An engineering drawing is produced by the computer detailing the forces that develop in each chord and web under the given design loads. The gauge, size and orientation of each metal connector plate is precisely specified as well as the size, strength and location of permanent bracing. The carpentry contractor responsible for setting the timber trusses in place, must also get a copy of the these drawings to make certain that the design conditions are met.
The strength and integrity of the roof truss depends on the integrity of its metal plate connectors. Normally, there are eight teeth per square inch. These plates are sized according to the level of stress that they have to transfer between members of the timber truss. Timber trusses are most often made with southern pine dimension lumber. Many roof truss manufacturers use computer-driven saws that produce multiple cuts quickly and precisely.
The species, the size and the grade of lumber for each piece on the component cutting list cut sheet is based on the magnitude of force that each must resist while under potential maximum design load. Highly stressed, top and bottom chords are usually made of lumber that has been stress-rated, either visually or by machine, with rules mandated by code and industry association, to ensure specified performance.
The webs of the wood truss, because they are usually subjected to lower stresses, are more often made from a lesser grade of lumber, such as 2, 3 grades.
In short, the component industry brought the age of computers into home and commercial building construction. Spearheaded by the innovations of component and truss plate manufacturers, as well as by manufacturers of machinery for truss and wall panel production, the building component industry today is continuously enhancing and refining the computer technologies that improve the way we build.
Likewise, computers create paper and mylar templates for wall layouts on panel machines, which guide workers in the placement of members on wall panel machines. While the major truss plate and machinery suppliers continue to improve the software they offer their component customers, literally hundreds of component manufacturers have refined their software systems.
Combined with independent suppliers of software that are cropping up and marketing their products, the interest in engineering design software systems is accelerating improvements in software development on a continual basis. Because engineered building components offer benefits for everyone in the construction chain — architect and designer, builder, and building-buyer alike — it took just a little more than two decades for truss products to spread completely across the United States.
Architects today enjoy free rein in building design because of their confidence that component manufacturers will be able to duplicate in construction the designs they put on paper. As recently as 30 years ago, almost all houses were roofed with simple, triangular fink trusses. Now, some single home designs may use as many as different kinds of roof trusses to give the building interesting roof lines as well as arched, vaulted, and coffered ceilings.
Sophisticated engineering systems allow component manufacturers to quickly and confidently produce what architects design. In addition, should an Architect or Building Designer err in Engineering, Design, load development, layouts, or material optimization, these same computer systems may allow component manufacturers to uncover the error and recommend a solution long before any blunders become costly at the job site.
Engineering safety-margin factors and code provisions are built into the software for any structures under design. Often, with the participation and approval of the Building Designer, component manufacturers can also suggest ways to reduce the cost of a structure, by using dimensions that make the best use of common building materials.
Though builders are probably among the most reluctant to change their practices, the advantages of using trusses and other engineered building components at the job site have eliminated their objections.
Components allow builders to create higher quality buildings in less time, at less cost. Using components, some builders have been able to double the number of structures they can complete in a given time as compared to piece-by-piece construction at the job site. For example, construction of a home at a job site using the old fashioned stick framing method generally requires six months to as long as a year, while the same house can be framed three to four times faster using components, and can be finished in as little as one to three months.
The advantages of component construction have been illustrated dramatically. In a component manufacturer in New Jersey built duplicate homes — one stick-built and the other component-built. One was constructed using conventional stick-framing practices while the other used trusses in the roof and floor, and panelized walls.
But wood and iron can resist tension and compression better and stone and United States had much wood so they made many wooden bridges in those times and most of them were truss bridges. Town's lattice truss, a very simple variant of truss, was patented in First half of 19th century saw very few truss bridges made of iron although the first patent for an iron truss bride was issued to Squire Whipple in But metal slowly started to replace wood, and wrought iron bridges started appearing in the U.
In time some places like Pennsylvania continued building truss bridges for long spans well into s, while other like Michigan started building standard plan concrete girder and beam bridges.
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