April_1966 — Page 47

Door blockouts on internal walls

Sliding completed. Note bracing trusses at the top.

Over these are threaded a series of hydraulic jacks one per rod which jack against steel yokes. These yokes in turn are connected to, and support, the 3 ft. 6 in. deep steel form- work to the walls which also rests on the ground floor slab.

As in the pilot project at Kwun Tong, the steel formwork can be brac- ed by means of tubular steel welded space frames which double as sup- ports for the slipform deck on which all the work is carried out.

Reinforcement

In addition to the jack rods, vertical mild steel reinforcement is placed in the first lift of wall prior to concret- ing. The first 3 ft. of concrete is placed at the normal rate of about 8 in. an hour, which means that by the time the last concrete has been poured in the top of the sliding form the concrete at the bottom of the form has hardened sufficiently to be- gin taking the load in conjunction with the ground floor slab.

Each jack is connected hydraulical- ly to a central pump controlled by one operator. By pressing the button on this central pump he causes each hy- draulic jack to climb slowly up its jack rod a travel distance of approx- imately 1 in.

With normal slipform work, this operation is carried out once every seven or eight minutes. The jacks automatically lift the whole of the assembly deck, bracing, formwork, materials and men and the system

Far East Architect & Builder April, 1966

B

Yoke, hydraulic jack and jack rod

is continuous until the full height of the wall has been poured.

Below the slipform a hanging scaf- folding is arranged from which any necessary surface treatment can be carried out and the concrete checked as it is cleared by the formwork. The hanging scaffold usually consists of steel brackets fixed to the waling with the timber catwalk 5 ft. to 6 ft. below the bottom edge of the platform.

The reinforcing is placed in posi- tion as the work progresses and a con-

siderable amount of reinforcement can be carried and stored in brackets attached to the external yokes.

It is possible to fix window and door frames directly into place. For exact location, vertical timber guides are screwed on to the frames con- tinuously so that there is no possibili- ty of the frames moving vertically or horizontally. Smaller cores. for in- stance to take intermediate floors or beams can be constructed either in timber or cardboard boxes.

General view of the concreting operation. Pioneer truck delivering ready-mixed con- crete can be seen at right.

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