Vietnam: Regulations on general guidelines for spreading main cables and tensioning cables of pedestrian suspension bridges

Vietnam: Regulations on general guidelines for spreading main cables and tensioning cables of pedestrian suspension bridges (Illustrative Image)

Under Circular 11/2014/TT-BGTVT, the general guidelines for spreading main cables and tensioning cables of pedestrian suspension bridges during the construction process of spreading and tensioning the cables of pedestrian suspension bridges in Vietnam are as follows:

1. Manufacture of main cables from cable strands

- Main cable strands are manufactured in the factory, imported, and delivered to the construction site in original packaging as per design. The steel wire used to manufacture the main cable strands must comply with Standard 22TCN 272-05. After manufacturing, the main cable strands are preserved, transported to the construction site, and assembled into the main cables. Each main cable bundle may include one or more cable strands depending on the specific design of each bridge.

- The main cable strands are arranged parallel to each other (with spaced positioning clips every 2-3 meters) or bundled into a large cable bundle.

r- The length of each cable strand depends on its position in the main cable bundle. Each cable strand is marked at a minimum of 5 points: one point at the lowest part of the main cable in the middle span, two points at the tower saddle tops, and two points at the anchorage positions. The length of the cable strand and the marking points must be pre-determined. When measuring, the length of the cable strand in an unstrained state is determined indirectly by measuring the length of the steel wire in a stretched state with a minimum stress equivalent to the stress in the cable on the bridge in an unstressed state.

- To spread the main cable across the river, a pilot rope can be used, pulled over the tower top, by manpower, boat, or float appropriate for specific conditions and contractor technology.

2. Manufacture of suspension cables

- If the suspension cables use cable strands, they must be manufactured in a factory according to design. The manufacturing, inspection, and acceptance of suspension cables must comply with ASTM A603 Standard.

- If using suspension rods made of round steel d=14-16 mm, they can be manufactured according to the design at the workshop or directly on the construction site.

3. Requirements for main cable clamps (main cable clips)

- The main cable clamp is a mechanical detail that must be manufactured in a specialized mechanical workshop with adequate conditions to ensure machining quality according to design.

- During manufacturing, production technology must be established and tested as well as training all participating personnel to understand the technical requirements to ensure product quality.

- All sharp corners must be rounded off.

- All cable clamps must undergo ultrasonic defect detection, be labeled with shape identifiers, and be packed into bundles.

Details can be found in Circular 11/2014/TT-BGTVT effective from June 15, 2014.

Ty Na

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