Fixing precast cladding wal!
Reinforcement and strand for floor beam
BILDIRI
PLADAK
曲臂
Floor beams in this block, spanning 60ft, between the cores, are supported by reinforced concrete transverse beams which in turn are supported by rein- forced concrete columns. Apart from the arrangement for connecting the air-conditioning ducts to the floor, this was a simple structural framing,
In the high block secondary beams would have obstructed the running of the air-conditioning ducts or necessi tated an increase in floor height. It was therefore decided to have no secon- dary beams and to use reinforced con- crete precast floor planks spanning 24ft. between main beams.
The main beams are in pairs, the reasons for adopting a double beam system being:
1) To reduce the depth of beams. 2) To minimize the weight of beams under 13 tons which a 15 ton track could take. Much lighter lifting equipment would be needed both at the casting yard and on the site.
Far East BUILDER, January 1971
Fig. 2. Framing plan for typical floor 3-11 high block
3) The steel form work could have many more uses.
4) To limit the total jacking load to 300 tons.
5) To suit the precast column casing which was used as permanent formwork.
The typical floor framing layout, Fig. 2, consists of a series of three 50ft. main beams spanning between two services cores and seven bents of 24ft. On the second floor, along the main frontage there is a 5ft. cantilever slab for proposed office space. The roof of the high block is a thin con- crete shell.
Structural Design
Floor Planks
For the high block's floor planks a reinforced concrete construction was found to be more economical than prestressed concrete due to the fire resistance requirements. The floor planks were designed for an inverted
U-section with slightly inclined webs and rebates at the top running along the length of the units at the two sides to form keys for the in-situ concrete.
The units were designed to be simply supported to resist dead load and temporary construction loads. After the topping had been cast the whole section was then treated as con- tinuous to resist imposed loads. As a large deflection was expected under the simply supported condition, a in. upward tolerance was specified in the design.
Main beams
The design of the main beams was based on CP115 and CP116. In the de- sign of pre-tensioned units, the calcu lated concrete stress at transfer takes account of the reduction in stress in the tendons occasioned by the instan- taneous elastic deformation of the concrete. Computed stresses in con- crete and steel should not exceed
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