No_10_October_1969 — Page 34

TABLE I

Details of Concrete used

Location

Class

Specified

Average

used

minimum

strength

strength

obtained

28 days

28 days

Cement used for 1 cu. yd. of Concrete

Water used for 1 cu. yd. of concrete

Precast units

A

7200

7300

700 lb.

280 lb.

In-situ super-

structure

columns, piles

and pile caps

B%

5800

6100

630

285

Other works do

not come under

Class 'A'

C%

4750

5200

580

312

or 'B'

1) All strengths in lb/sq. in.

2) Samples taken as sets of 3 cubes (6 in.)

Prestressing steels in the con- crete beams are 0.276 in. diameter wires stressed by means of Freyssi- net equipment. Details of concrete mixes used in the work are given in Table 1.

The concrete stresses adopted in the design of the prestressed concrete beams are:

Bending compression: initial 2,500 p.s.i.; service 2,500 p.s.i.

―

-

Bending tension – nil. Principal tensile stress due to shear - 150 lb/sq. in.

All the prestressed concrete beams are manufactured at the work sites.

The road surface of the elevated structure will be laid with a 2 in. thick wearing course of hot rolled asphalt. Conventional lighting is not used due to apprehension about the visual effects both by day and by hight

arising from the many columns re- quired and in particular because of the problems associated with glare and variable lantern mounting heights. High mast lighting units will be used and sited at appropriate positions to give a minimum illumination level on the carriageways of approximately 2 lumens per sq. ft.

The ground under the elevated structures and the land between the slip roads will be turfed and beautified with flowers and trees, and pedestrian facilities will also be included.

The two trumpet interchanges are scheduled to be completed at the end of the year and the Jalan Toa Payoh/Whitley Road/Thomson Road interchange will be completed in 1970.

First section

Cutting along the southern peri- meter of Tao Payoh New Town is the first section of the pan island express- way that will ultimately link all Singapore's satellite towns and indus- trial estates together while speeding up traffic flow.

The expressway with dual three- lane carriageways and flyover inter- changes at limited access points is designed for traffic travelling at 50 miles an hour. As it extends in a circuit around the island, it will enable a fast-moving and relatively uninter- rupted circulation of traffic between

WITCHERS

Site-made precast beams being placed on the Jalan Toa Payoh/Whiteley Road/Thompson Road interchange

34

Far East BUILDER, October 1969