Journal Articles
https://hdl.handle.net/20.500.12504/83
Fri, 29 Sep 2023 12:56:05 GMT2023-09-29T12:56:05ZA comparative analysis of existing models and a new pushover analysis model of reinforced concrete sections
https://hdl.handle.net/20.500.12504/1422
A comparative analysis of existing models and a new pushover analysis model of reinforced concrete sections
Henry, Kimeze; Michael, Kyakula
Pushover analysis is mainly carried out using the concentrated plasticity model whereby when a point reaches yield, a hinge is placed at that point. The other is the yielded block spread plasticity model, whereby when a point reaches yield, an elastic sub-element of the beam is replaced by a yielded sub-element having a reduced cross-section and second moment of area. Both of these models ignore cracking. This study aims at giving an insight into the effects of considering cracking during modelling on the accuracy of estimating deformations in reinforced concrete (RC) structures during pushover analysis by proposing a spread cracking and yielding block model. The proposed model introduces a cracked sub-element to account for the gradual spread of cracking in the beam. A single-storey RC frame is used because it doesn’t pose the challenge of lateral load distribution. A comparison between the proposed model and the existing models shows an increment in the accuracy of the rotational, displacement, moment and lateral load capacities of 63.64%, 56.86%, 64.33% and 55.56% respectively.
Experimental results show that all theoretical models underestimate the ultimate floor displacements and lateral load capacities. The proposed model, however, has better accuracy on both fronts than both existing theoretical models.
Sun, 01 Jan 2023 00:00:00 GMThttps://hdl.handle.net/20.500.12504/14222023-01-01T00:00:00ZOsmotic consolidation of expansive soil
https://hdl.handle.net/20.500.12504/1332
Osmotic consolidation of expansive soil
Sam, Bulolo; E.C., Leong
The mechanical behavior of expansive soils is influenced by the concentration of salts in their pore water. Research
has shown that volume change of soil can occur due to a difference in salt concentration in the pore water between
different zones of the soil as a result of either osmotically-induced consolidation or osmotic consolidation. The effect
of the salt concentration of the pore water in unsaturated soil mechanics can be expressed as osmotic suction. Very
little work has been done to quantify the mechanical equivalence of osmotically-induced and osmotic consolidation.
This study attempts to quantify the mechanical stress equivalence of consolidation of an expansive soil submerged in
a salt solution. Two remoulded soil samples of kaolin - bentonite mixture in proportions of 70% – 30% and 90% -
10%, (kaolin – bentonite) by dry mass were submerged in different concentrated salt solutions to investigate the effect
of osmotic suction. Results showed that osmotic suction caused an additional settlement over the consolidation
settlement under a mechanical stress but does not affect the soil compressibility. The osmotic coefficient of volume
change (mπ) is only a fraction of the coefficient of volume change (mv).
Tue, 01 Jan 2019 00:00:00 GMThttps://hdl.handle.net/20.500.12504/13322019-01-01T00:00:00ZInterpretation of constant suction direct shear test
https://hdl.handle.net/20.500.12504/1328
Interpretation of constant suction direct shear test
Sam, Bulolo; Eng-Choon, Leong
Constant suction direct shear test enables the understanding of the failure mechanism in rainfall-
induced landslides. It can be conducted using a conventional direct shear apparatus with some modifications.
The constant suction direct shear test is carried out in two stages. In the first stage, the unsaturated soil
specimen is consolidated to the target net normal stress and matric suction then sheared in the second stage.
Matric suction is usually controlled using the axis-translation principle. It is commonly observed that the
shear stress of an unsaturated soil sheared in the direct shear shows a strain-hardening behaviour at large
displacements making the determination of the failure stress difficult. Hence, the objective of this study is
to critically examine the constant suction direct shear tests and the analysis of the test results to obtain the
shear strength parameters for unsaturated soils. Constant suction direct shear test data were collated from
the literature. It was found that the interpretation of the direct shear test has two inconsistencies: (1) taking
failure shear stress at arbitrary displacement strain or limit, dependent on the size of the direct shear
apparatus, and (2) correcting only shear stress for contact area. The effect of these two consequences on the
interpretation of the direct shear test range from negligible to significant. The study shows that arbitrary
determination of failure shear stress can be resolved by plotting the direct shear test results using a stress-
path plot. The effects of area correction are shown to be almost negligible for small horizontal displacements
of less than 2 mm for both square and circular shear boxes. A more consistent interpretation of the constant
suction direct shear test is demonstrated where both these inconsistencies are considered.
Sun, 01 Jan 2023 00:00:00 GMThttps://hdl.handle.net/20.500.12504/13282023-01-01T00:00:00ZModelling chlorine residuals in drinking water: a review
https://hdl.handle.net/20.500.12504/926
Modelling chlorine residuals in drinking water: a review
Onyutha, Charles; Kwio-Tamale, J. C.
World Health Organization’s guidelines on water quality limit concentrations of residual chlorine in drinking water to the range 0.2–5 mg/l. Modelling tends to be applied to understand how chlorine concentrations can be kept within the recommended limits. In this line, we reviewed 105 articles to show advances in modelling of chlorine residuals while focussing on both data-driven statistical models and process-based models. A total of 83 and 17% reviewed articles applied process-based models and statistical models, respectively. The most influential water parameters which were reported for chlorine decay were pH and temperature. For statistical models, modellers reported a wide range of sizes of training, testing, validation sub-samples, and number of neurons in the hidden layers of the network. Thus, the use of novel fitness function to concurrently seek for the most accurate and compact solution was recommended. Most studies applied coefficient of determination (despite its issues such as failure to quantify bias) to evaluate model performance. We recommended revised coefficient of determination and hydrological model skill score to be used as “goodness-of-fits” metrics since they can quantify model’s bias, and capacity to reproduce observed variability. We found that many modellers portrayed a common practice of not providing sufficient information (such as values of parameters) regarding their modelling results. For instance, 47% of the reviewed articles did not expressly specify the order of reaction in their chlorine decay modelling studies. The practice of not reporting sufficient pertinent information can affect reproducibility of results and hinder model improvement which would arise from possible follow-up studies.
1-18p.
Mon, 24 Jan 2022 00:00:00 GMThttps://hdl.handle.net/20.500.12504/9262022-01-24T00:00:00Z