4,298 research outputs found

    Flexible body dynamic stability for high performance aircraft

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    Dynamic equations which include the effects of unsteady aerodynamic forces and a flexible body structure were developed for a free flying high performance fighter aircraft. The linear and angular deformations are assumed to be small in the body reference frame, allowing the equations to be linearized in the deformation variables. Equations for total body dynamics and flexible body dynamics are formulated using the hybrid coordinate method and integrated in a state space format. A detailed finite element model of a generic high performance fighter aircraft is used to generate the mass and stiffness matrices. Unsteady aerodynamics are represented by a rational function approximation of the doublet lattice matrices. The equations simplify for the case of constant angular rate of the body reference frame, allowing the effect of roll rate to be studied by computing the eigenvalues of the system. It is found that the rigid body modes of the aircraft are greatly affected by introducing a constant roll rate, while the effect on the flexible modes is minimal for this configuration

    A New Class of Life Distribution based on Laplace Transform and It’s Applications

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    Based on the approach of Laplace transform, a new class of life distributions called used better than aged in increasing concave denoted by (UBAC(2)L) is introduced. The implication of our proposed class of life distribution with other classes is given. Some properties of UBAC(2)L class of life distribution are studied. By using the goodness of fit methodology, a new test statistic is proposed for testing exponentiality versus UBAC(2)L class of life distribution. Critical values of our test are calculated for complete and censored data. The power of the test and pitman’s asymptotic efficiency (PAE) for some commonly used distributions in reliability are calculated. Finally, a set of real data is used as an example to elucidate the use of the proposed test statistic for practical reliability analysis

    A New Class of Life Distribution based on Laplace Transform and It’s Applications

    Get PDF
    Based on the approach of Laplace transform, a new class of life distributions called used better than aged in increasing concave denoted by (UBAC(2)L) is introduced. The implication of our proposed class of life distribution with other classes is given. Some properties of UBAC(2)L class of life distribution are studied. By using the goodness of fit methodology, a new test statistic is proposed for testing exponentiality versus UBAC(2)L class of life distribution. Critical values of our test are calculated for complete and censored data. The power of the test and pitman’s asymptotic efficiency (PAE) for some commonly used distributions in reliability are calculated. Finally, a set of real data is used as an example to elucidate the use of the proposed test statistic for practical reliability analysis

    Seismic Capacity of Reinforced Concrete Interior Flat Plate Connections

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    The demand for modular steel buildings (MSBs) has increased because of the improved quality, fast on-site installation, and lower cost of construction. Steel braced frames are usually utilized to form the lateral load resisting system of MSBs. During earthquakes, the seismic energy is dissipated through yielding of the components of the braced frames, which results in residual drifts. Excessive residual drifts complicate the repair of damaged structures or render them irreparable. Researchers have investigated the use of superelastic shape memory alloys (SMAs) in steel structures to reduce the seismic residual deformations. This study explores the potential of using SMA braces to improve the seismic performance of typical modular steel braced frames. The study utilizes incremental dynamic analysis to judge on the benefits of using such a system. It is observed that utilizing superelastic SMA braces at strategic locations can significantly reduce the inter-storey residual drifts

    STR-885: FINITE ELEMENT MODELLING OF COMPOSITE HOLLOWCORE SLABS

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    Hollowcore slabs are commonly used for floor and roofs of residential and commercial buildings. Concrete topping, which is commonly cast for leveling purposes, can also be used to increase the load capacity of hollowcore slabs. The post-cracking behaviour of hollowcore slabs greatly affects their ultimate strength. The composite action adds another level of nonlinearity. This paper presents a comprehensive 3-D finite element model that can predict the behaviour of such composite slabs. Nonlinear springs were used to model the interface layer. The nonlinear material behaviour of the concrete and the prestressing strands were also accounted for. Innovative analysis technique to simulate the staged construction of composite hollowcore slabs is also presented. The proposed analysis is validated using results from a previous experimental study by the authors

    Analytical Modeling of the Interface between Lightly Roughened Hollowcore Slabs and Cast-In-Place Concrete Topping

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    Hollowcore slabs are commonly used in different types of structures. They are usually topped with a 50 mm concrete topping. Structural engineers can use this topping to increase the slab load carrying capacity. North American design standards relate the horizontal shear strength at the interface between hollowcore slabs and the concrete topping to the slab surface roughness. This paper presents results of four push-off tests on hollowcore slabs supplied by two manufacturers and roughened using a conventional steel broom. The tested slabs sustained higher horizontal shear stresses than those specified by the design standards. Utilizing the data from the push-off tests, an analytical model was applied to evaluate the shear and peel stiffnesses, ks and kp, of the interface between hollowcore slabs and concrete topping. Structural engineers can utilize ks and kp values to model the composite action between hollowcore slabs from the two manufacturers and concrete topping. The analytical model was also used to evaluate the actual distribution of shear and peel stresses

    Ductile Corrosion-Free GFRP-Stainless Steel Reinforced Concrete Elements

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    Corrosion of steel rebars is known to cause deterioration of concrete structures that can lead to catastrophic failures. To mitigate this problem, steel rebars can be replaced with Glass Fiber-Reinforced Polymer (GFRP) rebars. However, the lack of ductility of GFRP-reinforced elements has prevented their use in many structural applications, especially in seismic areas. Stainless Steel (SS) rebars are corrosion resistant and have adequate energy absorption and ductility. However, they are much more expensive than steel rebars. This paper proposes the combined use of SS and GFRP rebars to achieve ductile and corrosion-free elements. The first challenge for such a proposal relates to designing SS-GFRP reinforced concrete frame with adequate lateral performance in terms of initial stiffness, ductility, and strength. Design equations, which are based on a comprehensive parametric study, are developed to allow designing such a frame. A six-storey concrete frame is then designed using the proposed equations and its lateral performance is examined using pushover analysis

    Spectrographic Estimation of Fe Mg Ca, Zn, Sb and Pb in Blood Serum

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