Reliability analysis of shear design provisions for cold formed steel sections

This study focuses on the structural reliability analysis of cold-formed steel (CFS) sections under the ultimate limit state of shear. It considers two design models: the EN 1993-1-3 standard and its recent modification proposed by a previous study. The bias and uncertainty in these models were calibrated by comparing the design models’ prediction to 67 experimental results. Reliability analyses for the CFS beams, designed according to both models, were conducted using Monte Carlo Simulation (MCS) and the First Order Reliability Method (FORM). This analysis incorporated the model uncertainty and other parameters describing these models into the stochastic description. The 10% fractile of the reliability values for beams designed using the existing EN 1993-1-3 provisions showed values that were more conservative than those of the modified EN 1993-1-3 provisions, compared to the reliability target of 3.8. A FORM sensitivity analysis identified the yield strength of steel f y b and the resistance model uncertainty Γ R as the main positive drivers of uncertainty in the computed reliability indices of the design models. Additionally, a multiplicative modification factor was proposed for both the existing and modified versions of EN 1993-1-3, ensuring that these models optimally meet the specified reliability targets of 3.8 and 4.3 for Eurocode reliability classes 2 and 3, respectively. The proposed modifications maintain the partial factor γ M 0 at 1.0, as stipulated by the EN 1993-1-3 provisions for the resistance of the cross-section

Reliability analysis of shear design provisions for cold formed steel sections

This study focuses on the structural reliability analysis of cold-formed steel (CFS) sections under the ultimate limit state of shear. It considers two design models: the EN 1993-1-3 standard and its recent modification proposed by a previous study. The bias and uncertainty in these models were calibrated by comparing the design models’ prediction to 67 experimental results. Reliability analyses for the CFS beams, designed according to both models, were conducted using Monte Carlo Simulation (MCS) and the First Order Reliability Method (FORM). This analysis incorporated the model uncertainty and other parameters describing these models into the stochastic description. The 10% fractile of the reliability values for beams designed using the existing EN 1993-1-3 provisions showed values that were more conservative than those of the modified EN 1993-1-3 provisions, compared to the reliability target of 3.8. A FORM sensitivity analysis identified the yield strength of steel fyb and the resistance model uncertainty ΓR as the main positive drivers of uncertainty in the computed reliability indices of the design models. Additionally, a multiplicative modification factor was proposed for both the existing and modified versions of EN 1993-1-3, ensuring that these models optimally meet the specified reliability targets of 3.8 and 4.3 for Eurocode reliability classes 2 and 3, respectively. The proposed modifications maintain the partial factor γM0 at 1.0, as stipulated by the EN 1993-1-3 provisions for the resistance of the cross-section.</p

Reliability analysis of shear design provisions for cold formed steel sections

This study focuses on the structural reliability analysis of cold-formed steel (CFS) sections under the ultimate limit state of shear. It considers two design models: the EN 1993-1-3 standard and its recent modification proposed by a previous study. The bias and uncertainty in these models were calibrated by comparing the design models’ prediction to 67 experimental results. Reliability analyses for the CFS beams, designed according to both models, were conducted using Monte Carlo Simulation (MCS) and the First Order Reliability Method (FORM). This analysis incorporated the model uncertainty and other parameters describing these models into the stochastic description. The 10% fractile of the reliability values for beams designed using the existing EN 1993-1-3 provisions showed values that were more conservative than those of the modified EN 1993-1-3 provisions, compared to the reliability target of 3.8. A FORM sensitivity analysis identified the yield strength of steel fyb and the resistance model uncertainty ΓR as the main positive drivers of uncertainty in the computed reliability indices of the design models. Additionally, a multiplicative modification factor was proposed for both the existing and modified versions of EN 1993-1-3, ensuring that these models optimally meet the specified reliability targets of 3.8 and 4.3 for Eurocode reliability classes 2 and 3, respectively. The proposed modifications maintain the partial factor γM0 at 1.0, as stipulated by the EN 1993-1-3 provisions for the resistance of the cross-section.</p

Rainfall variability and trends over the African continent using TAMSAT data (1983-2020): towards climate change resilience and adaptation

This study reveals rainfall variability and trends in the African continent using TAMSAT data from 1983 to 2020. In the study, a Mann–Kendall (MK) test and Sen’s slope estimator were used to analyze rainfall trends and their magnitude, respectively, under monthly, seasonal, and annual timeframes as an indication of climate change using different natural and geographical contexts (i.e., sub-regions, climate zones, major river basins, and countries). The study finds that the highest annual rainfall trends were recorded in Rwanda (11.97 mm/year), the Gulf of Guinea (river basin 8.71 mm/year), the tropical rainforest climate zone (8.21 mm/year), and the Central African region (6.84 mm/year), while Mozambique (-0.437 mm/year), the subtropical northern desert (0.80 mm/year), the west coast river basin of South Africa (-0.360 mm/year), and the Northern Africa region (1.07 mm/year) show the lowest annual rainfall trends. There is a statistically significant increase in the rainfall in the countries of Africa’s northern and central regions, while there is no statistically significant change in the countries of the southern and eastern regions. In terms of climate zones, in the tropical northern desert climates, tropical northern peninsulas, and tropical grasslands, there is a significant increase in rainfall over the entire timeframe of the month, season, and year. This implies that increased rainfall will have a positive effect on the food security of the countries in those climatic zones. Since a large percentage of Africa’s agriculture is based only on rainfall (i.e., rain-fed agriculture), increasing trends in rainfall can assist climate resilience and adaptation, while declining rainfall trends can badly affect it. This information can be crucial for decision-makers concerned with effective crop planning and water resource management. The rainfall variability and trend analysis of this study provide important information to decision-makers that need to effectively mitigate drought and flood risk

Spatial Forecasting of the Landscape in Rapidly Urbanizing Hill Stations of South Asia: A Case Study of Nuwara Eliya, Sri Lanka (1996–2037)

Forecasting landscape changes is vital for developing and implementing sustainable urban planning. Presently, apart from lowland coastal cities, mountain cities (i.e., hill stations) are also facing the negative impacts of rapid urbanization due to their economic and social importance. However, few studies are addressing urban landscape changes in hill stations in Asia. This study aims to examine and forecast landscape changes in the rapidly urbanizing hill station of Nuwara Eliya, Sri Lanka. Landsat data and geospatial techniques including support vector machines, urban&ndash;rural gradient, and statistical analysis were used to map and examine the land use/land cover (LULC) change in Nuwara Eliya during the 1996&ndash;2006 and 2006&ndash;2017 periods. The multilayer perceptron neural network-Markov model was applied to simulate future LULC changes for 2027 and 2037. The results show that Nuwara Eliya has been directly affected by rapid urban development. During the past 21 years (1996&ndash;2017), built-up areas increased by 1791 ha while agricultural land declined by 1919 ha due to augmented urban development pressure. The pressure of urban development on forest land has been relatively low, mainly due to strict conservation government policies. The results further show that the observed landscape changes will continue in a similar pattern in the future, confirming a significant increase and decrease of built-up and agricultural land, respectively, from 2017 to 2037. The changes in agricultural land exhibit a strong negative relationship with the changes in built-up land along the urban&ndash;rural gradient (R2 were 0.86 in 1996&ndash;2006, and 0.93 in 2006&ndash;2017, respectively). The observed LULC changes could negatively affect the production of unique upcountry agricultural products such as exotic vegetables, fruits, cut flowers, and world-famous Ceylon tea. Further, unplanned development could cause several environmental issues. The study is important for understanding future LULC changes and suggesting necessary remedial measures to minimize possible undesirable environmental and socioeconomic impacts

Light-lift helicopter logging operations in the Italian Alps: a preliminary study based on GNSS and a video camera system

Terrain access is a critical factor influencing the feasibility of forest operations in steep mountainous terrain. Long extraction distances coupled with terrain obstacles can favor the use of helicopters in timber extraction in such areas. However, helicopter logging in the Italian Alps is not commonplace when compared to other Alpine regions, for example, in Switzerland and Austria. The use of light-lift helicopters has recently caught the attention of practitioners as an alternative to more traditional medium- to heavy-lift aircraft in the Alps. This article reports the findings of two preliminary case studies using light-lift helicopters for the extraction of high value timber and fire-damaged timber subsequently exposed to bark beetle disturbance. In order to provide a comprehensive analysis of the factors affecting helicopter logging productivity, the two case studies were separately analyzed using time-element analysis supported by on-board global navigation satellite system (GNSS) devices. Additio..

Spatiotemporal Variation of Urban Heat Islands for Implementing Nature-Based Solutions: A Case Study of Kurunegala, Sri Lanka

Changes in the urban landscape resulting from rapid urbanisation and climate change have the potential to increase land surface temperature (LST) and the incidence of the urban heat island (UHI). An increase in urban heat directly affects urban livelihoods and systems. This study investigated the spatiotemporal variation of the UHI in the Kurunegala urban area (KUA) of North-Western Province, Sri Lanka. The KUA is one of the most intensively developing economic and administrative capitals in Sri Lanka with an urban system that is facing climate vulnerabilities and challenges of extreme heat conditions. We examined the UHI formation for the period 1996–2019 and its impact on the urban-systems by exploring nature-based solutions (NBS). This study used annual median temperatures based on Landsat data from 1996 to 2019 using the Google Earth Engine (GEE). Various geospatial approaches, including spectral index-based land use/cover mapping (1996, 2009 and 2019), urban-rural gradient zones, UHI profile, statistics and grid-based analysis, were used to analyse the data. The results revealed that the mean LST increased by 5.5 °C between 1996 and 2019 mainly associated with the expansion pattern of impervious surfaces. The mean LST had a positive correlation with impervious surfaces and a negative correlation with the green spaces in all the three time-points. Impacts due to climate change, including positive temperature and negative rainfall anomalies, contributed to the increase in LST. The study recommends interactively applying NBS to addressing the UHI impacts with effective mitigation and adaptation measures for urban sustainability