truss — A framework of triangulated forms in which all loads are carried by compression or tension in each member of the frame. It is time for the fire service to make peace with an old nemesis: the truss . For too long, the fire service has vilified this structural engineering marvel. Trusses...
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truss — A framework of triangulated forms in which all loads are carried by compression or tension in each member of the frame.
It is time for the fire service to make peace with an old nemesis: the truss. For too long, the fire service has vilified this structural engineering marvel. Trusses are strong, efficient, reliable, predictable and, once you get to know them, pretty cool. Trusses have been around longer than the fire service has existed in North America.
In this article, you will get to know the truss. You will understand the components of a truss. You will understand how a truss works. Later, you will discover the most unreliable, unpredictable and dangerous factor at any fireground operation.
It is time for the fire service to acknowledge that without lightweight building construction, in particular truss construction, many communities in North America could not afford to have a modern fire department. Because of the high cost of conventional building construction, it would be too expensive to build strip malls and warehouse stores. It would be too expensive to build garden-type, multi-family complexes. Without lightweight building construction, most of us couldn't afford to own a home. It is quite possible that the structure within which you are currently reading this article would not exist. I'm perfectly serious about the fire service embracing the truss as a reliable and predictable engineering marvel rather than perpetuating irrational fear and loathing akin to the villager's irrational fear of Victor Frankenstein's "engineered" monster. Had the village-folk been open-minded and taken the time to understand Frankenstein's creation, they may have liked the big guy.
Truss trivia Command-O-Quiz: When were trusses first used in building construction?
- After World War II
- Medieval Europe
- America's Industrial Revolution
- The Roman Empire
Answer: d. Roman Empire. Roman engineers and architects used simple trusses to support bridges and roofs. These trusses were capable of spanning up to 60 feet. Many believe that the ancient Greeks used rudimentary trusses for residential structures.
The earliest known description of a true truss appeared in The Ten Books of Architecture (De Architectura) published in the first century BC by the Roman architect Vitruvius. The text describes a simple truss: "…the upper parts of all buildings contain timber work to which various terms are applied. The main beams are those which are laid upon columns and pilasters; tie-beams and rafters are found in the framing."
After the fall of the Roman Empire, the use of trusses in building construction disappeared for centuries until Europe began extricating itself from the Dark Ages. Used in Romanesque and Gothic cathedrals during the Middle Ages, European wood roof trusses were a continuation of Roman design and building traditions. The oldest surviving detailed plans of trusses were published in 1570 by an Italian architect, Andrea Palladio. The Palladian style borrowed from the classical Roman principles he rediscovered, explained and applied in his works. His designs for bridges comprised of timber and iron straps were well in advance of any truss construction into the 19th century.
It wasn't until the 1800s that truss design became a function of engineering calculations rather than "rules of thumb" passed from generation to generation of skilled craftsmen to their apprentices. The rise of structural engineering as a profession paralleled the American Industrial Revolution. In 1850, D.I. Jourawski, a Russian engineer, developed the first method for analyzing truss behavior.
In the United States, mid-1800 carpentry manuals included rudimentary information on truss design. However, it wasn't until 1871 that a carpentry manual included procedures for engineering analysis of simple truss behavior. Truss design became a technically advanced engineering form with the design and construction of railroad bridges. It was during this period that patents were bestowed for proprietary truss designs.