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جستجوی مقالات مرتبط با کلیدواژه « simply supported » در نشریات گروه « عمران »

تکرار جستجوی کلیدواژه «simply supported» در نشریات گروه «فنی و مهندسی»
  • معصومه سلطانی *، بهروز عسگریان
    تیرهای جدار نازک المان بسیار مهمی در سازه های فولادی هستند. در این اعضا، با توجه به نحوه بارگذاری جانبی و همچنین بر اساس تقارن و یا عدم تقارن سطح مقطع عضو، امکان وقوع کمانش جانبی-پیچشی وجود دارد. لذا در این پژوهش به بررسی پایداری تیرهای جدار نازک با نیم رخ نامتقارن در برابر کمانش جانبی-پیچشی پرداخته شده است. بدین منظور، در اولین گام در تحلیل پایداری جانبی تیرها، با استفاده از روابط حاکم بر تغییر شکل اعضای جدار نازک و اصل پایستگی انرژی پتانسیل، معادلات دیفرانسیل تعادل تیر با سطح مقطع نامتقارن تحت بارگذاری جانبی تعیین می گردد. معادلات پایداری جانبی بدست آمده در حضور پارامترهای لنگر خمشی، نامتقارنی سطح مقطع و زاویه پیچش، یک دستگاه معادلات دیفرانسیل وابسته است. سپس با استفاده از شرایط مرزی حاکم بر خمش، معادله تعادل پیچش مستقل گشته و معادله دیفرانسیل مرتبه چهار با ضرایب متغیر حاصل شده تنها وابسته به پارامتر تغییر شکل پیچشی عضو جدار نازک خواهد بود. در ادامه، با استفاده از روش عددی تقریبی اختلاف محدود مرکزی و فرضیات حاکم بر این روش معادله دیفرانسیل مرتبه چهار بدست آمده حل می گردد و در نهایت، با توجه به شرایط مرزی حاکم بر تیرهای دو سر مفصل و با استفاده از روش حل مقادیر ویژه مقدار بار بحرانی کمانش محاسبه می شود. نتایج بدست آمده از روش معرفی شده با مقادیر ارائه شده توسط محققان دیگر و مقادیر حاصله از نرم افزار Ansys مقایسه گشته اند.
    کلید واژگان: تیرهای جدار نازک, بار کمانش جانبی-پیچشی, نیم رخ نامتقارن, تیر دوسر مفصل, روش اختلاف محدود}
    M. Soltani *, B. Asgarian
    In this paper, the lateral-torsional stability of simply supported thin-walled beams with mono-symmetric section subjected to bending loads has been studied by means of a numerical method based on the finite difference method (FDM). To fulfill this purpose, the equilibrium equations for elastic thin-walled members with linear behavior are derived from the stationary condition of the total potential energy. In the applied energy method, effects of initial stresses and load eccentricities from shear center of cross-sections are also considered. Finite difference method is one of the most powerful numerical techniques for solving differential equations especially with variable coefficients. Between various computational methods to solve the equilibrium equation, finite difference method requires a minimum of computing stages and is therefore very suitable approach for engineering analysis where the exact solution is very difficult to obtain. The main idea of this method is to replace all the derivatives presented in the governing equilibrium equation and boundary condition equations with the corresponding central finite difference expressions. Finally, the critical buckling loads are then derived by solving the eigenvalue problem. In order to present the accuracy of the proposed method, several numerical examples including lateral-torsional behavior of prismatic beams with mono-symmetric sections are considered. In order to illustrate the correctness and performance of FDM, the evaluated results are compared to the finite element simulations and other available methods.
    Keywords: Thin-Walled Beams, Lateral-Torsional Buckling, Mono-Symmetric Sections, Simply Supported, Finite Difference Method}
  • P. Markandeya Raju *, G. V. Rama Rao, G. Himala Kumari, E. Gowthami
    The first step in the design of plate girder is to estimate the self-weight of it. Although empirical formulae for the same are available, the level of their accuracy (underestimate or overestimate) with respect to actual self-weight is not known. In this paper, optimized sections are obtained for different spans subjected to different live load carrying capacities and self-weights are estimated. EXCEL solver, which adopts Reduced Gradient Method (RGM) was applied for optimization. The objective function was chosen as Cross-sectional area with twelve constraints based on LRFD (IS 800: 2007) design specification for safety and serviceability. Simply supported (laterally restrained) plastic symmetric cross section without stiffeners is adopted for study. A mathematical model was developed based on best-fit curves between self-weight, span and live load carrying capacity and their trend line equations are obtained. The study revealed that, the ratio of self-weight to load carrying capacity was parabolic for a given span. The results from this equation are compared with the conventional formula and the standard deviation of the proposed model with respect to actual self-weight is in the range of -0.03 to 2.29 while that from the conventional model is in the range of -0.04 to 9.18.
    Keywords: symmetrical, plate girder, optimization, simply supported, excel solver, self, weight, load carrying capacity, constraints, plastic section, laterally restrained}
  • M. Raju Ponnada*, R. Sandeep Thonangi
    Pre-stressing is becoming a most common and indispensable technique in the recent past for beams and girders in buildings and bridges. This paper presents the application of Finite Difference Method (FDM) for finding deflections in Pre-Stressed Concrete (PSC) beams with non-prismatic sections. Equations are derived for dead and live load bending moment, eccentricity, and depth at any required section. Based on these equations, it is initially established that conventional techniques cannot be adopted for finding deflections in pre-stressed concrete beams with non-prismatic cross-sections and hence FDM was adopted as an alternative. The calculated deflections using FDM are compared with those obtained from equivalent STAAD.Pro. Model and they found to be in close agreement.
    Keywords: Deflection, non, prismatic, serviceability, prestressing, FDM, double integration, simply supported}
  • M. Raju Ponnada, R. Vipparthy
    Prestressing steel has been popular in the recent past, due to the developments in the field of anti-corrosive coatings. The literature substantiates the application of technique of prestressing to steel structures both in safety and economy point of view. However, for all design calculations, the maximum allowable span for a given load carrying capacity is based on maximum deflection which is calculated by principle of superposition (considering the effect of prestress and total load individually). This paper proposes a method of arriving at expression for deflection of simply supported, prestressed homogenous steel I-beams calculated by considering the combined effect of prestressing and total load. A straight tendon configuration with an eccentric prestressing force is considered for study.
    Keywords: Deflection, prestressed steel, superposition, pure bending, load carrying capacity, simply supported, homogenous}
  • M. Raju Ponnada, R. Vipparthy
    Prestressing steel has been popular in the recent past, due to the developments in the field of anti-corrosive coatings. The literature substantiates the application of technique of prestressing to steel structures both in safety and economy point of view. However, for all design calculations, the maximum allowable span for a given load carrying capacity is based on maximum deflection which is calculated by principle of superposition (considering the effect of prestress and total load individually). This paper proposes a method of arriving at expression for deflection of simply supported, prestressed homogenous steel I-beams calculated by considering the combined effect of prestressing and total load. A straight tendon configuration with an eccentric prestressing force is considered for study.
    Keywords: Deflection, prestressed steel, superposition, pure bending, load carrying capacity, simply supported, homogenous}
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