Scielo RSS <![CDATA[Journal of the South African Institution of Civil Engineering]]> vol. 64 num. 1 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b>A mathematical model for determining engineering soil classifications from pedological data</b>]]> Various pedological soil classification systems exist worldwide, including an internationally accepted system and various national systems, many of which have been incorporated into databases that include maps. Various physical and chemical soil properties are used for classifying soils according to these pedological systems. This paper proposes an approach which may be used to determine the engineering properties of soils from the physical and chemical properties that are used to pedologically classify soils by systems, and, in particular, the South African Binomial System. These engineering properties include the USCS and AASHTO classification groups which may, in turn, be used as a means of rapidly determining the general suitability of areas for proposed development, particularly during the reconnaissance investigation stages of transportation route locations and township developments, with a resultant saving of time and money. The model was verified using data from the study area, as well as from an area located approximately 190 km from the study area. A total of 88% of the classification groups determined by the model, in the study area, were correct. Furthermore, only 6% of the classifications were incorrect by a maximum of two groups. The classifications determined for the soils outside the study area were all correct. <![CDATA[<b>Utilising Land Type data for geotechnical investigations</b>]]> In South Africa, a Land Type Survey (LTSS) has been conducted of the entire country. The information available from the LTSS is readily and inexpensively made available to the public (in the form of maps and accompanying memoirs). This survey includes information on the climate, terrain and soils. The soil information given includes qualitative data (such as pedological classifications, soil profiles and soil types), as well as quantitative physical and chemical properties of representative soils tested. Such information is used primarily for agricultural purposes. This paper proposes an approach for inferring information, of relevance in reconnaissance geotechnical engineering surveys, from Land Type data, to supplement geotechnical investigation data. The proposed procedure was verified using actual information from a geotechnical report. This investigation indicated that general engineering properties can be inferred from qualitative pedological data. In addition, statistically significant engineering properties (including the grading, Atterberg Limits and the USCS and AASHTO classifications) were determined from quantitative pedological data, in 86% of cases, for the soils considered. It is evident from this research that data from the Land Type survey data can be successfully used for geotechnical investigation purposes for certain developments (such as roads and townships) where the depth of interest is relatively shallow. <![CDATA[<b>Incorporation of additional information into the South African Wind Load Formulation</b>]]> The South African wind loading standard SANS 10160-3:2019 recently adopted an improved map of characteristic basic wind speeds and increased the wind loading partial safety factor from 1.3 to 1.6. These changes represent an overhaul of the design wind loads throughout South Africa and were the result of several studies on the wind loading standard. Since these studies were conducted, substantially more wind speed data has been made available. This investigation aimed to use this data to assess the current design loads by estimating location-specific design values that maintain the current reliability level of the standard. A statistical test was developed to assess whether the design values in SANS 10160-3:2019 could be supported by the new data. It was found that several updates could be considered. These were incorporated into a new recommended map of basic wind speeds that could be considered for inclusion in the next revision of SANS 10160-3. <![CDATA[<b>Assessment of local sewage sludge ash as a supplementary cementitious material - effects of incineration temperature and cooling rate of the ash</b>]]> This paper reports on the possible use of sewage sludge ash as a pozzolanic supplementary cementitious material to Portland cement. Samples of sewage sludge were incinerated at 700°C, 800°C and 900°C and these were then cooled in the furnace (F ISSA), in air (A ISSA) or by quenching in water. The resulting ashes were ground to suitable fineness and used to prepare cement pastes and mortars in which the binder consisted of 30% ash and 70% Portland cement. The paste samples were used for microscopic and chemical assessment of the evolution of hydration products, while the mortars were used to assess the effects of the ashes on workability and compressive strength of laboratory-prepared samples using a water/binder ratio of 0.5. Fly ash was used as a reference pozzolanic material to assess the performance of sewage sludge ashes. Analysis of the sewage sludge ashes showed the presence of cementitious compounds and hydration products that suggest that this material can be used as a partial replacement of Portland cement. However, sewage sludge ash reduces the workability of the mortar. Compressive strength results indicate that the highest strength is obtained when the sewage sludge is incinerated at 900°C and then quenched in water. <![CDATA[<b>Evaluation of the seismic response of a reinforced concrete footing with stub column to increasing peak ground acceleration using pseudo-dynamic experimentation</b>]]> The pseudo-dynamic experimentation technique was investigated to evaluate the damage occurring in a reinforced concrete footing with stub column due to the overall response of a linear elastic two-storey, two-bay moment-resisting steel frame structure that is subjected to an earthquake excitation with increasing peak ground acceleration. The implicit Newmark's method with static condensation was utilised in the present study to solve the governing equation of motion of the multi-degree-of-freedom system. Five pseudo-dynamic experiments were performed by scaling the El Centro ground motion record, which occurred in California on 18 May 1940, to produce peak ground accelerations that ranged between 0.34 g and 2 g. All the laboratory experiments were undertaken under a constant axial load for the duration of the applied earthquake excitation, and utilised Rayleigh damping to model the energy loss within the overall structure. The pseudo-dynamic method provides a reliable method to relate damage suffered by the stub column due to the overall structure's response to the applied earthquake excitation. The method enables the structural capacity and failure mechanisms of the reinforced concrete stub column to be observed in relation to the seismic demand. The hysteretic response of the stub columns and energy dissipation characteristics were determined, and it was shown that the yield strength of the longitudinal reinforcement within the stub column has a significant impact on the maximum shear capacity and damage incurred by the stub column. The damage is more pronounced with an increase in the number of cycles of vibration, particularly at displacements that exceed the yield strength of the reinforcement. An increase in the hysteretic energy dissipated by the reinforced concrete stub column results in a concomitant increase in the observed damage to the stub column in the form of concrete cracking, reinforcement yielding and spalling of the concrete. <![CDATA[<b>What leads to severe multi-vehicle crashes on mountainous expressways in Western China?</b>]]> This paper investigates the occurrence and severity of collisions involving multiple vehicles on mountain expressways (MMEs) in Western China. A total of 1 521 crash samples occurring on one typical mountain expressway in Shaanxi, China, between 2012 and 2017, were analysed through a partially constrained generalised ordered logit to identify the significant risk factors contributing to the severity of such crashes. Elasticity analysis was performed to quantify the effects of each independent explanatory variable on the collision severity outcomes. Fourteen total explanatory variables were found to have a significant and pronounced influence on the likelihood of MME crashes. These include the type of collision, the at-fault driver's age, driving while fatigued, cell phone use while driving, alcohol-impaired driving, speeding, risky following and dangerous overtaking behaviour, sharp curves in the roadway and slippery pavement conditions, seasons, day of the week, time of day, and adverse weather (rain/snow/fog). The impacts of the variables on the collision severity were also explored. Taken together, the findings may serve as a useful guide for developing legislation and technical countermeasures to ensure traffic safety on mountain expressways in Western China.