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EXACT SOLUTION FOR TEMPERATURE-DEPENDENT BUCKLING ANALYSIS OF FG-CNT-REINFORCED MINDLIN PLATES ABSTRACT: This research deals with the buckling analysis of nanocomposite polymeric temperature-dependent plates reinforced by single-walled carbon nanotubes (SWCNTs). For the carbon-nanotube reinforced composite (CNTRC) plate, uniform distribution (UD) and three types of functionally graded (FG) distribution patterns of SWCNT reinforcements are assumed. The material properties of FG-CNTRC plate are graded in the thickness direction and estimated based on the rule of mixture. The CNTRC is located in a elastic medium which is simulated with temperature-dependent Pasternak medium. Based on orthotropic Mindlin plate theory, the governing equations are derived using Hamilton’s principle and solved by Navier method. The influences of the volume fractions of carbon nanotubes, elastic medium, temperature and distribution type of CNTs are considered on the buckling of the plate. Results indicate that CNT distribution close to top and bottom are more efficient than those distributed nearby the mid-plane for increasing the stiffness of plates. منبع دانلود EXACT SOLUTION FOR.pdf

PREDICTING THE BUCKLING CAPACITY OF STEEL CYLINDRICAL SHELLS WITH RECTANGULAR STRINGERS UNDER AXIAL LOADING BY USING ARTIFICIAL NEURAL NETWORKS Z. Kalantari and M. S. Razzaghi Abstract A parametric study was carried out in order to investigate the buckling capacity of the vertically stiffened cylindrical shells. To this end ANSYS software was used. Cylindrical steel shells with different yield stresses, diameter-to-thickness ratios (D/t) and number of stiffeners were modeled and their buckling capacities were calculated by displacement control nonlinear static analysis. Radial basis function (RBF) neural networks were used to predict the buckling capacity of shells. Herein 70 percent of the results of numerical analyses were used to train the neural network and the remainders were used to test and validate the results of neural networks. Results of this study showed that RBF neural networks are useful tools to predict the buckling capacity of vertically stiffened cylindrical shells. It was also shown that buckling capacities of stiffened shells exponentially vary by distance of adjacent stiffeners (unstiffened length). Keywords Buckling, cylindrical shells, stiffener, Artificial Neural Networks چکیده به منظور بررسی ظرفیت کمانش پوسته های مطالعات پارامتریک پوسته های استوانه ای با سخت کننده های قائم، مطالعات پارامتریک به انجام رسید. برای این منظور از نرم افزار ANSYS استفاده شد. پوسته ای استوانه ای فولادی با تنش جاری شدن، نسبت ارتفاع به قطر و تعداد سخت کننده های گوناگون مدلسازی شدند و ظرفیت کمانش آنها با استفاده از تحلیل استاتیکی غیر ارتجاعی با کنترل تغییر مکان محاسبه شد. به منظور پیش بینی ظرفیت محوری کمانش از شبکه عصبی RBF استفاده شد. برای این منظور هفتاد درصد از نتایج خروجی تحلیل های عددی برای آموزش شبکه استفاده شدند و مابقی برای تست و صحت سنجی نتایج کنار گذاشته شدند. نتایج این پژوهش نشان می دهد، شبکه های عصبی RBF ابزاری مناسب برای پیش بینی ظرفیت کمانش پوسته های استوانه ای با سخت کننده قائم هستند. علاوه بر این نشان داده شد که تغییرات ظرفیت کمانش پوسته ها با فاصله سخت کننده های مجاور (طول مهار نشده) به صورت نمایی تغییر می کند. منبع دانلود 28-8-7.pdf

Buckling of Stiffened Thin-Walled Cylindrical Shells under Axial Compression with Symmetrical Imperfections Armin A.NobakhtNamin This study aimed to investigate the effects of stiffeners on buckling of thin cylindrical shells under uniform axial compression. To this end, more than 300 finite element models of stiffened cylindrical shells were prepared. The variables considered are shell thickness, number, dimension and the location of the vertical and horizontal stiffeners as well as circular symmetrical imperfections. Results show that the stiffeners can increase buckling of the stiffened cylindrical shells under axial compression. It is also shown that buckling of the cylindrical shells is susceptible to some circular imperfection patterns. In this context, buckling graph of the models are compared with each other; obviously, the stiffened shells with more stiffeners have upper buckling graph in force - displacement curves. منبع دانلود JSEG281354307400.pdf

Validated finite element techniques for quasi-static cyclic response analyses of braced frames at sub-member scales M. Lotfollahi a,1, M.M. Alinia a,2, E. Taciroglu b,⇑,2 a Department of Civil Engineering, Amirkabir University of Technology, Tehran, Iran b Department of Civil and Environmental Engineering, University of California, Los Angeles, CA 90095, USA a b s t r a c t In this study, a numerically robust finite element procedure is described, which is based on explicit time-stepping, for high-fidelity simulations of inelastic and post-buckling cyclic responses of braced frame systems. The use of an explicit time-stepping method with properly chosen increments permits accurate results while avoiding (implicit) equilibrium iterations throughout the entire loading history, during which multiple yielding and buckling events occur. A number of essential techniques for properly calibrating the discrete models and to constrain their responses in order to obtain quasi-static outcomes are provided. The procedure is globally and locally validated (verified) using experimental data (implicit numerical simulations) from three types of specimens—namely, individual braces, and single and multi-story braced frame systems with diagonal and X-brace arrangements—under both monotonic and cyclic loading protocols. Results from these validation and verification studies indicate that the proposed simulation methodology can accurately capture sub-member (i.e., plastic hinges), member, and system behavior very accurately; and thus, it can be confidently used—e.g., as a virtual laboratory—to predict the responses of braced frames with configurations and dimensions other than those tested, and to seek optimum designs beyond those offered by basic guidelines. 2015 Elsevier Ltd. All rights reserved. Keywords: Finite element verification and validation Dynamic explicit analysis Static implicit analysis Quasi-static solution Buckling Braced frame systems Cyclic loading [Hidden Content] gh.part1.rar gh.part2.rar