Scielo RSS <![CDATA[Journal of the South African Institution of Civil Engineering]]> http://www.scielo.org.za/rss.php?pid=1021-201920150002&lang=es vol. 57 num. 2 lang. es <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>Effectiveness of economic incentives on clients' participation in health and safety programmes</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-20192015000200001&lng=es&nrm=iso&tlng=es The use of economic incentives to improve health and safety (H&S) performance in the construction industry in general has been investigated by various scholars. However, few studies have looked at the impact of economic incentives on construction clients, especially in the developing world. This paper reports findings on the feasibility of incentives to influence construction clients to perform on H&S. The investigation was conducted using a Delphi technique to determine the impact significance of economic incentives or disincentives on construction clients' H&S performance. A panel of experts in construction H&S was assembled from most regions of the world. A three-round iterative Delphi study aimed at establishing consensus from the expert panel was then conducted. The study found that economic factors have critical impact significance on clients' H&S performance, and that clients were 'very likely' to implement various H&S elements as a result of the economic incentives and or disincentives. There is little research on the use of incentives to influence construction clients' H&S performance and the effectiveness of such incentives. This gap in literature, and the need for improvement in construction H&S performance, motivated the current study. Therefore it was necessary to investigate specifically the extent to which economic incentives could be used to influence construction clients to become involved in H&S programmes. Economic incentives are considered to be a proactive way of improving H&S performance among other key parties, such as employees in the construction industry. The paper reports on the findings from an analysis of the impact significance of economic incentives on clients. It underscores the point that economic incentives or disincentives for construction clients are necessary to encourage them to actively participate in H&S programmes, hence resulting in performance improvement. <![CDATA[<b>Development of a saturation and stress-dependent chord modulus model for unbound granular material</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-20192015000200002&lng=es&nrm=iso&tlng=es Unbound granular material is used in the pavement structure and usually comprises the bulk of the structural and foundation layers of a typical South African pavement. The term unbound granular material refers to the classification of natural material, which has not been modified in any way. Unbound granular material is classified from a G1 to G10 quality according to its fundamental behaviour and strength characteristics. Young's modulus and Poisson's ratio are theoretical concepts of linear elasticity that can at best approximate experimental results of actual material elastic response. In their basic linear elastic form, Young's modulus and Poisson's ratio are rather poor approximations of actual unbound granular material behaviour. The non-linear, stress-dependent behaviour of unbound granular material can, however, be simulated using the linear elastic model as a basis, but with a proper constitutive material model that adheres to the observed material behaviour. The objective of this paper is to utilise a chord modulus model and calibrate it for a range of unbound granular material classifications. The model was calibrated for five bulk material samples, ranging from G2 to G8. The calibration process included linking variables of the model to mathematical functions that approximate the trends observed when variables were considered against degree of saturation. A parametric analysis indicated that the saturation-and stress-dependent chord modulus model realistically predict material behaviour. The trends depict the stress-dependent behaviour of unbound granular material, where an increase in initial modulus is observed for increasing confinement pressure, as well as initial stress softening with increasing stress ratio followed by stress stiffening. It can be concluded from the results presented in this paper that a saturation- and stress-dependent chord modulus model could be refined and calibrated for crushed and natural unbound granular material. This refinement did not negatively influence the accuracy or ability to realistically predict the material behaviour. The preliminary conclusions reported in this paper indicate that the chord model formulation yield satisfactory predictions, especially when the model is calibrated for each individual material type. <![CDATA[<b>A proposal for the probabilistic sizing of rainwater tanks for constant demand</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-20192015000200003&lng=es&nrm=iso&tlng=es In recent years there has been an international trend towards installing rainwater tanks in an attempt to save water. This study investigates the possibility of simplifying the process of sizing a rainwater tank for optimal results under constant water demand. The required size of a rainwater tank is influenced by the Mean Annual Precipitation, the size of the roof which is being used for harvesting, the water demand, the desired certainty of supply and the rainfall patterns. The study investigates the use of a generalised equation of the form y = a(x - 1)b + c, where x is a runoff parameter, y is a storage parameter and a, b and c are constants which differ for each location, depending on rainfall characteristics. Results obtained using the generalised equation are compared to results obtained by simulating tank behaviour over a 16-year period (1994-2009) at three rainfall stations. The results suggest that such an equation can be used to estimate the storage capacity of a rainwater tank. <![CDATA[<b>Using small-strain stiffness to predict the load-settlement behaviour of shallow foundations on sand</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-20192015000200004&lng=es&nrm=iso&tlng=es Foundation settlement prediction is a challenging task due to the difficulties associated with the quantification of the soil stiffness and the abundance of available analysis methods. Of the different soil stiffness moduli that may be measured, the initial small-strain stiffness is important since it can be measured both in the field and the laboratory, and settlement prediction methods using this parameter are becoming more common. The objective of this paper is to present a settlement prediction method for shallow foundations that only uses small-strain stiffness as input parameter. The method was developed by conducting physical modelling in the geotechnical centrifuge at the University of Pretoria to quantify the behaviour of shallow foundations on sand. Bender and extender elements were used to obtain the small-strain stiffness profile below the foundation before it was vertically loaded and the load-settlement curve determined. The tests were conducted on different density sands corresponding to loose, medium-dense and dense sand. A non-linear stepwise analysis approach was used in conjunction with a softening function, with variables calibrated to obtain the best fit solution for the different sand densities. Results indicate that the accuracy of the proposed method decreases as the sand density increases, but that load-settlement behaviour can be predicted with reasonable accuracy. <![CDATA[<b>Some shortcomings in the standard South African testing procedures for assessing heaving clay</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-20192015000200005&lng=es&nrm=iso&tlng=es Design of foundations for most light structures in South Africa, and in particular for low-cost housing, relies heavily on particle size analysis and the determination of Atterberg Limits. The tests for these properties are currently performed in commercial materials testing laboratories using the procedures of the CSIR's Technical Methods for Highways Part 1 (TMH1) (CSIR 1986). SANS 3001 (SANS 2011) is being phased in to replace TMH1. Both are primarily concerned with road construction. Investigations at the Central University of Technology indicate serious shortcomings in both of these norms in the context of foundation design for light structures. Highly plastic material is not usually used as road construction material, and these methods may be adequate to simply identify material so plastic that they should not be used in road construction. Structural foundations, particularly for low-cost housing, do not usually have this option; it is essential to estimate the actual heave potential. This investigation suggests that some of the changes proposed in SANS 3001 may be beneficial for heave assessment, but the most likely application of SANS 3001 could be unsatisfactory in many cases. <![CDATA[<b>Adjudication in South African construction industry practice: Towards legislative intervention</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-20192015000200006&lng=es&nrm=iso&tlng=es Adjudication in South African construction practice has, through various initiatives of the South African government and Construction Industry Development Board, the increased use of international standard form construction contracts, and the South African High Court's robust approach in enforcing adjudicators' decisions, become relatively commonplace in both the public and private sectors as the first tier in dispute resolution procedures on construction projects across the South African construction industry. This paper considers several judgements of the South African courts dealing with adjudication and certain of the South African government and Construction Industry Development Board's initiatives which, together with South African construction industry adjudication practice, combine in solidifying a foundation for the implementation of a legislative framework underpinning the application and practice of adjudication in the South African construction industry. <![CDATA[<b>Untreated aeolian sand base course for low-volume road proven by 50-year old road experiment</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-20192015000200007&lng=es&nrm=iso&tlng=es The Hoopstad long-term pavement performance experiments constructed in 1962 between Hoopstad and Bultfontein in the Free State Province of South Africa included a 90 m section of a finegrained, nonplastic, A-2-4(0), aeolian, Kalahari-type sand as unstabilised base course. After 50 years and approximately 1.0M E80 all the experimental sections are still carrying traffic, none has been rehabilitated and none appears to have ever failed. The results of a pavement evaluation carried out in 2013 indicate that similar sand can be used unstabilised as base course for a Category C or D low-volume road designed to carry up to at least 0.1M E80/lane over 20 years, provided it is compacted to refusal or at least 100% MAASHO on a good support, is well drained, well sealed with at least the equivalent of a double seal, and that the shoulders also offer good lateral support and drainage. The seal must also be sufficiently wide to accommodate the traffic expected. Such a design offers tremendous potential for the construction of relatively inexpensive, all-weather, low-volume roads in the vast area of arid and semi-arid southern Africa in which similar sands and a scarcity of gravels occur. <![CDATA[<b>Hazard of sinkhole formation in the Centurion CBD using the Simplified Method of Scenario Supposition</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-20192015000200008&lng=es&nrm=iso&tlng=es A large part of the land south of Pretoria is underlain by dolomite from the Chuniespoort Group of the Transvaal Supergroup. In South Africa, dolomite rock has a notorious reputation for the formation of sinkholes and subsidences. Thousands of people reside and work in the Centurion area, where numerous sinkholes have occurred, causing damage and in some instances loss of property and even lives. Centurion has rapidly densified over the last 40 years, with an increase not only in the number of people, but also in the density of waterborne services. This paper proposes draft guidelines for the allocation of an Inherent Hazard Class for percussion boreholes, referred to as the 'Simplified Method of Scenario Supposition'. This method was then used to classify the Centurion CBD and surrounding area.