution of Structural Engineers |
| Projects | Baker Building,Cambridge University Engineering Department |
| Significant design | Morrison shelter |
| Significant advance | Plastic theory of structural analysis |
| Awards | IStructE Gold Medal OBE Fellow of the Royal Society[1] |
John Fleetwood Baker, Baron Baker (19 March 1901 – 9 September 1985) was a British scientist and structural engineer.[2][3][4]
Baker was born inLiscard, Cheshire, a son of J. W. Baker and Emily Fleetwood. He was educated atRossall School andClare College, Cambridge, and married Fiona Mary MacAlister Walker in 1928.
After graduation, Baker worked with theAir Ministry on structural problems ofairships. 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 alower bound on the collapse load, and is hence always safe. Until then, all design of steel structures was based onelastic theory of design. In 1932 he was awarded theTelford Gold Medal of theInstitution of Civil Engineers for the work.[5]
In 1933 Baker became Professor of Engineering atBristol University, after which he wasscientific adviser to the Design and Development Section of theMinistry of Home Security from 1939 to 1943. In this time he created theMorrison indoor shelter, using his plastic theory of structural analysis. Baker was appointed anOfficer of the Order of the British Empire (OBE) in the1941 Birthday Honours.[6]
From 1943 to 1968, he was Professor ofMechanical Sciences and Head of Department atCambridge 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 1956 Baker was elected aFellow of the Royal Society and awarded theirRoyal Medal in 1970.[1] In the1961 Birthday Honours he received aknighthood,[7] having the honour conferred byHM The Queen on 5 July 1961.[8]
In 1963 he became an honorary graduate as Doctor of Science at theUniversity of Edinburgh. He was created alife peer asBaron Baker,ofWindrush in theCounty of Gloucestershire on 1 February 1977.[9]
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 ofBrown 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 atCambridge University, and Baker presented an undergraduate lecture on the principles of design of theMorrison shelter as an interesting introduction to his theory of plastic design of structures; in 1968 this lecture was attended byPrince Charles, and it can be summarised as follows:
It was impractical to produce a design 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 a nearby blast, and the floor of the first storey pivoted about its other end (supported by a largely intact wall) and killed the inhabitants. The Morrison shelter was therefore designed to be able to withstand the upper floor falling, of a typical two-storey-house undergoing a partial collapse. 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.[10] 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.[11]
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