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● Disadvantages of Truss Bridges
>> 2. How does a truss bridge work?
>> 3. What are the advantages of a truss bridge?
>> 4. What are the disadvantages of a truss bridge?
>> 5. Where can I find examples of truss bridges?
A truss bridge is a type of bridge whose load-bearing superstructure is composed of a truss, a structure of connected elements, typically forming triangular units[13]. The connected elements are usually straight and may be stressed from tension, compression, or sometimes both in response to dynamic loads[13].
The individual pieces of a truss bridge intersect at truss joints, or panel points[10]. The connected pieces forming the top and bottom of the truss are referred to respectively as the top and bottom chords[10]. The sloping and vertical pieces connecting the chords are collectively referred to as the web of the truss[10].
The component parts of a truss bridge are stressed primarily in axial tension or compression[10]. A single-span truss bridge is like a simply supported beam because it carries vertical loads by bending[10]. Bending leads to compression in the top chords (or horizontal members), tension in the bottom chords, and either tension or compression in the vertical and diagonal members, depending on their orientation[10].
A truss bridge is a load-bearing structure that can hold weight from above by directing it to the foundation below[1]. Every truss bridge contains vertical, horizontal, and diagonal members[1]. The horizontal members, also known as chords, help reinforce the bridge to support the weight[1]. The top chords are in compression, while the bottom chords are in tension[1]. The diagonal (and sometimes the vertical) members will connect to the chords to transfer the compression and tension forces[1]. Then the resultant triangular shapes are part of the truss bridge's unique design[1]. The trusses give the structure the strength it needs to handle the load, often with less raw materials & weight than that of a beam bridge[1]. The bridge is supported by an abutment at each end of the truss where the load is transferred to the ground[1].
Truss bridges offer several advantages in construction[8]:
- High Strength The triangular shape that the supports are placed in give it a great amount of strength[2]. This gives it the ability to carry heavy traffic loads, making it ideal for dense population areas[2].
- No Span Restrictions One of the most appealing properties of a truss bridge is that it can be built over very long as well as very short distances[2]. This makes it available to be built just about anywhere with little problems[2].
- Road Placement The truss bridge is one of the only types of bridges that allows for the road to be placed on top of it, rather than built into it[2]. This makes it very easy to construct and integrate into existing construction processes[2].
- Relatively Economical There are very minimal amounts of materials needed to build a truss bridge, and each piece is used very efficiently[2]. The amount of waste is small, and in combination, cheap and light materials are often used[2].
- Rapid Installation: Truss structures are prefabricated in factories and easily assembled on-site, leading to quicker construction timelines[8].
- Increased Span Length: Their triangular force distribution minimizes force concentration, allowing for longer span lengths[8].
- Accessibility: Triangular spaces between truss members create pathways for electrical and mechanical installations[8].
- Efficient use of materials: A truss bridge is economical to construct primarily because it uses materials efficiently[13].
Despite their strengths, truss structures have limitations[8]:
- Large Amount of Maintenance Required Very close and involved maintenance of all of the various components of the bridge are necessary with truss bridges[2]. Each part plays an integral role in the integrity and safety of the bridge, requiring close monitoring[2][5]. Every inch of the structure plays a significant role in how the span performs[5]. There are several additional connections and components in this design that create a higher risk of failure at some point[5].
- Difficult Design To Execute Precise and often complicated designing is involved in building a truss bridge that is appropriate for the area it needs to cover[2]. The perfect sizing, spacing, and proportions have to be considered[2]. Truss bridges require perfect construction to work and they must distribute weight evenly[11].
- Heavy Weight The overall weight of the structure can be very heavy[2]. This poses problems when it needs to be built in areas without much support[2]. Often times, additional support beams are necessary[2].
- Low Weight Capacities Truss bridges were first built with lightweight vehicles in mind[2]. With the heavy-duty vehicles that are common in today's world, they cannot withstand as much traffic as they were originally intended[2]. Older truss bridges designed for light traffic can have a lower weight tolerance[11].
- Material Waste Possibilities One of the biggest risks of building a truss bridge is having a mishap with construction or design[2]. The specifications for the bridge have to be perfect in order for it to work the way it is supposed to[2]. If any of this is off at all, then a large amount of materials can go to waste because of how much is needed for only a small portion of the bridge[2].
- Space Taker The support that truss bridges require can take up quite a bit of space[2]. The construction of these bridges could affect surrounding areas and the water beneath it[2][5]. The interconnecting triangular components need to be large in order to bear and distribute heavy loads[5][14]. The structure of a truss bridge is large by design, hence can take up quite a bit of space[5]. This means that in certain places, the truss bridge may not be the best option or might need adjustment of existing structures in order to accommodate these bridges[5].
- Not The Best Option When it first came to conception, the truss bridge was a perfect solution to many limits in construction and materials[2]. Since then, however, many that have been built have been reevaluated and replaced with more efficient and structurally sound types of bridges[2].
- Space Requirement: The interconnected triangular components require ample space, particularly in large truss bridges[8].
- Maintenance Costs: Truss structures can incur high maintenance costs, especially for extensive projects[8][14].
- Weight: Due to their size, truss structures can be heavy[8].
- Less attractive: Less attractive to look at compared to modern concrete bridges[11].
- Requires Specialists: Requires architectural and engineering specialists, which means less use of general laborers and steelworkers[11].
- Tokyo Gate Bridge, Kōtō City, Japan[11].
- Astoria-Megler Bridge, Columbia River, USA[11].
- Quebec Bridge, Canada[11].
Truss bridges are a common type of bridge that utilizes a truss, a structure of connected elements usually forming triangular units, to bear loads[13]. They offer several advantages, such as high strength, no span restrictions and efficient use of materials[2][13]. However, they also have disadvantages, including high maintenance costs, space requirements, and potential material waste[2][8]. Despite these limitations, truss bridges remain a popular choice for many construction projects due to their strength and versatility[2].
A truss bridge is a bridge whose load-bearing superstructure is composed of a truss, a structure of connected elements, usually forming triangular units[13]. The connected elements are typically straight and may be stressed from tension, compression, or sometimes both in response to dynamic loads[13].
A truss bridge works by transferring the weight from above to the foundation below using vertical, horizontal, and diagonal members[1]. The top chords are in compression, while the bottom chords are in tension[1]. The diagonal and vertical members connect to the chords to transfer the compression and tension forces[1]. The triangular shapes in the truss design provide the structure with the strength it needs to handle the load[1]. The bridge is supported by an abutment at each end of the truss where the load is transferred to the ground[1].
The advantages of a truss bridge include high strength, no span restrictions, road placement flexibility, relative economic efficiency, rapid installation, increased span length, accessibility for electrical and mechanical installations, and efficient use of materials[2][8][13].
The disadvantages of a truss bridge include the need for a large amount of maintenance, difficult design execution, heavy weight, low weight capacities, potential for material waste, large space requirements, and high maintenance costs[2][5][8]. They can also be less attractive compared to modern concrete bridges and require architectural and engineering specialists[11].
Examples of truss bridges include the Tokyo Gate Bridge in Kōtō City, Japan; the Astoria-Megler Bridge on the Columbia River, USA; and the Quebec Bridge in Canada[11].
[1] https://aretestructures.com/how-does-a-truss-bridge-work/
[2] https://navajocodetalkers.org/the-pros-and-cons-of-truss-bridges/
[3] https://blog.wordvice.cn/common-transition-terms-used-in-academic-papers/
[4] https://www.tn.gov/tdot/structures-/historic-bridges/what-is-a-truss-bridge.html
[5] https://honestproscons.com/truss-bridge/
[6] https://gist.github.com/allenfrostline/c6a18277370311e74899424aabb82297
[7] https://aretestructures.com/what-is-a-truss-bridge-design-and-material-considerations/
[8] https://www.linkedin.com/pulse/exploring-truss-structures-construction-features-types
[9] https://b3logfile.com/pdf/article/1653485885581.pdf
[10] https://www.britannica.com/technology/truss-bridge
[11] https://blog.enerpac.com/7-types-of-bridges-every-engineer-should-know-about/
[12] https://www.xiahepublishing.com/2475-7543/MRP-2022-801
[13] https://en.wikipedia.org/wiki/Truss_bridge
[14] https://www.machines4u.com.au/mag/truss-bridges-advantages-disadvantages/
[15] https://blog.csdn.net/Oomai_/article/details/134718108
