Curved top chord and a straight bottom chord
A truss bridge is a bridge whose load-bearing superstructure is composed of a truss, a structure of connected elements forming triangular units. The connected elements (typically straight) may be stressed from tension, compression, or sometimes both in response to dynamic loads. A Post truss is a hybrid between a Warren truss and a double-intersection Pratt truss. Invented in 1863 by Simeon S. Post, it is occasionally referred to as a Post patent truss although he never received a patent for it. The Ponakin Bridge and the Bell Ford Bridge are two examples of this truss. The top chord was curved in the manufacturing process. This type of bowstring truss (as manufactured by Timber Structures, Inc.) was known as a Tim Truss. The webs were often solid sawn members. The top chords were originally made with multiple leaf chords where the curvature was cut into the solid sawn chord members. A second style of bowstring truss used glued-laminated chords. The top chord in these trusses was curved in the laminat The basic types of truss bridges shown in this article have simple designs which could be easily analyzed by 19th-and early 20th-century engineers. A truss bridge is economical to construct because it uses materials efficiently. A Post truss is a hybrid between a Warren truss and a double-intersection Pratt truss. Invented in 1863 by Simeon S. Post, it is occasionally referred to as a Post patent truss although he never received a patent for it. The Ponakin Bridge and the Bell Ford Bridge are two examples of this truss. Attacking the Fire. When working a fire that involves a building with a bowstring truss, there are many critical elements to consider: 1  Be extremely cautious with your risk analysis; carefully weigh the risk vs. benefit of placing firefighters inside or on these structures. Fires in buildings with bowstring truss roofs can confound even the most experienced chief officer; often, they may not know that the building has a bowstring truss roof, which is usually due to either a lack of preplanning or a lack of communicating an informal (or formal) preplan. Learning how to make a bow string regardless of your surroundings can make the difference between eating or starving in a survival situation. Bow strings can be made out of various materials including thread, string, and cord that may already be located within your clothes or survival pack. 1 The bowstring will secure to the bow using these notches. 2  If the bow you have is a handmade bow or bow material found in the natural area then a notch at the top and bottom of the bow should be made. 3  Measure the string and string the bow. Bowstring trusses are made with a curved top chord and a straight bottom chord. The top chords were originally made with multiple leaf chords where the curvature was cut into the solid sawn chord members. A second style of bowstring truss used glued-laminated chords. The top chord in these trusses was curved in the laminating process. While these trusses have carried the roof load for decades, it is not uncommon to receive calls regarding broken trusses following a heavy snow event Japanese bowstring (tsuru) and woven bowstring holder (tsurumaki). A bow string joins the two ends of the bow stave and launches the arrow. Desirable properties include light weight, strength, resistance to abrasion, and resistance to water. See Kyūdō. Looped strings are made of one or more continuous loops of material. Modern strings are often made as a single continuous loop: this is then served to give the final form. Disadvantages include the lesser amount of fiber at the ends, where wear is most likely; this may be overcome by serving the string. 1 Measure out the string to fit this length requirement. 2  String the bow with the bow string. 3  This is done by simple attaching the ends of the bow string into the notches of the bow. 4  Once this is done make sure that the string is secure. 1 The bowstring will secure to the bow using these notches. 2  If the bow you have is a handmade bow or bow material found in the natural area then a notch at the top and bottom of the bow should be made. 3  Measure the string and string the bow. Buildings built with bowstring truss roof structures have a number of other factors that can make them susceptible to collapse. For example, bowstring trusses can be constructed of wood or steel, but most often, they’re made of wood—often heavy timber. They also have construction features that make firefighting in these buildings different than other buildings. Fires in buildings with bowstring truss roofs can confound even the most experienced chief officer; often, they may not know that the building has a bowstring truss roof, which is usually due to either a lack of preplanning or a lack of communicating an informal (or formal) preplan.
https://en.wikipedia.org/wiki/Truss_bridge http://www.westernwoodstructures.com/index.php/white-papers/bowstring-trusses/ https://en.wikipedia.org/wiki/Truss_bridge http://www.firefighternation.com/article/firefighter-safety/bowstring-truss-roof-construction-hazards http://www.mademan.com/mm/how-make-bow-string.html/ http://www.westernwoodstructures.com/index.php/white-papers/bowstring-trusses/ https://en.wikipedia.org/wiki/Bowstring http://www.mademan.com/mm/how-make-bow-string.html/ http://www.firefighternation.com/article/firefighter-safety/bowstring-truss-roof-construction-hazards
what is a bowstring truss made out of