Developments in the USA
It was in the early 1900s when designers in the USA began to be innovative in the use of steel for long span structures.
The major developments in long span iron and steel roof structures took place, principally, in Europe. It was in the not until the first half of the twentieth century when designers in the USA were a major source of innovation. But it is the case that in the early 1800s American bridge engineers began to use trussed structures (the Fink truss) similar to those being used in France in bridge design, and also in railway stations and factories.
But, as in Europe, lack of technical understanding is evident in some early structures and this led to significant levels of redundancy in some structures. The bridge structure here (near Virginia) exemplifies these early over- complex structures.
Again, as in Europe, the iron truss gradually gained favour in a variety of building structures. A good early example of this is the Library of Congress in the Capitol Building Washington built between 1852 and 1854 where iron trusses provided the roof structure.
In the 1920s firms such as Ford Motors adopted mass production methods which, in turn, generated particular building types. Albert Kahn was a pioneer of the integrated industrial designs which ensued.
It was after the turn of the century when particularly important developments took place. The 1920s saw a rapid expansion in the mass production industries as typified by firms such as Ford Motors. These mass production industries introduced Operations and Methods analysis and this, in turn, led to highly developed factory layouts.
In the 1930s the widespread use of forklift trucks and the desire to be able to alter production layouts brought about the need for deep, wide span industrial buildings.
Deep lattice trusses had been in use for some time in bridge design and it was this technology which Kahn adapted for many of his buildings. Even lighting levels in the production areas were achieved by the development of the Monitor Roof form of construction which allowed a controlled amount of south light into the building to compliment the north light. The overall lighting was significantly better than in north light structures but this was accomplished without the penalty of high levels of insulation or heat loss.
Because deep, open structures were involved overhead gantries and servicing ducts were usually easy to accommodate in such structures.
Examples of this form of construction include the press shop for Chrysler at Detroit (1936)
However, the greatest tour de force in this family of Kahn structures was the Assembly Building for the Glenn Martin Aircraft Company at Baltimore (1937)
At the Glenn Martin trusses 30 feet (9m) deep spanned over 300 feet to give a column-free floor area of 500 feet by 330 feet, the monitor effect being achieved by bridging alternately between the top and bottom chords of these trusses.
In the 1940s industries supporting the war effort continued to provide a need for new long span industrial buildings.
Examples from this era include the Boeing bomber factory at Wichita, Kansas (by the Austin Company incorporating 300 ft. trusses supporting 10 ton underslung crane) and the Singer Sewing Machine Company factory at Finderne, New Jersey (which required a flexible workbench layout and in which the services are within the structural roof depth).
Increasingly in the 1950s and 60s industrial buildings were characterised by high levels of servicing. The deep-plan, highly serviced, windowless box was here.
A particular problem which the flat truss is prone to in these long span buildings is lateral instability. Narrow, deep structures like this tend to buckle sideways under load and Kahn solved this problem in the Martin Building by uniting adjacent trusses with the structure running at right-angles to the main structure to form a kind of integral trough structure. More recent developments have been to make the one-way spanning structure wider by forming the truss into a 'V' truss or 'V' beam or to make the structure span in two directions; hence the birth of the space frame.
