August_1970 — Page 42

Loop slip road of Chatham Road flyover

Chatham Road flyover

In view of the inadequacy of the junction of Chatham Road/Gascoigne Road/Princess Margaret Road and the heavy traffic that had to negotiate it to and from industrial East Kowloon, Kai Tak Airport, Jordan Road vehicular ferry and the New Territories, long delays were experienced during peak hours. Due to the proximity of railway tracks and other properties it was im- practicable, if not impossible, to design a junction layout which would cater for all traffic movements.

It was decided, therefore, to elimi- nate minor movements and to provide grade-separation for the main traffic flows. The movement between Prin- cess Margaret Road and Chatham Road North was also eliminated; it would have involved rebuilding the existing railway bridge of limited capa- city, and an alternative route to East Kowloon became available at newly completed Fat Kwong Street situated about a mile north of the junction.

The flyover starts in Chatham Road South and joins with Princess

Margaret Road. The heavy eastbound traffic from Tsim Sha Tsui is taken over the flyover and down the loop slip road to merge with the east moving traffic in Gascoigne Road. The new junction has now been in opera- tion for nearly a year and is proving satisfactory.

The structure, about 1,000 ft. long, including ramps comprises four 60 ft. spans and ramps on retained fill. It provides a 24 ft. wide two-lane car- riageway for the northbound traffic and an 18 ft. wide carriageway (one lane plus additional width to pass a broken-down vehicle) for the south- bound flow. A 4 ft. central divide separates the carriageways. The deck is a hollow slab type consisting of pre- cast, prestressed beams 2 ft. 5 in. deep placed side by side and a 5 in. in-situ concrete topping.

Two trough beams and 18 I-beams were needed for each span. In order to achieve a flush soffit the beams were recessed at the ends and rest on in- verted 'T' capping beams which were cast monolithic with three 3 ft. 3 in. diameter columns to form a rigid frame, founded on piles (Fig. 2).

Two pedestrian subways were con- structed in this contract one under Chatham Road South and another under the loop slip road as a continua- tion of the north pavement along Gas- coigne Road. The subways (10 ft. x 8

38

51-6#

2-9′′

240"

4-0′′

18:0

2"Asphalt wearing course

5" in-situ concrete copping

18-0

18'-0"

Pile cap

· Rectangular steel railing

Precast beams

323" dia. columns

Ground level

18′′x18′′ precast piles

Fig. 2

CROSS SECTION OF CHATHAM ROAD FLYOVER

F

6.0" dia. column

Far East BUILDER, August 19