We can see the beam bridges every where, but the difference from one another will be its type of design.The key differences, however, all come down to the design, location and composition of the truss.
"A truss bridge is that in which truss will be the load supercomposing structure"
SIMPLE DEF : Truss is a formation produced by triangular components, in accordance with the truss bridge drawings, and coupled at joints known as nodes. The triangular units forming the truss are slim and straight in form.
.The connected elements (typically straight) may be stressed from tension, compression, or sometimes both in response to dynamic loads.
"A truss bridge is that in which truss will be the load supercomposing structure"
SIMPLE DEF : Truss is a formation produced by triangular components, in accordance with the truss bridge drawings, and coupled at joints known as nodes. The triangular units forming the truss are slim and straight in form.
.The connected elements (typically straight) may be stressed from tension, compression, or sometimes both in response to dynamic loads.
STRUCTURE AND DESIGN :
The structure and design of the truss bridge has been done by using newtons' laws of motion according to statics. Int he bridge vertical members are in tension,lower horizontal members in tension, shear, and bending, outer diagonal and top members are in compression, while the inner diagonals are in tension.
And there's another reason why a truss is more rigid than a single beam: A truss has the ability to dissipate a load through the truss work. The design of a truss, which is usually a variant of a triangle, creates both a very rigid structure and one that transfers the load from a single point to a considerably wider area.
The truss may carry its roadbed on top, in the middle, or at the bottom of the truss. Bridges with the roadbed at the top or the bottom are the most common as this allows both the top and bottom to be stiffened, forming a box truss. When the roadbed is atop the truss it is called a deck truss (an example of this was the I-35W Mississippi River bridge). When the truss members are both above and below the roadbed it is called a through truss (an example of this application is the Pulaski Skyway), and where the sides extend above the roadbed but are not connected, a pony truss or half-through truss.
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| THROUGH TRUSS |
A single beam spanning any distance undergoes compression and tension. The very top of the beam gets the most compression, and the very bottom of the beam experiences the most tension. The middle of the beam experiences very little compression or tension. This is why we have I-beams, which provide more material on the tops and bottoms of beams to better handle the forces of compression and tension.
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| DECK TRUSS |
And there's another reason why a truss is more rigid than a single beam: A truss has the ability to dissipate a load through the truss work. The design of a truss, which is usually a variant of a triangle, creates both a very rigid structure and one that transfers the load from a single point to a considerably wider area.
TRUSS USED IN BRIDGES:
Allan truss :
It is on the based on the Howe truss.
Bailey bridge :
Designed for military uses, the prefabricated and standardized truss elements may be easily combined in various configurations to adapt to the needs at the site. In the image at right, note the use of doubled prefabrications to adapt to the span and load requirements. In other applications the trusses may be stacked vertically.
BALTIMORE BRIDGE :
The Baltimore truss is a subclass of the Pratt truss. A Baltimore truss has additional bracing in the lower section of the truss to prevent buckling in the compression members and to control deflection. It is mainly used for rail bridges, showing off a simple and very strong design.
Bowstring arch truss :
The bowstring arch through truss bridge was patented in 1841 by Squire Whipple. While similar in appearance to a tied-arch bridge, a bowstring truss is a truss and thus has diagonal load-bearing members. These diagonals result in a structure that more closely matches a Parker truss or Pratt truss than a true arch.
CANTILEVER TRUSS :
Most trusses have the lower chord under tension and the upper chord under compression. In a cantilever truss the situation is reversed, at least over a portion of the span. The typical cantilever truss bridge is a "balanced cantilever", which enables the construction to proceed outward from a central vertical spar in each direction. Usually these are built in pairs until the outer sections may be anchored to footings. A central gap, if present, can then be filled by lifting a conventional truss into place or by building it in place using a "traveling support".
Howe truss :
A truss having upper and lower horizontal members, between which are vertical and diagonal members; the vertical web members take tension, and the diagonal web members are under compression.
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