Truss Bridges, Types, Design Benefits, and Components Overview
Economically, truss bridges with spans between 100 and 200 meters have been employed. A bridge truss derives its economy from its two major structural advantages:
(a) the primary forces in its members are axial forces,
(b) greater overall depth permissible with ite open web construction leads to reduced self-weight when compared with solid web systems. The erection of a truss bridge is considerably simplified because of the relative lightness of the component members. A truss bridge’s visual appeal is questionable, mostly due to the elevation’s intricacy and the members’ varying orientations.
Types of Components
The major types of bridge trusses are shown in Fig The most common form is shown in Fig. (a) for the deck type and (b) for the through type.
The Pratt truss shown in Fig. Because the shorter verticals are in compression and the longer diagonals are in tension, 4 is thought to be favorable. If there is a chance that the diagonal stress could reverse, some of the panels in the middle might have counters.
The diagonals of the Pratt truss slope downward towards the center, whereas the diagonals of the Warren truss alternate downward toward the centre and downward away from the center. Panels of a Warren truss may be subdivided as in Fig. 4. (d) in order to provide better support for the deck, the arrangement shown referring to a through truss. Sub-division reduces the unsupported length by half and hence leads to more slender members, especially in compression. However, it also leads to higher unit prices of steel, less attractive final structure and higher secondary stresses in some cases. The k-bracing system shown in Fig. 4(e) is convenient when the depth of a bay is of the order of twice its length. The top chords may be curved in case of longer spans, as in Fig. 4. (f) and (g).
The various components of a typical through truss highway bridge are indicated schematically in Fig. 5. These components are:
- flooring
- stringers
- floor beams
- two main trusses
- lateral bracing provided at the top and bottom chord levels to cater to horizontal transverse loads
- sway frames.
Stringers carry the loads from the floor and are designed as simple beams. Floor beams transmit the load from stringers to the bottom nodes of the truss, and they are designed to simply beams. spanning between trusses. The top laterals consisting of struts and diagonal provide rigidity to the structure stabilise the compression chord, and carry the main part of the wind loads to the bridge portals.
Advantages of Truss Bridges
Extremely strong:- Truss bridges have an enormous load-bearing capability because of their interconnecting triangle structure. By distributing the weight from the road over its complex structure, the structure efficiently controls both compression and tension. This indicates that no component of the building is bearing an excessive amount of weight. In a sense, the strength of a chain is determined by its weakest link.
Uses materials effectively:- Despite having numerous interconnected components, the truss bridge’s utilization of materials is incredibly efficient. Every component contributes, and materials like steel, iron, and wood are all used to their fullest potential. When compared to other bridge designs, the construction of a big truss bridge might be a particularly cost-effective choice.
Withstands extreme conditions:- Truss bridges excel in situations where other bridge types, such beam and arch bridges, might not be a practical choice. They can go long distances and are frequently employed in hazardous areas like the deep gorges that separate mountain summits. Truss bridges are frequently used to support railroads in mountainous regions.
Roadways built on to the structure:- The truss bridge can support its highway on its framework, unlike other bridge designs. The load can be supported on a bottom truss, which is located beneath the main truss construction, along the middle (through truss), or above (deck truss). Because of the alternatives, the truss bridge is both cost-effective to construct and adaptable.
Disadvantages of Truss Bridges
Requires a lot of space:- By design, a truss bridge has a huge structure. To support and distribute significant weights, the connecting triangle components must be large. This implies that the truss bridge might not be the ideal choice in some constrained areas.
High maintenance costs:- Scale economies! There are many parts used in the truss bridge. Since each of these is reasonably light and efficiently utilized in the design, it makes financial sense to create a massive truss bridge. However, there are a lot of pieces that can be costly to maintain. Regular and thorough maintenance is necessary for a truss bridge, just like for any other load-bearing construction. With so many components to maintain, this may be costly and time-consuming.
Also Read:- Steel Bridges Types and Benefits
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