CERS - 2024

Permanent URI for this collectionhttp://192.248.9.226/handle/123/22814

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item: Conference-Abstract
Construction quality framework for school buildings in Sri Lanka
(Department of Civil Engineering, University of Moratuwa, 2024) Thoradeniya, BRWMD; Jayasinghe, C; Ariyaratne, IE; Pasindu, HR; Damruwan, H; Weerasinghe, P; Fernando, L; Rajapakse, C
The built environment of schools plays a crucial role in shaping the educational experience, yet Sri Lanka has faced ongoing concerns regarding the quality of school construction, despite significant government investment in education. To address this issue, a comprehensive study was conducted with the primary objective of developing a construction quality framework specifically tailored for school buildings in Sri Lanka. This framework aimed to establish clear standards and guidelines for the design, construction, and maintenance of school buildings, ensuring that they meet the necessary safety, functionality, and sustainability criteria. An extensive literature review was undertaken to systematically break down the processes involved in school building construction and to conduct background research on contemporary quality standards. The breakdown included the following key phases: project initialization, design and construction, operations and maintenance, and rectification and building condition. Data collection was carried out through multiple methods, including case study reports from the National Building Research Organization (NBRO), which covered 58 buildings across 22 schools. Surveys of school stakeholders and expert interviews were also conducted. The NBRO reports included visual observations and both destructive and non-destructive testing techniques. The survey aimed to assess the efficiency of operations and maintenance processes, while expert interviews provided insights into the procurement procedures of school buildings. The collected data were analysed using statistical methods to categorize and prioritize the defects identified in the construction process. This analytical approach facilitated the identification of the most common and critical defects, along with their correlation to the overall condition of the buildings. The defects were categorized based on their location and severity, offering a clear understanding of recurring issues in school construction. The analysis revealed significant issues in design, construction, and maintenance practices, with gaps in maintenance protocols and challenges such as financial constraints and bureaucratic delays. The importance of addressing these defects proactively, particularly in critical structural elements such as slabs, columns, and beams, was emphasized to ensure the durability and safety of school buildings. The proposed framework was validated through its application to a school building construction project in the Northwestern Province, which encompassed two phases—one completed and the other ongoing. This validation demonstrated the framework's effectiveness in improving construction quality and addressing prevalent issues. The outcomes of this methodological approach provided valuable insights into the construction quality of school buildings in Sri Lanka. By identifying and prioritizing defects throughout the entire construction process, the study established a basis for minimizing or eliminating these issues in future construction projects. The insights gained from this research contribute to the formulation of targeted construction guidelines for school buildings in Sri Lanka, aligning with the evolving needs of the Sri Lankan education system.
item: Conference-Abstract
Effect of preloading and endplate imperfections in bolted connections: Moment-rotation characteristics through explainable artificial intelligence
(Department of Civil Engineering, University of Moratuwa, 2024) Dharmawansha, DAST; Herath, HMST; Pasindu, HR; Damruwan, H; Weerasinghe, P; Fernando, L; Rajapakse, C
Stainless-steel is a popular engineering material due to its durability, high resistance to corrosion, aesthetic appeal, ease of construction and maintenance, recyclability, and ductility. It is often used in a wide range of structural engineering applications such as frames, buildings and bridges. Across these diverse applications, steel connections are a crucial component as they ensure the unified performance of the structure. This study investigated the effect of bolt preloading, endplate imperfections, and geometric parameters on the connection moment rotation response of extended endplate bolted connections. This study employed a validated numerical model against experimental results from the structural testing laboratory of the University of Moratuwa, further validated against experimental results available in the literature. The validated numerical model was then used to investigate the impact of varying levels of bolt preloading and imperfections on rotational stiffness. The results showed that rotational stiffness increases by 134% with ultimate preloading. Residual deformation from welding causes initial imperfections in bolted endplate connections, with V-shape, C-shape, and W-shape imperfections identified in the literature. This study examines the impact of C-shape and V-shape imperfections on rotational stiffness. The results indicate that V-shape imperfections have minimal influence if the level of imperfection is limited to the criterion of (endplate depth)/300, while C-shape imperfections significantly affect rotational stiffness, even within acceptable limits. A novel explainable machine learning approach was utilized to investigate the influence of geometric parameters on the moment-rotation response of connections. A comprehensive numerical modelling approach (validated using related work) was used to generate data for various input features, such as endplate thickness, bolt diameter, overall section width, overall depth, web thickness, flange thickness, vertical bolt spacing, and horizontal bolt spacing. An artificial neural network (ANN), extreme gradient boosting (XGB), random forest (RF), and k-nearest neighbours (KNN) were employed alongside Shapley additive explanations (SHAP) to interpret the trained models. Analysis shows that endplate thickness strongly governs the moment-rotation behaviour of the bolted endplate connections. Moreover, SHAP explanations align with the generally accepted behaviour of steel extended endplate bolted connections according to EN 1993-1-8.
item: Conference-Abstract
Mechanical behaviour of rice husk ash and cement–stabilized peat under different curing periods
(Department of Civil Engineering, University of Moratuwa, 2024) Narasinghe, NMNT; Sampath, KHSM; Pasindu, HR; Damruwan, H; Weerasinghe, P; Fernando, L; Rajapakse, C
The problematic nature of peat due to its high organic content, substantial compressibility, and low shear strength, frequently requires stabilization to make it appropriate for construction. This research focuses on enhancing peat soil properties for construction purposes, particularly focusing on areas in Sri Lanka where peatlands present significant challenges for infrastructure development. With involvement in sustainable and cost-effective solutions, the study investigates the efficacy of using Rice Husk Ash (RHA) and cement as stabilizers for natural peatlands. In fact, this approach offers a solution for traditional stabilizers while harnessing the beneficial properties of RHA – a waste product, to enhance the peat stabilization process. This method aims not only to improve the mechanical properties of peat but also to provide an alternative to traditional stabilizers like lime or cement, which are linked to higher carbon dioxide emissions. The suitable mix proportions of RHA and Portland composite cement (PCC) and their effects on peat's Unconfined Compressive Strength (UCS) were obtained from laboratory experiments, under different curing conditions and curing periods. The prepared samples were subjected to UCS tests to determine the stabilized peat's peak strength and stress-strain behavior. The strength and stiffness of the stabilized peat were calculated using observed test results and analyzed by comparing it with the properties of natural peat. The findings suggest that a specific mix proportion of RHA and PCC, under a defined curing period, significantly enhances the UCS, shear strength, and stiffness of peat. The optimal curing condition was identified as submerging in water with a 1.25 kN/m2 surcharge load and maintaining in-situ conditions, where stabilized samples were cured at low temperatures. It is evident from the study that different mix proportions resulted in varying strength gain variations across different curing periods, including 7 days, 28 days, 45 days, 60 days, and 80 days. In conclusion, mixing peat with 10% PCC + 10% RHA and curing for 60 days under submerged curing with a surcharge would yield optimum strength and stiffness. After evaluating the mechanical properties, Scanning Electron Microscope (SEM) images were taken to identify the behavior of the microstructure. The microstructure reveals a hollow, perforated cellular structure, along with a minor network of fibrous elements. Voids between peat soil particles have filled with C-H-S bonds. This observation suggests that while RHA may offer certain benefits as a secondary stabilizing material, excessive reliance on it may not be conducive to achieving the desired strength properties in stabilized peat soil. However, there is a possibility of partially replacing cement with RHA which would result in the strength and stiffness gain up to anticipated levels. By demonstrating the positive impact of these materials on peat stabilization, the research contributes to the field of geotechnical engineering, offering a viable solution for construction on peatlands.
item: Conference-Abstract
Assess the impact of internal curing in roller compacted concrete using roof tile waste as fine aggregates
(Department of Civil Engineering, University of Moratuwa, 2024) Dilsara, VGS; Jayantha, WRAN; Mampearachchi, WK; Pasindu, HR; Damruwan, H; Weerasinghe, P; Fernando, L; Rajapakse, C
The construction industry is increasingly prioritizing sustainable and eco-friendly practices, resulting in a growing interest in utilizing waste materials in concrete production. As environmental concerns continue to grow, innovative solutions are becoming essential to reduce waste and promote sustainability. One promising approach involves incorporating waste materials into concrete as internal curing agents (ICAs) to address the challenges associated with proper concrete curing. Proper curing is essential for enhancing the durability and mechanical properties of concrete, but conventional curing methods often have limitations, especially in concrete with a low water/cement ratio. This has led to a significant focus on exploring alternative methods, with internal curing gaining considerable attention. The concept of internal curing involves utilizing materials based on the ability to absorb and release water within the concrete matrix. This facilitates a more consistent and extended curing process. This research intends to address a gap in sustainable construction practices by assessing the feasibility of using roof tile waste as an internal curing aggregate (ICA) to replace fine aggregates in roller-compacted concrete (RCC). The utilization of roof tile waste not only encourages recycling and reduces landfill waste but also leverages its water absorption and desorption properties to improve the curing process. The research involved a comprehensive series of laboratory experiments to assess the potential usage of roof tile waste as an ICA. Furthermore, the study evaluates the impact of roof tile waste on the mechanical properties of RCC, specifically focusing on compressive strength, tensile strength, and flexural strength. To achieve this, RCC samples were cast with varying percentages of roof tile aggregates (RTA) replacing fine aggregates: 5%, 10%, and 15%. Each sample was subjected to testing to assess its performance compared to externally cured conventional RCC and uncured conventional RCC. The findings from the experiments revealed that the incorporating of roof tile waste as an ICA significantly affects the mechanical properties of RCC. The optimal performance for internal curing with RTA occurs at a 10% replacement level, balancing the benefits of internal moisture retention and the mechanical integrity of the concrete. The research emphasizes that utilizing 10% RTA replacement can lead to significantly improved early-age properties, demonstrating an 18% increase in 3-day compressive strength compared to traditionally cured RCC. This advancement is advantageous for pavement construction as it facilitates quicker access to traffic and shortens construction schedules. However, the study also identified certain constraints. Even though the early compressive strength displayed substantial enhancement, the tensile and flexural strengths of RCC samples with RTA were lower than those of conventionally cured RCC. This indicates that while roof tile waste is effective in enhancing early age compressive strength, further optimization is needed to improve its impact on tensile and flexural properties.
item: Conference-Abstract
Numerical simulation of progressive collapse of structures under blast loads
(Department of Civil Engineering, University of Moratuwa, 2024) Vandabona, NT; Fernando, PLN; Pasindu, HR; Damruwan, H; Weerasinghe, P; Fernando, L; Rajapakse, C
The growing need for blast-resistant designs in structural engineering is driven by the rising threat of terrorism, accidental explosions, and the significant risk of progressive collapse. This study presents a numerical procedure for analyzing the progressive collapse of Reinforced Concrete (RC) framed structures due to blast loads, addressing the gap in current methodologies. Traditional approaches such as the Alternate Load Path method, which are code-based and threat-independent, mainly focus on sudden column loss scenarios but do not fully capture the dynamic nature of blast-induced, threat-dependent collapses. Hence this study addresses the need for a computationally efficient and reliable method to predict and model progressive collapse under blast loading. This study employs a comprehensive numerical investigation using Finite Element Method where a seven-storeyed RC building is assessed for progressive collapse under blast loading. Progressive collapse analysis was executed using a commercially available Finite Element Analysis software, adhering to the Linear Static Procedure specified in the General Services Administration (GSA) guidelines, while blast load scenarios were examined through a nonlinear direct integration time history analysis. Different blast parameters, including charge weight and standoff distances, are varied to evaluate their impact on the structural integrity of the building. The study differentiates between threat-independent analysis, considering four column removal locations, and threat-dependent (blast-induced) scenarios with three distinct column removal positions. The scope of this study delves only into the perimeter blast scenarios neglecting the internal explosions. Demand Capacity Ratios (DCR) of columns were calculated to determine the susceptibility of the building to progressive collapse, with a DCR greater than 1 indicating failure. The numerical model was validated against the GSA baseline model. In threat-independent analysis, 30%, 60%, 22%, and 44% of the considered columns under corner, long side, short side, and interior column removal scenarios respectively exceeded the acceptable DCR criteria. In threat-dependent analysis, 100% of the considered columns under each blast induced column removal scenario exceeded the acceptable DCR criteria. This emphasizes the need for scenario-based planning in structural design to reduce collapse risks. The identification of critical columns, for threat-independent analysis as those directly above the removed column and on the topmost floor and for threat-dependent analysis as ground floor columns adjacent to the removed column, reveals potential weak points for progressive collapse initiation. The analysis of blast-induced progressive collapse reveals significantly higher DCR values than threat-independent assessments. Even the minimum percentage increases of DCRs when transitioning from threat-independent to threat-dependent analysis reaches high values up to 995%, 325%, and 981% for corner, long side, and short side column removal scenarios respectively. This specifies the importance of integrating blast resistance into the structural design of high-risk buildings. As a result, this study contributes to the understanding of structural dynamics under blast loads and offers a framework for the analysis of progressive collapse in RC buildings.
item: Conference-Abstract
Use of streamflow and satellite remote sensing soil moisture data for jointly calibrating the tank model
(Department of Civil Engineering, University of Moratuwa, 2024) Pabasara, GK; Gunawardhana, HGLN; Pasindu, HR; Damruwan, H; Weerasinghe, P; Fernando, L; Rajapakse, C
Hydrological modelling in arid river basins is particularly complex due to the pronounced seasonal variability in water levels fluctuating between aridity and inundation. Solely relying on a single parameter, such as streamflow data, to calibrate hydrological models in these basins can be insufficient to capture intricate interdependencies of hydrological processes. This study aimed to optimize the lumped hydrological Tank Model to accurately simulate the complex hydrological behaviour of the Maduru Oya River Basin in Sri Lanka. Further, the research investigated the use of satellite (remote sensing)-derived soil moisture data in the hydrological modelling framework, highlighting the capability of advanced technologies to enhance the reliability of hydrological predictions. The study commenced with the collection and preprocessing of climatic data, followed by the imputation of missing values using the Closest Station Patching Technique. Root zone soil moisture data derived from the Soil Moisture Active Passive Level 4 (SMAP L4) product were acquired and pre-processed using the Cumulative Distribution Function (CDF) Matching method. The primary focus of the study was the optimization of the Tank Model through a sequential joint calibration technique with the Kling-Gupta Efficiency (KGE) chosen as the optimization criterion. This process involved optimizing the model using both single-variable calibration with streamflow data and multi-variable calibration with streamflow and soil moisture data. Multi-variable optimization was conducted using a weighted approach that assigned different contributions to soil moisture α and streamflow -α in determining model performance. This approach was implemented across 11 distinct calibration scenarios, with the parameter α varying systematically from 0 to 1 in increments of 0.1. The results demonstrated satisfactory streamflow simulation performance under single-variable optimization, with KGEQ values of 0.872 and 0.848 for calibration and validation, respectively. These findings underscored the Tank model's ability to accurately represent the hydrological processes within the Maduru Oya - Padiyathalawa sub-watershed. The inclusion of root zone soil moisture data (RSRZSM) significantly improved model performance, as evidenced by KGEQ values exceeding 0.850 for all calibration scenarios except α = 1. Multi-variable optimization techniques further reinforced the potential for enhanced overall model performance. The most accurate and reliable streamflow simulations (KGEQ = 0.890) were achieved with a minimal 10% and 90% contributions from soil moisture and streamflow respectively (α = 0.1 calibration scenario). Furthermore, the study emphasized the critical role of remote sensing data, specifically SMAP L4 retrievals, in characterizing the soil moisture intricacies of the study area, particularly in regions with limited in-situ measurements. The study further recommends continued validation to ensure robust model predictions. Due to the short calibration and validation periods used to minimize climatic data discrepancies, long-term validation was deemed essential for assessing model performance. In addition, the study recommended investigating alternative multi-objective optimization approaches, such as Genetic Algorithms, and incorporating more satellite data for other hydrological processes.
item: Conference-Abstract
Urban flood assessment targeting flood risk mitigation: A case study focusing on changing environments
(Department of Civil Engineering, University of Moratuwa, 2024) Jayawardane, JMPM; Rajapakse, RLHL; Siriwardana, CSA; Pasindu, HR; Damruwan, H; Weerasinghe, P; Fernando, L; Rajapakse, C
Among natural disasters, flooding has become a frequently significant catastrophic event causing considerable damage in urban environments in a global context. The anthropogenic changes in urban areas, along with climate change, have intensified urban floods (UFs). Metro Colombo area, Sri Lanka, is highly susceptible to UFs due to its geographical location, congested urban expansions, drainage deficiencies, lowered retention abilities, etc. Within the study, a qualitative, in-depth flood risk assessment is conducted based on a hazard assessment, vulnerability assessment, and exposure assessment for administrative units of Divisional Secretariat Divisions (DSDs). Under each assessment, six or seven influential elements were selected and assessed based on the remote sensing satellite imagery data and census data as published by the Department of Census and Statistics, Sri Lanka (DCS). Extracted data was used to develop criteria maps for influential elements, utilizing ArcGIS Pro, spatial data processing software. Utilizing the generated maps, hazard indices, vulnerability indices, and exposure indices were calculated, and by merging them, risk indices for DSDs were calculated. In a subsequent study, the influential nature of changing land use patterns due to the effects of urbanization and changing climatic conditions was analysed for aggravating UFs. Reduced infiltration, disturbance to man-made drainage or natural runoff pathways, refilling of retention and detention areas, etc., have directly influenced the intensification of effects in urban flood events. Within this section of the study, land use changes were assessed from 2003 to 2023, using remote sensing satellite imagery, and a relationship between change in runoff coefficient and flood occurrences was generated. Subsequently, a projected climate assessment was undertaken for two (2) shared socio-economic pathways (SSP 1-2.6 and SSP 5-8.5) to execute a quantitative comparison of the exceedance probabilities of several threshold precipitation limits A pilot study was undertaken for “Madiwela South Diversion” using HE -RAS software to identify the inundation areas and depths for “with and without” measure scenarios The method successfully presented a satisfactory hazard map with four main flood hazard levels, and 11.36% of the total research area was reported as “high hazard” from the generated risk map, Colombo DSD indicated the highest risk index of 0.54, following Kesbewa, Kaduwela, and Thimbirigasyaya, with risk indices of 0.34, 0.29, and 0.28, respectively. These calculated risk index values can be utilized to reduce future flood risk by prioritizing high-risk-rated administrative divisions in executing flood mitigation measures. Through the assessment for evaluating the effect of land-use change, results revealed that standardized runoff coefficient and flood frequency are highly correlated, having an 82% correlation coefficient at a 0.90 significant level, indicating that the change in the runoff coefficient is highly related to flood occurrence. Further, Blue-Green Infrastructure (BGI) was proposed in the study as a sustainable attempt at flood mitigation.
item: Conference-Abstract
Effect of crease curvature on bending stiffness in curved crease origami
(Department of Civil Engineering, University of Moratuwa, 2024) Weerasekara, WMHGLCB; Mallikarachchi, HMYC; Pasindu, HR; Damruwan, H; Weerasinghe, P; Fernando, L; Rajapakse, C
Deployable systems play a vital role in design optimisation of spacecrafts. Limited payload capacity in launch vehicles often conflicts with the demand for large-area systems required for better performance in the operational phase. The art of origami enables the storage of a large surface structure in a compact volume by utilising plastically deformed fold lines known as creases. Origami can be categorised into two types as straight crease origami and curved crease origami based on the geometry of the crease. Straight crease origami demonstrates rigid foldability while curved crease origami facilitates smooth and efficient folding by incorporating panel bending. The use of curved creases in deployable membranes reduces the required number of creases compared to straight creases ultimately leading to less production time and better quality deployed surface. The bending stiffness of the crease and the external force required to fold the membrane are key aspects that influence the packaging efficiency. The main objective of this research is to assess the effect of crease curvature on the bending stiffness of curved creases. The study encompassed quasi-static folding and unfolding experiments of curved-crease specimens with different crease radii made of 80 gsm printer paper to understand crease behaviour. Furthermore, numerical models were developed to simulate the crease behaviour of curved creases and validated against experiments in order to develop prediction tools for future designs. The resistive force resulting in bending a curved crease specimen was measured experimentally for rectangular specimens with overall dimensions of 60 mm × 100 mm while varying crease radii from 35 mm to 75 mm. Additionally, the force-displacement response was recorded for flat sheets with dimensions of 50 mm × 60 mm and 100 mm × 60 mm to compare the bending stiffness of curved creases to that of a flat sheet having similar overall dimensions. The results demonstrate that the initial bending stiffness of curved-crease specimens with a low crease radius is lower but becomes higher at the maximum folded state compared to specimens with a high crease radius. Additionally, it was observed that the contribution of the unrestrained half of the specimen significantly increases the bending stiffness of a curved crease specimen during the folding motion for lower crease radius, whereas the contribution remains almost constant for higher crease radius. Numerical models of curved creases, developed in the commercial software Abaqus using a segmented curved-crease modelling approach incorporating straight crease characteristics, accurately estimate experimental reaction forces, indicating that the characteristics of straight creases can be used in modelling curved creases.
item: Conference-Abstract
Point of fixity of laterally loaded piles on layered soils
(Department of Civil Engineering, University of Moratuwa, 2024) Subhasinghe, RMKR; De Silva, LIN; Pasindu, HR; Damruwan, H; Weerasinghe, P; Fernando, L; Rajapakse, C
Piles are critical structural elements that often face lateral loads from various sources, including moving vehicles on bridges, wind, waves, slope movement, and seismic activities. These lateral loads can cause substantial bending moments and lateral deflections in piles, which can compromise the structural integrity of the foundation. The point of fixity is a widely used concept in the design of laterally loaded piles, providing the necessary rigidity to withstand these forces and minimize deflections. While several analytical methods have been developed to determine the point of fixity in single-layered soils, their effectiveness and applicability in multilayered soils remain less certain. This study investigates the validity of two commonly used analytical methods, Broms method and Kocsis method for determining the point of fixity in multilayered soils. The depth of fixity was estimated using average soil properties and compared against results obtained from more advanced approaches, including finite element modelling and p-y curve analysis, which consider distinct properties of individual soil layers. A comprehensive parametric study was also conducted to examine the influence of various factors, such as soil type, soil layer thickness, pile diameter, magnitude of lateral and axial loads, and pile embedment length, on the point of fixity. The comparison revealed significant differences between the analytical methods, particularly in the context of predominantly cohesive soils. The Broms and Kocsis methods estimated the depth of fixity to be between 1.0 and 2.0 times the pile diameter below the ground surface, while the p-y curve and FEA methods yielded slightly more conservative values, ranging from 1.0 to 1.5 times the pile diameter. In predominantly cohesionless soils, the estimated fixity depths were more consistent across all methods, varying between 1.0 and 1.5 times the pile diameter below the ground surface. These findings highlight potential limitations in the applicability of traditional analytical methods to multilayered soils and underscore the importance of refining these approaches for more accurate and reliable design. The parametric study further revealed that for long (flexible) piles, the depth of fixity is generally not significantly affected by factors such as surrounding soil type, layer thickness, axial load, and pile length. However, pile diameter and lateral load were found to have a substantial impact on the depth of fixity, with the effects varying depending on the analytical method employed and the soil's cohesive or cohesionless nature. Interestingly, the study also found that, even in single-layered soils, the Broms and Kocsis methods could yield results that significantly deviate from those obtained via p-y curve analysis. This discrepancy underscores the necessity for further detailed studies, including experimental work with instrumented pile tests, to enhance the accuracy and reliability of these methods. Overall, the study suggests that the point of fixity in predominantly cohesive soils ranges from 0.5 to 2.5 times the pile diameter below the ground surface, whereas in predominantly cohesionless soils, it ranges from 0.5 to 2.0 times the pile diameter.
item: Conference-Abstract
Evaluating the effectiveness of treatment solutions on blue stain fungi growth in pine wood plantations in Sri Lanka
(Department of Civil Engineering, University of Moratuwa, 2024) Rathuge, LR; Hewage, IS; Mendis, MS; Halwatura, RU; Pasindu, HR; Damruwan, H; Weerasinghe, P; Fernando, L; Rajapakse, C
The presence of blue stain fungi in pine wood plantations causes a significant challenge to the pine wood industry. Because of the visible discoloration due to the presence of fungi, it significantly reduces the market value of the wood. This study was conducted to explore the occurrence of blue stain fungi growth in pine wood plantations in Sri Lanka, with a focus on assessing the effectiveness of various wood treatment solutions. The research was conducted over six months, at a pinewood plantation in Bandarawela. The primary objective was to compare the effectiveness of different treatment solutions on the occurrence of blue stain fungi in treated versus non-treated wood samples. 27 wood samples prepared from freshly cut pine trees were used in this study. The samples were treated using four different solutions: two inorganic preservatives, Anti-blue and Anti-boron which are widely available in the market, and two innovative organic preservatives developed in Sri Lanka: Final Solution Without Mud (FSWOM) and Final Solution With Mud (FSWM). Samples were immersed in the solutions for 48 hours for the treatment, using the dipping method. To assess the impact of treatment timing, two sets of samples were prepared: one set was treated within 7 days of cutting, and another set within 7 to 14 days. To provide a baseline for comparison, a control set of non-treated samples was maintained. The results demonstrated that all treated samples showed significantly reduced blue stain fungi growth compared to the non-treated samples. Both inorganic preservatives, Anti-blue and Anti-boron, were highly effective in mitigating the blue stain fungi growth. Remarkably, the organic preservatives were also successful. FSWM was the most effective organic solution matching the performance of the commercially available inorganic preservatives. FSWOM, while slightly less effective than FSWM, still provided good protection against blue stain fungi, indicating the potential of organic solutions in wood preservation. It revealed that adding paddy field mud significantly enhanced the antifungal properties of these organic preservatives, approaching the level of effectiveness of the inorganic preservatives. Additionally, the study found that the timing of the treatment whether applied within 7 days or 7 to 14 days after cutting did not significantly affect the effectiveness of the treatment solutions. This implies that there is flexibility in the timing of treatment without compromising its effectiveness. The study concludes that both organic and inorganic preservatives are effective in mitigating blue stain fungi growth in pine wood. More specifically, the organic preservative FSWM provides an effective and environmentally friendly alternative to inorganic preservatives, thereby enhancing wood preservation techniques.
item: Conference-Abstract
Study on the effect of seawater on making and curing of unreinforced concrete applications
(Department of Civil Engineering, University of Moratuwa, 2024) Kulathunga, RMMJ; Nanayakkara, D; Nanayakkara, SMA; Pasindu, HR; Damruwan, H; Weerasinghe, P; Fernando, L; Rajapakse, C
Concrete, an essential component of worldwide infrastructure, depends significantly on fresh water for its manufacturing, contributing to freshwater scarcity in many regions. As construction demands increase, transitioning to alternative water sources is important to minimize environmental impact and ensure long-term sustainability. Traditional reinforced concrete structures can experience corrosion when they come into contact with seawater, as the chloride content in seawater can lead to the deterioration of the structures. As a result, seawater is not deemed suitable for these specific applications due to the potential damage it can cause. However, it is possible to use seawater in non-reinforced concrete applications, where there is no risk of corrosion. Existing studies present conflicting results regarding the effects of seawater on concrete, with some indicating positive impacts, while others report minimal or no impact on the mechanical properties of concrete. The main objective of the study is to investigate the effect of incorporating seawater in the production and curing processes of unreinforced concrete. Specifically, the study aims to compare and analyse the properties of concrete mixed with seawater and subsequently cured with seawater, in contrast to conventional freshwater concrete. Fresh and hardened concrete properties were evaluated for the following scenarios: concrete mixed and cured with fresh water, concrete mixed and cured with seawater, and concrete mixed with freshwater but cured with seawater. The properties of fresh concrete, specifically slump and slump loss, were evaluated, while the hardened concrete properties, including compressive strength, splitting tensile strength, and drying shrinkage, were tested at four different curing ages (3, 7, 28, and 56 days). This was done to understand the influence of seawater on the hydration process and to assess the variation in these properties over time. The results show that the mixing of seawater has a negligible effect on the slump but leads to an increased slump loss, indicating that the workability loss is higher in seawater-mixed concrete compared to freshwater-mixed concrete. The use of seawater in curing also shows a minimal impact on the properties of hardened concrete. In addition, there is a significant difference in the mechanical performance of concrete when comparing seawater and freshwater concrete. Seawater-mixed concrete shows higher compressive strength in early ages, however, in the later stages the variation becomes less significant between the two concrete types. Early age splitting tensile strength is slightly higher in seawater-mixed concrete however at later ages it becomes considerably low compared to freshwater-mixed concrete. Seawater-mixed concrete exhibits higher drying shrinkage over time compared to freshwater-mixed concrete. Based on the findings of this research, seawater could be recommended for curing unreinforced concrete. For further research studies, it is recommended to investigate the long-term effect of the seawater on making and curing of unreinforced concrete, focus on the effect of seawater on other properties of concrete such as setting time, permeability, electrical resistivity, etc.
item: Conference-Abstract
Assessment of disaster resilience in hospitals: a case study based framework development for Sri Lankan context
(Department of Civil Engineering, University of Moratuwa, 2024) Marasinghe, MMGC; Damruwan, HGH; Siriwardana, CSA; Dhanapala, S; Wijesekara, N; Wedamulla, A; Pasindu, HR; Damruwan, H; Weerasinghe, P; Fernando, L; Rajapakse, C
Hospitals are essential infrastructures that must maintain continuous operation during and after disasters to ensure the safety of patients and staff while providing medical services, even under surge conditions. Given the critical nature of these facilities, assessing their disaster preparedness is of utmost importance. This study addresses the limitations of the World Health Organization's Hospital Safety Index (HSI) when applied to Sri Lankan hospitals, leading to the development of the Structural Safety of Hospitals Assessment for Sri Lanka (SSH-SL). The study presents a comprehensive framework for evaluating hospital safety, divided into three primary modules: structural safety (utilizing SSH-SL), functional safety, and emergency and disaster management. Enhancements were made to the latter two modules to better align with the specific needs of the Sri Lankan context. The framework introduces a set of equations to calculate the safety index for each module, which then assigns safety levels and provides recommendations for improvement. This framework was applied to assess 15 government hospitals, revealing significant concerns across all three modules, underscoring the need for targeted interventions to enhance hospital resilience in Sri Lanka. The results from the assessment indicate that the structural safety levels of the 15 hospitals are generally at or above average level, suggesting that these facilities can operate during disaster conditions, though steps must be taken to ensure safety of both patients and staff. In terms of functional aspects, the majority of hospitals demonstrated a safety level of average or above, with two hospitals exhibiting below-average safety levels. Regarding Emergency and Disaster Management, 11 out of the 15 hospitals displayed high safety levels, whereas two hospitals had low safety levels. Immediate actions are necessary for hospitals with below-average safety levels, with a focus on implementing both short-term and long-term remedies. Additionally, limitations of the framework were identified during the hospital assessment process. The architectural safety submodule, under functional safety, was recognized as a critical submodule requiring modifications. Several assessment criteria specific to the Sri Lankan context were identified and subsequently incorporated into the existing submodule. Following these adjustments, a Delphi Study was conducted on the enhanced submodule, utilizing a panel of experts to gauge their consensus. Based on the survey results from the Delphi Study, weights were assigned to each assessment criterion within the submodule, leading to the derivation of a comprehensive safety score for the architectural safety of hospital buildings.
item: Conference-Abstract
Enhancing streamflow prediction in Sri Lankan River Basins using AI models: A comparative study of wet and dry zones
(Department of Civil Engineering, University of Moratuwa, 2024) Karunarathna, SMSD; Rajapakse, RLHL; Pasindu, HR; Damruwan, H; Weerasinghe, P; Fernando, L; Rajapakse, C
Artificial Intelligence (AI) techniques have gained significant attention in recent years for their application in various engineering domains, including hydrology. Groundwater modelling, streamflow prediction, precipitation forecasting, temperature forecasting, and time series generation for rainfall are some of the hydrological applications that have benefited from AI techniques. In Sri Lanka, water resource management is challenging due to the country's geographical characteristics, seasonal rainfall patterns, and growing water demands. Traditional methods used in water resource management have limitations and rely on complex parameters, which often result in less accurate predictions of rainfall-runoff, flood events, and drought conditions, impeding effective water resource management. To enhance water resource management practices in Sri Lankan River basins, AI methodologies were integrated into hydrological modelling. Two river basins were chosen as representatives of the wet and dry zones in Sri Lanka: the Ellagawa sub-basin from the Kalu River basin for the wet zone, and the Thanamalwila sub-basin from Kirindi Oya basin for the dry zone, covering the period from October 1, 2000, to September 30, 2011. The pivotal recurrent neural network (RNN) architectures such as Long Short-Term Memory (LSTM) and Gated Recurrent Unit (GRU) are highly effective for modelling time series data, especially when it comes to streamflow prediction. These models are excellent at capturing temporal dependencies, which is significant for streamflow as it depends on previous data and weather. In this study, both the physically-based semi-distributed HEC-HMS hydrological model and AI models such as RNN-LSTM and RNN-GRU were applied to evaluate their predictive capabilities in streamflow forecasting. The performance of these models was assessed using objective criteria including Nash-Sutcliffe Efficiency (NSE), Mean Ratio of Absolute Error (MRAE), and the coefficient of determination (R²). The observed and predicted streamflow hydrographs and flow duration curves (FDC) were generated to evaluate model goodness of fit and time series graphical comparability. The study findings indicate that the LSTM model is superior to both the GRU and HEC-HMS models in predicting streamflow, with an MRAE of 0.42 and NASH of 0.82 for the LSTM model in wet zone river basins. The LSTM algorithm used the best values of R2, which were 0.88 and 0.87 for the testing and training phases, respectively. The proposed model may be used to develop other basins in the wet zone. However, for the Thanamalwila sub-basin, the results of both AI and physical-based models were poor, likely due to inaccurate input features and inherent mismatches between rainfall and streamflow. Better input features are essentially required to improve the model training and simulation process. Therefore, the integration of AI techniques presents an opportunity for Sri Lanka to overcome existing limitations in hydrological modelling and enhance its resilience to water-related challenges. By embracing innovative approaches and leveraging available data, Sri Lanka can strengthen its capacity for water resource management and adaptation to climate change impacts, ultimately fostering sustainable development and resilience in the face of evolving environmental conditions.
item: Conference-Abstract
Design-informed optimization of 2D skeletal structures using convolutional neural networks
(Department of Civil Engineering, University of Moratuwa, 2024) Jayaweera, JANN; Herath, HMST; Pasindu, HR; Damruwan, H; Weerasinghe, P; Fernando, L; Rajapakse, C
Structural optimization aims to find the most efficient material distribution within a design domain by minimizing material usage, self-weight, and strain energy, while maximizing strength. Optimization approaches often use compliance as the objective function and volume as a constraint, which can result in designs that may not fully meet the practical requirements of civil and structural engineering due to potential inadequacies in structural integrity. To address this issue, design-informed optimization integrates structural optimization with design codes such as EN 1993-1-1, ensuring that optimized designs comply with structural integrity requirements and real-world applicability. Existing design-informed optimization algorithms typically rely on iterative schemes, which are computationally intensive and require specialized expertise. To overcome these challenges, this study introduces a novel computer vision-based framework that predicts design-informed optimized frames and accurately identifies member sizes using image processing techniques coupled with probabilistic section classifiers. This framework utilizes input parameters such as span, height, and load to predict the topology, size, and layout of optimized frames that satisfy structural adequacy criteria. It is particularly beneficial for assembly-based manufacturing, where precise member section prediction is crucial for construction efficiency and material optimization. The framework consists of three stages. In Stage 1, the CNN64 model generates a low-resolution layout of the optimized frame using input parameters such as span, height of the design domain, and load. In Stage 2, the CNN512 model refines this layout to produce a high-resolution image of the optimized frame, where section sizes are assigned. These models are trained on varying parameters including fixity, design domain, and load conditions. Stage 3 involves a member section identification algorithm that classifies the optimal structural section sizes through image processing techniques. The efficacy of the framework was validated using simply supported and cantilever beam datasets, achieving pixel accuracies of 94.6% and 91.8%, respectively. Post-calibration, the section identification algorithm, which accounts for unavoidable errors such as generator residuals and section identification errors, achieved near 100% accuracy, demonstrating the robustness of the probabilistic section classifier. Compared to alternative architectures, the CNN64+CNN512 framework consistently outperformed others in metrics such as pixel accuracy, true positive rate, and binary cross-entropy in both datasets. It also demonstrated a significant reduction in computational loss, further confirming its computational efficiency. Overall, the analysis reveals that the CNN64+CNN512 model not only provides superior performance in prediction accuracy but also strikes an effective balance between computational efficiency and model complexity.
item: Conference-Abstract
Effect of tie beams on the behavior of isolated foundation systems
(Department of Civil Engineering, University of Moratuwa, 2024) Gunathilaka, LTD; De Silva, LIN; Pasindu, HR; Damruwan, H; Weerasinghe, P; Fernando, L; Rajapakse, C
The stability of isolated foundation systems is crucial to the structural integrity and safety of buildings, especially in regions with varying load conditions. Tie beams, widely used to connect isolated footings, play an integral role in this process. However, their impact on bearing capacity and settlement characteristics is often overlooked in standard analyses. This research primarily aimed to explore the influence of tie beams on the settlement characteristics and overall performance of isolated foundation systems. A comprehensive methodology combining both model experiments and finite element analysis (FEA) was employed to achieve these objectives. Initially, two model experiments were conducted using small-scale prototype structures: one with a single isolated footing and another with two footings connected by a tie beam. These experiments aimed to validate the FEA results by comparing the experimental settlement data with the simulated outcomes. Two distinct models of the foundation system were developed, each based on a typical three-story building with 16 isolated footings. This setup was designed to simulate a realistic structural scenario and evaluate the impact of tie beams under varying loading conditions. The footings were loaded with varied loadings in the range of 350 kN to 1300 kN to simulate real-world scenarios. One model included tie beams connecting the footings, while the other omitted them, allowing for a comparative analysis of their effects on settlement and structural integrity. The findings reveal that incorporating tie beams significantly reduces the maximum individual settlement, with a decrease of up to 22 mm (43%). Furthermore, the inclusion of tie beams narrowed the variation in settlement across individual footings, resulting in a more uniform distribution of settlements. Differential settlements were notably reduced, with all values staying under 2 mm, reflecting a 92% reduction compared to the model without tie beams. In conclusion, the inclusion of tie beams significantly reduces both settlements and differential settlements, contributing to a more uniform distribution of loads across isolated foundation systems. While positioning tie beams at the footing level may further reduce settlements, it also increases the forces acting on the tie beams, necessitating higher reinforcement and potentially leading to increased construction costs. The research recommends maintaining tie beams at ground level in general construction practices, except in scenarios where minimizing settlements is critically important. This study underscores the significance of tie beams in enhancing the performance and stability of isolated foundation systems, highlighting their essential role in mitigating settlement-related issues.
item: Conference-Abstract
Tsunami hazards: Assessment of exposure of Sri Lanka – Case study in Potuvil, Kalmunai and Nilaveli
(Department of Civil Engineering, University of Moratuwa, 2024) Liyanage, LDTD; Rathnasooriya, AHR; Pasindu, HR; Damruwan, H; Weerasinghe, P; Fernando, L; Rajapakse, C
Tsunamis, caused by impulsive disturbances such as undersea earthquakes, volcanic eruptions, and landslides, pose significant risks to coastal regions worldwide. This research focuses on assessing the tsunami exposure levels of Sri Lanka, specifically from potential future events generated in the Sunda Trench, using numerical modelling techniques. The study highlights the importance of understanding the varying degrees of risk along the coastline to enhance disaster preparedness and mitigate impacts. The Indian Ocean Tsunami of December 26, 2004, demonstrated the devastating effects of such events, particularly in Sri Lanka, where extensive loss of life and property occurred. Subsequent tsunami alerts underscored the need for accurate risk assessments, as damage levels varied significantly across different coastal areas. Sri Lanka's geographical location, in proximity to earthquake-prone zones like the Sunda Trench and the Makran Fault, exposes it to far-field tsunamis, providing a crucial time window for early warnings and evacuations. This research employs the Community Model Interface for Tsunami (ComMIT) to simulate various tsunami scenarios and analyse nearshore wave characteristics. The study focuses on Potuvil, Kalmunai, and Nilaveli, areas significantly impacted by the 2004 tsunami and characterized by high population density and growing tourism, increasing their vulnerability to coastal hazards. ComMIT, based on the Method of Splitting Tsunamis (MOST), is used for the numerical simulations, incorporating predefined earthquake sources and detailed bathymetric data. The simulations cover potential tsunami events from earthquakes of magnitudes 7.5 to 9.2 in four segments of the Sunda Trench. The results provide insights into the maximum wave amplitudes and arrival times at selected coastal locations. The findings reveal that the coastal areas of Potuvil, Kalmunai, and Nilaveli are highly exposed to tsunamis generated in the Sunda Trench, especially from high-magnitude earthquakes. Nilaveli and Potuvil show severe exposure to events with magnitudes 9.0 and 9.2, while Kalmunai faces substantial exposure to magnitude 9.2 earthquakes. These results are critical for enhancing disaster preparedness and risk mitigation in Sri Lanka's coastal regions. By identifying areas with high exposure, authorities can prioritize the development and implementation of early warning systems, evacuation plans, and infrastructure improvements. This research contributes to the broader goal of increasing resilience to natural disasters through informed decision-making at both local and national levels. Future research should continue to refine tsunami hazard assessments with updated data and advanced modelling techniques to ensure accurate predictions. Additionally, efforts to enhance public awareness and community preparedness are essential to foster a culture of resilience and proactive response to tsunami threats. Leveraging scientific research and collaborative efforts, Sri Lanka can effectively mitigate tsunami impacts, safeguarding lives, and livelihoods in its coastal communities.
item: Conference-Abstract
Impact of particle morphology on the shear behavior of quarry dust / sea sand - concrete interface in geotechnical structures
(Department of Civil Engineering, University of Moratuwa, 2024) Deshan, KAMM; Sampath, KHSM; Pasindu, HR; Damruwan, H; Weerasinghe, P; Fernando, L; Rajapakse, C
Soil-structure interaction is a fundamental consideration in geotechnical and structural engineering, influencing various applications such as pile systems, retaining walls, and other foundational structures. In recent years, the use of alternative materials like quarry dust and sea sand as complete replacements for traditional materials in ground improvement projects has gained attention due to their potential to enhance soil properties and overall geotechnical performance. This study focuses on the shear strength of the soil-concrete interface, particularly when utilizing quarry dust, river sand, and sea sand. The primary objective is to evaluate the influence of particle morphology on the shear behavior of these materials through a series of direct shear tests. Quarry dust, river sand, and sea sand samples were collected from different regions in Sri Lanka and subjected to thorough testing, including sieve analysis and direct shear tests, to investigate their gradation and interface shear behavior. The samples were tested in fully dry conditions, with particle sizes ranging from 0.075 mm to 2.36 mm. Additionally, particle morphology parameters such as angularity, roughness, roundness, and sphericity were quantified using image analysis techniques. These parameters were then correlated with the shear strength characteristics of the soil-concrete interface. Experimental results indicate that angular-shaped quarry dust particles exhibit an enhanced friction angle and interface friction angle by 10.8% and 12.4%, respectively, with an increase in angularity from 1.091 to 1.122, compared to spherical or rounded particles. Additionally, with an increase in regularity from 0.76 to 0.81, the interface friction angle decreased from 27.40 to 24.80, and the friction angle decreased from 32.40 to 28.90, marking percentage decreases of 9.7% and 11.0%, respectively. When comparing the coefficient of uniformity (Cu) values of the quarry dust, river sand, and sea sand samples, it was identified that higher Cu values correspond to higher friction angles and interface friction angles. The friction angle has increased by 4.7% and 15.6%, respectively, at the soil interface and the soil-concrete interface when the Cu value rises. Additionally, an increase in particle sizes increases the shear strength of samples. For instance, for a normal stress of 150 kPa, when the particle size increases from 0.075 mm to 2.36 mm, the shear strength increases by 21.2%. The study concludes that quarry dust, with its angular and irregular particles, can enhance the shear strength of soil-concrete interfaces, making it a suitable material for geotechnical applications. However, the developed correlations are valid only within the analyzed particle size range, and further studies are recommended to extend the applicable range and include the effects of moisture content on interface shear strength.
item: Conference-Abstract
Development of bond stress-slip models for CFRP / concrete bond exposed to mild acidic exposure
(Department of Civil Engineering, University of Moratuwa, 2024) Ravidu, AKS; Chandrathilaka, ERK; Gamage, JCPH; Pasindu, HR; Damruwan, H; Weerasinghe, P; Fernando, L; Rajapakse, C
Carbon Fiber Reinforced Polymer (CFRP) is widely used in various industries due to its excellent mechanical properties, including a high tensile strength-to-weight ratio and resistance to corrosion. However, the bond performance of CFRP with concrete can be adversely affected by exposure to mild acidic environments, which can originate from sources such as acidic rains, soil, sewage, and industrial activities. This study focuses on developing an understanding of the bond stress-slip behaviour of CFRP/concrete joints exposed to acidic conditions, specifically examining the impact of different bond curing temperatures and exposure periods in a mildly acidic environment. The experimental results, obtained from a previous study, involved CFRP/concrete single-lap shear specimens exposed to a sulphuric acid solution with a pH value of 2 for 15, 30, and 90 days. Those specimens were cured at ambient temperature (28 °C), 65 °C, and 75 °C to investigate the effects of curing conditions on bond performance. The experimental results from that study provided data on load-displacement behaviour and failure modes under those varying conditions. Complementing the experimental work, a finite element model (FEM) was developed using a commercially available finite element software to simulate the bond behaviour of CFRP/concrete joints. A modified version of Simplified concrete damage plasticity model was used as the material model for concrete, while a linear elastic model was employed for the CFRP, and the adhesive was modelled using a damage evolution model to account for potential degradation. The numerical model was validated against the experimental data, showing a strong correlation in predicting the load-displacement behaviour of the joints under different curing and exposure conditions. The results of the study indicated that curing temperature significantly influenced the bond strength of CFRP/concrete joints. Specimens cured at 65 °C exhibited the highest failure loads, suggesting that elevated temperature curing enhanced the bonding mechanism. However, curing at temperatures beyond the glass transition temperature (Tg) of the epoxy resin resulted in a reduction of bond strength. Furthermore, prolonged exposure to acidic environments degraded the bond strength, with noticeable reductions observed after 90 days of exposure. This degradation is due to chemical reactions with the acid that weaken the bond interface. Parametric studies were also conducted to assess the effects of adhesive layer thickness and different types of CFRP on bond performance. An adhesive thickness of approximately 1 mm was found to be optimal for maximising bond strength. Additionally, the use of CFRP with a higher modulus showed marginal improvements in joint strength but did not significantly alter the overall failure behaviour when exposed to a mildly acid environment
item: Conference-Abstract
Assessing future low-flow variations in a dry zone river basin under changing climate conditions
(Department of Civil Engineering, University of Moratuwa, 2024) Tharuka, WMS; Gunawardhana, HGLN; Pasindu, HR; Damruwan, H; Weerasinghe, P; Fernando, L; Rajapakse, C
Climate change significantly alters the low-flow regimes of river basins worldwide and presents significant challenges to water-scarce regions, especially in dry regions. This current study investigates the impact of climate change on projected low-flow variations in the Maduru Oya River Basin in Sri Lanka, focusing on the reach to the Padiyathalawa stream-gauge station. The study utilizes a lumped hydrological modeling framework, which used the HEC-HMS rainfall-runoff model to simulate streamflow behavior considering anticipated climate scenarios. Projections for future precipitation were obtained from the CNRM-CM6-1 Global Climate Model (GCM), which is part of the Coupled Model Intercomparison Project Phase 6 (CMIP6), and subsequently downscaled through the Long Ashton Research Station Weather Generator (LARS-WG) according to two Shared Socioeconomic Pathways (SSPs): SSP2-4.5 and SSP5-8.5. The precipitation data, downscaled to the local scale, were integrated into the HEC-HMS model to forecast future river discharge and investigate possible changes in low-flow characteristics. The 7Q10 low-flow index, which is defined as the minimum average flow in a continuous seven-day period with a recurrence interval of ten years was used for estimating and comparing low-flow characteristics. The model parameters were calibrated and validated using historical data from 1997 to 2019. Three objective functions namely: Nash-Sutcliffe Efficiency (NSE), Mean Relative Absolute Error (MRAE), and Percent Error in Peak Flow (PEPF) were used for optimizing model parameters. Future precipitation was projected for short-term (2021-2040), medium-term (2041-2060), and long-term (2061-2080) durations. The projected precipitation data was subsequently input into the developed HEC-HMS model to obtain future streamflow projections for the specified periods. The results of the climate change scenario analysis showed that precipitation may vary due to climate change within the range of -16 % to -5 % for the 2021-2040 period, - 4 % to 1 % for the 2041-2060 period, and 1 % to 21 % for the 2061-2080 period. The results indicated a likely increase in low-flow values across both SSP scenarios. The flow-duration analysis showed that the Q90 flow, representing the flow level that exceeds 90% of the time, is expected to increase, reflecting an upward change in streamflow for low-flow conditions. These findings are important for water resource managers working in the area to plan for and adapt to the impacts of altered low-flow regimes that can impact water supply, agriculture, and overall ecosystem health. Further studies should consider incorporating the use of hydrological models coupled with diverse climate scenarios to better capture the uncertainties related to climate predictions and land-use changes. These would provide a better understanding of the impacts of climate change on river basin hydrology in dry regions like the Maduru Oya River Basin.
item: Conference-Abstract
Web crippling behaviour of curved cold-formed steel unlipped channel beams
(Department of Civil Engineering, University of Moratuwa, 2024) Karunaratne, RDPYK; Herath, HMST; Pasindu, HR; Damruwan, H; Weerasinghe, P; Fernando, L; Rajapakse, C
Cold-formed steel (CFS) sections are increasingly utilized in various building applications such as purlins, decks, wall studs, and floor joists, due to their inherent characteristics over hot roll sections. With the increasing popularity of curved structures in architectural and structural designs, understanding the structural performance of curved CFS elements is important. CFS channel sections are prone to localized bearing failures known as web crippling under concentrated forces due to their higher web slenderness. Although numerous studies have been undertaken to investigate web crippling behaviour of straight CFS channel beams, the response of curved CFS beams to web crippling has not been explored yet. Therefore, this study investigates the web crippling behaviour of curved CFS unlipped channel beams. Through a series of experimental tests conducted on curved CFS unlipped channel beams with different curvatures, including both flanges inward and outward curved, subjected to interior-two-flange (ITF) loading conditions, the study evaluated the resistance of these curved beams to web crippling. The experimental results indicate that the initial curvature has a significant impact on the web crippling capacity. Notably, the flange inward curvature enhances the web crippling capacity, whereas the flange outward curvature diminishes it compared to straight, unlipped channel sections. Furthermore, the design guidelines commonly used for predicting web crippling capacity were evaluated for consistency and reliability compared to the experimental results. It was found that outlining the inconsistencies of using the guidelines developed for straight beams in evaluating the web crippling capacities of curved CFS unlipped channel sections. In order to further investigate the web crippling response of curved channel beams, finite element models were developed. Finite element models developed for straight beams were validated against experimental results done in this study and available in the literature, demonstrating good agreement in terms of failure modes, capacity, and load-deflection curves. A parametric study was carried out to evaluate the key parameters influencing the web crippling behaviour of curved beams. In summary, this research carried out experimental and associated numerical studies on curved CFS channel sections subjected to web crippling under the ITF load case. It was found that the curvature of the beam is significant, considerably improving the knowledge and understanding of the web crippling behaviour of curved channel beams.

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