STAIRCASE RISES TO 14 STOREYS
Single helix design aided
by model tests
A
STAIRCASE inside the new 14- storey Central Electricity Board's headquarters in Kuala Lumpur runs the full height of the building in a continuous helix. At each floor level it flattens to form a landing and these landings, cantilevered from one of the beams framing the stair well, are its sole support.
The architect, Mr. A.A. Geeraerts, was anxious that the staircase should be as attractive as possible because of its prominence in the building. He chose a flat slab form of construction with the thinnest possible waist depth. The waist sec- tion eventually used was 34in. deep at each edge and 9in. at the centre, with a curved soffit profile.
The beams supporting the stair
landings and connecting corridors were themselves limited to a low depth/span ratio and are liable to deflect appreciably under load.
In plan the radius of the inner face of the helix is 2ft. 2 in. and the stair width 5ft. lin. The height of each stair flight is 10ft. 8in., and the risers swept an angle of 277°. The stair live load was taken at 100 lb. per sq. ft. for design purposes.
Design Factors
Calculations for the stair were based on papers prepared by Mr. J.S. Cohen and Mr. A.M.C. Holmes. They gave the following design fac- tors:
Max. longitudinal bending moment 186,000 lb. in.
View from the bottom of the stair well. The concrete is as stripped and not yet cleaned down.
Max. torsional moment
207,000 lb. in.
Max. radial bending moment
782,000 lb. in. A number of assumptions had to be made however in arriving at these factors and it was felt that they could only be justified by carrying out a loading test
This test was supervised by the consulting engineers for the building. Bolton Hennessy Cogan and Associ- ates, Kuala Lumpur.
The model chosen for the test was a full scale single flight of stair iden- tical to the actual flight to be con- structed between the ground and
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1/2" DIA. H.T. BARS AT 4 C/C TOP & BOTTOM
3/8" DIA. H.T. STIRRUPS AT 5 C/C WITH CENTRE STIRRUP 3/8" DIA. AT 1-3′′ C/C
Waist cross section
Far East Architect & Builder January, 1965
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