The effect of beam section property on the behavior of modular prefabricated steel moment connection

Seyed Morteza Kazemi,Mohammad Reza Sohrabi,Hasan Haji Kazemi 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.32 No.6

The specially prefabricated steel moment connections with pyramid head is one of the significant innovations in the steel structures forms to improve the installation time and simplify the construction procedure. The beams in this structure form are supported by two top and bottom angles and web double angles. Such a configuration despite its advantages increases the welding operation and filed installation time and costs. In this paper, the effect of using beams with channel and I section in three classes of seismically compact, seismically non-compact, and slender section according to width-to-thickness ratio on the behavior of the connection was investigated under monotonic and cyclic loading. Modeling was performed by ABAQUS and verified by the results of an experimental specimen. The findings indicated that using I and channel section instead of angle section reduces the amount of welding materials as well as easing the installation procedure. However, it has no significant effect on the ultimate strength and ductility of the connection. Furthermore, if the beam section is seismically compact, this form is considered as a special moment frame that has a rotation capacity up to 0.04 radians without any reduction in connection moment resistance.

Evaluation the behavior of pre-fabricated moment connection with a new geometry of pyramidal end block under monotonic and cyclic loadings

Seyed Morteza Kazemi,Mohammad Reza Sohrabi,Hasan Haji-Kazemi 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.29 No.3

Researchers have been long studying new building implementation methods to improve the quality of construction, reduce the time of assembly, and increase productivity. One of these methods is the use of modular pre-fabricated structural forms that are composed of a beam, column, short column, pyramidal end block, and connection plates. In this study, a new geometry for the pyramidal end block was proposed that helps facilitate the assembly procedure. Since the proposed configuration affects the performance of this form of connection, its behavior was evaluated using finite element method. For this purpose, the connection was modeled in ABAQUS and then validated by comparing the outputs with experimental results. The research proceeded through analyzing 16 specimens under monotonic and cyclic loading. The results indicated that using the pyramidal end block not only makes the assembly process easier but also reduces the out-of-plane displacement of the short column webs and the vertical displacement of beam end. By choosing appropriate section properties for column and beam, the connection can bear a rotation up to 0.01 radians within its inelastic region and a total of 0.04 radians without any significant reduction in its bearing capacity.

Design equations for prefabricated steel moment connections

Seyed Morteza Kazemi,Mohammad Reza Sohrabi,Hasan Haji Kazemi 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.80 No.3

Recently, modular prefabricated steel moment connections have been widely studied by several researchers. These connections are made of tubular columns that are ended to horizontal plates at both sides, an inter-story short column, and truss beams that are joined to the connecting plates using top and bottom plates. In this study, a series of equations have been developed and presented for designing each component of this type of connection. Then, to verify the proposed equations, the connection was modeled in ABAQUS and then the results extracted from the equations and modeling were compared. The findings indicated that the proposed equations have the required accuracy.

BNBTS More than Brominating Agent: Green and One-pot Route for the C-N Bond Formation in Water from Alkenes

Kazemi, Foad,Kakroudi, Mazaher Abdollahi Korean Chemical Society 2013 Bulletin of the Korean Chemical Society Vol.34 No.2

In this paper, in addition to introducing efficient method for bromohydrin and bromoether preparation, simple, green and efficient method to C-N bond formation from alkene and N,N'-Dibromo-N,N'-1,2-ethanediyl-bis(p-toluenesulfonamide) [BNBTS] in water was investigated. The reaction between alkenes, ${\beta}$-cyclodexterin, and BNBTS took place in water afterward, by making media basic; it will give the corresponding valuable building blocks in good yields (45-79%).

Field Study of Effects of Night Shifts on Cognitive Performance, Salivary Melatonin, and Sleep

Kazemi, Reza,Motamedzade, Majid,Golmohammadi, Rostam,Mokarami, Hamidreza,Hemmatjo, Rasoul,Heidarimoghadam, Rashid Occupational Safety and Health Research Institute 2018 Safety and health at work Vol.9 No.2

Background: Night shift work is associated with many problems such as sleep deprivation, sleepiness, decreased cognitive performance, increased human errors, and fatigue. This study set out to measure cognitive performance, melatonin rhythms, and sleep after different consecutive night shifts (7 vs. 4) among control room operators (CORs). Methods: The participants included 60 CORs with a mean age of 30.2 years (standard deviation, 2.0) from a petrochemical complex located in Southern Iran. Cognitive performance was assessed using the n-back task and continuous performance test. To evaluate melatonin, saliva was collected and tested by enzyme-linked immunosorbent assay. To assess sleep and sleepiness, the Pittsburgh Sleep Quality Index and Karolinska Sleepiness Scale were used, respectively. Results: Individuals who worked 7 consecutive night shifts had a significantly better cognitive performance and sleep quality than those who worked 4 consecutive night shifts. However, salivary melatonin profile and sleepiness trend were not affected by shift type. Conclusion: The main duty of CORs working night shifts at the studied industry included managing safety-critical processes through complex displays; a responsibility that demands good cognitive performance and alertness. It is suggested that an appropriate number of consecutive night shifts in a rotating shift system should be planned with the ultimate aim of improving CROs performance/alertness and enhancing safety.

A curtain traveling pluviator to reconstitute large scale sand specimens

Kazemi, Majid,Bolouri, Jafar B. Techno-Press 2018 Geomechanics & engineering Vol.14 No.2

The preparation of repeatable and uniformly reconstituted soil specimens up to the specified conditions is an essential requirement for the laboratory tests. In this study for large samples replication, the simultaneous usage of the traveling pluviation and curtain raining technique is used to develop a new method, called the curtain travelling pluviator (CTP). This simple and cost effective system is based on the air pluviation approach, whilst reducing the sample production time, can reproduce uniform samples with relative densities ranging from 25% to 96%. In order to investigate the resulting suitability and uniformity from the proposed method, a series of tests is performed. The effect of curtain traveling velocity, curtain width, drop height, and flow rate on the parameters of the sample is thoroughly investigated. Increase in the curtain velocity and drop height leads to the increase in relative density for the sand specimen. Increase in curtain width typically resulted in the reduction of relative density. Test results reveal that the terminal drop height for the sand specimen in this study is more than 500 mm. Relative density contour lines are presented that can be utilized in optimizing the drop height and curtain width parameters. Sample uniformity in the vertical and horizontal orientation is investigated through the sampling containers. Increasing relative density tends to result in the higher sample repeatability and uniformity.

H_∞ filter design for offshore platforms via sampled-data measurements

Kazemy, Ali Techno-Press 2018 Smart Structures and Systems, An International Jou Vol.21 No.2

This paper focuses on the $H_{\infty}$ filter design problem for offshore steel jacket platforms. Its objective is to design a full-order state observer for offshore platforms in presence of unknown disturbances. To make the method more practical, it is assumed that the measured variables are available at discrete-time instants with time-varying sampling time intervals. By modelling the sampling intervals as a bounded time-varying delay, the estimation error system is expressed as a time-delay system. As a result, the addressed problem can be transformed to the problem of stability of dynamic error between the system and the state estimator. Then, based on the Lyapunov-Krasovskii Functional (LKF), a stability criterion is obtained in the form of Linear Matrix Inequalities (LMIs). According to the stability criterion, a sufficient condition on designing the state estimator gain is obtained. In the end, the proposed method is applied to an offshore platform to show its effectiveness.

Selective Transport of Lead(II) through a Bulk Liquid Membrane Using a Cooperative Carrier Composed of Benzylaza-12-crown-4 and Oleic Acid

Kazemi, Sayed Yahya,Shamsipur, Mojtaba Korean Chemical Society 2005 Bulletin of the Korean Chemical Society Vol.26 No.6

A chloroform membrane system containing a given mixture of benzylaza-12-crown-4 and oleic acid is introduced for the selective and efficient transport of $Pb^{2+}$ ion. The transport was capable of moving metal ions ‘up-hill’. In the presence of ${S_2O_3}^{2-}$ion as a suitable metal ion acceptor in the receiving phase, the amount of lead ion transport across the liquid membrane after 150 minutes is (95.0 ${\pm}$ 1.7)%. The selectivity and efficiency of lead transport from aqueous solution containing $Tl^+,\;Ag^+,\;Mg^{2+},\;Ca^{2+},\;Co^{2+},$ $Ni^{2+},\;Cu^{2+},\;Zn^{2+},\;Hg^{2+}$ and $Cd^{2+}$were investigated. In the presence of thiosulfate as a suitable masking agent in the source phase, the interfering effects of $Ag^+\;and\;Cu^{2+}$ were diminished drastically.

High Velocity Impact Response of Basalt Fibers/Epoxy Composites Containing Graphene Nanoplatelets

E. Kazemi-Khasragh,F. Bahari-Sambran,M. Hossein Siadati,R. Eslami-Farsani 한국섬유공학회 2018 Fibers and polymers Vol.19 No.11

The effects of adding surface modified graphene nanoplatelets (GNPs) in various weight percentages (0, 0.1, 0.2, 0.3, 0.4, 0.5 with respect to matrix) on the high velocity impact response of basalt fibers/epoxy composites were evaluated. High speed mechanical stirrer and ultrasonic waves were used for the dispersion of GNPs in the epoxy matrix, and hand layup method was utilized for the fabrication of the composite samples. High velocity impact testing was performed using a conical projectile. The results demonstrated that the maximum improvement in the impact limit velocity and energy absorption occurred in the 0.3 wt.% GNPs nanocomposite, i.e., 11 and 23 %, respectively. Also, the electron microscopy studies revealed that the addition of GNPs contributed in improving the impact properties by influencing the matrix and thus enhancing the interfacial characteristics between the basalt fibers and the matrix.

Weight Cycling: To Be or Not To Be?

( Mohsen Kazemi ) 국제태권도학회 2017 International Symposium for Taekwondo Studies Vol.2017 No.-

Purpose: The objective of this study was to investigate the practice of weight cycling/cutting among Taekwondo athletes and its safety and appropriateness as a classification meth-od. Methods: A literature review was conducted using the STARLITE mnemonic (Sampling strategy, Type of study, Approaches, Range of years, Limits, Inclusion and exclusions, Terms used, Electronic sources). PubMed/MEDLINE, CINAHL, SPORTDiscus and Rehabilitation & Sports Medicine Source databases were searched using “Tae Kwon Do,” “Taekwondo,” “performance or winning,” and “weight”. The search was limited to human subjects and English language, peer reviewed articles (e.g., randomized controlled trials, review of literature, and cohort studies) and journals. There was no limitation with respect to the date of published papers included. Case studies were excluded from this review. Results: This search yielded 15 papers. A second search was conducted using, “Tae Kwon Do” or “Taekwondo AND weight,” which yielded 48 citations of which 10 papers were deemed to be relevant. A subsequent hand search revealed three more papers. There is an endemic problem of weight cycling among martial artists including Taekwondo (TKD) athletes in hope of increase chance of winning. The elite TKD athletes seemed to have better strategies in weight cycling than novice athletes. There has been no correlation between the amount of rapid weight loss (RWL) and winning, which may be a result of the recovery period between weigh-in and competition and the anaerobic nature of TKD. However, this does not eliminate the risks associated with RWL. To date, there are no guidelines or bylaws set by the World Taekwondo Federation (WTF) with regards to weight cycling and RWL. Conclusions: Monitoring weight loss program and prohibiting hazardous RWL practices must be instituted by the WTF for the safety of the athletes. Alternatively, utilizing the height category instead of weight would significantly decrease the practice of RWL and its ill effects on the athletes and provide a more even playing field with respect to competition in striking martial arts. Further investigation of this hypothesis is needed.