Experimental and numerical assessment of beam-column connection in steel moment-resisting frames with built-up double-I column

Seyed Mehdi Dehghan,Mohammad Amir Najafgholipour,Seyed Mohsen Ziarati,Mohammad Reza Mehrpour 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.26 No.3

Built-up Double-I (BD-I) columns consist of two hot rolled IPE sections and two cover plates which are welded by fillet welds. In Iran, this type of column is commonly used in braced frames with simple connections and sometimes in low-rise Moment Resisting Frames (MRF) with Welded Flange Plate (WFP) beam-column detailing. To evaluate the seismic performance of WFP connection of I-beam to BD-I column, traditional and modified exterior MRF connections were tested subjected to cyclic prescribed loading of AISC. Test results indicate that the traditional connection does not achieve the intended behavior while the modified connection can moderately meet the requirements of MRF connection. The numerical models of the connections were developed in ABAQUS finite element software and validated with the test results. For this purpose, moment-rotation curves and failure modes of the tested connections were compared with the simulation results. Moreover to avoid improper failure modes, some improvements of the connections were evaluated through a numerical study.

The different aspects of attractive toxic baits containing fipronil for control of the German cockroach (Blattella germanica)

Mehdi Khoobdel,Hossein Dehghan,Mohammad Ali Oshaghi,Esmail Amiri Ghannat Saman,Abouzar Asadi,Mustapha Ahmed Yusuf 환경독성보건학회 2022 환경독성보건학회지 Vol.37 No.4

The use of Attractive Toxic Baits (ATBs) is considered to be a low-risk practical method for controlling cockroaches. This study evaluates the attractiveness of a lab-made, fipronil-containing bait, and its effect on the food consumption and mortality of the German cockroach Blattella germanica, under field and laboratory conditions. Different developmental stages of the cockroach were used to determine their preferred carbohydrate/protein rich foods and examine the effectiveness of lab-made baits. The analysis of variance (ANOVA) with Tukey’s Test was determined using SAS 9.1 and GraphPad Prism software programs. The significance level was considered at p<0.05. The most-consumed foods were carbohydrate-rich foods (biscuit and banana powder) and food consumption rate was highest in non-gravid females. The most attractive bait ingredients were 20% roasted peanut butter, 50% biscuit and 30% banana powder. The highest lethality was recorded from the baits containing 0.02% fipronil under laboratory conditions, while infested houses baited with the lab-made bait showed 76.5% and 100% decline, respectively, in cockroach numbers in the first- and fourth-week post-baiting. In conclusion, palatable foods with a pleasant odour, like biscuit powder, banana powder and peanut butter were the most effective ingredients for the ATBs. The ATBs impregnated with 0.02% fipronil provide a promising approach for control of the German cockroach. However, there is a need to evaluate the potentials of the lab-made baits, under laboratory and field conditions, in the control of other health-important cockroaches.

Seismic response of built-up double-I column in steel moment resisting frame using welded external diaphragm plate

Amir Tabebordbar,Seyed Mehdi Dehghan,Farshid Fathi,Mohammad Amir Najafgholipour 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.41 No.5

Built-up Double-I (BD-I) columns have been commonly used for mid-rise steel-frame structures in Iran. These columns consist of two hot rolled IPE sections which are connected by two cover plates and fillet welds. Until 2017, BD-I columns were employed in intermediate moment resisting frames (MRF) using welded flange plate (WFP) connections. To evaluate the seismic behavior of the connections, four samples were made and tested based on cyclic loading according to AISC 341-16. It was concluded that typical samples cannot satisfy the seismic provisions related to intermediate MRFs. In contrast, the proposed connections retrofitted with two-part external diaphragms were able to satisfy not only the seismic requirements related to intermediate MRFs but also those related to special MRFs according to AISC. The numerical modeling of these samples was performed using ABAQUS finite element software. This study compared the hysteresis moment-rotation curves, plastic strains, and behavior modes in both experimental samples and numerical models.

Free vibration analysis of functionally graded cylindrical shells with different shell theories using semi-analytical method

Majid Khayat,Seyed Mehdi Dehghan,Mohammad Amir Najafgholipour,Abdolhossein Baghlani 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.28 No.6

In this study, the semi-analytical finite strip method is adopted to examine the free vibration of cylindrical shells made up of functionally graded material. The properties of functionally graded shells are assumed to be temperature-dependent and vary continuously in the thickness direction according to a simple power law distribution in terms of the volume fraction of ceramic and metal. The material properties of the shells and stiffeners are assumed to be continuously graded in the thickness direction. Theoretical formulations based on the smeared stiffeners technique and the classical shell theory with first-order shear deformation theory which accounts for through thickness shear flexibility are employed. The finite strip method is applied to five different shell theories, namely, Donnell, Reissner, Sanders, Novozhilov, and Teng. The approximate procedure is compared favorably with three-dimensional finite elements. Finally, a detailed numerical study is carried out to bring out the effects of power-law index of the functional graded material, stiffeners, and geometry of the shells on the difference between various shell theories. Finally, the importance of choosing the shell theory in simulating the functionally graded cylindrical shells is addressed.

Stereological study of testes following experimentally-induced unilateral cryptorchidism in rats

Javad Sadeghinezhad,Fatemeh Yarmahmoudi,Mohammad Mehdi Dehghan,Saeed Farzad Mohajeri,Ehsan Roomiani,Hadis Bojarzadeh,Mahdi Aghabalazadeh Asl,Ava Saeidi,Margherita De Silva The Korean Society for Reproductive Medicine 2023 Clinical and Experimental Reproductive Medicine Vol.50 No.3

Objective: Cryptorchidism is one of the main causes of infertility and can result in testicular cancer. This study aimed to present quantitative data on the damage caused by cryptorchidism using stereological analysis. Methods: Thirty newborn rats were randomly divided into control and experimental groups. The experimental group underwent surgery to induce unilateral cryptorchidism in the left testis, whereas the control group underwent a sham surgical procedure 18 days after birth. The testes were removed at designated time points (40, 63, and 90 days after birth) for stereological evaluation and sperm analysis. Total testicular volume, interstitial tissue volume, seminiferous tubule volume and length, and seminiferous epithelium volume and surface area were measured. Other parameters, such as sperm count, sperm morphology, and sperm tail length, were also examined. Results: Statistically significant differences (p<0.05) were observed between the experimental and the control groups at different ages regarding the volumes of various parameters, including the surface area of the germinal layer, the length of the seminiferous tubules, sperm count, and sperm morphology. However, no significant differences were observed in the epithelial volume and the sperm tail length of the groups. Conclusion: Given the substantial effect of cryptorchidism on different testicular parameters, as well as the irreversible damage it causes in the testes, it is important to take this abnormality seriously to prevent these consequences.

The influence of graphene platelet with different dispersions on the vibrational behavior of nanocomposite truncated conical shells

Majid Khayat,Abdolhossein Baghlani,Seyed Mehdi Dehghan,Mohammad Amir Najafgholipour 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.38 No.1

This work addresses the free vibration analysis of Functionally Graded Porous (FGP) nanocomposite truncated conical shells with Graphene PLatelet (GPL) reinforcement. In this study, three different distributions for porosity and three different dispersions for graphene platelets have been considered in the direction of the shell thickness. The Halpin–Tsai equations are used to find the effective material properties of the graphene platelet reinforced materials. The equations of motion are derived based on the higher-order shear deformation theory and Sanders’s theory. The Fourier Differential Quadrature (FDQ) technique is implemented to solve the governing equations of the problem and to obtain the natural frequencies of the truncated conical shell. The combination of FDQ with higher-order shear deformation theory allows a very accurate prediction of the natural frequencies. The precision and reliability of the proposed method are verified by the results of literature. Moreover, a wide parametric study concerning the effect of some influential parameters, such as the geometrical parameters, porosity distribution, circumferential wave numbers, GPLs dispersion as well as boundary restraint conditions on free vibration response of FGP-GPL truncated conical shell is also carried out and investigated in detail.

Predictors and Outcomes of Vitrectomy and Silicone Oil Injection in Advanced Diabetic Retinopathy

Alireza Ramezani,Hamid Ahmadieh,Amin Rozegar,Masoud Soheilian,Morteza Entezari,Siamak Moradian,Mohammad H Dehghan,Homayoun Nikkhah,Mehdi Yaseri 대한안과학회 2017 Korean Journal of Ophthalmology Vol.31 No.3

Purpose: To evaluate visual and anatomical results and identify factors that influence vitrectomy and silicone oil(SO) injection outcomes in proliferative diabetic retinopathy (PDR). Methods: This retrospective study included 236 eyes with PDR that were undergoing vitrectomy and SO injectionwith >3-month follow-up. The primary outcomes were final best-corrected visual acuity (BCVA) and retinalattachment rate. Results: At the final visit (mean, 88 ± 58 weeks), complete, partial, and no retinal attachment were observed in86.9%, 10.6%, and 2.5% of patients, respectively. A total of 155 eyes had experienced SO removal, while 81had SO in place. The mean initial BCVA was 1.9 ± 0.7 logarithm of the minimum angle of resolution (logMAR)and significantly improved to 1.7 ± 0.8 logMAR (p = 0.001). Initial macular detachment (adjusted odds ratio[AOR], 0.25), development of iatrogenic break (AOR, 0.25), and use of heavy SO (AOR, 0.13) were independentlyassociated with a lower risk of final retinal attachment, and SO removal was associated with a higherincidence (AOR, 7.55). Better baseline BCVA was associated with a higher risk of final BCVA ≥20 / 200. Conclusions: Despite an encouraging outcome based on anatomical data in advanced PDR treated with vitrectomyand SO, the functional prognosis was not satisfying for patients. Eyes with better vision at baseline hada more favorable prognosis, whereas eyes with initial macular detachment, intraoperative iatrogenic break, orheavy SO showed more unfavorable outcomes. In selected cases, extending the time of SO use did not worsenthe prognosis.