Compact Sections Research Articles

Section moment capacity tests of LiteSteel beams

The LiteSteel beam (LSB) is a new cold-formed hollow flange channel section developed by OneSteel Australian Tube Mills using their patented dual electric resistance welding and automated continuous roll-forming process. It has a unique geometry consisting of torsionally rigid rectangular hollow flanges and a relatively slender web. In addition to this unique geometry, the LSB sections also have unique characteristics relating to their stress–strain curves, residual stresses, initial geometric imperfections and hollow flanges that are not encountered in conventional hot-rolled and cold-formed steel channel sections. An experimental study including 20 section moment capacity tests was therefore conducted to investigate the behaviour and strength of LSB flexural members. The presence of inelastic reserve bending capacity in these beams was investigated in detail although the current design rules generally limit the section moment capacities of cold-formed steel members to their first yield moments. The ultimate moment capacities from the tests were compared with the section moment capacities predicted by the current cold-formed and hot-rolled steel design standards. It was found that compact and non-compact LSB sections have greater moment capacities than their first yield moments. The current cold-formed steel design standards were found to be conservative in predicting the section moment capacities of compact and non-compact LSB sections, while the hot-rolled steel design standards were able to better predict them. This paper has shown that suitable modifications are needed to the current design rules to allow the inclusion of available inelastic bending capacities of LSBs in design.

Kernel sections and (almost) periodic solutions of a non-autonomous parabolic PDE with a discrete state-dependent delay

In this paper, we consider the long time behavior of a non-autonomous parabolic PDE with a discrete state-dependent delay. We study the existence of compact kernel sections and unique complete trajectory of the corresponding problem. Furthermore, we obtain the (almost) periodic solution which attracts all solutions provided the time dependent terms are (almost) periodic with respect to time $t$.

The Influence of Timber Panels on Architecture

Since timber is naturally directional, timber products become directionally neutral only due to the progress in manufacture technology. This work studies timber panels with a view to analyse their influence on the architectural form. From a design point of view, two sub-categories are defined. These are solid panels, and optimised panels. Solid panels have a homogeneous and compact section and their thicknesses are relatively small. Composite panels are generally made up with two boards and an inner structure to which they are bonded. The work concludes that the two main typologies of timber panels influence design in a different way: due to their homogeneous inner structure, solid panels allow flexible cutting of the openings, and loads and supports can be placed with few limitations. In the other hand, optimised section panels require more planning and should be treated as finished elements.

Compact kernel sections for dissipative non-autonomous Zakharov equation on infinite lattices

In this paper, we first prove the existence of compact kernel sections for dissipative non-autonomous Zakharov lattice dynamical system, then we obtain an upper bound of fractal dimension of the compact kernel sections, and finally we establish an upper semicontinuity of the compact kernel sections.

Moment Redistribution in Continuous Steel-Concrete Composite Beams with Compact Cross Section

The paper investigates the design of continuous steel-concrete composite beams with compact cross section using the elastic analysis with limited redistribution. The permissible moment redistribution which satisfies the requirements of the ultimate limit state (collapse) and serviceability limit state (crack width in the concrete slab) was computed. An advanced finite element program accounting for all mechanical nonlinearities and time-dependent phenomena (creep and shrinkage of concrete) was used. An extensive parametric analysis aimed to determine the influence of several geometrical parameters on the permissible moment redistribution was carried out on propped cantilevers and fixed-end beams. The analyzed parameters include the shape of the steel profile, the ratio between the depths of concrete slab and steel beam, the steel to concrete area ratio, and the reinforcement percentage of the concrete slab. The analysis was limited to compact steel sections (AISC 360-05) or class 1 steel sections (Eurocode 3) and low ductility reinforcing steel (elongation at maximum load εru=2.5%). The moment redistribution domain which satisfies the rotation compatibility in the critical sections, due to the attainment of the rupture of the reinforcement or the local buckling of the steel profile, and the control of cracking (<0.3 mm) in service was evaluated and compared with the limits recommended by current codes of practice. A proposal for the allowable moment redistribution domain according to the limits of the study was given.

CRYSTALLINE GRAVITY

Matter interacting classically with gravity in 3+1 dimensions usually gives rise to a continuum of degrees of freedom, so that, in any attempt to quantize the theory, ultraviolet divergences are nearly inevitable. Here, we investigate a theory that only displays a finite number of degrees of freedom in compact sections of space-time. In finite domains, one has only exact, analytic solutions. This is achieved by limiting ourselves to straight pieces of string, surrounded by locally flat sections of space-time. Next, we suggest replacing in the string holonomy group, the Lorentz group by a discrete subgroup, which turns space-time into a 4-dimensional crystal with defects.

Flexural Capacity of Compact Composite I-Girders in Positive Bending

Current American Association of State Highway and Transportation Officials (AASHTO) bridge specifications for compact composite steel girders in positive bending with adjacent compact pier sections limit the allowable maximum strength to a value between the full plastic moment and the hypothetical yield moment of the cross section as a function of the depth of web in compression. The strength prediction equations derived using these methods provide conservative values when compared to the results of the parametric studies used to develop the equations. Recent experimental tests coupled with finite-element analysis and mechanistic evaluations of the cross-section flexural capacity suggest that larger capacities may be achieved than those determined from AASHTO’s prediction equations. This paper presents an assessment of the behavior of composite positive bending specimens. A summary of a comprehensive literature review is provided coupled with results of the analytical and experimental evaluation of the nominal moment capacity of composite girders. Lastly, a less conservative design moment capacity expression developed from this assessment is provided.

Energy Absorption Capacity of Composite Beams

Local buckling may occur in the compression flange of rectangular hollow-section beams under cyclic repeated loading arising from earthquakes. Once a local mechanism forms, residual strength rapidly reduces within a few cycles. This is true even for compact sections under static bending. This paper aims to study the experimental behaviour and ultimate moment capacity of unfilled and concrete-filled rectangular hollow sections subjected to cyclic reversible loading. Two types of filler material were used - normal mix concrete and fly ash concrete. The effect of filler materials, section slenderness, loaddeflection response, moment-strain behaviour, first cycle peak load, ductility, stiffness degradation and energy absorption of concrete –filled RHS beams are studied.

Food for Thought: The Stories behind the Things We Eat (review)

Reviewed by: Food for Thought: The Stories behind the Things We Eat Deborah Stevenson Robbins, Ken Food for Thought: The Stories behind the Things We Eat; written and illus. with photographs by Ken Robbins. Porter/Roaring Brook, 2009 [48p] ISBN 978-1-59643-343-4$17.95 Reviewed from galleys Ad Gr. 4-7 "Every kind of food has its story. Here are just a few of them," says veteran photo-documentarian Robbins, here turning his attention to apples, oranges, potatoes, tomatoes, grapes, bananas, mushrooms, corn, and pomegranates. Each foodstuff receives a few pages comprising tidbits about its cultivation and use and snippets of lore surrounding it, partnered with spot art and full-page photographs. The result is unfortunately scattershot in focus, and the material is variable in veracity (there are no sources listed), interest (the book leads with some of its dullest material) and significance (are kids even going to get the joke that President Reagan's favorite vegetable was ketchup?). The title still offers some digestible information in its compact sections, though, especially on agriculture and agribusiness, and the voice is often lively and opinionated. The full-page photographic illustrations are particularly dramatic, with the produce imbued with somberly glowing hues and backed with cloudy evening skies for an effect that suggests period still lifes. Despite the book's flaws, browsers may find interest in some of the slices of vegetal information, and it could be a diverting adjunct to more serious explorations of contemporary food practice. [End Page 378] Copyright © 2009 The Board of Trustees of the University of Illinois

An automated image analysis procedure to evaluate compacted asphalt sections

A new image analysis program is presented to determine morphological and textural properties of aggregates, asphalt binder and air voids in compacted asphalt mixes. The procedure involves scanning cut sections of laboratory or field specimens and estimating volumetric properties based on a pseudo 3D algorithm. Properties that are calculated include gradation, asphalt content, air void content, amount of flat/elongated particles, distribution of particle orientations, air void profiles, and various particle shape and textural measures. Validation of the code for specimens for which reference values were available indicates generally good predictions, particularly with regard to gradation and asphalt content. The objective of the study has been to develop a robust procedure that is easy to use, cost efficient, environmentally friendly and that can be used as a means to determine asphalt characteristics for quality control and quality assurance purposes. The new analysis technique may also find application in the study of SEM resin-impregnated soil thin sections and concrete cross sections.

Effect of coagulation on the structure and property of PAN nascent fibers during dry jet wet-spinning

The paper has studied the effect of coagulation process on the structure and property of polyacrylonitrile nascent fibers during dry jet wet-spinning. The coagulation process to form polyacrylonitrile fibers has been studied by examination of FTIR, XRD, and SEM and so on. The results indicated that compared with coagulation directly, polyacrylonitrile nascent fibers gradually formed with fine crystallites and high degree of crystallization were achieved, the flex vibration peak of S=O gradually decreased, and less solvents remained in the nascent fibers with compact cross section morphology. At the same time, nascent fibers with less DMSO under different draw ratios showed higher fracture intensity and lower elongation.

Stress-Triaxiality in Zr-2.5Nb Pressure Tube Materials

Abstract The crack growth resistance of irradiated Zr-2.5Nb pressure tubes is controlled by the initiation of voids and their subsequent growth and coalescence. The presence of particles that contribute to void nucleation is determined by the operating conditions/history of the pressure tube and by the concentration of pre-existing species, which is a function of the manufacturing process. The susceptibility of the pressure tubes to void nucleation is determined by the number and distribution of particles, the deformation properties of the matrix, and the stress state at the crack tip. The effect of irradiation on zirconium material is to increase the yield stress but to reduce the work hardening ability of the matrix and to promote strain localization, which, in turn, leads to void nucleation. Void nucleation is also enhanced by high values of stress triaxiality at or near the crack tip. For irradiated pressure tube material, both small-scale curved compact tension specimens and large-scale burst test sections are used to characterize the crack growth resistance. However, the measured fracture toughness can depend on the specimen geometry due to differences in constraint. The present investigation uses three-dimensional finite element analyses to characterize stress triaxiality at the crack tip in these different specimen geometries. Results of the numerical analyses are compared to the experimental evidence that provide qualitative evidence of differences in stress triaxiality at the crack tip for different specimen geometries.

Linear Induction Motors with Modular Winding Primaries and Wound Rotor Secondaries

Linear induction motors commonly use double layer windings, which produce good sinusoidal travelling fields, but have relatively bulky end windings and use either half-filled slots or overhanging coil sides at the ends of the machine. Long stator systems are difficult since it is not possible to butt stator modules against each other. Arguably the simplest and most cost effective winding uses modular construction where the coils are planar and do not overlap. Here the end winding is compact and stator sections can be butted together. However modular windings do not produce high quality travelling fields. Two space harmonics of closely the same magnitude are produced that travel in opposite directions, giving induced currents and opposing forces with little net force in plate rotors. The difficulty can be resolved if a wound secondary with a double layer winding is used instead of a plate. Here a substantial induced emf and current is produced only by the field for which the secondary is wound, so that force is produced only in one direction. The use and properties of modular windings for short rotor machines are explored using finite element analysis and the results are validated by practical tests. It is concluded that inexpensive modular windings can be used with wound secondaries to good effect particularly in long stator situations; for example, for electromagnetic launch and urban transport systems.

Comparison of the structure and mechanical properties of bovine femur bone and antler of the North American elk (Cervus elaphus canadensis)

Antler and limb bone have a similar microstructure and chemical composition. Both are primarily composed of type I collagen and a mineral phase (carbonated apatite), arranged in osteons in compact (cortical bone) sections and a lamellar structure in the cancellous (spongy or trabecular bone) sections. The mineral content is lower in antler bone and it has a core of cancellous bone surrounded by compact bone running through the main beam and tines. The mineral content is higher in the compact compared with the cancellous bone, although there is no difference in ratios of the mineral elements with calcium. Mechanical tests (bend and compression) on longitudinal and transverse orientations of dry and rehydrated compact bone of North American elk (Cervus elaphus canadensis) antlers are compared with known data on other antlers as well as bovine femora. Both dry and rehydrated bones are highly anisotropic, with the bending and compressive strength and elastic modulus higher in the longitudinal than in the transverse direction. There is no significant difference between the bend strength and elastic modulus between dry and rehydrated samples tested in the transverse direction. The elastic modulus measured from the bending tests is compared with composite models. The elastic modulus and bend strengths are lower in the rehydrated condition, but the strain to failure and fracture toughness is much higher compared with dry samples. All antler bone mechanical properties are lower than that of bovine femora. The antler has a much higher fracture toughness compared with bovine femora, which correlates with their main function in intraspecific combat as a high impact resistant, energy absorbent material. A model of compression deformation is proposed, which is based on osteon sliding during shear.

A Note on nonautonomous klein-gordon-schrödinger equations with homogeneous dirichlet boundary condition

This note discusses the long time behavior of solutions for nonautonomous weakly dissipative Klein-Gordon-Schrödinger equations with homogeneous Dirichlet boundary condition. The authors prove the existence of compact kernel sections for the associated process by using a suitable decomposition of the equations.

A Locally Finite Model for Gravity

Matter interacting classically with gravity in 3+1 dimensions usually gives rise to a continuum of degrees of freedom, so that, in any attempt to quantize the theory, ultraviolet divergences are nearly inevitable. Here, we investigate matter of a form that only displays a finite number of degrees of freedom in compact sections of space-time. In finite domains, one has only exact, analytic solutions. This is achieved by limiting ourselves to straight pieces of string, surrounded by locally flat sections of space-time. Globally, however, the model is not finite, because solutions tend to generate infinite fractals. The model is not (yet) quantized, but could serve as an interesting setting for analytical approaches to classical general relativity, as well as a possible stepping stone for quantum models. Details of its properties are explained, but some problems remain unsolved, such as a complete description of the most violent interactions, which can become quite complex.

Hollow and concrete filled steel hollow sections under transverse impact loads

Steel hollow sections are used extensively in the construction, offshore, mining and security industries. In many applications these sections are concrete filled in order to gain strength advantages under axial compression loads. These sections may be subjected to transverse impact loads from accidental or intentional impacts or explosive events. This paper reports an experimental and analytical investigation of hollow and concrete filled steel square hollow (SHS) section beams subjected to low velocity, large mass transverse impacts at the beam mid-span. Three different section sizes were tested as fully clamped beams, where the impact energy was sufficiently large so as to cause complete failure of the beam by tensile tearing. It is shown that non-compact hollow sections undergo local deformations beneath the impactor, and when concrete filled these sections can sustain greater transverse impact loads as the local deformations are restricted from forming. The effect is shown to be less pronounced for compact sections. An elastic–plastic theoretical method is developed to establish the force–displacement and energy absorption relationships for hollow and concrete filled sections, and is shown to compare well with the experimental results. The local reduction of the section at the point of load application is explicitly included. A design procedure is developed whereby the analyst may use a deflection, force or energy limit to design hollow and concrete filled steel SHS members for transverse impact loads.

Model for Cyclic Inelastic Buckling of Steel Braces

The paper presents a model for the inelastic buckling behavior of steel braces. The model consists of a force-based frame element with distributed inelasticity and fiber discretization of the cross section. With this approach, the response of the element can be derived by integration of the uniaxial stress-strain relation of the fibers and can account for kinematic and isotropic hardening as well as the Bauschinger effect of the material. The interaction between axial force and bending moment is thus accounted for. Even though the element only accounts for small deformations in the basic system, large displacement geometry is included in the nonlinear transformation of the force-deformation relation of the basic element following the concept of the corotational formulation. With this approach, two elements for each brace suffice to yield results that match an extensive set of experimental data of braces with different cross sections and slenderness ratios. Even though the model does not account for the effect of local buckling, this phenomenon does not seem to appreciably affect the global response of braces with compact sections.

Compact kernel sections for lattice systems with delays

In this paper, we consider the existence, upper semi-continuity and singular limiting behavior of compact kernel sections for the process associated to non-autonomous lattice systems with delays.

Finite dimensionality and upper semicontinuity of compact kernel sections of non-autonomous lattice systems

In this paper, we first establish a criteria for finite fractal dimensionality of a family of compact subsets of a Hilbert space, and apply it to obtain an upper bound of fractal dimension of compact kernel sections to first order non-autonomous lattice systems. Then we consider the upper semicontinuity of kernel sections of general first order non-autonomous lattice systems and give an application.