Introducing the Innovative Post-tensioned Connection with the Rigid Steel Node

Ali Jahangiri,Farhad Behnamfar,Mohammad Jahangiri 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.4

Securing strength, stiffness, and ductility in connections is one of the most important goals in structural design. After the Northridge earthquake, most steel moment resistant frames were damaged due to sudden fractures in beam-to-column connections. This resulted in the reconsideration of connection design and performance. As an alternative to weld connections, some researchers proposed the implementation of post-tensioned connections. In the present paper, the innovative connection is a combination of high strength steel frames which, through a rigid steel node above and below the beam flanges, provide the required stiffness, strength and ductility. Advantages of this connection include self-centering capability, lack of residual deformations, and energy dissipation which are analyzed using numerical and experimental methods. The modeling procedure and the cyclic behavior of the connection are studied and the analytical and the experimental results are compared. The results show that the cyclic responses observed in numerical simulations are in agreement with those from the experimental task and that the connection is superior to conventional moment resisting connections. The assumptions employed in simplifying simulations demonstrated high accuracy revealing an improvement in the seismic behavior of the connection.

Failure analysis of gas turbine generator cooling fan for 14o and 19o - blades angle of attack

Ali Jahangiri,Seyed Ebrahim Moussavi Torshizi,Seyed Majid Yadavar Nikravesh 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.4

In gas turbine power plants, a fan is used as a cooling system to dissipate generated heat in coils (copper conductors) and generator electric circuits at the end sides of its rotor. In some cases, fracture of blades causes short circuit between rotor and stator and consequently generator explosion and made lot of financial problems. The fracture of cooling fan blades has been occurred five times at the turbine side of the generator in our case of study, just 100 hr after resuming operation after overhaul. Using numerical analysis as well as laboratory investigation - includes visual inspections, metallography and SEM - can help better finding failure problems that cause blade failures. A series of numerical analysis was performed to diagnose the cause of failure possibility. CFD analysis is used to study the airflow distribution in order to observe probable separation phenomenon and pressure forces that they are imposed to fan blades due to operation. A finite element method was utilized to determine the stresses and dynamic characteristics of the fan blade (natural frequencies,stresses and vibrations).

Human Error Analysis in a Permit to Work System: A Case Study in a Chemical Plant

Jahangiri, Mehdi,Hoboubi, Naser,Rostamabadi, Akbar,Keshavarzi, Sareh,Hosseini, Ali Akbar Occupational Safety and Health Research Institute 2016 Safety and health at work Vol.7 No.1

Background: A permit to work (PTW) is a formal written system to control certain types of work which are identified as potentially hazardous. However, human error in PTW processes can lead to an accident. Methods: This cross-sectional, descriptive study was conducted to estimate the probability of human errors in PTWprocesses in a chemical plant in Iran. In the first stage, through interviewing the personnel and studying the procedure in the plant, the PTW process was analyzed using the hierarchical task analysis technique. In doing so, PTWwas considered as a goal and detailed tasks to achieve the goal were analyzed. In the next step, the standardized plant analysis risk-human (SPAR-H) reliability analysis method was applied for estimation of human error probability. Results: The mean probability of human error in the PTW system was estimated to be 0.11. The highest probability of human error in the PTW process was related to flammable gas testing (50.7%). Conclusion: The SPAR-H method applied in this study could analyze and quantify the potential human errors and extract the required measures for reducing the error probabilities in PTW system. Some suggestions to reduce the likelihood of errors, especially in the field of modifying the performance shaping factors and dependencies among tasks are provided.

Predicting the velocity distribution of Rushton turbine impeller in mixing of polymeric liquids using fuzzy neural network models

Ali Aminian,Mansour Jahangiri 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.5

Velocity profiles are helpful for the confident design of mixing tanks and chemical reactors in mixing processes. A fuzzy model and an artificial neural network have been presented for accurate prediction of velocity distributionof Rushton turbine impeller (RTI) for the mixing of polymeric liquids in the lower transition region: 35<Re'<1800. Local tangential and radial velocities were predicted along the discharge plane of the impeller. Experimental data wereused for training, validation, and testing the neuromorphic models. The presented models are very accurate and reliablein predicting the velocity profiles over wide ranges of polymer concentrations and rotational speed. Comparison of thesuggested fuzzy model and the empirical correlations shows that the proposed model outperforms the other alternativesboth in accuracy and generality. The results show that the proposed neuromorphic models can successfully be usedfor prediction of velocity distribution in agitated tanks for viscoelastic polymeric fluids.

Needle Stick Injuries and their Related Safety Measures among Nurses in a University Hospital, Shiraz, Iran

Jahangiri, Mehdi,Rostamabadi, Akbar,Hoboubi, Naser,Tadayon, Neda,Soleimani, Ali Occupational Safety and Health Research Institute 2016 Safety and health at work Vol.7 No.1

Background: This study aimed to determine the prevalence and factors related to needle stick injuries (NSIs) and to assess related safety measures among a sample of Iranian nurses. Methods: In this cross-sectional study, a random sample of 168 registered active nurses was selected from different wards of one of the hospitals of Shiraz University of Medical Sciences (SUMS). Data were collected by an anonymous questionnaire and a checklist based observational method among the 168 registered active nurses. Results: The prevalence of NSIs in the total of work experience and the last year was 76% and 54%, respectively. Hollow-bore needles were the most common devices involved in the injuries (85.5%). The majority of NSIs occurred in the morning shift (57.8%) and the most common activity leading to NSIs was recapping needles (41.4%). The rate of underreporting NSIs was 60.2% and the major reasons for not reporting the NSIs were heavy clinical schedule (46.7%) and perception of low risk of infection (37.7%). A statistically significant relationship was found between the occurrence of NSIs and sex, hours worked/week, and frequency of shifts/month. Conclusion: The study showed a high prevalence of NSIs among nurses. Supportive measures such as improving injection practices, modification of working schedule, planning training programs targeted at using personal protective equipment, and providing an adequate number of safety facilities such as puncture resistant disposal containers and engineered safe devices are essential for the effective prevention of NSI incidents among the studied nurses.

Using microwave heating for synthesis of SrCO3 nanostructures with different morphologies

Hasan Jahangiri,Mehdi Ranjbar,Mohammad Ali Taher,Hanif kazerooni 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.21 No.1

Strontium carbonate (SrCO3) nanostructures were synthesized successfully via simple microwaveapproach by Sr(NO3)2, carbonate powder and sodium hydroxide (NaOH) as reagents. The effects ofmicrowave time and power were investigated on product size and morphology. The products werecharacterized with X-ray diffraction pattern (XRD), scanning electron microscopy (SEM), transmissionelectron microscopy (TEM), Ultraviolet–visible (UV–vis) and room temperature photoluminescencespectroscopy (PL).

Needle Stick Injuries and their Related Safety Measures among Nurses in a University Hospital, Shiraz, Iran

Mehdi Jahangiri,Akbar Rostamabadi,Naser Hoboubi,Neda Tadayon,Ali Soleimani 한국산업안전보건공단 산업안전보건연구원 2016 Safety and health at work Vol.7 No.1

Background: This study aimed to determine the prevalence and factors related to needle stick injuries (NSIs) and to assess related safety measures among a sample of Iranian nurses. Methods: In this cross-sectional study, a random sample of 168 registered active nurses was selected from different wards of one of the hospitals of Shiraz University of Medical Sciences (SUMS). Data were collected by an anonymous questionnaire and a checklist based observational method among the 168 registered active nurses. Results: The prevalence of NSIs in the total of work experience and the last year was 76% and 54%, respectively. Hollow-bore needles were the most common devices involved in the injuries (85.5%). The majority of NSIs occurred in the morning shift (57.8%) and the most common activity leading to NSIs was recapping needles (41.4%). The rate of underreporting NSIs was 60.2% and the major reasons for not reporting the NSIs were heavy clinical schedule (46.7%) and perception of low risk of infection (37.7%). A statistically significant relationship was found between the occurrence of NSIs and sex, hours worked/ week, and frequency of shifts/month. Conclusion: The study showed a high prevalence of NSIs among nurses. Supportive measures such as improving injection practices, modification of working schedule, planning training programs targeted at using personal protective equipment, and providing an adequate number of safety facilities such as puncture resistant disposal containers and engineered safe devices are essential for the effective prevention of NSI incidents among the studied nurses.

Human Error Analysis in a Permit to Work System: A Case Study in a Chemical Plant

Mehdi Jahangiri,Naser Hoboubi,Akbar Rostamabadi,Sareh Keshavarzi,Ali Akbar Hosseini 한국산업안전보건공단 산업안전보건연구원 2016 Safety and health at work Vol.7 No.1

Background: A permit to work (PTW) is a formal written system to control certain types of work which are identified as potentially hazardous. However, human error in PTW processes can lead to an accident. Methods: This cross-sectional, descriptive study was conducted to estimate the probability of human errors in PTWprocesses in a chemical plant in Iran. In the first stage, through interviewing the personnel and studying the procedure in the plant, the PTW process was analyzed using the hierarchical task analysis technique. In doing so, PTWwas considered as a goal and detailed tasks to achieve the goal were analyzed. In the next step, the standardized plant analysis risk-human (SPAR-H) reliability analysis method was applied for estimation of human error probability. Results: The mean probability of human error in the PTW system was estimated to be 0.11. The highest probability of human error in the PTW process was related to flammable gas testing (50.7%). Conclusion: The SPAR-H method applied in this study could analyze and quantify the potential human errors and extract the required measures for reducing the error probabilities in PTW system. Some suggestions to reduce the likelihood of errors, especially in the field of modifying the performance shaping factors and dependencies among tasks are provided.

Dynamic analysis of train-bridge system under one-way and two-way high-speed train passing

Meysam Jahangiri,Jabar-Ali Zakeri 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.64 No.1

In this paper, the dynamic responses of train-bridge system under one-way and two-way high-speed train passing are studied. The 3D finite element modeling is used and the bridge and train are modeled considering their details. The created model is validated by the results of the dynamic field test. To study the effect of train speed, different train passing scenarios are analyzed, including one-way passing, two-way passing in different directions at same speeds, and two-way passing in different directions at different speeds. The results show that the locations of maximum acceleration are different in one-way and two-way passing modes, and the maximum values in two-way passing mode are higher than those in one-way passing mode, while the maximum accelerations in both modes are almost identical. The displacement and acceleration values in different scenarios show peaks at speeds of 260 and 120 km/h, due to the proximity of the natural frequencies of the bridge and loading frequencies of the train at these speeds.

Validity Assessment of the Persian Version of the Nordic Safety Climate Questionnaire (NOSACQ-50): A Case Study in a Steel Company

Yousefi, Yadolah,Jahangiri, Mehdi,Choobineh, Alireza,Tabatabaei, Hamidreza,Keshavarzi, Sareh,Shams, Ali,Mohammadi, Younes Occupational Safety and Health Research Institute 2016 Safety and health at work Vol.7 No.4

Background: The Nordic Safety Climate Questionnaire-50 (NOSACQ-50) was developed by a team of Nordic occupational safety researchers based on safety climate and psychological theories. The aim of this study was to develop and validate the Persian version of NOSACQ-50 and assess the score of safety climate on a group of workers in a steel company in Iran. Methods: The Persian version of NOSACQ-50 was distributed among 661 employees of a steel company in Qazvin Province (Iran). Exploratory factor analysis (EFA) and confirmatory factor analysis were used to determine the dimensions of the questionnaire. The reliability of the questionnaire was assessed using Cronbach ${\alpha}$ coefficient. Pearson correlation test was applied to investigate the correlation between different dimensions. Results: The results of EFA showed that the Persian version of NOSACQ-50 consisted of six dimensions. The Cronbach ${\alpha}$ coefficient of the questionnaire was 0.94. The mean score of safety climate in all dimensions was 2.89 (standard deviation 0.60). Conclusion: The Persian version of NOSACQ-50 had a satisfactory validity for measuring safety climate in the studied Iranian population.