The Rongjiang Bridge, located in Jieyang City, Guangdong Province, China, is an integral part of the Xiamen-Shenzhen high-speed railway route. Boasting the title of the longest bridge in the world with a main span of 660 meters, it is a remarkable feat of engineering that features two flexible steel arches and rigid girders.
Constructed for the purpose of accommodating high-speed railway traffic, the Rongjiang Bridge is widely regarded as the most challenging long-span bridge ever built for such a purpose. The construction process was riddled with numerous obstacles, including the sheer scale of the project and the need for highly specialized components. Despite these challenges, the Rongjiang Bridge was successfully completed, showcasing the ingenuity and expertise of the construction team involved.
Model of Rongjiang Bridge
The article delves into the various structural elements of the Rongjiang Bridge, providing insights into its design, foundation details, and the construction procedure. Key factors associated with the bridge’s design are also highlighted, shedding light on the critical aspects considered during its construction. The article presents a comprehensive overview of the Rongjiang Bridge, covering its structural components, design considerations, foundation specifications, and construction process.
1. Structural Components of the Rongjiang Bridge
The Rongjiang Bridge comprises of three major structural components: the main girder, gusset plates, and the deck system. The main girder consists of four continuous spans of steel truss girders and two steel arches. On the other hand, the approach bridges are composed of prestressed concrete beams that measure 32 meters in length and are supported by simple supports. The steel truss girder has a weight of around 15,000 tons, while each single beam weighs approximately 70 tons.
For the steel components that are thicker than 40 mm, Q370-qE steel was utilized in the main bridge. Meanwhile, the more slender steel components, such as the supporting frameworks, were made of Q370-qD steel. The choice of concrete materials also varied depending on the specific structural elements. The pile foundations were made of concrete with a strength grade of C30, while piers were built using concrete with a strength grade of C35. Lastly, the pile caps were constructed with concrete of strength grade C40.
1.1 Main Girder of the Rongjiang Bridge
The main girder of a bridge was constructed using two components of an N-type triangular truss with vertical bars. The main trusses were separated by a distance of 15 meters from center to center and had an internode distance of 11 meters. There were a total of 20 and 10 internodes provided in the middle and side span of the bridge, respectively.
The height of the steel truss was limited to 15 meters and 30 meters in the middle span and at the supports, respectively. To increase the flexibility of the bridge, steel arches were added to the main girder. The shape of the steel arch was a parabola, allowing for a wider range of movement. The flexible arch had a span of 220 meters and a height of 44 meters, resulting in a rise to span ratio of 1/5.
The main truss beam consisted of three members, namely the lower chord, the upper chord, and the diagonal chord. These members were joined together using gusset plates and high-strength bolts. The truss members had either a box shape or an H-shaped cross-section, while the connecting rods had an H-shaped cross-section.
1.2 Gusset Plate
The Rongjiang Bridge extensively utilized gusset plates, including the E-11 plate, which is a fundamental component of the bridge’s design. The E-11 gusset plate is specifically located at the intersection of the steel truss girder and the flexible arch.
The stress experienced by the E-11 gusset plate is intricate due to its connection to ten different members. The E-11 gusset plate comprises five distinct types of steel plates, labeled N1, N2, N3, N4, and N5. The thickness of N1 is 50 mm, while N2 and N3 are 42 mm, and N4 and N5 have a thickness of 40 mm.
1.3 Deck System of the Rongjiang Bridge
The Rongjiang Bridge features a unique ballasted track deck arrangement, which is a first in the world of high-speed railway networks. The deck is composed of three distinct sections: the ballast bed, cushion, and steel deck. The spacing between the two tracks is 4.6 meters, and the sidewalk and ballast tank are 1.3 meters and 9 meters wide, respectively.
A light cushion was installed between the steel deck and ballast bed using the CAP high adhesion layer. To ensure waterproofing, the MMA system was used. A protective layer was created using a layer of C40 polypropylene fiber mesh concrete, with a thickness of 38 mm and a 12 mm thickness of AP high adhesion pad, to reinforce the CAP high adhesion lightweight layer.
To increase rigidity, the steel deck was connected to the lower chord with a spacing of 11 meters between the transverse beams. At each main transverse connection, three minor connections were provided at a spacing of 2.75 meters. An inverted T-shaped cross-section was chosen for the transverse beam connection.
The U-type ribs and I-type ribs were arranged on the deck panel of the bridge to create an orthotropic bridge deck system.
2. Design Criteria of the Rongjiang Bridge
The Rongjiang Bridge was specifically created to cater to a high-speed railway network. The designers took into consideration various design criteria to ensure the safety and efficiency of the bridge. One of the main constraints was the maximum speed, which was restricted to 250 km/h. Additionally, the longitudinal radius of the curve was set at 4500 m, while the maximum slope was limited to 6%.
To ensure the bridge could withstand the load and pressure, the ZK live load was chosen to design the railway track. The designers also selected standard load cases based on global standards for wind load, earthquake load, and dead load. These measures were taken to ensure that the bridge could safely bear the weight of trains, passengers, and any external factors such as wind or earthquakes.
Overall, the designers of the Rongjiang Bridge focused on creating a safe and reliable structure that would cater to the needs of a high-speed railway network. The various design criteria and standards chosen aimed to ensure that the bridge would withstand the test of time and provide a smooth and efficient experience for commuters.
3. Foundation Details of the Rongjiang Bridge
The Rongjiang Bridge was constructed using pile foundation, and it required three types of steel support piers: middle span pier support, side span pier support, and auxiliary pier support. The middle span pier support and side span pier support were designed with capacities of 10,000 tons and 7500 tons, respectively. On the other hand, the auxiliary pier support had a design capacity of 1500 tons.
To ensure excellent performance in dynamic loading for high-speed railways, the construction of the bridge used a hollow pier, which had a maximum height of 45 meters. The pile foundation for the bridge had a circular cross-section and provided two types of piles with diameters of 2 meters and 2.8 meters. The maximum depth of the pile foundation for the bridge was 110 meters
4. Construction Procedures
The main bridge was designed with V-shaped stiffening chords to create a continuous steel girder. To connect the other spans of the bridge, flexible steel arches were utilized. However, joining these flexible steel arches with the steel truss girder posed a significant challenge.
To address the connection issues, a plan was developed to construct the continuous steel truss girder with the flexible arch on different levels using a staged closure approach. This method involved constructing the continuous steel truss beam before building the flexible steel arch structures.
To construct the steel truss girder, four dewing derrick cranes were utilized on four different platforms. The cranes were positioned such that one crane could complete the work up to the mid-span of the two primary spans.
Subsequently, the flexible steel arches were gradually elevated by two dewing derrick cranes, moving from the external edge of the two flexible arch ribs to the focal point of the main bridge. At the intermediate pier, a butt joint was established to indicate the closing operation of the derrick cranes. The Rongjiang Bridge construction was completed by following these steps.
FAQs
Which is the world’s longest bridge with a rigid girder and flexible arch?
The Xiamen-Shenzhen high-speed railway network in China boasts the Rongjiang Bridge, which holds the distinction of being the longest bridge worldwide with a combination of a rigid girder and flexible arch. This engineering project is a significant feat of construction and spans an impressive distance. Its unique design blends the rigidity of a girder with the flexibility of an arch, making it a one-of-a-kind engineering marvel. The Rongjiang Bridge is a testament to China’s expertise in engineering and its commitment to pushing the boundaries of what is possible in modern construction.
What is the design speed of trains passing through the Rongjiang Bridge?
The train that is intended to run on Rongjiang Bridge has a designated design speed of 250 kilometers per hour. This means that the train is designed and built to operate at a maximum speed of 250 km/h when traveling on the Rongjiang Bridge. The term “design speed” is commonly used in transportation engineering to refer to the maximum safe speed at which a particular mode of transportation, such as a train, can operate under specific conditions. In this case, the design speed of 250 km/h for the train on Rongjiang Bridge indicates the maximum speed that it can safely and efficiently travel on that particular bridge.
What is the grade of steel and concrete used in the construction of the Rongjiang Bridge?
The main bridge utilized Q370-qE steel for all steel components thicker than 40 mm. On the other hand, the supporting frameworks utilized Q370-qD steel, which is more slender.
Different strength grades of concrete were chosen for various parts of the bridge. For instance, C30, C35, and C40 concrete were used for the pile foundations, piers, and pile caps, respectively.
How was the connection made between the flexible steel arches and the steel truss girder of the Rongjiang Bridge?
The method employed for connecting the continuous steel truss girder and flexible arch on different levels involved the utilization of staged closure. The erection process began with the construction of the continuous steel truss beam, followed by the implementation of the flexible steel arch structures. By adopting this approach, the connection between the two structures was made possible.