Investigation of the effect of impact load on concrete-filled steel tube columns under fire

Concrete-filled steel tube (CFST) columns are increasingly used in the construction of high-rise buildings which require high strength and large working space especially at lower stories. As compared to reinforced concrete columns, existence of the exterior steel tube not only bears a portion of axial load but also most importantly provides confinement to the infill concrete.with the confinement provided by the steel tube, axial strength of the infill concrete can be largely enhanced.this paper presents the investigation effect of impact load on concrete-filled steel tube columns under fire by numerical simulations using ABAQUS software.the results indicate that the CFST sections with larger confinement factor ξ=1.23 behaved in a very ductile manner under lateral impact. And the sections with smaller confinement factor ξ=0.44  generally behaved in a brittle mechanism

Investigation and Prediction of the Land Use/Land Cover (LU/LC) and Land Surface Temperature (LST) Changes for Mashhad City in Iran during 1990–2030

Mansourmoghaddam, M., Rousta, I., Cabral, P., Ali, A. A., Olafsson, H., Zhang, H., & Krzyszczak, J. (2023). Investigation and Prediction of the Land Use/Land Cover (LU/LC) and Land Surface Temperature (LST) Changes for Mashhad City in Iran during 1990–2030. Atmosphere, 14(4), 1-21. [741]. https://doi.org/10.3390/atmos14040741 --- Funding: This study was supported by the Shanghai Municipal Science and Technology Commission within the international cooperation framework of the Youth Scientists from the “One Atmosphere 2023, 14, 741 18 of 21 Belt and One Road” countries (2020–2023), and partially supported by the FCT (Fundação para a Ciência e a Tecnologia) under the project UIDB/04152/2020—Centro de Investigação em Gestão de Informação (MagIC).Studies on how cities are affected by urban heat islands (UHI) are critical nowadays for a better understanding of the connected effects and for providing helpful insights for sustainable city development planning. In this study, Landsat-5 Thematic Mapper (TM), Landsat-7 Enhanced Thematic Mapper+ (ETM+), and Landsat-8 Operational Land Imager (OLI) images were used to assess the dynamics of the spatiotemporal pattern of land use/land cover (LU/LC) and land surface temperature (LST) in the metropolitan city of Mashhad, Iran in the period between 1990 and 2019. The Markov chain model (MCM) was used to predict LU/LC and LST for 2030. In the analyzed LU/LC maps, three LU/LC classes were distinguished, including built-up land (BUL), vegetated land (VL), and bare land (BL) using the maximum likelihood (ML) classification method. The collected data showed different variations in the geographical pattern of Mashhad LST during the research period that impacted the LST in this metropolis. The study evaluated the variations in LU/LC classes and evaluated their impact on the LST. The value of the LST was positively correlated with the occurrence of the built-up land (BUL), and with the bare land areas, while it was negatively correlated with the occurrence of the VL areas. The analysis of changes observed over three decades with 10-year intervals and the prediction of the LU/LC and LST for 2030 constitute an important contribution to the delineation of the dynamics of long LU/LC and LST records. These innovative results may have an important impact on policymaking fostering environmental sustainability, such as the control and management of urban expansion of Mashhad in connection with UHI.publishersversionpublishe

Decadal Spatial-Temporal Variations in the Spatial Pattern of Anomalies of Extreme Precipitation Thresholds (Case Study: Northwest Iran)

This study focused on decadalvariations of extreme precipitation thresholds within a 50-year period (1961–2010) for 250 stations of Iran’s northwest. The 99th percentile was used as the threshold of extreme precipitation. In order to analyze threshold cycles and spatial autocorrelation pattern dominating extreme precipitation thresholds, spectral analysis and Gi (known as HOTSPOT) were used respectively. The results revealed that the highest threshold of extreme precipitation occurred along the Ghoosheh Dagh mountain range. Additionally, in all the five studied decades, the highest positive anomalies were observed in the same region (i.e., the Ghoosheh Dagh). The findings also showed that the intensity of positive spatial autocorrelation pattern of extreme precipitation thresholds experienced a declining trend in recent decades. At the same time, extreme precipitation weighted mean center indicated that they followed an ordered pattern during the studied period. The results of harmonic analysis demonstrated that, in all decades, short-term (2–4 years) and mid-term (4–8 years) cycles of extreme precipitation thresholds were dominated. However, especially the southwest of the studied area, the return period of extreme precipitation thresholds was as long as the studied period, a phenomenon that indicates the existence of a trend in extreme precipitation thresholds of these regions.Peer Reviewe

Investigating Cyclic and Pushover Performance of Different Metallic Yielding Dampers

One of the most widely used and applicable solutions for limiting the damages of earthquakes to steel structures is using Metallic Yielding Dampers as a type of passive devices to dissipate the received energy. Maintaining a proper balance in the design of these devices is a delicate matter as each of the different types have advantages and disadvantages. In this research, different types of metallic dampers are compared using finite element simulation which is performed by means of ABAQUS package. Modeling process is described and verified by comparing the results to a previously published experimental paper on the subject. For assuring more accuracy a mesh convergence analysis is performed to determine the suitable mesh size. Afterwards, cyclic and pushover analysis are performed on each damper and results are presented and discussed. Effective stiffness and damping of each damper, both general and average, is extracted using proper equations and finite element results. Finally, for deeper understanding of dampers behavior, internal forces of the dampers are derived and compared. It was shown that design equations are fairly accurate. As the height of the dampers increases, their effective stiffness and damping reduces and the dampers behavior leans towards flexural behavior. Based on cyclic and pushover analysis, Steel Plate Dampers (SPD) have the highest stiffness and energy dissipation. Also, SPD and Double Pipe Dampers (DPD) are the most suitable to reach a demanded stiffness, damping and have the most stable performance. At the end of the paper, a list of conclusions is presented

Seismic fragility assessment of reinforced concrete moment frames retrofitted with strongback braced system

This study focused on analysing the seismic fragility and retrofitting of reinforced concrete flexural frames using strongback braced system. Using the steel strongback braced system as a means of seismically strengthening and retrofitting reinforced concrete moment frames (RCMFs), this research aims to enhance the effectiveness of RCMFs. In this study, RCMFs of 5-, 10-, and 15-stories are designed according to the first and fourth editions of the Iran Earthquake Standard 2800. The RCMFs designed according to the first edition are strengthened and reinforced using the SB system. The studied structures were analyzed under incremental static loading and time history analysis. The results show that the yield force and maximum base shear for the structures designed with the fourth edition, compared to the structures designed with the first edition, have increased by 1.28–1.42. This demonstrates the necessity of improving structures constructed according to the first edition. Meanwhile, the results of the retrofitted structures with strongback braces show the same or better performance than newly designed structures. The results of the fragility analysis show that the addition of the strong bracing system significantly improves the performance of the structures and brings them closer to the 4th edition standards. The retrofitting system reduces drift ratio between floors and reduces structural damage

Quantifying the Effects of Green-Town Development on Land Surface Temperatures (LST) (A Case Study at Karizland (Karizboom), Yazd, Iran)

Several earth science investigations depend heavily on knowing the surface energy budget and determining surface temperature. The primary factor affecting the energy balance in the surface physical processes of the planet is the land surface temperature (LST). Even in the case of small-scale green areas like local parks, plants have a significant impact on the climate of cities. The goal of this study was to estimate the construction-related impacts of the Karizland green town (green belt) on the LST of its surroundings over time, for the years 2013 (before construction began), 2015, 2020 and 2022 (after construction was completed). LST values and hot spot analyses were employed for thermal condition evaluation purposes on Landsat-8 satellite images, and normalized difference vegetation index (NDVI) and fractional vegetation cover (FVC) indices were used for examining the vegetation change. The results showed that after the establishment of the green town, the mean NDVI and FVC grew by 275% and 950%, respectively, compared to the initial period, which resulted in the addition of approximately 208.35 ha of green space to the study area. In this regard, the results showed that after these changes, compared to the first period, the mean LST decreased by 8%. In addition, the area of the class of hotspot analysis with less than 90% confidence increased by 9%. The results illustrated that almost 20% of the data in the LST range was below 55 °C in 2013, near 57 °C in 2015, and around 51 °C in 2020 and 2022. The results also showed a negative relationship between the distance from the established settlement and the values of NDVI and FVC in 2022 of 91% and 89% and in 2020 of 67% and 69%, respectively. Every year, LST has had a significant negative relationship with the NDVI and FVC of that year and a positive relationship with the LST of the following years, such that the correlation decreases in later years. In order to control LST and the temperature surrounding cities, this research strongly advises managers to develop these green towns

A review on potential roles of vitamins in incidence, progression, and improvement of multiple sclerosis

Multiple Sclerosis (MS) is an inflammatory and neurodegenerative disease, with unknown etiology. Vitamins, as important micronutrients playing different roles in body, seem to be important in MS pathogenesis. In vitro, in vivo and human studies, supports the protective role of some vitamins in MS occurrence or progression. Current study reviews recent insights and reports about the importance of vitamins in MS incidence or progression. In accordance, the importance of all water and fat-soluble vitamins in MS pathogenesis based on observational studies in human population and their role in the function of immune system as well as possible therapeutic opportunities are discussed in depth throughout this review. Keywords: Multiple sclerosis, Experimental autoimmune encephalomyelitis, Vitamin A, Vitamin E, Vitamin D, Folic acid, Vitamin B 12, Vitamin