Vietnam: Selection of bridge diagram and general layout for designing pedestrian suspension bridges

Vietnam: Selection of bridge diagram and general layout for designing pedestrian suspension bridges (Illustrative Image)

Circular 11/2014/TT-BGTVT stipulates the selection of bridge diagram and general layout for designing pedestrian suspension bridges in Vietnam as follows:

1. Apply a single-span diagram with 2 bridge towers arranged on piers (abutments) at stable riverbanks or streams, with no risk of erosion on both banks as shown in Figure 2 of Appendix I issued with this Circular.

2. To reduce siltation and erosion of riverbanks or streams near the bridge, the two towers and piers (abutments) positions may be positioned further inland. Suppose hydrological and hydraulic conditions pose a risk of erosion in front of the pier (abutment) foundation. In that case, it is necessary to arrange protective structures for the pier (abutment) foundation that are sufficiently stable and strong.

3. The ratio of the main cable sag (f) to the span length (L) must be selected between f/L = 1/8 and 1/12.

4. The relative camber of the bridge deck after construction must not be less than 1/100 L.

5. The two angles of inclination of the main cable at the tower top position towards the abutment and span should be equal.

6. To increase the stability of the span structure, the main cable diagram can be applied close to the bridge deck system in the middle span (with no hangers at that point).

7. The requirement for the natural frequency of the span structure in the vertical and horizontal directions must not be coincident or multiple of each other.

8. The longitudinal slope of the approach road may not be steeper than 6% depending on local conditions.

9. The elevation of the bottom beam must be at least 1 meter higher than the design water level (to avoid the impact of floating trees on the bridge beam in case of major floods).

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

Ty Na

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