Research Papers - Department of Civil Engineering
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Publication Embargo Resilience of masonry infilled reinforced concrete school buildings in low to moderate seismic regions: case study of Sri Lankan schools(Springer Science and Business Media, 2025-12-08) Raheem, S; Thamboo, J; Mallikarachi, C; Wijesundara, K; Dias, PThe resilience of school buildings in high seismic regions is widely emphasised and evaluated. However such resilience in low-to-medium seismic regions are generally overlooked due to the lower probability of occurrence and low-to-medium intensities expected. Nonetheless, nominal seismic provisions should be provided for the life safety of pupils occupying these school buildings. Therefore, this study was focused on assessing the level of seismic resilience of school buildings in low-to-medium seismic regions, where the archetypal school buildings in Sri Lanka and the seismic demand in the country were taken as the case study. A framework to quantify resilience, incorporating social recovery aspects, was adopted to evaluate the seismic resilience. The resilience of the same archetypal school buildings subjected to different nominal retrofitting methods was also assessed to verify the improvement in resilience compared to un-retrofitted buildings. The epistemic and aleatory uncertainties were incorporated by using 25 different recorded seismic accelerograms and Monte-Carlo simulation of material properties (twenty sets of randomised values), respectively; with 500 combinations (aleatoric and epistemic) being analysed for each building type considered. Seismic resilience indices (RIs) obtained indicate that the school buildings with retrofitted configurations are certainly better than un-retrofitted ones, especially for higher hazard levels. Increases in the RIs are in the range of 36.6–91.2% for the highest hazard level. Sensitivity analyses were also carried out to ascertain parameter influence on RIs. The proposed nominal retrofitting solutions for these school building archetypes generate adequate resilience against the seismic hazards demarcated for the country.Publication Embargo Uniaxial compressive response of cement mortar with waste aluminium fibre sourced from electrical distribution cables(Springer Science and Business Media, 2025-01) Perera K.D.Y.G.; Ahamed Y.L.F; Somarathna H.M.C.C; Jayasekara D.A.B.P.M; Mohotti D; Raman S.NElectrical distribution and communication cables cease to function for transmission when their length is insufficient, and it is considered as it approaches the end of their useful lives. Further, the disposal techniques are not eco-friendly. This study aimed to evaluate the feasibility of cement mortar systems with the inclusion of aluminium fibre extracted from electrical distribution cables. Two diameters of 1.35 mm and 1.70 mm and two lengths of 10 mm and 15 mm fibres were used while incorporating four volume ratios, particularly 0.5%, 1.0%, 1.5%, and 2.0% to evaluate the effect of the length, diameter and volume ratios. The compression test and density test were performed to study the behaviour of Metal Fibre Reinforced Mortar (MFRM) systems under both dry and wet states. Compared to conventional mortar, the ultimate compressive strength of MFRM systems was increased up to 39.4% in 1.5% of fibre addition under the 28-day dry state, where the 1.5% volume ratio showed the best performance under compressive loads. Strain at ultimate strength, modulus of elasticity and strain energy also showed improvements with the fibre inclusion up to 74.4%, 87.3%, and 106.6% respectively. Fibres with higher aspect ratios showed significant effectiveness among the aforementioned fibre variations. The overall results highlighted that the MFRM with 1.5% of fibres performed expertly with 15 mm length and 1.35 mm diameter under compression loadsPublication Embargo Machine learning prediction of web-crippling strength in cold-formed steel beams with staggered slotted perforations(Elsevier Ltd, 2025-01) Gatheeshgar, P; Ranasinghe R.S.S; Simwanda, L; Meddage D.P.P.; Mohotti, DThe application of staggered slotted perforations in cold-formed steel (CFS) members is increasingly prominent in modern construction. Understanding the web-crippling strength of CFS beams, especially those with staggered slotted perforations, is crucial in structural engineering. This study employs machine learning (ML) models to predict the web-crippling strength of these beams under one-flange loading conditions, specifically interior-one-flange and end-one-flange loading. The research utilises a comprehensive dataset comprising 576 web-crippling strength results obtained through numerical modelling. The dataset includes parameters such as yield strength, thickness, corner radius, slot length, slot width, and bearing plate length. Four different ML algorithms—k-nearest neighbour (KNN), random forest (RF), support vector regression (SVR), and artificial neural network (ANN)—are developed and evaluated. Performance metrics, including coefficient of determination (R²), mean squared error (MSE), root mean square error (RMSE), mean absolute error (MAE) and mean normalised bias (MNB) are used to assess model accuracy. The random forest model outperforms others in both the training and testing phases. Shapley additive explanation (SHAP) and partial dependence plots further analyse the influence of input features on web crippling strength. This study presents a robust ML-based approach for predicting web crippling strength, providing engineers with a time-efficient alternate method.Publication Embargo Selecting suitable passive design strategies for residential high-rise buildings in tropical climates to minimize building energy demand(Elsevier Ltd, 2025) Perera, U.S; Weerasuriya A.U; Zhang, X; Ruparathna R; Tharaka M.G.I; Lewangamage C.SPassive design strategies (PDS) are a fitting solution to reduce the ever-growing energy cost of residential high-rise buildings in tropical regions. However, PDSs’ building energy saving potential significantly varies with local climate conditions, but it has been sparsely investigated. Hence, this study investigated the energy-saving efficiency of eight common PDSs integrated into a typical residential high-rise building in three sub-climates: extremely hot humid (0 A), very hot humid (1 A), and warm humid (3 A) defined by ASHRAE for the tropical climate. This study developed a Building Performance Analysis (BPA) workflow with a BIM-based simulation framework and local and global sensitivity analyses for the building energy analysis. The global sensitivity analysis revealed that low e-coating on glasses is the most influential PDS for 0 A and 1 A climates, but it has a negative effect in the sub-climate zone 3 A. The low-conducting exterior walls are the most effective PDS in the sub-climate zone 3 A, but they are poorly performed in the other two sub-climate zones. Based on the energy calculation and sensitivity analysis, this study proposes the best PDS groups, saving up to 40.1 %, 63.5 %, and 31.7 % of average annual building consumption in the sub-climate zones, 0 A, 1 A, and 3 A climates.Publication Open Access Effectiveness of Porous Concrete Pavements in Removing Total Suspended Solids from Urban Stormwater Runoff(International Society for Environmental Information Sciences, 2025-05-25) Wijewickrama D.; Miguntanna N; Siriwardhana K.D; Kalaimathy S.N.; Kantamaneni K; Rathnayake UThis study investigates the effectiveness of total suspended solids removal in porous concrete pavement (PCP) with only changing aggregate size of the mix design and the thicknesses of the pervious concrete pavement specimen. The study used two different aggregate sizes, 10 ~ 14, and 14 ~ 19 mm, with a third mix percentage consisting of 50% of both aggregate sizes. Water content was main-tained low in the mix designs since it influenced the porosity of the concrete and the water flow rate after solidifying the concrete. Slump tests were done to find the workability and all 3 mix designs’ slump was near zero, and casted cubes were used to determine t he compres-sive strength of each mix design. The results revealed that aggregate size had a direct impact on compressive strength, with smaller aggregate mix designs having higher strength. The study validated PCP’s filtration properties as well as the percentage removal of total suspended solids. The removal efficiency was found to increase with the thickness of the PCP and the use of smaller aggregate sizes. Also, data revealed that where higher porosity facilitates improved filtration and reduces Total Suspended Solids (TSS) in st orm water runoff. Furthermore, Infiltration data shows, where higher TSS Reduction Efficiency is associated with improved infiltration capacity, effectively mitigating the impact of stormwater runoff on water quality. According to the study, PCP is a better alternative for stormwater management systems and may be utilized for harvesting and cleaning purposes as non-portable water. The findings of this study might assist in determining the individual performance of each porous concrete pavement type and encourage wider use of these pavements to reduce the need for impermeable surfaces for stormwater management.Publication Embargo Feasibility of hydrological modelling for intermittent streams using HEC-HMS: a process evaluation(Taylor and Francis, 2025-01-08) Perera, M. D.D; Gomes, P.I.AThe use of hydrological software in simulating the rainfall–runoff relationships of intermittent streams is rather unfound due to their dynamic flow regimes. This study assessed the feasibility of using Hydrologic Engineering Center–Hydrologic Modelling System (HEC-HMS), a widely used open-source hydrological modelling software, in discharge simulation of intermittent streams in a dry tropical zone. Individual calibration was required for each stream, even in adjoining sub-catchments with the same geology and climate. Event-based models with transitional periods captured seasonal variations in catchment characteristics. Strong correlations (Pearson’s r > 0.7, P < 0.05) between observed and simulated discharges indicated model success and, after calibration for one season, flows of the next (similar) season could be predicted without further adjustments. Baseflow and channel infiltration were the most sensitive parameters in the wet and dry seasons, respectively. This study demonstrated the possibility of building accurate hydrological models for intermittent streams by incorporating seasonal variations and extensive calibration.Publication Open Access Evaluation of mesoscale physical habitats in sediment and water quality improvement – a mesocosm study for urban canals(Inderscience Publishers, 2025) De Zoysa, S; Chandeep, K. A.T; Pathirathne, P.H.D.R; Gomes, P.I.AThis study investigated the applicability of different types of attenuation processes (i.e., aeration and stirring) with and without dilution in nutrients (nitrogen and phosphorous) and sulphide-polluted sediment cleanup via laboratory mesocosms. Attenuation refers to the decline in contaminant concentration, a phenomenon driven by processes like dilution, mixing, and dispersion. Dilution, a remedial method involving the blending of contaminated water with uncontaminated often happens with uncontaminated runoff or a tributary. Regardless of the seasons, aeration, stirring, combined aeration and stirring, and dilution generally resulted in better removal efficiency of pollutants. Aeration combined with stirring showed notable improvements across multiple water quality parameters, and parameters seemed to be treatment type dependent, but without any significant differences. Dilution reduced electrical conductivity and increased dissolved oxygen but did not influence ammoniacal nitrogen and phosphate. The energy consumption for a unit percentage improvement via aeration and stirring was 0.04–0.25 USD and 0.03–0.15 USD, respectively. Therefore, relying solely on attenuation processes without dilution is deemed economically infeasible in real or prototype applications. This research sheds light on potential applications including pros and cons, emphasising the need for a balanced approach, and setting the stage for future studies.Publication Embargo Nonlocal strain gradient modeling of vibration energy harvesting in fluid-immersed bimorph sandwich nanoplates under thermal environment(American Institute of Physics, 2025-02-07) Roodgar Saffari, P; Senjuntichai, T; Rajapakse, NThis research details a method for mathematically simulating and assessing thermal vibration energy harvesting in laminated bimorph nanoplates in fluid contact. The model uses the piezoelectric characteristics of the outer layers and the functionally graded (FG) core material to transform thermal stresses into electrical energy efficiently. Nanostructures' size effects and nonclassical behavior are captured by the nonlocal strain gradient theory (NSGT). Combining the Navier-Stokes equations with the electromechanical equations obtained from Hamilton's principle, first-order shear deformation theory (FSDT), and Gauss's law yields an advanced multi-physics model. The FG core exhibits variations by the power law principle and is composed of both ceramic and metal components. Analytical solutions are obtained for the frequency response functions that relate the electrical power output to the external circuit load resistance by solving the coupled electromechanical-fluid equations. A thorough investigation is conducted to analyze how different elements impact energy harvesting performance using parametric studies. These factors include the configuration of the harvester (either parallel or series piezoelectric connections), nonlocal and strain gradient effects, temperature gradients, fluid depth, electrical load, geometric dimensions, and the material properties of the piezoelectric layers, and functionally graded core.Publication Embargo Durability and mechanical performance of glass and natural fiber-reinforced concrete in acidic environments(Elsevier Ltd, 2025-02-28) Justin, S; Thushanthan, K; Tharmarajah, GThis study investigates the mechanical and durability characteristics of fiber-reinforced concrete when exposed to acidic environments. The research focuses on the effects of adding 1 % of treated coir fibers (TCF), treated rice husk fibers (TRH), and glass fibers (GF), along with 5 % silica fume (SF), to concrete. Experimental results show that the inclusion of these fibers and SF enhances both compressive and tensile strengths, with the most significant improvements observed in GF-reinforced concrete. The durability of the concrete was tested by immersing samples in acidic solutions with pH values of 3 and 5 for 28 days. Ultrasonic Pulse Velocity (UPV) tests indicated that the concrete’s quality remained stable, while compressive strength tests revealed an increase in strength, particularly in samples exposed to pH 5. Sorptivity tests, which measure water absorption, indicated higher initial absorption rates due to the porous nature of fiber-reinforced concrete. However, as hydration progressed, the rate decreased. SEM images show that incorporating silica fume improves the microstructure of the specimens benefitting the strength of the structure. The study concludes that concrete reinforced with GF and SF exhibits superior mechanical properties and durability in acidic environments, making it a promising material for use in harsh conditionsPublication Embargo Framework for generating high-resolution Hong Kong local climate projections to support building energy simulations(American Institute of Physics, 2025-03-07) Wang, J; Kudagama, B.J; Perera, U.S; Li, S; Zhang, XFiner resolution climate model projections are essential for designing regional building energy consumption and adaptation strategies under changing climate conditions. However, projections from Global Climate Models (GCMs) are typically coarse in resolution and subject to biases and uncertainty. To address this, the present study uses bilinear interpolation and morphing statistical downscaling to obtain high spatial (around 10 km) and temporal (hourly) resolution weather data, for more accurate estimations of future residential building energy consumption under climate change. An empirical quantile mapping bias-correction technique is applied to adjust the projection data from 44 GCMs under four representative Shared Socioeconomic Pathways (SSPs): SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5. The bias-corrected data are validated against meteorological observations from the Hong Kong Observatory's King's Park station. The hourly data are then converted to typical meteorological year data and used as input for EnergyPlus to predict future energy consumption patterns in public rental housing in Hong Kong. Case studies under the four SSPs show that climate change will significantly impact residential building energy use. Energy consumption is projected to increase by up to 14.0% for harmony-type buildings, 12.8% for trident-type buildings, and 12.4% for slab-type buildings by the end of the century under the SSP5-8.5 scenario, highlighting the urgent need for adaptive building design and energy policy measures.