"Since the introduction of the pin connected steel truss in the United States in 1847 as a truss that could be actually designed, there has been very few basic changes in the truss as a structure. True, web members have been sloped or braced in many different ways to best adapt the truss for the structural materials being used, and over the protests of many , pin connections have almost wholly given way to riveted or arc welded connections, however, the basic idea of using all members as two force members has prevailed. Concern over the existence of bending stresses in the truss members served to delay the general adoption of connections that might permit these stresses to be introduced in the members. Even today there is much concern over detailing trusses in such a way as to minimize these "secondary" stresses.
Early in this century the Vierendeel - or rigid frame - truss became popular in Europe and through savings in steel, has proven economical. The Vierendeel truss in its early form consisted of a series of quadrangular rigid frames and was not considered suitable for adoption to American construction due to the complex riveting details necessary to obtain the continuity and rigidity of joints necessary for equilibrium in a truss of this form. The present form of the Vierendeel truss found in Europe is somewhat similar to that of the tied arch bridge in America and, due to high fabrication costs, fabrication costs, is not suitable here for medium and short spans - or externally indeterminate spans of greater length.
The objections to both the early and the present forms of the Vierendeel truss for use in America stem from the fact that the (labor to materials cost ratio) in America is much higher than it is in Europe.
Welding has been popular in the structural field, in America, for approximately twenty years, but is still not used as extensively in trusses as economy might warrant. This is due, in part, to the concern of many designers over the "secondary" stresses that could be introduced by rigid joints. Rigid joints are practically unavoidable in welding construction. Since welding would simplify the joint details and automatically produce the continuity sought, it appears to the author that the early form of the Vierendeel truss with welded joints might have considerable merit in the present day structural field in America.
The rigid frame truss is a highly hyperstatical structure - three times redundant for every panel - and most of the American literature on this truss has concerned itself chiefly with the development of "simplified" methods for its analysis. In the authors own investigations he found five startling different formulas for finding the inflexion points in the vertical chords - the first step in most methods of analysis. The concluding argument for many of the methods was data showing some sort of conformation with a mechanical analysis usually by models. The Beggs Deformeter apparatus is such a mechanical device, and is very popular for reviews and conformations or this type. It is the author's opinion that this apparatus could be used, to many advantages, for the entire design.
The purpose of this study is, through the use of the Beggs Deformeter apparatus for stress analysis, to make an economy study - from stand point of material and labor - of the rigid frame bridge truss for use in America"--Introduction, pages 1-3.
Carlton, E. W.
Civil, Architectural and Environmental Engineering
M.S. in Civil Engineering
Missouri School of Mines and Metallurgy
v, 82 pages
© 1951 Donald Lee Dean, All rights reserved.
Thesis - Open Access
Library of Congress Subject Headings
Iron and steel bridges
Strains and stresses
Bridges -- Design and construction
Print OCLC #
Electronic OCLC #
Link to Catalog Recordhttp://laurel.lso.missouri.edu/record=b2378252~S5
Dean, Donald Lee, "An economy study of Vierendeel trusses" (1951). Masters Theses. 4088.