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In this research, ultra-low cycle fatigue in retrofitted connections with R-RBS1 and R-RBS2 drilling patterns has been investigated using experimental and numerical methods. The connection was retrofitted with the RBS1 pattern, with a 1% increase in seismic capacity, which failed in the 6% drift angle cycle. While the connection was retrofitted with the R-RBS2 pattern failed in the 5% drift angle cycle. In both connections retrofitted with R-RBS1 and R-RBS2 patterns, the place of damage caused by ultra-low cycle fatigue was in the drilling area. [ABSTRACT FROM AUTHOR]

The test results on hourglass specimens of steel under repetitive sine loads provide graphs that indicate the stress range in terms of the number of cycles to failure and are known as S-N curves. Using this curve, it is determined that if the applied stress is less than a certain level, failure will not occur as the number of load cycles increases. The S-N curve can be affected by several factors such as yield stress, temperature, surface properties, and corrosion. In this research, the S-N curve has been investigated for two types of high-strength steels, S690 and S460, as well as two types of mild-strength steels, S235 and S355, at 25°C, and S355 with corrosion. The numbers of samples used for S235 and S460 steels were 45 each while S355 and S690 steels were 36 each and for S355 with corrosion was 15 with the high cycle fatigue curve obtained for them. To investigate the effect of plate thickness on the high cycle fatigue of the samples, four sets of 24-piece S235 steel samples, being 96 samples in total, were made of plates with different thicknesses of 8, 12, 15, and 20 mm and tested. Finally, a four-story three-span steel moment frame was designed, and under the Northridge earthquake record, the high cycle fatigue was investigated. It was observed that the high cycle fatigue was not effective for the mentioned structure under the Northridge earthquake record, but in the corroded structure, damage from high cycle fatigue occurs under this record. [ABSTRACT FROM AUTHOR]

Background: Healthcare workers (HCWs) have a high risk of catching SARS-CoV-2 infection. Seroprevalence studies can provide related data on HCWs with a history of infections. Despite numerous seroepidemiological reports of COVID-19 in different groups, there are no such reports for HCWs working in Rafsanjan City, Iran. This study aimed to determine the SARS-CoV-2 seroprevalence among HCWs. Methods: Blood samples were obtained from 295 participants, including healthcare personnel and administrative staff. The SARS-CoV-2 IgG antibody was measured by the ELISA method, and the obtained data were analyzed with the Chi-square test and logistic regression. A P<0.05 was considered statistically significant. Results: The previous exposure to COVID-19 was higher in HCWs than in administrative department staff. Fifteen out of 130 (11.5%) participants had experienced SARS-CoV-2 infection without any symptoms. The results of logistic regression indicated that traveling (OR: 018, 95% CI: 0.08-0.74, P=0.001), occupation (OR: 0.2, 95% CI: 0.01-0.94, P<0.05), history of respiratory problems (OR: 0.15, 95% CI: 0.01-1.94, P<0.05), and major clinical signs (OR: 8.09, 95% CI: 3.7-17.66, P<0.001) are important factors which affect SARS-CoV-2 IgG antibodies. Conclusion: Our results indicated an occupational risk for SARS-CoV-2 infection among HCWs. Because some HCWs are asymptomatic, their communication, such as traveling, must be controlled, and it is necessary to ensure the safety of HCWs and reduce their transfer to the community and patients. [ABSTRACT FROM AUTHOR]

In order to optimize the energy requirements (heating/cooling) of a multi-zone greenhouse, and investigate its heat recovery potential, a mathematical, dynamic energy model, coded in the MATLAB/Simulink platform, is developed. For validation, a case study in cold climate conditions is evaluated. This dynamic model, based on both energy and water vapor mass balances, was able to calculate the year-round monthly energy demand for the case study. The model calculations were compared with actual energy consumption data and were shown to have an accuracy between 6% and 15.5% for different months. The results highlighted the potential of applying a heat recovery strategy, whether with a Phase Change Material (PCM) or a Heat Recovery Ventilator (HRV). It is shown that using a HRV can reduce the energy demand of the greenhouse by 5% for January and 4% for December. Regarding the greenhouse radiation performance, the south roof contributes the most to solar heat gain in winter and summer, while the north wall makes the minimum contribution. Consequently, it is proposed to increase the area of the south roof and insulate the north wall. Thus, an asymmetrical roof configuration can receive 6% more solar radiation. Calculations show that an east-west greenhouse orientation lowers energy demand by 3%. [ABSTRACT FROM AUTHOR]

In order to determine the performance level of steel structures or to strengthen them, it is necessary to determine the ultimate capacity of their connections under the influence of extremely low cycle fatigue caused by cyclic load. On the other hand, the ultimate capacity or failure of the connections, under unavoidable monotonic loadings such as explosions or fires, needs to be determined in order to predict the progressive collapse in structures utilizing intermediate and/or special moment frames. In this study, the ultimate capacity of welded connections, subjected to monotonic loading, is estimated using the Stress Modified-Critical Strain model (SMCS). However, the Cyclic Void Growth Model (CVGM) is used to investigate connection capacity under cyclic loading. These models could be used to estimate the ultimate capacity of connections to determine the performance levels of the structures where it is not practical or possible to test laboratory specimens. In this paper, the ultimate capacity of connections are obtained based on the crack initiation criterion in three types of moment connections, namely reduced beam section (RBS), welded unreinforced flange-welded web (WUF-W), and increased beam section (IBS) moment connections; (1) subjected to monotonic loading in the column removal scenario by using the (SMCS) model, and (2) under cyclic loading by using the (CVGM). This research shows that by using the ductile fracture models, it is possible to predict the ultimate capacity and fracture mode of the welded moment connections with great accuracy. The results of this investigation, using fracture models, indicate that out of the three types of connections, the seismic rotational capacity of the IBS moment connection is the largest (0.05 radians), next is RBS (0.044 radians), and WUF-W is the last (0.04 radians) with the least rotational capacity under cyclic loading. The results also reveal that the rotation capacity of the connections under monotonic loading is two to three times the capacity of the same connection under cyclic loading (IBS:0.20 radians, RBS: 0.16 radians and WUF-W: 0.147 radians). [ABSTRACT FROM AUTHOR]

Slip factor is one of the most important parameters used in centrifugal pumps performance prediction. Knowing this parameter as a function of flow rate seems essential for off-design performance prediction. In this paper, it is intended to establish the slip factor dependence upon flow rate for a centrifugal pump using computational fluid dynamics. For this purpose, the full 3DRANS equations in coupled with RNG k - ε turbulence model were solved for several flow rates ranging from 45% to 120% of rated condition by means of a commercial code, CFX. In the steady state, this simulation is defined by means of the multi-reference frame technique, in which the impeller is situated in the rotating reference frame, and the volute is in the fixed reference frame. The validity of the numerical model was confirmed by matching the calculated characteristic curves with the associated experimental data. It was found that there is a good coincidence between the numerical results and available experimental data of global performance, local velocity distribution and slip factors. A comparison was performed among the well-known slip models which reveals, that the slip factor variations can be predicted very well using CFD analysis. [ABSTRACT FROM AUTHOR]

This paper presents a numerical investigation of the impact of a wind-driven surface fire, comparable to a large wildfire, on an obstacle located downstream of the fire source. The numerical modelling was conducted using FireFOAM, a coupled fire-atmosphere model underpinned by a large eddy simulation (LES) solver, which is based on the Eddy Dissipation Concept (EDC) combustion model and implemented in the OpenFOAM platform (an open source CFD tool). The numerical data were validated using the aerodynamic measurements of a full-scale building model in the absence of fire effects. The results highlighted the physical phenomena contributing to the fire spread pattern and its thermal impact on the building. In addition, frequency analysis of the surface temperature fluctuations ahead of the fire front showed that the presence of a building influences the growth and formation of buoyant instabilities, which directly affect the behaviour of the fire's plume. The coupled fire-atmosphere modelling presented here constitutes a fundamental step towards better understanding the behaviour and potential impacts of large wind-driven wildland fires in wildland-urban interface (WUI) areas. [ABSTRACT FROM AUTHOR]