Scielo RSS <![CDATA[Journal of the South African Institution of Civil Engineering]]> vol. 52 num. 1 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b>Infilling annual rainfall data using feedforward back-propagation Artificial Neural Networks (ANN)</b>: <b>application of the standard and generalised back-propagation techniques</b>]]> Water resource planning and management require long time series of hydrological data (e.g. rainfall, river flow). However, sometimes hydrological time series have missing values or are incomplete. This paper describes feedforward artificial neural network (ANN) techniques used to infill rainfall data, specifically annual total rainfall data. The standard back-propagation (BP) technique and the generalised BP technique were both used and evaluated. The root mean square error of predictions (RMSEp) was used to evaluate the performance of these techniques. A preliminary case study in South Africa was done using the Bleskop rainfall station as the control and the Luckhoff-Pol rainfall station as the target. It was shown that the generalised BP technique generally performed slightly better than the standard BP technique when applied to annual total rainfall data. It was also observed that the RMSEp increased with the proportion of missing values in both techniques. The results were similar when other rainfall stations were used. It is recommended for further study that these techniques be applied to other rainfall data (e.g. annual maximum series, etc) and to rainfall data from other climatic regions. <![CDATA[<b>An experimental study of non-Newtonian fluid flow in rectangular flumes in laminar, transition and turbulent flow regimes</b>]]> New and extensive results are reported on the flow of a range of non-Newtonian fluids, including aqueous suspensions of bentonite and kaolin, and aqueous solutions of synthetic polymer carboxymethyl cellulose (CMC), flowing down inclined flumes of rectangular cross-section of three different sizes. In particular, these tests elucidate the role of shear-thinning viscosity, with and without the presence of a yield stress, on the flow behaviour in flumes over a wide range of conditions of Reynolds numbers spanning the range 1<Re<10(4), thereby embracing both the laminar and transitional flow regimes, and possibly the turbulent regimes. Furthermore, the flumes could be tilted up to 5ยบ from the horizontal. This extensive experimental study has facilitated the delineation of the role of the Froude number in the nature of flow, as well as the cessation of laminar flow conditions in such industrially important systems. The results reported here can be used to design flumes for shear-thinning and/or viscoplastic fluids. <![CDATA[<b>Background to draft SANS 10160 (2009)</b>: <b>part 4 seismic loading</b>]]> This paper provides a critical overview of the background to the revisions which led to the formulation of Part 4, Seismic Loads, of the South African Standard SANS 10160. The paper also presents a comparison to demonstrate the calibration of the standard against other international standards. Eurocode 8 was used as the principle reference for the formulation of the revised clauses. The clauses for seismic design of SANS 10160 are based on the concept of regular buildings with suitable detailing to allow the necessary ductile behaviour. The paper points out a need to review the use of a redundancy factor which makes provision for a possible lower design peak ground acceleration value and the behaviour factor for reinforced concrete shear walls. The damage limitation criteria also need to be based on Eurocode 8. It is shown that the revised formulation provides lower design forces for regular buildings than in the current standard. This is, however, dependent on the choice of a design nominal peak ground acceleration for the various regions in the country. The available information on nominal peak ground acceleration is presented, and it is pointed out that a decision is needed on the choice of this important parameter for the seismic zones of South Africa. <![CDATA[<b>Wind-tunnel testing of sports stadia to optimise their use and safety</b>]]> Several wind-tunnel studies of sports stadia were recently carried out at the CSIR's Boundary-Layer Wind-Tunnel Laboratory in Pretoria. This paper gives a brief background to wind-tunnel modelling, highlights the relevant aspects of representing large structures and demonstrates the applicability and usefulness of boundary-layer wind-tunnel technology in addressing design challenges and optimising large-scale sports facilities. <![CDATA[<b>Partial factors for selected reinforced concrete members</b>: <b>background to a revisionof SANS 10100-1</b>]]> The application of Eurocode EN 1992-1-1 in revising the South African standard for structural concrete design SABS 0100-1:1992 will require the determination of partial factors in accordance with the reliability requirements of the revised South African loading code SANS 10160:2010. The partial material factors γs for steel and γc for concrete are proposed in analysing the reliability of reinforced concrete slabs and short centrically loaded columns. It appears that the partial factors γs = 1,10 and γc = 1,40 are a suitable set of factors to be considered in the foreseen revision of the code. Further research is required on the model uncertainty for different structural members (flexural members, shear, columns, walls) and the theoretical models of basic resistance variables related to quality control.