The hydraulic roughness of the 82,8 km long, 5,33 m diameter, 47,6 m'/sec design capacity Orange-Fish Tunnel was comprehensively tested during commissioning in 1975. The tunnel friction was spot-tested in 1984 and then comprehensively tested again in successive years from 1988 to 1990. These tests showed a hydraulic aging rate for the concrete-lined pressure tunnel that was greater than that expected at design stage and, indeed, outside commonly used ultimate design roughnesses.
Timber has been neglected as a structural material in South Africa. The authors discuss the pros and cons of structural timber and suggest that timber has an important role to play in structural engineering. Methods of enhancing the competitiveness of structural timber are suggested. Deficiencies in the South African Timber Design Code are pointed out, possible research topics are discussed and recommendations on improving the image of timber as a structural material are made.
The technical note considered a structured approach to establishing the determinacy of plane frames utilizing internal isolated hinges - hence the title IIH technique. External support conditions and the internal member arrangement of frames were considered individually and a final assessment determined by combining these separate analyses. Methods for dealing with support types, rigid joints and member location were discussed and comparisons were made with the long established 2j - 3 approach to determinacy.