Compact Sections Research Articles

Strength design optimization of structural steel members according to Eurocode 3

In order to design a steel member subjected to a bending moment and an axial load, there are an infinite number of possible solutions of I- or H‐steel cross-sections, the doubly-symmetric solution being just one of them. This paper presents a procedure to obtain the optimal steel cross-section from the infinite number of possible solutions. The process is based on the Reinforcement Sizing Diagrams employed in reinforced concrete strength design. The procedure looks for any type of solution regarding compact or non-compact steel sections. All aspects related to local instabilities are taken into account, as well as some special considerations in order to address the global instabilities associated with the slenderness of the steel element.

Experimental Research on Interface Mechanic Behavior of the Composite Steel-Concrete Beams

Experiments were conducted on 7 simply-supported composite steel-concrete beams (SCB) with compact steel sections to investigate their interface mechanic behavior. The influences of different loading mode, degree of shear connection and stud arrangement are discussed. The test process, specimen failure matter and uplift distribution along the span of the beam are analyzed. Based on the experimental research, the formulae are derived for the interface slip and uplift rigidity of the stud in composite steel-concrete beams. The present values bench-mark finite element analysis of load bearing capacity and deflection of composite steel-concrete beams.

A lower bound on the barrier parameter of barriers for convex cones

Let $${K \subset \mathbb R^n}$$ be a regular convex cone, let $${e_1,\ldots,e_n \in \partial K}$$ be linearly independent points on the boundary of a compact affine section of the cone, and let $${x^* \in K^{0}}$$ be a point in the relative interior of this section. For k = 1, . . . , n, let l k be the line through the points e k and x *, let y k be the intersection point of l k with $${\partial K}$$ opposite to e k , and let z k be the intersection point of l k with the linear subspace spanned by all points e l , l = 1, . . . , n except e k . We give a lower bound on the barrier parameter ν of logarithmically homogeneous self-concordant barriers $${F: K^{0}\to \mathbb R}$$ on K in terms of the projective cross-ratios $${q_k = (e_k,x^*;y_k,z_k)}$$ . Previously known lower bounds by Nesterov and Nemirovski can be obtained from our result as a special case. As an application, we construct an optimal barrier for the epigraph of the $${||\cdot||_{\infty}}$$ -norm in $${\mathbb R^n}$$ and compute lower bounds on the barrier parameter for the power cone and the epigraph of the $${||\cdot||_p}$$ -norm in $${\mathbb R^2}$$ .

Unique Fock quantization of scalar cosmological perturbations

We investigate the ambiguities in the Fock quantization of the scalar perturbations of a Friedmann-Lema\^{i}tre-Robertson-Walker model with a massive scalar field as matter content. We consider the case of compact spatial sections (thus avoiding infrared divergences), with the topology of a three-sphere. After expanding the perturbations in series of eigenfunctions of the Laplace-Beltrami operator, the Hamiltonian of the system is written up to quadratic order in them. We fix the gauge of the local degrees of freedom in two different ways, reaching in both cases the same qualitative results. A canonical transformation, which includes the scaling of the matter field perturbations by the scale factor of the geometry, is performed in order to arrive at a convenient formulation of the system. We then study the quantization of these perturbations in the classical background determined by the homogeneous variables. Based on previous work, we introduce a Fock representation for the perturbations in which: (a) the complex structure is invariant under the isometries of the spatial sections and (b) the field dynamics is implemented as a unitary operator. These two properties select not only a unique unitary equivalence class of representations, but also a preferred field description, picking up a canonical pair of field variables among all those that can be obtained by means of a time-dependent scaling of the matter field (completed into a linear canonical transformation). Finally, we present an equivalent quantization constructed in terms of gauge-invariant quantities. We prove that this quantization can be attained by a mode-by-mode time-dependent linear canonical transformation which admits a unitary implementation, so that it is also uniquely determined.

Refined free vibration analysis of one-dimensional structures with compact and bridge-like cross-sections

The free vibration analysis of beam structures with compact and bridge-like sections is presented in this paper. Refined beam models are used. Their derivation is embedded in the Carrera Unified Formulation (CUF) framework, which allows us to obtain any-order theories with no need for ‘ad hoc’ formulations. Up to fifth-order models are used; classical (Euler–Bernoulli and Timoshenko) beam theories are considered as particular cases of the linear expansion. The finite element (FE) formulation is used in order to analyze arbitrary geometries and boundary conditions. Comparisons with analytical and solid 3D models from commercial code analyses are given. Natural frequencies and modal shapes are investigated. The results have revealed excellent accuracy in the bending frequency computation. Higher-order theories have shown enhanced capabilities to predict more complex phenomena such as torsional frequencies, bending/torsional coupling due to non-symmetrical cross-section and ‘shell-like’ modal shapes characterized by significant cross-section distortions. Moreover, the proposed formulation has shown it is capable in reducing the computational cost significantly.

Numerical Analysis and Comparative Study of the Cross-Sectional Capacity of Structural Steel Members in Fire

The cross-sectional capacity of steel sections subjected to fire is strongly affected by the decreasing stiffness during heating and the nonlinear stress-strain relationship of steel at elevated temperatures. This paper analyses the cross-sectional capacity of common steel sections subjected to combined axial compression and biaxial bending moments at both ambient and elevated temperatures considering section yielding and local buckling effects. The results of a parametric study using the finite element approach are presented as temperature-dependent normalized N-M interaction curves and are compared to results using elastic and plastic interaction formulae. A comparative study shows that European fire design models may lead to conservative results for semi-compact and slender cross sections (class 3 and 4 sections) due to the partial plastic capacity of these sections. However, for steel members predominately subjected to axial compression the design models may lead to unconservative results due to local buckling deflections that occur even for plastic and compact sections (class 1 and 2).

Compactness-like properties and compact sections

There are several covering properties of topological spaces which have been successfully characterised by multi-selections of l.s.c. set-valued mappings. The present paper is devoted to a similar problem but now involving sections instead of multi-selections. It deals with compactness-like properties and sections represented by compact subsets of the range. Several applications are also given.

Field-Scale Evaluation of Lysimeters Versus Actual Earthen Covers

Abstract This paper presents the design, construction, and monitoring of two uncompacted and one compacted clay field-scale test sections that were built and instrumented at a landfill near Detroit (Michigan). This was accomplished to capture the differences in the hydraulic and hydrologic responses of actual caps overlying the municipal solid waste (MSW) versus the corresponding lysimeters. While the lysimeter pans were installed in the middle of each of the three test sections to measure percolation, the instrumented area of the test section was expanded upslope and downslope of the lysimeter to monitor the soil water storages within and beyond the lysimeter footprint. About 35 sensors were installed in each of the three test sections to monitor water contents, water potentials, soil temperatures, water levels, and gas pressures. The soil water storages for the uncompacted test sections that were underlain by the waste were typically greater than those for the corresponding lysimeters. However, for the compacted test section, there was no significant difference between the soil water storage for the actual cap and the lysimeter. The percolation rate for the compacted clay test section was on the order of a few millimeters per year, while that for the uncompacted test sections were in the order of tens of centimeters per year. This difference is attributed to the two order of magnitude lower hydraulic conductivity of the compacted clay. The field data collected in this project validates previously published numerical results regarding hydraulic differences between lysimeters and actual caps.

Compact Wideband Bandstop Filter With Five Transmission Zeros

A compact parallel-coupled transmission line section, connected at their both ends, is presented to obtain multiple transmission zeros. As much as five transmission zeros can be obtained. The zeros can be arranged to design a sharp rejection wideband bandstop filter (BSF). A lossless transmission line model is used to analyze the structure and hence to obtain closed form expressions for the -parameters and design graphs to facilitate the filter synthesis procedure. Theoretical predictions are validated by fabricating a BSF in microstrip line technology. The single filter unit provides 29 dB stopband over a fractional bandwidth of 60% at the mid-band frequency of 1.47 GHz.

판폭두께비에 따른 유공 보의 내력에 관한 실험

Web openings can be used to pass utilities through beams and to minimize story height. Decreasing building height reduces both the exterior surface and the interior volume of a building, which lowers operational and maintenance cost, as well as construction cost. Recently, using composite structures and PEBS(Pre-Engineered Building System) has steadily increased. Sometimes it requires non-compact section for web to reduce steel usage. According AISC Design Guide, the web opening should be only provided in the compact section. In this study, the changes in buckling load, yielding strength, and the deformation of specimens were evaluated experimentally for the non-compact section steel beam.

Multi-element focused ion beams using compact microwave plasma ion source

Focused ion beams (FIB) are widely used for research and applications in nanoscience and technology. We have developed a compact microwave plasma based multi element FIB (MEFIB) system in order to widen the applications and overcome the limitations faced by conventional Liquid Metal Ion Source (LMIS) based FIB systems, that provide primarily Ga ions. The MEFIB source provides high density plasmas (∼1.5 × 1011 cm−3) in a compact cross section. Recently the ion energy spread in the plasma meniscus from where the beams are extracted is found to be small (∼5 eV) [1–3]. The beam extraction and focusing are carried out using electrostatic multi electrode assembly. AXCEL INP and SIMION simulation codes are employed for the design of electrostatic Einzel lenses for beam focusing. The beam focal point is measured using a specially designed three slit Faraday cup and the spot size is measured by the micrography of craters formed by the focused ion beams impinging on copper and aluminium substrates. The initial experimental results show a focused beam spot size of ∼ 25 micron which is in good agreement with the simulations. By further reduction of electrode apertures and operating the second Einzel lens at higher potentials, submicron focused ion beams can be expected.

ANALYSIS-BASED 2D DESIGN OF STEEL STORAGE RACKS

The paper presents a study of the capacities of steel rack frames based on linear analysis (LA), geometric nonlinear analysis (GNA), and geometric and material nonlinear analysis (GMNIA). In the case of linear and geometric nonlinear analyses, the design is carried out to the Australian cold-formed steel structures AS/NZS4600. The study includes braced, unbraced, and semi-braced frames, and compact and noncompact cross sections. The paper shows axial force and bending moment paths for geometric and geometric and material nonlinear analyses, and explains the differences observed in the design capacities obtained using the different types of analysis based on these paths. The paper provides evidence to support the use of advanced GMNIA for the direct design of steel rack frames without the need for checking section or member capacities to a structural design standard.

A Strength Model for Square CFT Stub Columns with Compact Sections

This paper presents an investigation of ultimate strength of square CFT stub columns with compact sections. The beneficial composite action between the steel tube and the filled concrete is taken into account and a new analytical model for predicting the axial capacity of square CFT stub columns with compact sections is proposed. Experimental results of 89 axially loaded square CFT stub columns published in the literature are then used to verify the proposed strength model. Results show that the proposed strength model provides a direct, compact, and efficient representation of the ultimate strength of square CFT stub columns made with not only normal strength but also with high strength steel tubes and concrete.

Design of a New Wide Bandwidth TE01-Mode Converter

This study presents the design and cold testing of a Q-band TE01-mode converter. Integrating Marie transducer and the design of Ching-Fang Yu and Tsun-Hsu Chang, we have improved the design of circular TE01-mode converter. The working principle of each section are analyzed and discussed. Two identical converters are joined back-to-back to explore the field symmetry and to examine the existence of competing modes. The angle-independent transmissions manifest high mode purity. This converter features high back-to-back converting efficiency, high mode purity, compact converting section , and broad bandwidth (18% at a 1-dB transmission).

An Evaluation on the Width-Thickness Ratio of the Rotation Capacity of HSB800 Steel Flexural Members

The width-thickness ratio of the rotation capacity of the HSB800 steel flexural members are evaluated in this study. First of all, the properties of high-performance steel are analyzed from the tension coupon test - SS400, SM490, HSB800. By the result, high-performance steel have the three properties - the high yield ratio, the low modulus of elasticity strain-hardening, and the low strain at tension stress. The rotation capacity of the HSB800 steel flexural members are evaluated using F.E. program. By the F.E result, the HSB800 steel flexural members are not satisfied in the current code that rotation capacity, R>3 in compact section. Based in the experiment and theories, this study suggested limiting the width-thickness ratio of HSB800 steel satisfied in the current code. So, the limitation of width-thickness ratio of the HSB800 steel are conservative than the width-thickness ratio in the code.

Experimental Research on the Composite Steel-Concrete Beams with Partial Shear Connection

Experiments were conducted on 5 simply-supported composite steel-concrete beams (SCB) with compact steel sections to investigate their deflection behaviors. The influences of degree of shear connection and stud arrangement are discussed. The load-deflection relationships and the interface slip distribution along the span of the beam are analyzed. Based on the experimental research and theoretical analyses, the formulae are derived for the rigidity of the composite steel-concrete beams with partial shear connection. The predicted of deflection values are in good agreement with the experimental results.

Seismically induced cyclic buckling of steel columns including residual-stress and strain-rate effects

Compression buckling tests were performed on four full-scale W-shaped column specimens to investigate the buckling response of columns in multi-storey braced steel frame structures subjected to seismic strong ground motions. The test protocols included monotonically and cyclically applied concentric and eccentric axial loading. One test was conducted under dynamic cyclic loading. End moments were applied on one cyclic test. The columns were W310×129 compact (class 1) sections made with ASTM A992 steel. Weak axis buckling was studied and the column had an effective slenderness ratio of 48. The response of the test columns was also examined using numerical simulations based on fibre discretization of the member cross-section. Column residual stresses and strain rate effects on the material properties were both characterized and accounted for in the numerical models. The study showed that steel columns can sustain several cycles of inelastic buckling under seismic induced loading while maintaining sufficient compressive resistance to support the applied gravity loads. Residual stresses affected the column response only at the first buckling occurrence with a gradual reduction of the columns’ tangent stiffness prior to buckling as well as a reduction of the column’s compressive resistance. High strain rates anticipated during strong earthquakes increased the column buckling and post-buckling strengths. The cyclic buckling response of steel columns can be predicted adequately when using nonlinear beam–column elements and cross-section fibre discretization provided that residual stresses and strain rate effects are included in the modelling.

INJECTION AND EXTRACTION SYSTEMS FOR THE MUON FFAG RING IN THE NEUTRINO FACTORY

Non-scaling FFAG (NS-FFAG) rings have been proposed as a solution for muon acceleration in the Neutrino Factory. In order to achieve small orbit excursion and small time of flight variation, lattices with a very compact cell structure and consequent short straight sections are required. The resulting geometry, combined with the large transverse emittance of the muon bunch, places very challenging constraints on the injection/extraction systems. The injection/extraction system requires a set of distributed kickers, a superconducting septum and increased aperture in some of the main ring magnets. A scheme for both injection and extraction for a FFAG with triplet geometry is presented. In addition, a solution for the required kicker magnets is proposed.

Chiral modulations in curved space I: formalism

The goal of this paper is to present a formalism that allows to handle four-fermion effective theories at finite temperature and density in curved space. The formalism is based on the use of the effective action and zeta function regularization, supports the inclusion of inhomogeneous and anisotropic phases. One of the key points of the method is the use of a non-perturbative ansatz for the heat-kernel that returns the effective action in partially resummed form, providing a way to go beyond the approximations based on the Ginzburg-Landau expansion for the partition function. The effective action for the case of ultra-static Riemannian spacetimes with compact spatial section is discussed in general and a series representation, valid when the chemical potential satisfies a certain constraint, is derived. To see the formalism at work, we consider the case of static Einstein spaces at zero chemical potential. Although in this case we expect inhomogeneous phases to occur only as meta-stable states, the problem is complex enough and allows to illustrate how to implement numerical studies of inhomogeneous phases in curved space. Finally, we extend the formalism to include arbitrary chemical potentials and obtain the analytical continuation of the effective action in curved space.

Plastic load bearing capacity of multispan composite highway bridges with longitudinally stiffened webs

The introduction of the Eurocodes makes plastic design criteria available also for composite bridges, leading to more economical solutions compared with previous elastic design rules. Particularly for refurbishment old bridges with higher actual traffic loads, up to date outside the scope of the Eurocodes, strengthening should therefore be avoidable or at least be necessary only to a minor extent. For bridges with smaller spans and compact cross sections, the plastic load bearing capacity is clearly justified. In this work, however, the focus is placed on long span continuous composite bridges with deep, longitudinally stiffened girders, susceptible to local buckling. In a first step, the elastic - plastic cross section capacity of the main girder in bending is studied as an isolated case, based on high preloads acting on the steel girder only, due to the common assembling procedure without scaffolding. In a second step, the effects on the whole structure are studied, because utilising the plastic section capacity at midspan leads to a redistribution of internal forces to the supports. Based on the comprehensive study of an old, actual strengthened composite bridge, some limitations for plastic design are identified. Moreover, fully plastic design will sometimes need additional global analysis. Practical recommendations are given for design purposes.