daylight factor may be required to allow for other types of glazing material.
LOE OF OBSTkactrit TALİNE KLOPi ol OLAZION
Lime of pastqucfija IPIOSSA KATE OF $LAZION
1*
CROSS SECTION
Fig. 1. Example with sloping roof- flight, for application of Nomogram II.
The generally accepted average diffuse light transmission values for some of the alternative glazing ma- terials are given in Table 8 together with the correction factor to be ap plied in each case to the total day. light factors calculated as above.
When double glazing in ordinary clean clear glass is used. the trans- mission will vary with the angle of the incident light. but for most prac- tical purposes a correction factor of 0.9 applied to the total daylight factor will suffice.
SUMMARY OF METHOD
The steps previously described are summarized for convenient reference (1) Calculate the sky component by means of the B.R.S. Simplified Day- light Tables. the Waldram Diagram, or the B.R.S Daylight Factor Pro-
tractors.
(Continued from page 98)
It will consist of 24 spans of a nominal length of 55 feet each, a south approach ramp of 169 feet in length and a north approach ramp of 220 feet. The ramps will be of normal stone-faced concrete retaining wall construction with selected fill,
The piers supporting the flyover roadway will be "T"-shaped in order to maintain the ground level road- ways within the existing road reserve. Of standard reinforced concrete con- struction, the piers will be four feet wide at the base with a maximum width of eight feet at the top of the pier leg. The 36-foot-long "arms" of the piers will be identical for each pier, varying from six feet deep at
108
(2) If there is an external obstruc- tion seen through the window cal culate the externally reflected 'com- ponent by one of these methods. (3) Calculate the internally reflected component by means of the B.R.S. Inter-reflection Formula, Simplified Daylight Tables, or Nomograms.
(4) Apply any necessary correction to item (3) for deterioration of the decorations.
(5) Add the three components of the daylight factor together.
(6) Apply any further corrections to the daylight factor to allow for dirt on glass. window framing and other types of glazing material.
ALTERNATIVE METHOD
Another method of calculation is available whereby daylight factors can be derived without going through the separate steps just described. This method makes use of the results of extensive laboratory studies in which daylight factors were measured in a model room for a wide range of conditions. The re- sults have been put into the form of a slide rule known as a Daylight factor Calculator which enables day- light factors to be read off directly for a wide range of wall, ceiling and floor reflection factors and ceiling heights. The slide rule and an exam- ple of its operation are illustrated in Principles of Modern Building. Volume 1 (see list below),
The values given on the slide rule relate strictly to the particular kind of rectangular room used in the laboratory study, but simple correc- tion factors enable some extrapola. tion to other conditions.
the centre to 4 feet at the outside edges.
The elevated roadway will be car- ried on either pre-stressed concrete beams or universal steel beams, which in turn will support the seven-inch- thick reinforced concrete road slab.
It is proposed to
use coloured cement in the road slab in order to eliminate as far as possible the effect of glare.
Lighting for the flyover will be specially designed and will be placed in the guard rails erected on the edge beams. Special lighting units will be used on the under side of the pier "arms" to illuminate the roadway at ground level.
PUBLICATIONS ON THE DAYLIGHTING OF
BUILDINGS
The following publications can be obtained from Her Majesty's Stationery Office at the prices shown. The prices quoted in brackets include post- age.
Principles of Modern Building,
Vol. 1. 20s. Od. (21s. 5d.) Vol. 1. 17s. 6d. (18s. 6d.) Architectural Physics-Lighting by R. G. Hopkinson, 1963.
£2 10s. Od. (£2 12s. 9d.) Simplified daylight tables by R. G. Hopkinson, J. Long- more and A. M. Graham. National Building Studies Special Report 26, 1957. Is. 9d. (2s. Id.) Some general principles of the
lighting of buildings.
Building Research Station Digest No. 70 (first series), (1954). 4d. (7d.)
The lighting of factories by M.J.
Keyte and H.L. Gloag. Factory Building Stadies No. 2. 1959, 3s. 6d. (3s. 10d.) Protractors for the computation of daylight factors by A.F. Dufton.
Building Research Technical Papers No. 28, 1946. 1s. 3d. (Is. 6d.) Daylight Factor Protractors Nos. 1 and 2 6s. Od. (6s. 3d.)
3 and 4
8s. Od. (8s. 4d.)
5 and 6
6s. Od (6s. 3d.)
7 and 8
8s. Od. (8s. 4d.)
6s. Od. (6s. 3d.)
9 and 10
Prepared at the British Building Research Station. Garston. Herts, Crown copyright.
There will be no pedestrian traffic on the flyover.
Tenders were recently called for the construction of the elevated road- way together with the partial recon- struction of sections of Nairn Road and the complete reconstruction of Waterloo Road at the roundabout to the unnamed road between Nos. 102 and 104 Waterloo Road.
Work is already in hand on the driving of reinforced concrete piles and the construction of the pile-caps for the 23 piers of the flyover.
Construction on the second phase of the flyover scheme will start when piling is finished immediately after the completion of the piling work.
THE HONG KONG & FAR EAST BUILDER-VOLUME 19, NUMBER 4