IAC News

1. Overview of Revisions
The current JSCE Standard Specifications for Concrete Structures are made up of the following sections: Basic Principles, Design, Materials and Construction, Maintenance, Dam Concrete, and Test Methods and Specifications. As part of the specifications established in 2022, the Basic Principles, Design, and, Maintenance sections were revised, with the Materials and Construction and Dam Concrete sections revised as part of the version of the specifications established in 2023. For the Basic Principles and Dam Concrete sections, it was the first revision in 10 years since the 2012 version of the specifications, and for the other sections, it was the first revision in approximately five years.

The overall features of the latest set of revisions are as follows:

(1) Bringing Renovation to the Forefront
The requirements and performance of social infrastructure change depending on shifts in society and the economic climate. The demand for not only new installations but also renovating existing structures and integrating new and old structures together has increased, and as such, there is a strong call for the specifications to also reflect this. Thus, there was a need for performance assessments of existing structures and to tackle problems arising along with integrating new and old structures, and as a result, efforts to link the Basic Principles, Design, and Maintenance sections have advanced.

(2) More thorough Explanations
The Standard Specifications for Concrete Structures are composed of a main text and explanations. In the explanations up to now, numerous expressions were considered similar to the provisions in the main text, and this was one of the reasons why the Standard Specifications for Concrete Structures were criticized for being difficult to understand. This issue was looked at closely in the latest set of revisions, with the explanations made more distinct from the main text to provide proper explanations.

(3) Publishing of a Digital Copy as well as a Physical Copy (Japanease Version)
Many people have asked about getting a digital copy of the Standard Specifications for Concrete Structures due to the digital copy being easier to carry around and search compared to the bulky physical version. The JSCE Publishing Committee began sales of a digital version of the previous 2017 edition in 2022. The latest edition is now available as both a physical and digital copy from the outset.

2. About the English Translation
Ever since the first edition of the Standard Specifications for Concrete Structures was published in 1931, it has been revised almost every five years to match the advancement of technology. An English version of the specifications was also produced for the 1986, 2002, and 2007 editions. While an English version was no longer produced from the 2007 edition onward, the need to share this information with the wider global community was reaffirmed and an English version of the latest edition was produced after about two years of hard work. Currently, the original Japanese version of the Standard Specifications for Concrete Structures is divided into different volumes such as the Basic Principles, Design, Materials and Construction, and Maintenance sections, with each section made up of a “Main Text” section that forms the backbone of the performance-based specifications, as well as a “Standards” section that indicates the standard technical information. The latest English version places an emphasis on effectively communicating the structure and overview of the specifications from start to finish, with a full translation of the “Main Text” of each section and an abridged translation of the “Standards” section compiled into a compact book. For many people to get easy access and read the specifications, a digital version was made available for free online. However, due to reasons relating to the schedule for translating the original Japanese version into English, the content was based on the previous 2017 edition of the specifications. I hope the English version of the specifications proves useful in sharing technical information about concrete structures in Japan with the rest of the world, as well as in training, research, and practical work.

・JSCE Concrete Committee Website: https://www.jsce.or.jp/committee/concrete/e/index.html
 

【Reported by Concrete Committee】

Sumire
Watanabe
(JICA)

My first business trip when joining the Japan International Cooperation Agency (JICA) was to Democratic Republic of the Congo. After traveling eight hours or so by car on National Road 1, a bumpy road stretching 350 km from the capital of Kinshasa, we arrived at the city of Matadi. The Matadi Bridge lies at the point where the colossal Congo River, which is the second-longest river in Africa, intersects with the country’s main logistics artery, National Road 1. The Matadi Bridge is a 722-meter-long suspension bridge that was built 41 years ago with Japanese ODA when the Democratic Republic of the Congo was still called the Republic of Zaire.

While the Matadi Bridge was 39 years old when I visited the site in 2022, it had not once undergone any large-scale repairs. Nonetheless, the bridge had been kept well looked after, with the paint coating of the bridge in good shape, everything up to the drainage channels kept clean, and the hanger ropes nice and tense. With trucks and people constantly going over the bridge, it was obvious that the bridge is an important structure in supporting the country’s logistics and the lives of its people.

The history of Japan assisting work related to this bridge dates back a long way, with the Japanese engineers preaching the importance of maintenance and management to the Congolese engineers from the outset of the construction. The trust between the Japanese and Congolese engineers was strong, and despite assistance from Japan ceasing during the civil war in Congo during the 1990s, the previous generation of the Hashimori Task Force contacted the consultants and construction operators in Japan and were able to maintain the Matadi Bridge themselves while receiving guidance remotely. Assistance from Japan later resumed in 2012, and in the same year, the Project to Improve Maintenance and Management Capabilities was launched to help improve the proficiency of bridge inspections, maintenance, and management, as well as to train young engineers. In 2014, under the Matadi Bridge Maintenance Plan, a cable ventilation and drying system was installed as a measure to prevent the main cables from corroding. The ability to maintain and manage the Matadi Bridge was further improved by these projects, and it was awarded the JSCE 2022 Infrastructure Maintenance Project Award. While staying in the Republic of Congo, I met people who were involved in the construction of the bridge from day one. What made a lasting impression on me was how these people, despite growing old, treated the Matadi Bridge with such affection as if it were one of their own children. From observing the interactions between the Congolese engineers, I really felt that the spirit of the Hashimori Task Force has been properly inherited by the young engineers who are currently at the frontline, maintaining and managing the bridge.

The series of projects related to the Matadi Bridge is an example of properly taking every step to transfer maintenance and management skills to ensure the structure is kept safe and in sound condition for many years to come rather than just working together to simply build something and move on to the next project. While JICA has engaged in a large number of initiatives and projects to maintain and manage roads, such as the Road Asset Management Cluster, I hope that we will actively continue to work to develop local engineers and ensure the infrastructure remains sound for the long term.

Lastly, while I was in Democratic Republic of the Congo I was able to walk across one of the main cables and climb to the top of one of the main towers of the Matadi Bridge. Once I started climbing I could not look down until I reached the main tower because it was so scary. The helmet that I was given had the logo of a Japanese company on it, perhaps because it was left there by an engineer who had stayed in the country long ago. This also gave me a sense of the long history of assistance Japan has played in building and maintaining this bridge.

Wide View of Matadi Bridge

Staff Undertaking Cleaning Work of Matadi Bridge

Truck Passing Over Matadi Bridge

【Reported by Sumire Watanabe, Japan International Cooperation Agency】

Takeshi Yamaguchi
(NEXCO CENTRAL)

1. Project overview
Over 130,000 vehicles travel from the Yokohama-machida Interchange to the Ebina Junction on the Tomei Expressway every day. This volume of traffic, as much as anywhere in Japan, results in chronic and extremely strenuous levels of congestion due to the concentration of traffic. The area near the Yamato Tunnel (Photo 1) in particular sees a lot of congestion caused by vehicles slowing down at the sagging section where the tunnel slopes downward before transitioning to an uphill slope, as well as at the entrance of the tunnel. That is why the addition of a lane near the tunnel with three lanes on each side was planned as part of the measures against congestion, and consequently, it was determined that the width of the Yamato Tunnel would have to be made wider to make this possible (Figure 1).

2. Design and installation that made the complex widening construction possible
Because the area of the widening construction work was a major traffic route, it was difficult to put in place long-term traffic restrictions during the construction work. Consequently, the work to constantly ensure three lanes were open on either side while at the same time widening this wide-profile tunnel was extremely difficult. The efforts taken in the design and construction stages to resolve this issue are shown below.

（1）Creative Efforts in Design Stage
To minimize the traffic lane restrictions during the construction period, it was necessary to reduce the reinforcement of existing parts as much as possible in the widening design.

In terms of the design, in addition to making the joint between the widened side walls and the top slabs more rigid, the soil springs were adjusted by improving the ground directly below the widened parts, and measures were taken against the ground sinking. Furthermore, how the tunnel would be widened was examined before choosing an approach in which the stress on the existing parts would be reduced after widening the tunnel (Figure 2). Efforts were also taken to reduce the top load by removing the existing soil cover of the tunnel. As a result, a design to widen the tunnel was implemented that would minimize the reinforcement of existing parts.

（2） Creative Efforts in Construction Stage
In planning the construction, a method was proposed in which the construction work could be carried out in a narrow work space during fixed traffic restrictions by installing a temporary guardrail (Figure 3). The construction method was to support the top slabs with temporary supports in order to remove the existing side walls. In the work on the main expressway road, work to transport, install, and remove the materials, etc. had to be done in a narrow 2.15-meter work space, especially for installing the temporary supports and removing the side walls.

The temporary supports were installed to and later removed from their predetermined positions efficiently by lowering pre-cast temporary supports from the top of the tunnel entrance using a crane and then hauling them into the work area inside the tunnel using a winch along transport rails laid on the work platform, rather than transporting and assembling the materials from the main roadway. In the plan to bring the temporary supports into the tunnel, prior examinations were made using a 3D model to check the work would be safe and assured (Figure 4, Photo 2).

Removal of the side walls was done by cutting the walls into blocks rather than smashing the concrete, and, despite the tight work space, the blocks were efficiently carried out of the tunnel with a highly mobile forklift (Photo 3).

3. Opening the Additional Lane
The construction work to widen the Yamato Tunnel was completed without any problems by bringing to fruition the plan and design to minimize the existing reinforcements and achieve the widening work in a tight space while ensuring the three lanes remained open for traffic (Photo 4). In July 2021, the opening of an additional lane in specific areas helped significantly reduce congestion near the Yamato Tunnel.

4. Infrastructure Maintenance Project Award Winner
The Yamato Tunnel Widening Project for the Tomei Expressway won the JSCE 2022 Infrastructure Maintenance Project Award. To close, I would like to take this opportunity to offer my sincerest gratitude to all the experts who helped in the design and construction of the project, as well as everyone involved in the surveys, design, and construction work.
 

The 2nd Laos-Japan Joint Seminar “Road Asset Management”