“Bridges” are advanced architectural structures of the past that have transformed transportation and allowed people to conveniently and efficiently travel from one place to another, reducing distance and time. However, have you ever noticed why each bridge has a different appearance? Whether it’s the shape, material, size, and more, besides functionality and aesthetics, the construction of each bridge has a hidden history and engineering principles at its core.
For the “Steel Bridge,” which uses steel as its construction material, it is widely known that steel possesses durable and strong properties, with a long lifespan. Therefore, it is commonly used in constructing fundamental structures of a country, making the construction of “Steel Bridges” a worthwhile investment in terms of budget allocation for national development. Today, we will take you on a journey to explore the behind-the-scenes stories and histories of famous steel bridges in Thailand, and discover why the bridges we are familiar with are built in the current form.
Today, WCE would like to delve into the background of four renowned bridges: the Phutthayotfa Bridge The Memorial Bridge (Bangkok), the Rama IX Bridge (Bangkok), the Chaloem Phrakiat Ratchakan Thi 9 Bridge (Phitsanulok), and the Kan Kheng Rail Bridge (Ratchaburi). Each bridge has its own design, function, and location, and each design is rooted in engineering principles. Let’s explore how these bridges are designed and which engineering principles they incorporate.
1. The Memorial Bridge (Bangkok)
The Memorial Bridge, commonly known as the ” Phra Phuttayotfa Bridge,” was built during the reign of King Rama VII, utilizing advanced construction technology and innovative techniques of that era. It was the first large-scale bridge constructed with steel that could be opened and closed to allow the passage of large ships. This feature was crucial as the bridge spanned the Chao Phraya River, which served as a major route for large vessels.
The bridge is designed for vehicular traffic, connecting Phra Nakhon and Thonburi across the Chao Phraya River. It has a steel structure with a length of 229.76 meters, a width of 16.68 meters, and a clearance height of 7.50 meters above water. When the bridge is opened, it creates a 60-meter-wide channel to allow the passage of large vessels.
Messrs Dorman Long & Co. Ltd from Middlesbrough, England, was the construction contractor responsible for this bridge. It was built with a reinforced concrete caisson in the middle of the river to support the upper structure made of steel. The Memorial Bridge features a truss design, which provides compression and tension support to the upper surface and underside of the bridge. This truss design is lightweight, aesthetically pleasing, and capable of handling heavy loads. It is particularly suitable for long-span bridges, eliminating the need for central supporting pillars. The Memorial Bridge is considered the most modern bridge of its time in Thailand.
2. Rama IX Bridge
The Rama IX Bridge, also known as the Suspension Bridge, is the first single-plane fan-type cable-stayed bridge in Thailand. It was constructed in the year 1987 and is used for vehicular traffic across the Chao Phraya River. The bridge has a total length of 2,716 meters, with the specific bridge span measuring 782 meters. It stands at a height of 41 meters above the water level.
The construction of a cable-stayed bridge is suitable for bridges with longer central spans compared to cantilever bridges but shorter than suspension bridges. In this type of bridge, large cables are used, attached to the high towers of the bridge, to support its weight. The Rama IX Bridge serves as a single point of load transfer, concentrating all the weight at the tower. Additionally, the cables also contribute to the overall balance of the bridge, allowing it to withstand the weight transferred from the cables and the bridge itself simultaneously.
3. Phra Ratchawang Chan Bridge (Phitsanulok)
The Phra Ratchawang Chan Bridge, also known as the Nan River Crossing Bridge, is a new landmark of Phitsanulok Province, connecting to the eastern bank of the Nan River near Wat Phra Sri Rattana Mahathat Woramahawihan. The bridge has a total length of 116 meters and features a steel arch bridge design. The main arch spans 80 meters without the need for a central pillar, adding to its beauty and modernity. This design also doesn’t obstruct the annual long-boat racing tradition held there.
The steel arch structure utilizes compression or pushing force as the resistance to bear the weight. The weight of the bridge is distributed in the form of compressive force along the arches, allowing the steel structure to have a slender and aesthetically pleasing shape. This bridge is considered the first steel arch bridge in Thailand.
The special features of the Phra Ratchawang Chan Bridge are its construction as a steel arch bridge, with a total length of 116 meters and an 80-meter span without a central pillar. Apart from being a beautiful and modern bridge, it is also highly durable and does not obstruct the annual long-boat racing tradition. The Phra Ratchawang Chan Bridge is also considered the first steel arch bridge in Thailand.
4. Ratchaburi Railway Bridge
Ratchaburi Railway Bridge, also known as the Karn Keung Railway Bridge, is one of the bridges along the dual-track railway between Nakhon Pathom and Nong Pla Lai. It is located parallel to the Chulalongkorn Bridge or the railway bridge crossing the Mae Klong River in Ratchaburi Province. This area was a bombing target by the Allied forces during World War II, resulting in the destruction of the Chulalongkorn Bridge. Additionally, seven locomotive heads and explosives sank underwater.
Although they are unexploded ordnances (UXOs), the recovery and disposal of all explosives could pose more risks. Therefore, the construction project of the dual-track railway that passes through this area required detailed planning and design. As a result, a special engineering technique was used, known as the extradosed bridge, with a total length of 340 meters and a bridge section spanning 160 meters. The bridge pillars are constructed on both riverbanks without any pillars under the water like other bridges.
This bridge is a combination of a cable-stayed bridge and a balanced cantilever bridge that uses cable stays for reinforcement. The extradosed bridge has similarities to a cable-stayed bridge as it has tall towers above the bridge deck and cable stays to support the bridge’s weight. However, the extradosed bridge has shorter towers and less steeply inclined cables compared to a cable-stayed bridge. This unique bridge design makes it the first extradosed railway bridge in Thailand.
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