Residual soils have a special significance in South Africa where they occur extensively. The business district of Johannesburg is largely founded on residual shales and lavas and this paper describes the properties of weathered Ventersdorp lava from the Braamfontein area. Particular attention is paid to the compressibility of the lava and to the settlement of structures founded thereon. The strength properties are also explored.
Waarnemings van die aantal voertuie wat bedien kan word deur 'n sekere lengte groen- plus geeltyd is by 'n groot aantal verkeersligbeheerde kruisings in die Pretoria-gebied gemaak. Daar is gevind dat die laanwydte, mits dit wyer as 2,8 m is, nie 'n betekenisvolle rol speel nie. Aan die ander kant speel die vertrekhelling wel 'n rol. Goeie ooreenstemming met resultate verkry in Australië en die Verenigde Koninkryk is gevind. 'n Ontwerpgrafiek word gegee.
The number of vehicles that can be served during a given length of green plus amber time was observed at a large number of signal controlled crossings in the Pretoria area. It was found that lane width, provided it is wider than 2,8 m, does not play a significant role. On the other hand departure slope was found to be of importance. Good agreement with results obtained in Australia and the United Kingdom was obtained. A design graph is supplied.
Simply supported and continuous solid slabs rectangular or skew in plan are in common use as bridge decks up to spans of about 18 m. Prestressing and ordinary reinforcement have traditionally been close competitors in this particular field and range of application, judging by the designs of completed bridges.
It is in the interest of the practising engineer and researcher alike to investigate practically, performance and cost implications of structures when studying possible solutions to a design problem. Details of the structural performance of a skew slab model representing a bridge deck and prestressed in two directions were reported in a previous paper. For the same slab a cost estimate and a comparison with various reinforced concrete solutions is now presented in this study.