BRIDGE DESIGN
“Beauty can be expressed in the structural efficiency, simplicity, and repetition of a bridge”
Bridge structure that spans horizontally between supports, whose function is to carry vertical loads. All significant bridges are built with the public’s money. Therefore, bridge design that best serves the public interest has a threefold goal: to be as efficient, economical, and elegant as safely possible. However, like any other structure, safety must be the top priority when building these bridges because people’s lives are at stake if something happens to their bridges. Skills for bridge engineers are also needed.
ELEMENTS OF BRIDGE DESIGN
There are six primary bridge forms: the beam, the truss, the arch, the suspension, the cantilever, and the cable stay.
- BEAM
Beam bridges are the oldest and most straightforward style, consisting of vertical piers and horizontal beams. A beam carries vertical loads by bending. A beam bridge’s strength depends on the power of the route and multiplies by adding extra piers. Whereas beam bridges are pretty long, the span, or distance between adjacent ports, is typically small.
2. TRUSS
A single-span truss bridge is like a supported beam because it carries vertical loads by bending. Bending leads to compression in the top chords (or horizontal members), the tension in the bottom chords, and either tension or reduction in the vertical and diagonal members, depending on their orientation. Trusses are popular because they use a relatively small amount of material to carry rather large loads.
3. ARCH
An arch bridge is a bridge whose main structure is composed of arches or reinforced arches. Arch bridges are very economical and advantageous if the horizontal reaction force caused by the loading of vertical loads is effectively applied and if they are appropriately designed to reduce the sectional details of members. Arch bridges have been widely used worldwide because of their unique aesthetics and are used for long-span bridges after suspension and cable-stayed bridges.
4. SUSPENSION
Suspension bridges are robust and might span long distances. They are high-priced. As a result, they take an extended time to create and need a large quantity of the fabric. They are sometimes found across harbors with tons of boat traffic. The first parts of a bridge are a try of main cables stretching over two towers and hooked up at every finish to an anchor. Smaller lines hooked up to most cables support the route.
5. CANTILEVER
A beam is said to be cantilevered when it projects outward, supported only at one end. A cantilever bridge is generally made with three spans, of which the outer spans are anchored down at the shore and cantilever out over the channel to be crossed. The cantilevers carry their loads by tension in the upper chords and compression in the lower ones
6. CABLE-STAY
Cable-stayed bridges carry the vertical main-span loads by nearly straight diagonal cables in tension. The towers transfer the cable forces to the foundations through vertical compression. The tensile forces in the lines also put the deck into horizontal compression.
Worst Bridge Collapses in History
1. Ponte des Barcas aka “Boats Bridge” in Porto (or Oporto), Portugal
In 1806, the first Porto bridge was inaugurated. However, the design of the bridge was very particular. At the time, the bridge was built by connecting several wooden boats together instead of building it with cables or structural members. However, in 1809, a tragic event happened. The French attacked the city of Portugal and over 4,000 people started to cross the bridge. The bridge at the time was not designed to hold so much weight, so it eventually collapsed, causing a lot of deaths. This incident is recorded as the worst bridge collapse because it caused the deaths of at least 4,000 people.
2. Eitai-Bashi Bridge in Tokyo, Japan
The wooden bridge was built in 1698, but the people living on either side of the bridge started arguing about who should be paying for the bridge repairs and maintenance. Under such disputes, the Eitai-Bashi Bridge was eventually left without care. During a big festival, the bridge became overloaded by the people crossing it, which collapsed and killed nearly 1,400 people. After the event, a second bridge was built using a more robust material (iron). However, the bridge collapsed again during the Great Kanto Earthquake. In 1926, the bridge was rebuilt using a muscular design as well as technologies and materials that could make the structure able to withstand the constant earthquakes near Japan.
These bridge structures are a great example of how engineers and designers can learn from their mistakes and improve accordingly.
CONCLUSION
Bridges are:
- A part of our civilization.
- The architecture of transportation routes.
- Everyday beauty.
They need to be safe and remain safe. If the bridge structure has an aesthetically pleasing appearance, it will improve city and landscape appearances. However, there are cases in which bridge structures deteriorate the landscape due to their ugly appearance.
Author: Shubham
REFERENCES
1.https://www.teachengineering.org/lessons/view/cub_brid_lesson02
2. https://www.midasbridge.com/en/solutions/arch-bridges
3. https://civiltoday.com/construction/bridge/347-suspension-bridge
4. https://www.britannica.com/technology/bridge-engineering/Truss
5.https://www.midasbridge.com/en/blog/newstrends/worst-bridge-collapse-in-history
