End Conditions Research Articles

Free vibration and buckling of heavy column with regular polygon cross-section

This paper deals with the free vibration and buckling of heavy column, considering its own self-weight. The column has a regular polygonal cross-section with a constant area. The column is applied to an external axial load as well as the self-weight. The five end conditions of the column are considered. Based on equilibrium equations of the column element, differential equations governing the vibrational and buckled mode shapes of column are derived. In solution methods, differential equations are numerically integrated by the direct integration method and eigenvalues of the natural frequency, buckling load and self-weight buckling length are calculated by the determinant search method. The numerical results of this study were in good agreement with those of the reference. Parametric study of the end condition, side number and self-weight on the natural frequency and buckling load was carried out.

Real-time measurement of stave thickness in a blast furnace using sacrificial ultrasonic waveguide

ABSTRACT A stave cooling system is a key element in the blast furnace which protects the outer shell from heat by providing uniform cooling. Real-time condition assessment of staves is essential to understand the wear mechanism of staves. Inspection rod/waveguide of known length which is made of copper was inserted through the steel shell till the inner end of the stave where the waveguide is susceptible to reduce in length as stave erodes with time. FEM analysis was done to find the ultrasonic parameters and lab-scale trials were taken on artificial waveguides with different end conditions. Based on the results, an ultrasonic-based real-time thickness measurement system was developed to continuously measure the length of the inspection rod/waveguide which eventually represents the stave thickness. System was installed in the plant, the data was captured and shown for 60 days from the date of the installation with an accuracy of more than 98%.

Vibration analysis of an axially functionally graded material non-prismatic beam under axial thermal variation in humid environment

The vibration analysis of an axially functionally graded material non-prismatic Timoshenko beam under axial thermal variation in humid environment is carried out using the harmonic differential quadrature method. In this modeling, the length and width of the beam remains constant whereas thickness of the beam is linearly varied along the axis of the beam. The material properties are temperature dependent and are assumed to be varied continuously along the axial direction according to power law distribution. Three types of temperature variations are considered in this study, that is, uniform temperature rise, linear temperature rise, and non-linear temperature rise. The temperature of the beam remains constant under uniform temperature rise condition and it is varied linearly and nonlinearly along the length of beam for rest of the conditions. The beam is subjected to uniform moisture concentration to impose humidity. Hamiltonian’s approach is used to derive the governing equations of motion. The resultant governing equations are then solved using the harmonic differential quadrature method to obtain the natural frequencies of the axially functionally graded material non-prismatic beam. The results obtained using the harmonic differential quadrature method are compared with results obtained for special cases. The effects of thermal variation, humidity, non-homogeneity parameter, and end conditions on natural frequencies of the non-prismatic beam are reported.

Free and forced vibration of double beam with arbitrary end conditions connected with a viscoelastic layer and discrete points

The Double-Beam System with Intermediate Supports composed of two parallel beams, arbitrary intermediate supports, and an optional interconnecting viscoElastic Layer (DBS-ISEL) has many engineering applications. However, few publications have developed the exact and explicit mode shape solutions of free vibrations of the DBS-ISEL by far, and the forced vibrations of the DBS-ISEL are not systematically treated. In this work, the free and forced vibrations of the general configuration of the DBS-ISEL under the general boundary conditions are systematically attacked. An analytical solution in closed-form is formulated based on the orthogonality conditions of the mode shape solutions. A general numerical solution is also presented. Numerical examples are demonstrated to show that the proposed solution agrees well with the literature. For the damped vibrations, the asymptotic deflections of the two beams converge to the static deflections. The parametric study shows that the intermediate elastic support could effectively modulate the deflections of the beams. This research is beneficial to the designing, monitoring and maintaining of the DBS-ISEL.

EXPERIMENTAL AND ANALYTICAL STUDY ON THE IMPACT BEHAVIOR OF STEEL–CONCRETE COMPOSITE SLAB

Concrete structures have been widely used for many years to resist impact loads. Steel–concrete composite structures may be considered efficient structures in the emerging modern construction field. Hence, the main objective of this research was to study the impact behavior of steel concrete composite slabs with different shear connectors and compare them with conventional slabs. Seven specimens of dimensions 500 × 500 × 50 mm were cast, which included plain cement concrete slabs, two reinforced cement concrete slabs with steel mesh and steel rebars as reinforcement, and four steel-concrete composite slabs with four different shear connectors: stud, tee, angle, and channel connectors. The composite action was achieved using a steel decking sheet welded with connectors on which the concrete layer was poured at the top. The test setup was fabricated with slots provided for specimens with simply supported end conditions and a mild steel drop weight. The specimens were impacted at the center of the span by dropping a steel mass from a free fall height of 1 m. The number of blows corresponding to the initial cracking and ultimate failure stages was recorded. The parameters that were used to compare the specimens were the impact energy absorbed, crack pattern, crack width, and increase in impact energy from the first blow to the last blow. The experimental results were very close to the analytical results obtained using ANSYS. The experimental and analytical results showed that the composite slabs with channel connectors performed better than the others, and it was proven that the composite slabs performed better under impact loading than conventional slabs.

The effect of end condition on spine segment biomechanics in compression with lateral eccentricity

During axial impact compression of the cervical spine, injury outcome is highly dependent on initial posture of the spine and the orientation, frictional properties and stiffness of the impact surface. These properties influence the “end condition” the spine experiences in real-world impacts. The effect of end condition on compression and sagittal plane bending in laboratory experiments is well-documented. The spine is able to escape injury in an unconstrained flexion-inducing end condition (e.g. against an angled, low friction surface), but when the end condition is constrained (e.g. head pocketing into a deformable surface) the following torso can compress the aligned spine causing injury. The aim of this study was to determine whether this effect exists under combined axial compression and lateral bending.Over two experimental studies, twenty-four human three vertebra functional spinal units were subjected to controlled dynamic axial compression at two levels of laterally eccentric force and in two end conditions. One end condition allowed the superior spine to laterally rotate and translate (T-Free) and the other end condition allowed only lateral rotation (T-Fixed). Spine kinetics, kinematics, injuries and occlusion of the spinal canal were measured during impact and pre- and post-impact flexibility.In contrast to typical spine responses in flexion-compression loading, the cervical spine specimens in this study did not escape injury in lateral bending when allowed to translate laterally. The specimen group that allowed lateral translation during compression had more injuries at high laterally eccentric force, saw greater peak canal occlusions and post-impact flexibility than constrained specimens.

Numerical Study on Buckling Resistance of Uniaxially Compressed Laminates Containing V-Shaped Edge Notch

The purpose of this study is to investigate the impact of a V-shaped cutout on the buckling strength of E-glass epoxy composite laminates. In aircraft components, cutouts are more often used for inspection, ventilation, access to critical areas, fitting a particular component, and increasing the strength to weight ratio of the structure. In this paper, symmetric and antisymmetric laminates of E-Glass/Epoxy unidirectional are used and the effect of notch parameters such as notch radius(r), depth of the notch(h), and notch angle(α) is observed under monoaxial compression. Effects of end conditions and plate aspect ratio(l/b) are analyzed. It is observed that the notch radius does not have a considerable effect on buckling strength but the notch angle after 90⁰ shows a good dip in buckling loads as compared to 30⁰,45⁰, and 60⁰. Depth of notch and end conditions creates a considerable loss in buckling strength. As the h/b ratio is increased, the drop in buckling strength becomes significant. Clamped -pinned end condition of the plate gives a lower value of load multiplier as compared to clamped -clamped. As we increase the l/b ratio of the plate, buckling of the plate becomes easier. The position of the notch (a) also affects buckling strength which is maximum for a/l=0.25 and minimum for a/l=0.5.

Weakening-induced Snap Instability as a Novel Reusable Force Protection Mechanism

We present a novel reusable force protection mechanism equipped with snap instability that is induced by weakening boundary conditions. The geometry of the proposed structure comprises one column and two flanges attached to its ends, and it allows the structural end conditions can alter between fixed supports and pinned supports. Switching between the fixed and the pinned supports results in elastic snap instabilities and it enables the structure to possess asymmetric equilibrium paths, whose loading and unloading paths are different. These snap instabilities induce hysteresis in the load-displacement curve, and external energy is converted in form of dynamic motion. After removing the external force, the structure elastically recovers to its initial configuration so that it can repeat the same force protection process. We report a combination of desktop-scale experiments, finite element simulations, and the Elastica analysis to explore the underlying mechanism of the unique structural behavior of the proposed structure. Given that the proposed reusable force protection mechanism exploits elastic instability, our study opens the possibility for practical applications over a wide range of length scales.

ANALYTICAL SOLUTION FOR NONLINEAR INTERACTION OF EULER BEAM RESTING ON A TENSIONLESS SOIL

The nonlinear interaction between an elastic Euler beam and a tensionless soil foundation is studied. Exact analytical solutions of the challenging problem are rather complicated. The basic obstacle is imposing compatibility conditions at lift-off points. These points are determined as a part of the solution although being needed to get the solution itself. In the current work, solutions are derived using the approximate Rayleigh-Ritz method. The principal of vanishing variation of potential energy is adopted. The solution is approximated using a set of suitable trial functions. Lift-off points are identified through an iterative procedure and compatibility conditions are satisfied implicitly. Results are presented for various cases, including clamped support and free end condition. Various distributed loading conditions are analyzed. Exact solutions are revised briefly. Accurate high order approximate analytical solutions are obtained using MAXIMA symbolic manipulator. The convergence of approximate solutions towards the exact solutions is verified. For each case detailed results of deflection, bending moment and shear are presented.

Stiffness of Rubber Bearings Considering Nonstandard Top and Bottom Boundary Conditions

AbstractTypical installations of seismic isolation assume flexurally rigid end conditions; however, in retrofit scenarios where bearings may be placed at the tops of columns or in bridges with tall...

Investigation on Flexural Behaviour of Cold Formed Latticed Built-Up Beam

There are two structural members used in steel construction the hot rolled members and the cold formed members. They are light members compared to the traditional heavier hot rolled steel structural members used in the field. They have high strength to weight ratio resulting in less dead weight making it a good option in construction of bridges roof trusses transmission line towers multi storied buildings and other structural members. This paper is done to understand the flexural capacity and to enhance it by developing innovative latticed cold formed steel beam. The impact of web opening of the cold formed beam on the flexural behavior of cold formed built-up I section under two point loading is investigated for the simply supported end conditions. Numerical analysis is performed using finite element analysis (FEM) software. From results, the load vs. Deflection curve, failure modes and ultimate load carrying capacity of the specimen presented in this paper. Therefore the main focus of this project is to investigate the flexural behavior of these steel members and by replacing the lattice hot rolled section by cold formed steel sections. The ultimate load carrying capacity with failure mode of simulated FEA models was compared with experimental results.

Splines solutions of boundary value problems that arises in sculpturing electrical process of motors with two rotating mechanism circuit

This study manages the numeric roots of the 7th-order linear & nonlinear boundary value problems(BVPs) utilizing another CB(Cubic-B) spline strategy. Cubic Spline interpolation is a different type of spline interpolation which is utilized very frequently to escape the problem of Runge’s phenomenon. That technique provides an interpolating polynomial which is evener and has lesser error than former interpolating polynomials such as Lagrange polynomial and Newton polynomial. The primary thought is that we have altered the BVPs to deliver another framework arrangement of linear equations. We develop the class of numerical techniques for a particular selection of the factors that are associated with CB Spline. The end conditions associated with the BVPs are determined. For each problem, the results obtained by CB Spline is compared with the exact solution. The absolute error(AE) for every iteration is calculated. To show the higher level of preciseness of CB Spline, the absolute errors of the CB Spline has been compared with different techniques such as Modified Decomposition Method(MDM), Differential Transform Method(DTM), Homotopy Perturbation Method(HPM), Variational Iteration technique(VIT) and observed to be more accurate. Graphs that describe the graphical comparison of CB Spline at n = 5 and n = 10 are also included in this paper. The calculation created here isn’t just for the numeric roots of the 7th-order BVPs. It also evaluates the derivative to the 7th-order derivative of the specific solution. A few models are represented, which depicting the practicality and capability of the suggested conspire.

Theoretical and methodological approach to the study of technological processes

The article investigates some issues of complex systems analysis and synthesis that contain local, discrete sources of temperature fields. The emphasis of the author's research lies in the calculation and optimization of the parameters of the laser action on the embryo. The biotechnological process is described by the boundary value problem of a non-stationary, multidimensional differential equation of thermal conductivity which satisfies the boundary conditions of heat flux, beginning and end of the laser action process. The author proposes an algorithm for calculation and optimization of the control parameters of laser action on multilayer microbiological material. The object of the study is the embryo under the action of a laser beam for fission. As a first approximation, at the stage of calculation and optimization of the parameters of the biotechnological process, the embryo is considered as a homogeneous body. The values of thermophysical characteristics are calculated by the method of expert evaluation of the parameters of the emitters. The correctness of the boundary value problem of the process of laser action on the embryo is proved by the author using the method of pseudodifferential operators. Seeking the solution of the boundary value problem in the form of the series, the analytical function of the temperature field distribution is obtained using the Fourier method of the separated variables in the article. Using the method of indeterminate coefficients, the author found the temperature of the laser action on the embryo. Using the approximate gradient method of finding local extrema and the method of directed search of local extrema, it is possible to obtain rational values of optimized parameters of the biotechnological process. The author outlines possible approaches for optimization of technical parameters of laser emitters. In his opinion, the results of research can be considered fundamental for the calculation and optimization of the parameters of the laser action on the embryo, taking into account the multilayer structure of the latter.

Experimental and numerical investigation of fixed-height cold-formed steel wall assemblies bearing on concrete slabs

Cold-formed steel bearing walls are frequently installed on concrete slabs, which do not provide perfectly rigid and uniform conditions. However, existing design guidance assumes bearing condition has no impact on axial capacity, though cold-formed steel compressive members are particularly susceptible to these end conditions. Additionally, studs are typically installed at the edge of the concrete slab, which is prone to spalling and geometric irregularities, and stud walls are occasionally installed inadvertently overhanging from them. In this paper, the impact of non-uniform and partial bearing conditions on the axial strength of cold-formed steel (CFS) wall assemblies is identified and characterized experimentally and numerically. Studs of various cross-sections and bearing conditions were considered. Bearing conditions include: full bearing (edge distance ≥ 20.32 cm (8 inches)), close to the edge, at the edge, and partially overhanging from the slab. In addition to the experiments, high-fidelity finite element modeling of all the systems was conducted to validate the experimental results and elucidate the impact of parameters not captured during the tests. The results provide a means of evaluating existing design guidelines presented in the North American Specification of the American Iron and Steel Institute (AISI S100-16). Twenty-seven tests were conducted on CFS wall assemblies. They reveal that there is a potential need for improvement of current AISI specifications, where all bearing conditions are assumed rigid and uniform. Design recommendations for improving the current specification are discussed.

Development and Validation of a Useful Taxonomy of Patient Portals Based on Characteristics of Patient Engagement.

Objective Taxonomies are classification systems used to reduce complexity and better understand a domain. The present research aims to develop a useful taxonomy for health information managers to classify and compare patient portals based on characteristics appropriate to promote patient engagement. As a result, the taxonomy should contribute to understanding the differences and similarities of the portals. Further, the taxonomy shall support health information managers to more easily define which general type and functionalities of patient portals they need and to select the most suitable solution offered on the market. Methods We followed the formal taxonomy-building method proposed by Nickerson et al. Based on a literature review, we created a preliminary taxonomy following the conceptional approach of the model. We then evaluated each taxa's appropriateness by analyzing and classifying 17 patient portals offered by software vendors and 11 patient portals offered by health care providers. After each iteration, we examined the achievement of the determined objective and subjective ending conditions. Results After two conceptional approaches to create our taxonomy, and two empirical approaches to evaluate it, the final taxonomy consists of 20 dimensions and 49 characteristics. To make the taxonomy easy to comprehend, we assigned to the dimensions seven aspects related to patient engagement. These aspects are (1) portal design, (2) management, (3) communication, (4) instruction, (5) self-management, (6) self-determination, and (7) data management. The taxonomy is considered finished and useful after all ending conditions that defined beforehand have been fulfilled. We demonstrated that the taxonomy serves to understand the differences and similarities by comparing patient portals. We call our taxonomy “Taxonomy of Patient Portals based on Characteristics of Patient Engagement (TOPCOP).” Conclusion We developed the first useful taxonomy for health information managers to classify and compare patient portals. The taxonomy is based on characteristics promoting patient engagement. With 20 dimensions and 49 characteristics, our taxonomy is particularly suitable to discriminate among patient portals and can easily be applied to compare portals. The TOPCOP taxonomy enables health information managers to better understand the differences and similarities of patient portals. Further, the taxonomy may help them to define the type and general functionalities needed. But it also supports them in searching and comparing patient portals offered on the market to select the most suitable solution.

Analysis of Propellant Weight under Re-Entry Conditions for a Reusable Launch Vehicle Using Retropropulsion

In this study, a minimum amount of required propellant was calculated by analyzing the sequence with various re-entry conditions. This study aims to obtain data related to variation in trajectory and required propellant weight according to various re-entry scenarios. The drag coefficient at various altitudes, velocities, and thrust was calculated through numerical simulations to raise the reliability of the results. The calculation results were compared to the optimal values extracted from the genetic algorithm. It was observed that the duration of the entry-burn phase is dominant to the total required propellant weight. As a general tendency, high entry-burn starting altitude, high ending Mach number, and low landing-burn starting thrust make the required propellant weight low. However, if the entry-burn ending condition is set to the Mach number, it is necessary to select an appropriate re-entry condition. Additionally, from comparisons with the optimized results, it was confirmed that accurate calculation of the drag coefficient is important to succeed a soft landing of RLV.

Compatability Behaviour on Cold Formed Steel for I Section and C Section in Variable Parameters

This Study represents compatibility on Cold formed steel in I-Section beams and C-section beams with variable length parameters was 1000mm, 1500mm, 2000 mm under simply supported end condition subjected to uniformly distributed loading. The Cold formed steel is of shell type in Numerical simulation is carried out using the Software ABAQUS. For validation the series of parameters studies have been carried out using the numerical model of different parameters, such as the effect of length, width, thickness. CFS I-Section steel in various thickness of 1mm, 2mm, 3mm and 4mm with same loading conditions. CFS C-Section steel in various uneven flange width such as 500mm at the top flange and bottom flange of different width such as 400mm, 300mm, 200mm respectively in variable lengths with various loading conditions and with the thickness of about 1mm. For both I-Section and C-Section Beams the Effective Length ranges, MISES(max and min) and deflections(max and min) were taken for the analyse of the Sections. This study gives the way of finding the effective Section by the analysis of behaviour of I-Section beam and C-Section beam through the deflection results in various length variations in the beam Section using the ABAQUS software for finding the Structural behaviour in the more accuracy manner by applying meshing more finer for the Element Section in the Analyse of beam. The loading condition and the supporting condition applied to the beam section in different loading for getting the effective Section. For further stability in effective section we can use different types of connection.

Analysis of RLW and MRLW equation using an improvised collocation technique with SSP-RK43 scheme

In this work, the regularized and the modified regularized long wave equations are solved using an improvised cubic B-spline collocation technique. Posteriori corrections are made in the cubic B-spline interpolant by forcing it to satisfy some specific interpolatory and end conditions, which results in the formation of improvised B-spline collocation technique. For temporal domain discretization, strong stability preserving Runge–Kutta scheme of third-order and four stages (SSP-RK43) is used. Seven important problems of the regularized and the modified regularized long wave equations are solved to demonstrate the applicability of the proposed technique. The motion of a single solitary wave, the interaction of two or more solitary waves, and the undulations of waves are shown graphically. These equations possess three invariants of motion namely mass, momentum, and energy, which need to remain constant with run time. For each problem, these invariants are calculated and it is observed that they coincide with exact values and remain preserved with time. The L2 and L∞ error norms are calculated at different time levels and CPU time is noted. Also, the stability analysis of the technique is carried out and is found to be conditionally stable.

A source‐sink model for water diffusion in an activated carbon fiber/phenolic composite

AbstractThe moisture absorption behavior of a composite comprising phenolic resin and activated carbon fibers was characterized. The resin starts with a water content from curing and the active fibers both adsorb water on their surface and absorb water in sub‐surface pores, acting as a sink or source of water. Measured data showed that the dependence of this water uptake on the surrounding relative humidity was highly nonlinear, and that the effective diffusion rate through the composite was very dependent on the starting and end conditions. A physically based model has been successfully developed to simulate this behavior. Diffusion was assumed to be Fickian and entirely through the resin, with a linear dependence of resin water content on external humidity. Water movement between resin and fibers was determined so as to maintain equilibrium, based on measured steady‐state water uptake curves across a range of relative humidities. This meant that in mid‐range humidities, most water movement was between fibers and resin rather than through the resin, giving low effective diffusion rates. This model and a simple Arrhenius expression for the diffusion coefficient through the resin enabled measured composite diffusion behavior to be accurately predicted over a range of temperatures and humidity changes.

A planar piecewise continuous lumped muscle parameter model for prediction of walking gait.

This work aims to develop a planar piecewise continuous lumped muscle parameter (PPCLMP) model that can utilize inputs that can be obtained in a clinical or home setting using simple tools (e.g. video cameras and inertial sensors) to predict human walking gait. The model characterizes the sagittal-plane movement of the lower limbs during the single stance phase as an inverted pendulum, the double stance phase as a kinematic chain, and the swing phase as a double pendulum. The joint angles and angular velocities at the end of one phase are used as the initial conditions of the next phase. The model predicts the gait cycle based on the initial joint angles and angular velocities via forward dynamics. The errors between the initial and end conditions are minimized by changing the input initial joint angles and angular velocities of the gait cycle. Sensitivity analysis showed that the errors between the initial and end conditions of a gait cycle were sensitive to the initial joint angles. The step length was sensitive to subject stature. The model only works for a certain range of initial conditions. The model can predict gait cycles based on forward dynamics and selects initial conditions that minimize the errors between the initial and end conditions of the gait cycle. The model utilizes 2-D representations of lower limbs and simplified representations of joint torques to reduce the required inputs for gait prediction and builds the foundation of gait assessment tools.