Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese - Volume 42, Issue 1, January 2000

The design of bracing to resist stability forces involves a complex interaction between the bracing system and the member. Most studies have involved sophisticated computer analysis and as such the behavioural aspects have been clouded, especially when the results of such studies evolve into design methods. <p>This paper deals with simplified mathematical models, which clearly illustrate the interaction between the stiffness and strength of the brace itself and the buckling capacity of the strut. The proposed design rules are consistent with the behaviour, have a sound theoretical basis and are simple enough to be applied directly in a design context.

Most reinforced concrete columns are square or rectangular in shape. For such, comprehensive design charts and software are available to enable design for combined compression and uniaxial bending. The columns designed to support loads such as those in multistorey apartment buildings are usually much wider than the thickness of masonry walls that are invariably part of the building construction system. However, it may be architecturally desirable to neatly blend the columns with the walls. This requires the columns to have the same thickness as the walls and these columns may then have to be T or + shaped. As an aid to the design of such columns, this article presents a comparative study of the predicted response to combined compression and uniaxial bending for the + and T shaped sections having the same cross section area and reinforcement content as an equivalent square section. It is shown that the + and T sections can effectively replace the square section.

The notable increase in problems related to the bracing of timber roofs clearly indicates that the time is ripe to seriously consider amended rules governing the design of such bracing. Burdzik et al have proposed a set of amended rules, which are founded on considering the stiffness of the bracing system as a primary criterion. These proposed amended rules are compared with the existing bracing requirements of SABS 0163 (1994) as well as with the requirements of the Eurocode, EC 5 (1992). As the proposed revised bracing rules have a stiffness and strength criterion, the strength and stiffness of nailed joints become an important component of the bracing system, which required further investigation. Despite the limited number of test results used to determine the impact of the stiffness criterion, the findings of this paper were confirmed by observations in the field.

The viability of employment-intensive (EI) techniques in road construction has been confirmed through research for a range of activities. This paper focuses on the drainage structures component of road construction, as this has not been considered to the same depth in previous research. It consists of two elements, namely the development of a technique selection methodology based on COTA (Choice Of Technique Analysis) and a subsequent analysis to select appropriate techniques based on case study projects. The output comprises the appropriate mix of labour- and machine-based techniques along with the appropriate design type for different sets of circumstances, which can be referred to as appropriate practice, or EI practice per definition. It was concluded that under most circumstances the substitution of EI practice for current practice almost doubles the local content of expenditure without extra cost. EI practice is recommended as the norm in the execution of such projects - not only for isolated low-level bridges and maintenance on low-traffic rural roads, but also for the drainage structures component of road construction projects. Whereas general guidelines are provided, it is recommended to practitioners that the selected mix of techniques for individual projects be based on a COTA analysis.