July_1970 — Page 35

TONNOCHY RD.

Legend:

Project limit

also proved extremely helpful that the contractor established good public rela- tions by visiting the occupiers and re- assuring them. In the event, piling operations went very smoothly - no accident occurred and no complaints were received.

The construction of the foundation inside the canal was carried out by diverting flow through one half of the canal while working in the other. Tim- ber sheetpiles and gunny bags were employed to divert the flow. In addi- tion, extensive pumping was necessary to ensure placing the pile cap concrete in the dry. Fortunately, there were no exceptional storms during this phase of the work.

Both flyovers are about 860ft. long, consisting of 12 spans of varying lengths to suit the road layout at ground. Where an exceptionally long span of 110ft. is needed over Hennessy Road,

this is achieved by constructing in situ concrete frames on both sides of the road, cantilevering out some 15ft. and placing prestressed beams on the canti- lever. Other spans vary between 65 and 80ft.

In order to provide pedestrian pave- ments and roads at ground level and at the same time not to impede the capa- city of flow in the canal the only possible place where the supports to the elevated structures could be located was along the longitudinal edge of the flyovers. The form finally adopted was inverted L-frames resting on pile caps, which form the invert slab of the canal, and tied by the canal roof slab.

The flyover deck, of beam and slab construction, rests on the cantilever L-frames which were prestressed in stages to cope with large bending mo- ments and shear forces. The prestres- sing was effected with P.S.C. 12/0.6in.

cables, the stressing force in each cable being some 190 tons. Six or eight cables were required in the cantiliver capping beams and eight or ten in the columns, depending on the length of the spans on either side of a frame.

The following was the sequence of construction (Fig. 4):

1. Cast column and beam

2. Stress cables a, b, 5, 6, 7 & 8 3. Remove propping to beam 4. Place precast beams for two spans

5. Stress cables c, f, g, h, 1, 2,3 & 4 6. Grout all stressed cables 7. Cast deck slab

8. Stress cables i & j and grout 9. Apply finishes to the deck

The contract for this flyover was awarded to Paul Lee Engineering Co. Ltd. in March 1968. It was substantial- ly completed in April 1970. The cost of the work was about HK$5,000,000.

VICTORIA HARBOUR

KELLET

Bowrington Canal extension-

ISLAND

Canal Road Flyover extension

To central

MARSH RD.

BLOUCESTER ROAD

Proje

JAFFE

CANAL RD

ROAD

PERCIVAL ST.

Project limit

To North point

CANNON ST.

Elevated structures & Ramps

REVISED LAYOUT OF WATER FRONT ROAD

BETWEEN TONNOCHY ROAD AND PERCIVAL STREET

Fig. 5

Far East BUILDER, July 1970

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