Nippon Steel corporation has developed Hat-type steel sheet pile in 2005, with an effective width of 900mm, which is the widest one-hot rolled SSP in the world.
Hat-type steel sheet pile has 4 types as shown below;

Figure.1 Types of Hat-type steel sheet pile
“See more details at: https://www.nipponsteel.com/vn/en/catalog/index.html”

• Figure.2 Relationship between unit weight
  and moment of inertia

• Figure.3 Description of the Type name

1) Cost reduction:
The effective width of the Hat-type steel sheet pile is 900mm, which is 2.25 times wider than conventional U-type steel sheet pile like type-III and type-IV, thus:
- Reduce the number of piles
- Reduce steel weight per wall length
- Reduce the number of junctions which leads to increases the water tightness

2) Ease of construction:
The interlocking joints of Hat-type steel sheet pile have asymmetric shape, so it allows one-directional connection to make construction ease preparation and piling.

3) Many applications:
- Apply to the transportation and hydraulic works.
- Not only applicable to permanent structures, but also applicable to temporary structures.

Figure.4 Cross-section between the Hat-type steel sheet pile and U-type steel sheet pile

U-type steel sheet piles transmits longitudinal shear force to adjacent piles at interlocks. If the shear force is not transmitted properly due to slippage at interlocks, moment capacity of the wall should be reduced and the wall deflection will increase. The degree of reduction is expressed by reduction factor, which stipulated in not only Vietnamese standards but also in Japanese and European standards.
On the other hand, for Hat-type steel sheet piles, this effect is not necessary to be considered because the interlocks are located on the outermost part of the wall where the shear force is negligible.

In hydraulic works, vibratory machine will be chosen. Vibratory machines for U-type steel sheet pile also applicable for Hat-type steel sheet pile.

Figure.7 Vibration method

Figure.8 Press-in method

Precondition: For a project that requires a 10-meter- width steel sheet pile wall, as shown in the table below, we need 25 conventional U-type steel sheet piles (type-IV) with 12 meters long and the total pile driving length is 300 meters. But if we apply Hat-type steel sheet pile, we only need 11.1 piles of 12 meters and the total pile driving length is only 133.2 meters.

Table 2. Comparison between U-type steel sheet pile (type-IV) and Hat-type steel sheet pile

Conclusion: Hat-type steel sheet pile reduces not only the material costs but also construction costs including material transportation cost.

Hat-type steel sheet piles are applicable not only for the permanent structures but also for the temporary structures.

a) Permanent structures
Waterproof sheet piles for river pilers and dams of hydraulic works in Vietnam.

Figure.9 Waterproof sheet piles

b) Temporary structures
Temporary cofferdam for both in the land and in the water.

Figure.10 Temporary cofferdam in the water

c) A project that Hat-type steel sheet pile applied in Vietnam
Project name: Tra Khuc River Downstream Dam Project
Usage: waterproof sheet pile
Type: NS-SP-10H x 14m
Qty: Approx. 1.4kt

Figure.11 Hat-type sheet pile in construction site

Figure.12 Cross section of the Dam

“See more details at: https://www.nipponsteel.com/vn/en/news/20200630_100.html”

Hat-type sheet pile is complied with material standards as well as design standards, thereby bringing high-quality products to the Vietnamese market, especially applied to transportation and irrigation works.

Table 3. National Standards

Some photos from the seminar
Many press units and TV channels such as VTC news, Agricultural newspaper, etc. came and covered the conference.

• 

  Delegates at the seminar

• 

  Japanese engineer of Nippon Steel Viet Nam
  presented in the seminar