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Home » Okumura Gumi Co., Ltd. Developed a new joint method for precast PC floor slabs, “Z Spiral Method”

Okumura Gumi Co., Ltd. Developed a new joint method for precast PC floor slabs, “Z Spiral Method”

[Okumura Gumi Co., Ltd.] Developed a new joint method for precast PC floor slabs, “Z Spiral Method”
*Okumura Gumi Co., Ltd.*
Press release: July 8, 2024
**
Developed a new joint method for precast PC floor slabs, “Z spiral method” *Reduces work time while ensuring sufficient fatigue durability* Okumura Gumi Co., Ltd. (Head office: Abeno-ku, Osaka City, President and CEO: Takanori Okumura) and Showa Concrete Industry Co., Ltd. (Head office: Gifu City, Gifu Prefecture, President and CEO: Murase) Daiichiro) uses precast (*1) PC (prestressed concrete) slabs (*2), which are mainly used for expressway bridges, using special
rectangular spiral reinforcements called “Z spiral reinforcements.” We have developed a joint construction method called “Z spiral construction method” that joins by
This makes it possible to shorten work time while ensuring sufficient fatigue durability.
*1: Concrete components pre-made in a factory.
*2: A component that directly receives the loads of cars, people, etc., and is made of concrete that has been pre-stressed.

Furthermore, the precast PC floor slabs bonded using this method have been proven to have a durability equivalent to 100 years through a wheel load running test (*3), and this performance certificate has been awarded to the Expressway Research Institute Co., Ltd. ( It was submitted to NEXCO Research Institute and was approved.
*3: A test that simulates repeated driving by a large vehicle to elucidate the failure mechanism of road bridge decks by measuring the strain and deformation of the deck slabs, as well as the effects of new types of deck slabs and various repair and reinforcement methods (fatigue durability gender) for the purpose of evaluation.

[Background]

According to East Japan, Central Japan, and West Japan Expressway Co., Ltd., more than 80% of expressways will have been in service for more than 30 years by around 2030, and the need for large-scale renewal is increasing as expressways continue to age. . In the future, it is expected that many expressways will undergo floor slab replacement work to replace existing concrete slabs with precast PC slabs, which will shorten the construction period by minimizing traffic
restrictions related to floor slab replacement. The development of technology to do this is desired.

Loop joints (see Figure 1), which are considered the standard construction method for deck replacement work, require placing reinforcing bars perpendicular to the bridge axis within the loop bars, which requires a lot of time and effort. I did.
Therefore, our company developed the “Z Spiral Construction Method”, which enables shortening of work time while ensuring sufficient fatigue durability.

Figure 1 Comparison of standard construction method and Z spiral construction method

[Overview of construction method]

In this construction method, instead of passing reinforcing bars in the direction perpendicular to the bridge axis through the loop reinforcements, special rectangular spiral reinforcements called “Z spiral reinforcements” are inserted into the top of the loop reinforcements and tied and fixed. This method has the following three features (see Figures 2 and 3).

Feature 1.: Work time can be shortened
Since Z spiral reinforcement and loop reinforcement are easy to bind, the work time required for reinforcing reinforcement can be
significantly reduced compared to standard construction methods. Feature 2: No need to set up scaffolding or secure a work yard In the case of standard construction methods, it is necessary to install scaffolding and secure a work yard in order to pass
reinforcing bars perpendicular to the bridge axis, but Z spiral bars do not require these as they can be inserted from the top of the deck.

Feature 3: No need to use special concrete
When changing from the standard construction method to another construction method, special concrete may be used as filler concrete to join the floor slabs. As with the standard method, this
construction method uses concrete with a design standard strength of 50N/mm2 whose quality is guaranteed at the time of shipment from the factory, so it requires the on-site mixing work and strength tests that occur with special concrete. I don’t.
Figure 2 Structure image of Z spiral construction method
Figure 3 Construction procedure of Z spiral construction method

【the next deployment】
In the future, we will actively propose this method for expressway deck replacement work and aim to popularize and develop it.

◆Company overview
OKUMURA ​​CORPORATION
(https://www.okumuragumi.co.jp/)
Address: 2-2-2 Matsuzaki-cho, Abeno-ku, Osaka City
Representative: Representative Director and President Takanori Okumura Business content: General construction industry and related operations

Showa Concrete Industry Co., Ltd. | SHOWA CONCRETE INDUSTRY
(https://www.showa-con.co.jp/)
Address: 1-1 Koran, Gifu City, Gifu Prefecture
Representative: Daiichiro Murase, Representative Director and President Business details: Design, manufacture and construction of prestressed concrete bridges and design, manufacture and sale of precast concrete products

[Contact information regarding this matter]
Okumura Gumi Co., Ltd.
Civil Engineering Headquarters Civil Engineering/Renewal Technology Department Hiroshige Moriya
TEL: 06-6625-3907
FAX: 06-6621-9315
E-mail: hiroshige.moriya@okumuragumi.jp

Showa Concrete Industry Co., Ltd.
Sales Headquarters Development Department Development Section Yuji Kunii
TEL: 058-255-3337 Mobile 080-4064-1350
FAX: 058-252-3177
E-mail: kuniiyas@showa-con.co.jp
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