The Oohi West Bridge Viaduct, located in Okayama Prefecture in western Japan, is a remarkable engineering feat designed to address chronic traffic congestion on National Highway 2, one of the country’s main trunk lines. Spanning the Oohi Bridge West crossing and intersecting with National Highway 180, the viaduct was built with careful consideration to maintain traffic flow, securing six inbound and outbound lanes during the daytime and four at night. The project required an innovative approach to construction, given the complex conditions and limited space between the highway lanes. This led to the adoption of a technical proposal/negotiation-type work order, fostering close collaboration between designers and contractors.
The viaduct’s superstructure integrates a 3-span continuous twin box girder with a steel orthotropic deck and steel piers. Under strict on-site conditions, including a narrow work yard, the construction team utilised advanced erection techniques to minimise disruption to road traffic. Notably, the project incorporated a superstructure/substructure-integrated erection method using a multiple-axle special bogie, which facilitated rapid construction and significantly reduced working hours. These innovative methods, alongside strategic structural changes, contributed to the overall success of the project, shortening the construction timeline while ensuring minimal impact on daily traffic.
In this interview, we spoke with Mr. Eiji Takada, Managing Executive Officer at FaB-Tech Japan, to explore the pivotal role steel played in the Oohi West Bridge Viaduct project and how this innovation has paved the way for future infrastructure developments.
Can you tell us how steel was incorporated into the Oohi West Bridge Viaduct project?
Steel was essential to the Oohi West Bridge Viaduct because of its strength-to-weight ratio. It allowed us to design large spans, minimising the number of supports on the busy highway below. Steel’s durability and flexibility were also key to managing the environmental challenges, while simplifying the construction process and reducing traffic disruption.
The bridge features a steel orthotropic deck. How did this design choice benefit the project?
The steel orthotropic deck is both strong and lightweight, which was critical for minimising weight while ensuring the bridge’s strength. This allowed us to use specialised transport vehicles and cranes to quickly assemble the structure, reducing on-site construction time and the impact on traffic.
The project saw a significant reduction in construction time. How did steel contribute to this efficiency?
Steel enabled the pre-assembly of large bridge sections off-site, allowing for efficient transportation and rapid installation using specialised vehicles. Compared to concrete, steel piers provided greater strength and flexibility, streamlining the construction process and enhancing both safety and efficiency. This approach significantly reduced the overall construction period, minimised traffic disruption, and improved traffic management.
The project benefited from Building Information Modeling (BIM) implementation. How did it contribute to shortening the construction timeline?
BIM and Construction Information Modeling (CIM) were utilised in the erection of the Oohi Bridge West Viaduct to optimise execution planning, quality, safety, and traffic control. By integrating 3D point cloud data with a 4D execution model, the construction sequence, interference, and worker coordination were improved. Additionally, virtual simulations, including a driver’s perspective video, enhanced communication with stakeholders and minimised rework by identifying potential issues in advance.
How do you see steel playing a role in future infrastructure projects in Japan?
Steel will continue to be a crucial material in infrastructure projects, especially for projects requiring fast construction and minimal disruption. In Japan, we are already seeing more steel used in bridges, high-rise buildings, and tunnels. The combination of steel’s strength, flexibility, and modern construction methods will drive future innovation.
What key lessons from the Oohi West Bridge Viaduct project would you recommend for future infrastructure projects?
Collaboration from the start is essential. The Early Contractor Involvement (ECI) system helped us make important design changes early on, ensuring a smoother process. Advanced construction methods, like integrated erection and specialised transport vehicles, also proved invaluable in speeding up the project.