Coulomb friction is considered as a mechanical approach to diminish the structural responses during the excitations. However, in case of severe oscillations supplementary mechanisms are employed besides the friction to mitigate the destructive effects of the vibrations in structures. Therefore, the main goal of this research is to develop a new Hybrid System (HS) which is a parallel combination of Viscous Damping (VD) and Coulomb friction for structures subjected to dynamic load. To achieve this goal, the effect of viscous damper is embedded in the equation of motion which is proposed by Den Hartog for a Single-Degree-of-Freedom (SDOF) Coulomb system, and has been extensively implemented for past few decades. In the considered numerical example in this study, implementing the proposed HDM in system resulted in decreasing the maximum displacement in the range of 1% to 98% for different amounts of force amplitude and viscous damping ratios. Also, applying the proposed HDM increased the time lag for about up to 24% for the frequency ratios greater than 1. The developed hybridized system in this study can be utilised as new generation of Tuned Mass Damper (TMD) to improve their energy dissipating efficiency under severe excitations.
Iran is the country in Western Asia most impacted by the COVID-19 outbreak. A survey was conducted among the general public in Iran aimed at investigating psychobehavioural issues related to the COVID-19 outbreak, namely (a) barriers to preventive measures against SARS-CoV-2 infection; (b) negative emotions towards SARS-CoV-2 infection; and (c) anxiety levels among the general public in Iran. A cross-sectional, web-based survey using an online questionnaire was carried out between 16 March and 1 April 2020. The six-item version of the State-Trait Anxiety Inventory (STAI-6) was used to assess anxiety levels. A total of 1,789 complete responses were received. Nearly 60% reported having difficulty in wearing a face mask to protect against SARS-CoV-2 infection. The mean and standard deviation (SD) for the total prevention barrier score was 35.8 (SD ± 7.1; range 18-68) out of a possible score of 72. Male respondents [odds ratio (OR) = 1.25; 95% confidence interval (CI) 1.03-1.51] and respondents who perceived their health status as poor/fair (OR = 1.49; 95% CI 1.31-1.82) were predictors of high prevention barriers. Negative emotions such as fear (74.6%) followed by depression (43.4%) and stigma (23.0%) associated with SARS-CoV-2 infection were reported. Respondents who perceived their health as poor/fair (OR = 2.19; 95% CI 1.57-3.04) reported a higher likelihood of having higher negative emotions. Findings on anxiety level revealed 68.0% (95% CI 65.8-70.1) reported moderate to severe anxiety. Respondents who perceived their health as poor/fair (OR = 3.46; 95% CI 12.22-5.40) and who were females (OR = 1.91; 95% CI 1.55-2.36) were predictors of moderate to severe anxiety. In conclusion, psychobehavioural interventions are needed to facilitate management and control of the COVID-19 outbreak.