Pub Date : 2023-09-25DOI: 10.4038/engineer.v56i3.7610
L. H. S. U. Balasooriya, B. R. G. A. Krishantha, K. K. Wijesundara
Popularity of tall buildings increases due to technological advances, but Code-based designs are conservative and not reliable for structures beyond 200 m height. Conducting a wind tunnel test is expensive and the resources are limited. Hence, numerical modelling is an alternative where Reynolds Average Navier Stokes Equation (RANSE) and Large Eddy Simulation (LES) are such numerical techniques.In recent Computational Fluid Dynamic (CFD) studies, it could be observed that results have considerable deviations in flow separating and high turbulent areas. Hence a structured mesh was used here to perform mesh refinement in such critical locations to refine only the required areas.The objective of this study is to compare the RANSE and LES in interpreting the wind structural interactions using a structured mesh arrangement. This study will be limited to tall buildings of height less than 200m, rectangular in shape. Hence Commonwealth Advisory Aeronautical Council (CAARC) standard building model was used as the subject and Simulation results will then be compared with the values of the wind tunnel test available in the literature.It could be observed that the results obtained by RANSE simulation for a structured mesh has a deviation less than 10%. But natural variations of the wind are more clearly indicated with LES with a deviation even less than 3% in turbulent regions.
{"title":"Comparison of RANSE and LES for Wind Structural Interaction","authors":"L. H. S. U. Balasooriya, B. R. G. A. Krishantha, K. K. Wijesundara","doi":"10.4038/engineer.v56i3.7610","DOIUrl":"https://doi.org/10.4038/engineer.v56i3.7610","url":null,"abstract":"Popularity of tall buildings increases due to technological advances, but Code-based designs are conservative and not reliable for structures beyond 200 m height. Conducting a wind tunnel test is expensive and the resources are limited. Hence, numerical modelling is an alternative where Reynolds Average Navier Stokes Equation (RANSE) and Large Eddy Simulation (LES) are such numerical techniques.In recent Computational Fluid Dynamic (CFD) studies, it could be observed that results have considerable deviations in flow separating and high turbulent areas. Hence a structured mesh was used here to perform mesh refinement in such critical locations to refine only the required areas.The objective of this study is to compare the RANSE and LES in interpreting the wind structural interactions using a structured mesh arrangement. This study will be limited to tall buildings of height less than 200m, rectangular in shape. Hence Commonwealth Advisory Aeronautical Council (CAARC) standard building model was used as the subject and Simulation results will then be compared with the values of the wind tunnel test available in the literature.It could be observed that the results obtained by RANSE simulation for a structured mesh has a deviation less than 10%. But natural variations of the wind are more clearly indicated with LES with a deviation even less than 3% in turbulent regions.","PeriodicalId":42812,"journal":{"name":"Engineer-Journal of the Institution of Engineers Sri Lanka","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135817617","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-25DOI: 10.4038/engineer.v56i3.7571
V. Viththagan, R. J. Wimalasiri, P. A. K. Karunananda
Fatigue failure of steel structures is one of the most urgent study areas due to the inherent catastrophic nature of the failure. Engineers have made a substantial contribution to the understanding of the fatigue phenomenon through several approaches. Heavy cyclic loads imposed on steel railway bridges have the potential to cause cracks in structurally important members. Initiated cracks propagate during its service and lead to a complete structural failure. Since it is not practical to continuously monitor the structural health of bridges, an accurate life prediction approach is necessary to predict failure. This study proposes the fracture mechanics approach for fatigue life prediction of the critical members of bridges. Standard compact tension C(T) specimens were prepared with a pre-crack to test the fatigue crack growth rate under different stress levels. The crack growth rate da/dN was calculated by plotting the crack length (a) vs the number of cycles (N). According to ASTM E647-15, the stress intensity factor range (ΔK) for the C(T) specimen was determined. Under the conditions of constant amplitude loading, a modified version of the Paris law was used to construct an empirical relationship between da/dN and ΔK. The results of the vibration analysis were used to validate the finite element model of a case study railway bridge in Sri Lanka. The Finite Element (FE) method was used to assess the life of the most critical bridge member, and its estimated remaining fatigue life is 14.5 years.
{"title":"Estimating Remaining Fatigue Life of Critical Members of Steel Railway Bridges using Fatigue Crack Growth Model","authors":"V. Viththagan, R. J. Wimalasiri, P. A. K. Karunananda","doi":"10.4038/engineer.v56i3.7571","DOIUrl":"https://doi.org/10.4038/engineer.v56i3.7571","url":null,"abstract":"Fatigue failure of steel structures is one of the most urgent study areas due to the inherent catastrophic nature of the failure. Engineers have made a substantial contribution to the understanding of the fatigue phenomenon through several approaches. Heavy cyclic loads imposed on steel railway bridges have the potential to cause cracks in structurally important members. Initiated cracks propagate during its service and lead to a complete structural failure. Since it is not practical to continuously monitor the structural health of bridges, an accurate life prediction approach is necessary to predict failure. This study proposes the fracture mechanics approach for fatigue life prediction of the critical members of bridges. Standard compact tension C(T) specimens were prepared with a pre-crack to test the fatigue crack growth rate under different stress levels. The crack growth rate da/dN was calculated by plotting the crack length (a) vs the number of cycles (N). According to ASTM E647-15, the stress intensity factor range (ΔK) for the C(T) specimen was determined. Under the conditions of constant amplitude loading, a modified version of the Paris law was used to construct an empirical relationship between da/dN and ΔK. The results of the vibration analysis were used to validate the finite element model of a case study railway bridge in Sri Lanka. The Finite Element (FE) method was used to assess the life of the most critical bridge member, and its estimated remaining fatigue life is 14.5 years.","PeriodicalId":42812,"journal":{"name":"Engineer-Journal of the Institution of Engineers Sri Lanka","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135817765","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-25DOI: 10.4038/engineer.v56i3.7572
G. A. T. Madushanka, K. D. W. Nandalal, L. P. Mutuwatta
Kalu Ganga, a major right-bank tributary of Amban Ganga, is one of the perennial rivers of Sri Lanka. Kalu Ganga Dam is a large gravity dam and a vital component of the complex Moragahakanda-Kalu Ganga Project built at Pallegama in the Matale District over the Kalu Ganga. A study was carried out to investigate and evaluate the present and future water availability of the Kalu Ganga reservoir. The present water availability is calculated using historical weather data, and the future water availability is estimated using predicted data extracted from downscaled climate change models. The study employed two Representative Concentration Pathway (RCP) scenarios, RCP 4.5 and RCP 8.5, of six climate models. Before being used, the climate change-predicted rainfall and temperature data were bias-corrected. Subsequently, the water availability was calculated using the rainfall-runoff model, Soil Water Assessment Tool (SWAT). The SWAT model was calibrated and validated using observed flow series at Laggala stream gauge on the Kalu Ganga. Using the same calibration settings, the SWAT model was then used to evaluate the potential impacts of climate change on streamflow in future scenarios. The SWAT, HEC-ResSim models and the climate change forecasted data have been shown to be useful tools for identifying climate change-driven water availability challenges, which can help with strategic water resources planning.
{"title":"Assessment of Water Availability in Kalu Ganga Catchment under Climate Change Effects","authors":"G. A. T. Madushanka, K. D. W. Nandalal, L. P. Mutuwatta","doi":"10.4038/engineer.v56i3.7572","DOIUrl":"https://doi.org/10.4038/engineer.v56i3.7572","url":null,"abstract":"Kalu Ganga, a major right-bank tributary of Amban Ganga, is one of the perennial rivers of Sri Lanka. Kalu Ganga Dam is a large gravity dam and a vital component of the complex Moragahakanda-Kalu Ganga Project built at Pallegama in the Matale District over the Kalu Ganga. A study was carried out to investigate and evaluate the present and future water availability of the Kalu Ganga reservoir. The present water availability is calculated using historical weather data, and the future water availability is estimated using predicted data extracted from downscaled climate change models. The study employed two Representative Concentration Pathway (RCP) scenarios, RCP 4.5 and RCP 8.5, of six climate models. Before being used, the climate change-predicted rainfall and temperature data were bias-corrected. Subsequently, the water availability was calculated using the rainfall-runoff model, Soil Water Assessment Tool (SWAT). The SWAT model was calibrated and validated using observed flow series at Laggala stream gauge on the Kalu Ganga. Using the same calibration settings, the SWAT model was then used to evaluate the potential impacts of climate change on streamflow in future scenarios. The SWAT, HEC-ResSim models and the climate change forecasted data have been shown to be useful tools for identifying climate change-driven water availability challenges, which can help with strategic water resources planning.","PeriodicalId":42812,"journal":{"name":"Engineer-Journal of the Institution of Engineers Sri Lanka","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135817763","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-25DOI: 10.4038/engineer.v56i3.7532
B. G. V. Sanjaya, J. M. R. S. Appuhamy, W. M. K. R. T. W. Bandara, S. Venkatesan, R. J. Gravina
The black pollution caused by the accumulation of Waste Tire Rubber (WTR) has engendered significant environmental and social consequences throughout the world by emphasizing the requirement of introducing a new approach to recycling WTR effectively. The recent research findings towards the utilization of End-of-Life Tires (ELT) to replace the Natural Aggregate (NA) in concrete have facilitated a promising way to handle the WTR while reducing the consumption of natural raw materials in the construction industry. However, the weak Interfacial Transition Zone (ITZ) between rubber aggregate and cement paste reduces the properties of Rubberized Concrete (RuC) and hinders its commercial usage. Among the many factors, the rubber particle size, shape, and Replacement Ratio (RR) significantly influence the performance of RuC. This paper reviews previous research findings relevant to the effect of the rubber particle size, shape, and percentage replaced in the concrete mix to pinpoint the further research gaps to be investigated. Overall, the previous findings indicate that the tire aggregate inclusion at a low level of replacement in the form of crumb rubber resulted in improved ductility and toughness with marginal impacts on workability, strength, and other mechanical properties of concrete compared to the control mix without WTR.
{"title":"Comprehensive Study on Rubber Particle Size and Replacement Ratio on Fresh and Hardened Properties of Rubberized Concrete: A Review","authors":"B. G. V. Sanjaya, J. M. R. S. Appuhamy, W. M. K. R. T. W. Bandara, S. Venkatesan, R. J. Gravina","doi":"10.4038/engineer.v56i3.7532","DOIUrl":"https://doi.org/10.4038/engineer.v56i3.7532","url":null,"abstract":"The black pollution caused by the accumulation of Waste Tire Rubber (WTR) has engendered significant environmental and social consequences throughout the world by emphasizing the requirement of introducing a new approach to recycling WTR effectively. The recent research findings towards the utilization of End-of-Life Tires (ELT) to replace the Natural Aggregate (NA) in concrete have facilitated a promising way to handle the WTR while reducing the consumption of natural raw materials in the construction industry. However, the weak Interfacial Transition Zone (ITZ) between rubber aggregate and cement paste reduces the properties of Rubberized Concrete (RuC) and hinders its commercial usage. Among the many factors, the rubber particle size, shape, and Replacement Ratio (RR) significantly influence the performance of RuC. This paper reviews previous research findings relevant to the effect of the rubber particle size, shape, and percentage replaced in the concrete mix to pinpoint the further research gaps to be investigated. Overall, the previous findings indicate that the tire aggregate inclusion at a low level of replacement in the form of crumb rubber resulted in improved ductility and toughness with marginal impacts on workability, strength, and other mechanical properties of concrete compared to the control mix without WTR.","PeriodicalId":42812,"journal":{"name":"Engineer-Journal of the Institution of Engineers Sri Lanka","volume":"73 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135817762","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-25DOI: 10.4038/engineer.v56i3.7607
V. Rajagopalasingam, T. Mikunthan, S. S. Sivakumar
Floods are one of the natural disasters causing economic, social, and environmental damage around the world, including in Sri Lanka. Flood susceptibility mapping is essential for flood prevention and mitigation measures. This study aimed to develop and validate a flood susceptibility map for the Kanakarayan Aru River Basin in Sri Lanka. Primary data were collected from water professionals and experts from Provincial Irrigation-Northern Province, Provincial Irrigation-Eastern Province, Disaster Management Centre, and Irrigation Department to decide the significance of flood causative factors. Secondary data of rainfall, digital elevation model, and GIS-based thematic data layers were collected from different agencies. GIS-based spatial multi-criteria decision analysis and analytical hierarchy process method were used for the study. A total of eight flood causative factors, i.e., elevation, slope, precipitation, land use and land cover, river proximity, drainage network density, topographic wetness index, and soil types were identified. Results show that the three mostrelevant factors of flood risk were precipitation (33%), drainage density network (17%), and surface slope (11%). The very high, high, and moderate flood risks occupy 12.5%, 23.4%, and 27.1% of the river basin areas, respectively. The validation process is executed based on the map's comparison of the historical flood locations of the different flood-susceptible zones and it provides a significant accuracy.
{"title":"Exploring Flood Susceptibility Mapping Using ArcGIS Techniques Integrated with Analytical Hierarchy Process under Multi-Criteria Decision Analysis in Kanakarayan Aru River Basin, Sri Lanka","authors":"V. Rajagopalasingam, T. Mikunthan, S. S. Sivakumar","doi":"10.4038/engineer.v56i3.7607","DOIUrl":"https://doi.org/10.4038/engineer.v56i3.7607","url":null,"abstract":"Floods are one of the natural disasters causing economic, social, and environmental damage around the world, including in Sri Lanka. Flood susceptibility mapping is essential for flood prevention and mitigation measures. This study aimed to develop and validate a flood susceptibility map for the Kanakarayan Aru River Basin in Sri Lanka. Primary data were collected from water professionals and experts from Provincial Irrigation-Northern Province, Provincial Irrigation-Eastern Province, Disaster Management Centre, and Irrigation Department to decide the significance of flood causative factors. Secondary data of rainfall, digital elevation model, and GIS-based thematic data layers were collected from different agencies. GIS-based spatial multi-criteria decision analysis and analytical hierarchy process method were used for the study. A total of eight flood causative factors, i.e., elevation, slope, precipitation, land use and land cover, river proximity, drainage network density, topographic wetness index, and soil types were identified. Results show that the three mostrelevant factors of flood risk were precipitation (33%), drainage density network (17%), and surface slope (11%). The very high, high, and moderate flood risks occupy 12.5%, 23.4%, and 27.1% of the river basin areas, respectively. The validation process is executed based on the map's comparison of the historical flood locations of the different flood-susceptible zones and it provides a significant accuracy.","PeriodicalId":42812,"journal":{"name":"Engineer-Journal of the Institution of Engineers Sri Lanka","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135817615","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-25DOI: 10.4038/engineer.v56i3.7608
M. N. C. Samarawickrama, U. G. A. Puswewala, H. S. Thilakasiri, K. M. L. A. Udamulla
The aim of this study is to review the different mechanisms employed in the estimation of static rock mass deformability modulus (𝐸𝑚) in rock engineering applications and to investigate the adoptability of the identified mechanisms in different rock masses. The paper discusses different evaluation criteria through experimental, empirical and other means, with their merits and demerits, including influential factors. It is known that deformability modulus of intact rock depends on the imposed stress, strain rate and the confining stress on the rock sample as well as the rock texture and structure. The results generated for 𝐸𝑚 by different in-situ tests are different and an appropriate in-situ test based on the rock mass conditions should be employed to obtain reasonable results. Empirical criteria are found to produce results of reasonable precision if appropriately adopted for specific rock mass conditions, while the back analysis method is widely adopted as an insitu estimation measure for the design of rock-sockets and tunnel support. It has also been reported that substantial reduction in 𝐸𝑚 occurs due to schistosity and larger test volumes, while it is sensitive to stress and discontinuity conditions. In this work, specific recommendations are made on the estimation of 𝐸𝑚 for different types of rock masses based on the findings and reviews reported in the literature.
{"title":"Review on the Estimation of Static Deformability Modulus of Rocks and their adoptability in Different Rock Masses","authors":"M. N. C. Samarawickrama, U. G. A. Puswewala, H. S. Thilakasiri, K. M. L. A. Udamulla","doi":"10.4038/engineer.v56i3.7608","DOIUrl":"https://doi.org/10.4038/engineer.v56i3.7608","url":null,"abstract":"The aim of this study is to review the different mechanisms employed in the estimation of static rock mass deformability modulus (𝐸𝑚) in rock engineering applications and to investigate the adoptability of the identified mechanisms in different rock masses. The paper discusses different evaluation criteria through experimental, empirical and other means, with their merits and demerits, including influential factors. It is known that deformability modulus of intact rock depends on the imposed stress, strain rate and the confining stress on the rock sample as well as the rock texture and structure. The results generated for 𝐸𝑚 by different in-situ tests are different and an appropriate in-situ test based on the rock mass conditions should be employed to obtain reasonable results. Empirical criteria are found to produce results of reasonable precision if appropriately adopted for specific rock mass conditions, while the back analysis method is widely adopted as an insitu estimation measure for the design of rock-sockets and tunnel support. It has also been reported that substantial reduction in 𝐸𝑚 occurs due to schistosity and larger test volumes, while it is sensitive to stress and discontinuity conditions. In this work, specific recommendations are made on the estimation of 𝐸𝑚 for different types of rock masses based on the findings and reviews reported in the literature.","PeriodicalId":42812,"journal":{"name":"Engineer-Journal of the Institution of Engineers Sri Lanka","volume":"59 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135817613","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-25DOI: 10.4038/engineer.v56i3.7603
P. A. K. Karunananda
No abstract available
没有摘要
{"title":"From the Editor…","authors":"P. A. K. Karunananda","doi":"10.4038/engineer.v56i3.7603","DOIUrl":"https://doi.org/10.4038/engineer.v56i3.7603","url":null,"abstract":"No abstract available","PeriodicalId":42812,"journal":{"name":"Engineer-Journal of the Institution of Engineers Sri Lanka","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135817612","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-25DOI: 10.4038/engineer.v56i3.7604
M. N. C. Samarawickrama, U. G. A. Puswewala, H. S. Thilakasiri, K. M. L. A. Udamulla
This study investigates the most appropriate empirical criteria to estimate the static rock mass deformability modulus (𝐸𝑚) in the design of rock-sockets in cast-in-situ bored pile construction. The in-situ 𝐸𝑚 values are initially estimated through back analysis of static pile load test data. Secondly, the rock mass deformability estimated from back analysis (𝐸𝑚b) are tested statistically against selected established empirical equations to determine whether the latter are appropriate for use in metamorphic rock terrain of Sri Lanka. It is found that the existing empirical criterion based on the square root of intact unconfined compressive strength (𝜎𝑐) derived from back analysis of pile load test results is appropriate for weak-poor rock masses. For strong-poor rocks, it is recommended to employ the equation based on 𝜎𝑐', and in general the two equations generate lower and upper bound solutions. The equation based on intact deformability modulus (𝐸𝑖) performs well in strong-excellent quality rock masses, while the equations based on 𝐸𝑖 and rock quality designation (𝑅QD) are found to be appropriate for weak-fair to excellent rock masses. Finally, a new set of equations appropriate for different rock mass types have been proposed through regression analysis along with appropriate design measures to be adopted.
{"title":"Estimation Criteria for Static Rock Mass Deformability Modulus for Rock-Socket Design in Metamorphic Rock Masses","authors":"M. N. C. Samarawickrama, U. G. A. Puswewala, H. S. Thilakasiri, K. M. L. A. Udamulla","doi":"10.4038/engineer.v56i3.7604","DOIUrl":"https://doi.org/10.4038/engineer.v56i3.7604","url":null,"abstract":"This study investigates the most appropriate empirical criteria to estimate the static rock mass deformability modulus (𝐸𝑚) in the design of rock-sockets in cast-in-situ bored pile construction. The in-situ 𝐸𝑚 values are initially estimated through back analysis of static pile load test data. Secondly, the rock mass deformability estimated from back analysis (𝐸𝑚b) are tested statistically against selected established empirical equations to determine whether the latter are appropriate for use in metamorphic rock terrain of Sri Lanka. It is found that the existing empirical criterion based on the square root of intact unconfined compressive strength (𝜎𝑐) derived from back analysis of pile load test results is appropriate for weak-poor rock masses. For strong-poor rocks, it is recommended to employ the equation based on 𝜎𝑐', and in general the two equations generate lower and upper bound solutions. The equation based on intact deformability modulus (𝐸𝑖) performs well in strong-excellent quality rock masses, while the equations based on 𝐸𝑖 and rock quality designation (𝑅QD) are found to be appropriate for weak-fair to excellent rock masses. Finally, a new set of equations appropriate for different rock mass types have been proposed through regression analysis along with appropriate design measures to be adopted.","PeriodicalId":42812,"journal":{"name":"Engineer-Journal of the Institution of Engineers Sri Lanka","volume":"70 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135817614","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-25DOI: 10.4038/engineer.v56i3.7609
Joseph Rohan Lucas
Lightning is a weather-related phenomenon with dire consequences for tall structures. The lightning protection adopted in Sri Lanka in stupas in ancient times, from the third century was adequate, as no lightning damage to stupas have been recorded in early times However, the present restoration of lightning protection may be inadequate as recent strikes have been detected due to improper new practices due to an absence of detailed recording of the lightning protection in ancient times. This paper discusses the lightning protection of stupas, especially of Ruwanweliseya from ancient times to the present, tracing the history of lightning protection from the Mahawansa and the Culawamsa. While the bulk of the lightning energy probably went through the stupa in ancient times, the modern protection tends to bring the energy to earth through the surface of the stupa and the compound at the bottom which can cause disastrous effects. Monitoring is recommended to be undertaken to see whether the dissipation of bulk of the lightning energy is through the stupa itself, even in the present day, or along the surface of the stupa and through the compound at the bottom.
{"title":"Lightning Protection of Stupas in Sri Lanka","authors":"Joseph Rohan Lucas","doi":"10.4038/engineer.v56i3.7609","DOIUrl":"https://doi.org/10.4038/engineer.v56i3.7609","url":null,"abstract":"Lightning is a weather-related phenomenon with dire consequences for tall structures. The lightning protection adopted in Sri Lanka in stupas in ancient times, from the third century was adequate, as no lightning damage to stupas have been recorded in early times However, the present restoration of lightning protection may be inadequate as recent strikes have been detected due to improper new practices due to an absence of detailed recording of the lightning protection in ancient times. This paper discusses the lightning protection of stupas, especially of Ruwanweliseya from ancient times to the present, tracing the history of lightning protection from the Mahawansa and the Culawamsa. While the bulk of the lightning energy probably went through the stupa in ancient times, the modern protection tends to bring the energy to earth through the surface of the stupa and the compound at the bottom which can cause disastrous effects. Monitoring is recommended to be undertaken to see whether the dissipation of bulk of the lightning energy is through the stupa itself, even in the present day, or along the surface of the stupa and through the compound at the bottom.","PeriodicalId":42812,"journal":{"name":"Engineer-Journal of the Institution of Engineers Sri Lanka","volume":"67 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135817616","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-25DOI: 10.4038/engineer.v56i3.7606
S. T. Siriwardana, N. T. S. Wijesekera
Water management and infrastructure designs all over the world are mostly associated with ungauged watersheds. The critical task is to estimate the streamflow at a desired location and then to convert the streamflow as design streamflow by incorporating safety factors. In the current setting, practicing engineers find a deficiency in guidelines to select a model and also find out ways to incorporate safety factors ensuring sustainable design of water infrastructure. The guideline of Irrigation Department, Sri Lanka, provides guidance on the use of an empirical model while the Snyder’s synthetic unit hydrograph method and HEC-HMS model are two other popular process-based models opted by most recent modelers to estimate watershed streamflow. The authors carried out a critical literature review and a case study in the Kalu river basin to investigate the issue of model selection faced by ungauged watershed modelers. A streamflow modeler of ungauged watersheds requires to responsibly select a streamflow model, model parameters and safety factors. In this context, the major challenge in the Sri Lankan practice is the unavailability of catchment studies with comparative evaluations of model studies with observed streamflow. The objective of the present work was to first determine the rationale for a design engineer to select a watershed model and parameters when computing design streamflow from an ungauged watershed and then to verify the selection using observed streamflow. Accordingly, the Irrigation Department Empirical Model (IDEM), Snyder’s UH Model (SUHM) and HEC-HMS model were selected and developed for Dunamale watershed of the Attanagalu river basin using methods and parameters from responsible publications. Then the model estimates were critically evaluated by comparing the observed streamflow. IDEM estimates of monthly yield estimations closely matched with the observed data. In the case of overall hydrographs, the IDEM indicated a MRAE value of 0.43 for design rainfall estimation, while the same for HEC-HMS model and SUHM method were 0.63 and 0.61, respectively. The qualitative review based on the uncertainties associated with the computations using IDEM, HEC-HMS and SUHM models classified them into three, as Moderately uncertain, Uncertainty between moderate and high, and Highly uncertain, respectively. The study concluded that, amongst the three selected models, the IDEM is still the best option available for an ungauged watershed modeler to compute design streamflow but pointed to the urgent need for upgrading the ID guidelines with focused research. The study pointed to the importance of identifying appropriate models and parameters for each watershed for meaningful use of process based streamflow models for design of water infrastructure. It was identified that explicit safety factors should be established to incorporate the uncertainties associated with the models and their parameters.
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