Research Papers - Department of Civil Engineering

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Start date: 2010Subject: search.filters.subject.multi-objective optimization

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Now showing 1 - 5 of 5
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    PublicationEmbargo
    Incorporating road safety Into rural road network pavement management
    (Taylor & Francis, 2021-06-25) Pasindu, H. R; Ranawaka, R. K. T. K; Sandamal, R. M. K; Dias, T. W. K. I. M
    Rural roads play an essential part in a country’s road network providing connectivity between the rural communities and the national roads. However, most of these roads are not maintained efficiently and safety issues are often not prioritised since pavement conditions are prioritised, especially in developing countries. Lack of reliable crash data, road condition monitoring regime are often cited as reasons. This study proposes a methodology to incorporate road safety performance in rural roads in maintenance planning using a multi-objective optimisation approach. Road safety performance is defined in terms of the Cumulative Safety Index (CSI), computed based on the severity, exposure, frequency of safety issues, identified in road safety audits. Safety performance and pavement condition-related indices such as International Roughness Index (IRI), pothole number, are included in the optimisation analysis. It comprises two objectives: minimise network IRI, and minimise network CSI. Applicability of the developed model has been demonstrated from the illustrative example of a rural road network. Results shows that roads with safety issues can also be prioritised in budget allocation while ensuring the network level pavement condition can be maintained at a reasonable level. This methodology offers a simplified approach to incorporate road safety issues in rural road PMS.
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    PublicationOpen Access
    Optimal control of urban sewer systems under enhanced water quality modeling
    (5th International conference on Sustainable Built Environment, 2014) Rathnayake, U. S
    Agricultural lands usually carry a considerable amount of phosphorous and nitrogen. This is due to the routinely added chemical fertilizers. Phosphorous is identified as a non-point source pollutant that causes eutrophication in surface waters. Even though, phosphorous is less mobile than nitrogen, soil erosion in agricultural lands leads to increase the phosphorous levels in surface water. Therefore, it is always better to consider phosphorous concentration when considering the receiving water quality due to combined sewer overflows (CSOs). Rathnayake and Tanyimboh’s optimal control model for urban sewer systems is capable of assessing water quality in receiving water due to CSOs. However, it only includes the concentrations of total suspended solids (TSS), chemical oxygen demand (COD), nitrates and nitrites (NOX), five-day biochemical oxygen demand (BOD) and total Kjeldahl nitrogen (TKN). Therefore, there is a necessity to improve the water quality analysis in Rathnayake and Tanyimboh’s optimal model. This paper presents an enhanced water quality approach, including phosphorous concentrations, in control of urban sewer networks. The enhanced model is applied to a real world combined sewer network. Results show that the enhanced model produces better approach compared to the existing Rathnayake and Tanyimboh’s control model.
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    PublicationOpen Access
    OPTIMAL CONTROL OF URBAN SEWER SYSTEMS–WHERE DO WE STAND TODAY?
    (SAITM, 2014-04-26) Rathnayake, U. S
    Combined sewer overflows (CSOs) are identified as one of the major environmental concerns at most of the cities to date. These untreated combined sewer overflows are directly discharged to the nearby natural water bodies and cause many environmental problems because of the increased pollution levels at natural water bodies. Constructing additional storage facilities, increasing conduit capacity, expanding pumping capacity and application of controlling strategies to utilize the existing storage in sewer network are the common mitigation solutions of CSOs. This research paper targets to present the state of art of control of combined sewer systems, including the author’s current research work in developing a holistic optimal control model for combined sewer systems.
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    PublicationOpen Access
    Multi-objective optimization of combined sewer systems using SWMM 5.0
    (2015-10-25) Rathnayake, U. S
    Combined sewer overflows (CSOs) are frequent in many cities during stormy weather. CSOs are not only an environmental issue but also induce an adverse aesthetic view for major cities, worldwide. Many engineering solutions have been proposed by researchers to reduce, if possible to avoid CSOs; however, most of these solutions require sewer network capacity enhancement. Therefore, most of the proposed engineering solutions are based on structural measures. However, they are not the best solutions since most of these measures require new structural components and thus capital requirement. Therefore, if possible, control of existing combined sewer networks to minimize the CSOs and their adverse environmental effects would be an ideal solution. However, a holistic control algorithm based on environmental concerns is yet to be tabled. Therefore, this paper presents an improved approach in control of existing combined sewer systems to minimize the adverse environmental effects due to the combined sewer overflows. A multi-objective optimization approach was developed, considering flows and water quality in combined sewer flows and the wastewater treatment costs. The presented multi-objective optimization approach shows a considerable improvement in controlling urban wastewater systems compared to the previous work by the same author. The improved algorithm has advantages in solution space of multi-objective optimization approach. Furthermore, it eliminates achievement of infeasible solutions unlike the other constrained multi-objective optimization approaches
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    PublicationOpen Access
    Migrating storms and optimal control of urban sewer networks
    (Multidisciplinary Digital Publishing Institute, 2015-12) Rathnayake, U. S
    Uniform storms are generally applied in most of the research on sewer systems. This is for modeling simplicity. However, in the real world, these conditions may not be applicable. It is very important to consider the migration behavior of storms not only in the design of combined sewers, but also in controlling them. Therefore, this research was carried out to improve Rathnayake and Tanyimboh’s optimal control algorithm for migrating storms. Promising results were found from the model improvement. Feasible solutions were obtained from the multi-objective optimization and, in addition, the role of on-line storage tanks was well placed.