Hollow Circular Cross-section Research Articles

Use of lignocellulosic biomaterials for sustainable development of bamboo strand lumber for structural applications

Bamboo is one of the fastest growing plants and has mechanical properties similar to timber. The main reasons for the popularity of bamboo in construction can be attributed to its low cost, local availability, and adequacy of simple, local tools, and skills for fabrication. Application of bamboo in construction is, however, normally limited to low-cost housing and temporary structures due to several factors including irregular shapes, hollow circular cross sections, and durability issues. This report presents the results of an investigation into production of an engineered bamboo lumber product. Bamboo culms were cut into smaller strands and were re-constituted into rectangular sections by gluing and pressing at 140 °C to 145 °C. This approach overcomes the presence of the inherent hollow core and randomizes the inter-nodes and other growth characteristics found in bamboo. The reconstituted bamboo strand lumber (RBSL) was developed using crushed Bambusa bambos species and phenol formaldehyde resin. The physical and mechanical properties of reconstituted bamboo strand lumber were evaluated as per IS 1734 (1983). From the results it was found that the BSL can be used as an alternate to timber to meet Sustainable Development Goals (SDGs) for building applications that will effectively transform the world.

Dynamics of a rotating hollow FGM beam in the temperature field

Abstract Dynamic responses and vibration characteristics of a rotating functionally graded material (FGM) beam with a hollow circular cross-section in the temperature field are investigated in this paper. The material properties of the FGM beam are assumed to be temperature-dependent and vary along the thickness direction of the beam. By considering the rigid-flexible coupling effect, the geometrically nonlinear dynamic equations of a hub–FGM beam system are derived by employing the assumed modes method and Lagrange’s equations. With the high-order coupling dynamic model, the effect of temperature variations under two different laws of motion is discussed, and the free vibration of the system is studied based on the first-order approximate coupling model. This research can provide ideas for the design of space thermal protection mechanisms.

Advances and Trends in Forming Curved Extrusion Profiles.

Curved profiles/sections have been widely used for manufacturing lightweight structures with high stiffness and strength due to aerodynamics, structural properties, and design reasons. Structural components fabricated using curved aluminum profiles satisfy the increasing demands for products used in many high-technology industries such as aerospace, shipbuilding, high-speed rail train, and automobile, which possess the characteristics of lightweight, high strength/stiffness relative to weight, superior aerodynamics performance, and aesthetics. In this paper, the advances and trends in forming techniques of curved extrusion profiles of metal alloys have been reviewed. The curved profile forming techniques are classified into three major categories: conventional cold bending technique, stress/moment superposed cold bending technique, and extrusion-bending integrated forming technique. Processes for innovative development in the field of forming curved profiles are identified; the extrusion-bending integrated technique which can directly form the billets into curved profiles by one single extrusion operation possesses the full potential for further innovation. Due to the nature of the research to date, much of the work referred to relates to hollow circular and rectangular tube cross-sections.

Multiscale optimization of specific elastic properties and microscopic frequency band-gaps of architectured microtruss lattice materials

This paper proposes the development of lattice materials with the concurrent consideration of their specific elastic mechanical properties and their corresponding phononic wave filtering capabilities. A multi-objective and multiscale design optimization problem is presented where the microscopic geometric parameters of truss-like lattice unit cells are introduced as design variables by means of beams cross-section shape transformers. The optimization problem is posed to maximize the stiffness and strength properties of lattice materials along with their frequency band-gap aspect ratios while minimizing their relative density. Floquet-Bloch theorem is employed for the frequency band-gap analysis while the homogenized mechanical properties are estimated using the Cauchy-Born hypothesis and the Hill-Mandel principle of macro-homogeneity. It is found that the band-gap aspect ratios are directly proportional to the macroscopic mechanical properties of the lattice, therefore posing a trade-off design problem. Two case studies are presented for the multi-objective optimization problem including the triangular and the Kagome patched honeycomb topologies. It is demonstrated that the design objectives are satisfied with “I” shaped, horizontally hollow circular or diamond cross-sections. Design charts are introduced which enable the definition of lattice microscopic geometrical attributes required for lattice material development with optimal static macroscopic and dynamic microscopic characteristics.

Band gap optimization of one-dimension elastic waveguides using spatial Fourier plane wave expansion coefficients

Periodic elastic waveguides, such as rods, beams, and shafts, exhibit frequency bands where wave reflections at impedance discontinuities cause strong wave attenuation by Bragg scattering. Such frequency bands are known as stop bands or band gaps. This work presents a shape optimization technique for one-dimensional periodic structures. The proposed approach, which aims to maximize the width of the first band gap, uses as tuning parameters the spatial Fourier coefficients that describe the shape of the cell cross-section variation along its length. Since the optimization problem is formulated in terms of Fourier coefficients, it can be directly applied to the Plane Wave Expansion (PWE) method, commonly used to obtain the dispersion diagrams, which indicate the presence of band gaps. The proposed technique is used to optimize the shape of a straight bar with both solid and hollow circular cross-sections. First, the optimization is performed using the elementary rod, the Euler-Bernoulli and Timoshenko beam, and the shaft theoretical models in an independent way. Then, the optimization is conducted to obtain a complete band gap in the dispersion diagrams, which includes the three wave types, i.e., longitudinal, bending, and torsional. All numerical results provided feasible shapes that generate wide stop bands in the dispersion diagrams. The proposed technique can be extended to two- and three-dimensional periodic frame structures, and can also be adapted for different classes of cost functions.

Parameters of Side Intrusion Beam Affecting on Crash Force Efficiency During Impact

Occupants safety is one of the most important criteria in car design. Due to the less space between occupant and side door, the scope of energy absorption is less. Hence in a case of side impact, the strength of side door is plays crucial role. A side intrusion beam is mount inside the side door and is also called side impact beam. During side impact, side intrusion beam gets deformed and it absorb the highest amount of energy compare to others parts of side door. And also for smooth bending during the impact, nearly equal amount of force should absorb during the whole bending process. So design of side intrusion beam is important part of vehicle door design. The various parameters of intrusion beam like, material of intrusion beam, shape of intrusion beam, dimensions, mounting of beam inside the door etc. are affected on the strength of side door. In present work using finite elements analysis the effect of important parameters of hollow circular cross section side intrusion beam on Crash Force Efficiency (CFE) is studied. The ABAQUS software is used to perform various finite element simulation. In the first part of this work most influential parameter is determine by Design of Experiments and ANOVA analysis, in a second part of this work relative effect of this influential parameter on crashworthiness of side intrusion beam is studied.

Численное исследование закритической работы стержней кольцевого поперечного сечения при внецентренном сжатии

Analysis results of hollow circular cross-section bars under bending and axial compression by the finite element method in different formulations with considering of overall buckling described. Qualitative comparison of the data obtained with the data of laboratory tests is made. Analysis parameters allowing achieving an optimal balance between analysis accuracy and speed are given.

Earth's earliest and deepest purported fossils may be iron-mineralized chemical gardens.

Recognizing fossil microorganisms is essential to the study of life's origin and evolution and to the ongoing search for life on Mars. Purported fossil microbes in ancient rocks include common assemblages of iron-mineral filaments and tubes. Recently, such assemblages have been interpreted to represent Earth's oldest body fossils, Earth's oldest fossil fungi, and Earth's best analogues for fossils that might form in the basaltic Martian subsurface. Many of these putative fossils exhibit hollow circular cross-sections, lifelike (non-crystallographic, constant-thickness, and bifurcate) branching, anastomosis, nestedness within ‘sheaths’, and other features interpreted as strong evidence for a biological origin, since no abiotic process consistent with the composition of the filaments has been shown to produce these specific lifelike features either in nature or in the laboratory. Here, I show experimentally that abiotic chemical gardening can mimic such purported fossils in both morphology and composition. In particular, chemical gardens meet morphological criteria previously proposed to establish biogenicity, while also producing the precursors to the iron minerals most commonly constitutive of filaments in the rock record. Chemical gardening is likely to occur in nature. Such microstructures should therefore not be assumed to represent fossil microbes without independent corroborating evidence.

Vibration analysis of rotating functionally graded tapered beams with hollow circular cross-section

The dynamic modeling and free vibrations of rotating functionally graded (FG) tapered cantilever beams with hollow circular cross-section are studied in this paper. To capture the additional dynamic stiffening terms, the axial shrinkage of the beam caused by the transverse displacement is considered. The dynamic equations of the system governing stretching motion, flapwise bending motion, and chordwise bending motion are derived via employing assumed modes method and Lagrange's equations. Based on the first order approximate coupling (FOAC) dynamic model, natural frequencies and mode shapes of the beam system are calculated by solving eigenvalue problem of the deduced dimensionless vibration equations. Influences of the angular speed, the hub radius, the slenderness ratio, the ratio of hollow radius to the root radius, the taper ratio, and the functional gradient index on natural frequencies are studied. Frequency veering and mode shape interaction are discussed when the bending-stretching mode coupling effect of the beam is considered.

Vibration analysis of a rotating axially functionally graded tapered beam with hollow circular cross-section

In this paper, the free vibrations of a rotating axially functionally graded (FG) tapered cantilever beam with hollow circular cross-section attached to a rigid hub are studied. To capture the additional dynamic stiffening terms, the longitudinal shrinkage of the beam is considered. The dynamic governing equations are derived via employing the assumed modes method and Lagrange’s equations. Through ignoring the higher-order quantities, the first order approximate coupling (FOAC) dynamic model can be acquired. Based on the FOAC dynamic model, influences of the angular speed, the taper ratio, the hub radius, the slenderness ratio, and the functionally gradient index on natural frequencies are studied. Frequency veering and mode shape interaction of the system are discussed when the bending-stretching (B-S) mode coupling effect of the beam is considered.

Analysis of warping and distortion transmission in mixed shell\u2013GBT (generalized beam theory) models

Warping and distortion are relevant kinematic features of thin-walled beam structures, which have a non-trivial analysis. On this basis, this paper not only evaluates the possible kinematic transmissions involving high-order warping and distortion, but also presents a procedure to analyze structures using mixed models based on shell and Generalized Beam Theory (GBT) elements. In this mixed beam-shell structure, the traditional shell elements are applied at structural detailing points, such as joints, and GBT elements are used to model the beams/columns. Such a modeling technique uses the benefits of both elements. Shell elements can easily simulate different types of geometry conditions and details, such as stiffeners and holes; meanwhile, for the beams and columns, GBT can provide high performance, accuracy, and an easy modeling approach with clear results. The numerical formulation is based on multi-freedom constraint techniques. Special attention is given to the Master–Slave method, which is developed based on GBT kinematic assumptions. Furthermore, there is a discussion concerning the choice of the master degrees of freedom and its implications in numerical performance. An example of a thin-walled hollow circular cross section illustrates the proposed approach and is compared with fully shell element models.

A degrading shear strength model for R.C. columns with hollow circular cross-section

This study aims contributing to the investigation about the shear strength of reinforced concrete members with hollow circular cross-section and ordinary concrete strength. First, a proper experimental database of tests carried out in the literature on hollow circular members is collected and analysed. Then, the few existing shear strength models from the literature or seismic codes considered suitable for hollow circular sections are discussed and compared with the experimental results. Starting from the lonely specific degrading model existing in the literature, new equations are proposed on mechanical bases for concrete, transverse reinforcement and axial load contributions to the shear strength and for the shear strength degradation due to increasing ductility demand. The new proposed model is finally validated by means of the collected experimental data. Numerical-versus-experimental comparisons show very good results in terms of predicting capacity of both maximum (not-degraded) and degraded shear strength. The relative percentage prediction error always results lower than 4% with a very limited dispersion. The proposed equations can be thus considered as a reliable improvement of existing shear strength models for the investigated structural typology.

Vibration of Toroidal Shells with Hollow Circular Cross-Sections

This paper presents a three-dimensional (3D) analysis for the natural frequencies of completely free, toroidal shells of revolution with hollow circular cross-sections by the Ritz method. The displacement components [Formula: see text], [Formula: see text], and [Formula: see text] in the radial, circumferential, and axial directions, respectively, are taken to be sinusoidal in time, periodic in [Formula: see text], and of the ordinary algebraic simple polynomials in the [Formula: see text] and [Formula: see text] directions. The potential (strain) and kinetic energies of the torus are formulated, and the upper bound values of the frequencies are obtained by a minimization procedure. As the degree of the polynomials increases, the frequencies computed converge to the exact values. Convergence to four-digit exactitude is demonstrated for the first five frequencies of the torus. Comparisons are made between the frequencies from the present 3D method, a 3D finite element method, experimental methods, and thin and thick ring theories.

Dijagrami interakcije za armiranobetonski šuplji kružni poprečni presjek

Opisan je postupak izrade dijagrama interakcije za armiranobetonske šuplje kružne poprečne presjeke prema normi HRN EN 1992-1-1. Zbog uvođenja novih razreda čvrstoće betona s nešto drugačijim parametrima proračunskog dijagrama naprezanje-relativna deformacija, dolazi do potrebe izrade novih dijagrama interakcije. Proveden je postupak proračuna temeljem kojeg su izrađeni dijagrami interakcije za šuplji kružni poprečni presjek za razrede betona od C12/15 do C50/60. Primjenom dobivenih dijagrama interakcije pojednostavljuje se postupak dimenzioniranja armiranobetonskih šupljih kružnih poprečnih presjeka.

Seismic Assessment of Existing Hollow Circular Reinforced Concrete Bridge Piers

ABSTRACT Experimental works in literature have paid proper attention to the seismic response of hollow circular piers only quite recently, despite their widespread use in existing bridges. Herein, experimental cyclic tests on two scaled reinforced concrete piers with hollow circular cross-section, representative of typical existing Italian bridges, are carried out. Design criteria, adopted setup, experimental response, and damage evolution are discussed. A focus on shear–critical piers is performed, collecting an experimental database of tests from literature. The more specific existing shear strength models are compared with the collected data. Model by Ranzo and Priestley [2001] has finally shown promising results.

Closed-form approximation of the axial force-bending moment interaction diagram for hollow circular reinforced concrete cross-sections

This paper proposes a simple closed-form approximation of the axial force-bending moment interaction diagram for solid and hollow circular reinforced concrete (RC) cross-sections with an arbitrary number of layers of longitudinal reinforcement. The implemented nonlinear material models are those of the European building code. Specifically, the parabola-rectangular strain-stress relation and the stress-block model are considered for the concrete in compression. On the other hand, the elastic-perfectly plastic behavior is assumed for the reinforcing steel bars. The proposed semi-exact closed-form approximation involves one parameter only, which is calibrated by means of a numerical optimization procedure taking into account a large database of cross-sections. Moreover, an efficient procedure is developed for the design of the outer layer of longitudinal reinforcement in solid or hollow circular RC cross-sections under combined axial force and bending moment (the mechanical ratio of any other layers of longitudinal reinforcement is considered as known function of the mechanical ratio of the outer layer of longitudinal reinforcement). Finally, several numerical examples are included to demonstrate the accuracy of the approximated axial force-bending moment interaction diagram and the effectiveness of the derived design procedure.

Structural identification of a cantilever beam with multiple cracks: Modeling and validation

This paper presents the structural identification problem of a multiple damaged cantilever beam with hollow circular cross-section. To consider multiple crack effects, the cantilever beam including cracks is considered for six damage scenarios. The problem is solved by the transfer matrix method analytically and the finite element method numerically. In addition, results are validated by experimental measurements. In analytical solution, the cracked Timoshenko beam is treated as an assembly of sub-segments linked by rotational springs to serve the crack's flexibility coefficient. Finite element models are constituted in ANSYS software for numerical solution. Ambient vibration tests are performed to extract the experimental dynamic characteristics using Enhanced Frequency Domain Decomposition (EFDD) and Stochastic Subspace Identification (SSI) methods. Measured and calculated natural frequencies and corresponding mode shapes for undamaged and damaged beams are compared with each other. Modal Assurance Criterion (MAC) and Coordinated Modal Assurance Criterion (COMAC) factors are obtained from the mode shapes and two set of measurements to establish the correlation between the measured and calculated values for identification of damage location.

Modal parameter identification and vibration based damage detection of a multiple cracked cantilever beam

Abstract This paper presents a detailed investigation on the modal parameter identification and vibration based damage detection of a multiple cracked cantilever beam with hollow circular cross-section. To consider multiple crack effects, a cantilever beam including cracks is considered for six damage scenarios. Finite element models are constituted in ANSYS software for numerical solutions. The results are validated by experimental measurements. Ambient vibration tests are performed to extract the dynamic characteristics using Enhanced Frequency Domain Decomposition (EFDD) and Stochastic Subspace Identification (SSI) methods. Calculated and measured natural frequencies and mode shapes for undamaged and damaged beams are compared with each other. Automated model updating is carried out using the modal sensitivity method based on Bayesian parameter estimation to minimize the differences for damage detection. In addition, modal assurance criterion (MAC) and coordinated modal assurance criterion (COMAC) factors are obtained from the mode shapes and two set of measurements to establish the correlation between the measured and calculated values for damage location identification.

Determining of Shear Modulus for the Samples Circular and Hollow Circular Cross-Section

The contribution is focused on estimating the shear modulus of the samples of circular and hollow circular sections by static method. The samples were loaded by simple torsion, individual sections were stressed by shear stress. Theoretical basis are determined by linear elasticity and strength theory and they define the relation between shear modulus, maximum shear stress and relative strains. Relative strains are determined by using measurement apparatus and measurement system Quantum X MX 840.

Parametric analysis of viscoelastic hyperboloidal helical rod

The objective of this study is to perform a pioneering research about a viscoelastic hyperboloidal helical rod having a standard type of distortional behavior and a Kelvin type of bulk compressibility. Field equations are based on the Timoshenko beam theory, and the exact curvatures of the hyperboloidal geometry are considered through the formulation. The numerical analysis is carried out by the mixed finite element method, considering the rotary inertia, in the Laplace space, and the results are transformed back to time space numerically using the modified Durbin’s algorithm. A cantilevered hyperboloidal helical rod having solid circular, hollow circular, and thin-walled hollow circular cross sections is handled, and the rod is loaded by rectangular and triangular impulsive types of point load at the tip. Through the analysis, different values of retardation time, three different relaxation functions associated with shear modulus, and three different creep functions associated with bulk modulus are handled. Finally, a benchmark example is presented, and the influence of the loading and the material parameters on the helix geometry is discussed.